2023

Jump to: 2022, 2021, 2020, 2018, 2017

11 pages, 2385 KiB

Open AccessArticle

The Effect of Alginate Concentration on Crystallinity, Morphology, and Thermal Stability Properties of Hydroxyapatite/Alginate Composite

by Wulandari Wulandari, Dini Muthiah Islami, Diana Vanda Wellia, Emriadi Emriadi, Vivi Sisca and Novesar Jamarun

Polymers 2023, 15(3), 614; https://doi.org/10.3390/polym15030614 - 25 Jan 2023

Cited by 5 | Viewed by 1564

Abstract

Hydroxyapatite (HAp) has been used for various applications such as orthopedics, drug delivery material, and bone tissue engineering. It is well known that HAp has a good biocompatibility and osteoconductivity, so HAp can be used in biomedical applications. Hydroxyapatite can be combined with [...] Read more.

Hydroxyapatite (HAp) has been used for various applications such as orthopedics, drug delivery material, and bone tissue engineering. It is well known that HAp has a good biocompatibility and osteoconductivity, so HAp can be used in biomedical applications. Hydroxyapatite can be combined with other materials, in particular polymer, to expand its range of applications. In this study, the polymer that will be used as a support for the HAp composite is alginate (Alg). The HAp/Alg composite has been synthesized by the precipitation method. The XRD results show that the crystal system of HAp was hexagonal. The spheric-like shaped particles can be observed from SEM images, and particle size distribution spread from 400 to 1100 nm. The EDS spectrum exhibited the peak of Ca, C, P, and O elements, indicating that alginate had interacted with hydroxyapatite in the synthesized composite. The as-fabricated composite showed not only good crystallinity but also high thermal resistance. Thermogravimetric-differential thermal analysis (TGA-DTA) revealed that the HAp/Alg composites have a constant weight at 750 °C, so it might be applied in advanced applications such as bioimaging, drug carrier, and other cancer treatments. Full article

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2022

Jump to: 2023, 2021, 2020, 2018, 2017

16 pages, 5271 KiB

Open AccessArticle

Surface Modification of Sulfur-Assisted Reduced Graphene Oxide with Poly(phenylene sulfide) for Multifunctional Nanocomposites

by Minsik Choi, Junghwan Kim, Yuna Oh, Jaesang Yu, Sung-Gi Kim, Heejoun Yoo, Seongwoo Ryu, Nam-Ho You and Bon-Cheol Ku

Polymers 2022, 14(4), 732; https://doi.org/10.3390/polym14040732 - 14 Feb 2022

Cited by 3 | Viewed by 2169

Abstract

The sulfur on the sulfur-assisted reduced graphene oxide (SrGO) surface provides the origin of poly(phenylene sulfide) PPS-grafting via S_NAr mechanism. In-situ polymerization from sulfur on SrGO afforded surface modification of SrGO, resulting in enhanced dispersibility in PPS. The tensile strength, electrical [...] Read more.

The sulfur on the sulfur-assisted reduced graphene oxide (SrGO) surface provides the origin of poly(phenylene sulfide) PPS-grafting via S_NAr mechanism. In-situ polymerization from sulfur on SrGO afforded surface modification of SrGO, resulting in enhanced dispersibility in PPS. The tensile strength, electrical and thermal conductivities, and flame retardancy of PPS-coated SrGO were efficiently enhanced using highly concentrated SrGO and masterbatch (MB) for industrial purposes. Three-dimensional X-ray microtomography scanning revealed that diluting MB in the PPS resin afforded finely distributed SrGO across the PPS resin, compared to the aggregated state of graphene oxide. For the samples after dilution, the thermal conductivity and flame retardancy of PPS/SrGO are preserved and typically enhanced by up to 20%. The proposed PPS/SrGO MB shows potential application as an additive for reinforced PPS due to the ease of addition during the extrusion process. Full article

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2021

Jump to: 2023, 2022, 2020, 2018, 2017

16 pages, 7124 KiB

Open AccessArticle

Hybrid Silica-Based Fillers in Nanocomposites: Influence of Isotropic/Isotropic and Isotropic/Anisotropic Fillers on Mechanical Properties of Styrene-Butadiene (SBR)-Based Rubber

by Mariapaola Staropoli, Vincent Rogé, Enzo Moretto, Joffrey Didierjean, Marc Michel, Benoit Duez, Pascal Steiner, Georges Thielen, Damien Lenoble and Jean-Sébastien Thomann

Polymers 2021, 13(15), 2413; https://doi.org/10.3390/polym13152413 - 22 Jul 2021

Cited by 13 | Viewed by 2483

Abstract

The improvement of mechanical properties of polymer-based nanocomposites is usually obtained through a strong polymer–silica interaction. Most often, precipitated silica nanoparticles are used as filler. In this work, we study the synergetic effect occurring between dual silica-based fillers in a styrene-butadiene rubber (SBR)/polybutadiene [...] Read more.

The improvement of mechanical properties of polymer-based nanocomposites is usually obtained through a strong polymer–silica interaction. Most often, precipitated silica nanoparticles are used as filler. In this work, we study the synergetic effect occurring between dual silica-based fillers in a styrene-butadiene rubber (SBR)/polybutadiene (PBD) rubber matrix. Precipitated Highly Dispersed Silica (HDS) nanoparticles (10 nm) have been associated with spherical Stöber silica nanoparticles (250 nm) and anisotropic nano-Sepiolite. By imaging filler at nano scale through Scanning Transmission Electron Microscopy, we have shown that anisotropic fillers align only in presence of a critical amount of HDS. The dynamic mechanical analysis of rubber compounds confirms that this alignment leads to a stiffer nanocomposite when compared to Sepiolite alone. On the contrary, spherical 250 nm nanoparticles inhibit percolation network and reduce the nanocomposite stiffness. Full article

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10 pages, 2374 KiB

Open AccessArticle

by Min Ye Koo, Hon Chung Shin, Jonghwan Suhr and Gyo Woo Lee

Polymers 2021, 13(11), 1867; https://doi.org/10.3390/polym13111867 - 04 Jun 2021

Cited by 6 | Viewed by 2774

Abstract

We designed and tested a manufacturing process that resulted in the formation of composites with maximized electrical conductivity and optimized electromagnetic interference (EMI) shielding effectiveness (SE) properties. Single-walled carbon nanotube (SWCNT) paper, which is a microscopic aggregate of van der Waals force interaction, [...] Read more.

We designed and tested a manufacturing process that resulted in the formation of composites with maximized electrical conductivity and optimized electromagnetic interference (EMI) shielding effectiveness (SE) properties. Single-walled carbon nanotube (SWCNT) paper, which is a microscopic aggregate of van der Waals force interaction, was impregnated with semi-cured epoxy to make SWCNT prepregs. These prepregs were completely cured into SWCNT/epoxy composites. Fabricating and curing processes were executed under proper temperature cycle depending on the time. We inspected SWCNT paper and the interfacial state between the SWCNTs and epoxy in the composite with a field emission-scanning electron microscopy and calculated the SWCNT weight fraction through thermogravimetric analysis measurements. Using these observations, electrical conductivity and EMI SE were investigated according to thickness which could be controlled by the suggested manufacturing process as 1-, 5- and 10-layer composites. Finally, we determined ideal composite thickness and the associated number of prepreg layers using skin depth theory. Full article

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15 pages, 4412 KiB

Open AccessArticle

High-Strength GO/PA66 Nanocomposite Fibers via In Situ Precipitation and Polymerization

by Ao Gu, Jian Wu, Liming Shen, Xiaoyan Zhang and Ningzhong Bao

Polymers 2021, 13(11), 1688; https://doi.org/10.3390/polym13111688 - 22 May 2021

Cited by 13 | Viewed by 3155

Abstract

The uniform dispersion of graphene oxide (GO) and strong interfacial bonding are the key factors in achieving the high mechanical strength of GO/polymer composites. It is still challenging to prepare GO/PA66 composites with uniform GO dispersion by the in situ polymerization method. In [...] Read more.

The uniform dispersion of graphene oxide (GO) and strong interfacial bonding are the key factors in achieving the high mechanical strength of GO/polymer composites. It is still challenging to prepare GO/PA66 composites with uniform GO dispersion by the in situ polymerization method. In this paper, we prepare GO/PA66 salt nanocomposite by in situ precipitating PA66 salt with GO in ethanol. The GO/PA66 nanocomposite fibers are then fabricated using the as-prepared GO/PA66 salt by in situ polymerizing and melt spinning. By tuning the GO content, the tensile strength and Young’s modulus of the GO/PA66 fibers are increased from 265 ± 18 to 710 ± 14 MPa (containing 0.3 wt% GO) and from 1.1 ± 0.08 to 3.8 ± 0.19 GPa (containing 0.5 wt% GO), respectively. The remarkable improvements are attributed to the uniform dispersion of GO in the GO/PA66 salt nanocomposite via ionic bonding and hydrogen bonding in the in situ precipitation process, and the covalent interfacial bonding between the GO and PA66 during the in situ polymerization process. This work sheds light on the easy fabrication of high-performance PA66-based nanocomposites. Full article

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10 pages, 2730 KiB

Open AccessArticle

Characterization of Biocompatible Hydrogel Lenses Using Methacrylic Acid with Neodymium Oxide Nanoparticles

by Min-Jae Lee, Seon-Young Park and A-Young Sung

Polymers 2021, 13(10), 1575; https://doi.org/10.3390/polym13101575 - 14 May 2021

Cited by 2 | Viewed by 1802

Abstract

We prepared hydrogel contact lenses containing nanoparticles of neodymium oxide and methacrylic acid (MA) to investigate their effect on the physical and chemical properties of the lens. Neodymium oxide nanoparticles improved the tensile strength without affecting wettability. The tensile strength, wettability, and light [...] Read more.

We prepared hydrogel contact lenses containing nanoparticles of neodymium oxide and methacrylic acid (MA) to investigate their effect on the physical and chemical properties of the lens. Neodymium oxide nanoparticles improved the tensile strength without affecting wettability. The tensile strength, wettability, and light transmittance were all increased when MA was added in a specific ratio. To confirm the safety of the newly used nanoparticles, test on absorbance, eluate, and pH change were conducted and it was found that the safety level was satisfactory. In conclusion, it was confirmed that durable contact lenses can be manufactured with neodymium oxide nanoparticles, and most of the basic elements of the lens such as transparency, strength, and wettability could be improved using MA, which is a hydrophilic material. It is believed that the study will be helpful as part of basic research to use new materials. Full article

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18 pages, 1722 KiB

Open AccessReview

Polymer Nanocomposites for Photocatalytic Degradation and Photoinduced Utilizations of Azo-Dyes

by Emily Z. Wang, Yigui Wang and Dequan Xiao

Polymers 2021, 13(8), 1215; https://doi.org/10.3390/polym13081215 - 09 Apr 2021

Cited by 16 | Viewed by 3627

Abstract

Specially designed polymer nanocomposites can photo-catalytically degrade azo dyes in wastewater and textile effluents, among which TiO₂-based nanocomposites are outstanding and extensively explored. Other nanocomposites based on natural polymers (i.e., chitosan and kaolin) and the oxides of Al, Au, B, Bi, [...] Read more.

Specially designed polymer nanocomposites can photo-catalytically degrade azo dyes in wastewater and textile effluents, among which TiO₂-based nanocomposites are outstanding and extensively explored. Other nanocomposites based on natural polymers (i.e., chitosan and kaolin) and the oxides of Al, Au, B, Bi, Fe, Li, and Zr are commonly used. These nanocomposites have better photocatalytic efficiency than pure TiO₂ through two considerations: (i) reducing the hole/electron recombination rate by stabilizing the excited electron in the conducting band, which can be achieved in TiO₂-nanocomposites with graphene, graphene oxide, hexagonal boron nitride (h-BN), metal nanoparticles, or doping; (ii) decreasing the band energy of semiconductors by forming nanocomposites between TiO₂ and other oxides or conducting polymers. Increasing the absorbance efficiency by forming special nanocomposites also increases photocatalytic performance. The photo-induced isomerization is exploited in biological systems, such as artificial muscles, and in technical fields such as memory storage and liquid crystal display. Heteroaryl azo dyes show remarkable shifts in photo-induced isomerization, which can be applied in biological and technical fields in place of azo dyes. The self-assembly methods can be employed to synthesize azo-dye polymer nanocomposites via three types of interactions: electrostatic interactions, London forces or dipole/dipole interactions between azo dyes, and photo alignments. Full article

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35 pages, 6706 KiB

Open AccessReview

Recent Developments in Nanocellulose-Reinforced Rubber Matrix Composites: A Review

by Darren Yi Sern Low, Janarthanan Supramaniam, Apinan Soottitantawat, Tawatchai Charinpanitkul, Wiwut Tanthapanichakoon, Khang Wei Tan and Siah Ying Tang

Polymers 2021, 13(4), 550; https://doi.org/10.3390/polym13040550 - 12 Feb 2021

Cited by 33 | Viewed by 7250

Abstract

Research and development of nanocellulose and nanocellulose-reinforced composite materials have garnered substantial interest in recent years. This is greatly attributed to its unique functionalities and properties, such as being renewable, sustainable, possessing high mechanical strengths, having low weight and cost. This review aims [...] Read more.

Research and development of nanocellulose and nanocellulose-reinforced composite materials have garnered substantial interest in recent years. This is greatly attributed to its unique functionalities and properties, such as being renewable, sustainable, possessing high mechanical strengths, having low weight and cost. This review aims to highlight recent developments in incorporating nanocellulose into rubber matrices as a reinforcing filler material. It encompasses an introduction to natural and synthetic rubbers as a commodity at large and conventional fillers used today in rubber processing, such as carbon black and silica. Subsequently, different types of nanocellulose would be addressed, including its common sources, dimensions, and mechanical properties, followed by recent isolation techniques of nanocellulose from its resource and application in rubber reinforcement. The review also gathers recent studies and qualitative findings on the incorporation of a myriad of nanocellulose variants into various types of rubber matrices with the main goal of enhancing its mechanical integrity and potentially phasing out conventional rubber fillers. The mechanism of reinforcement and mechanical behaviors of these nanocomposites are highlighted. This article concludes with potential industrial applications of nanocellulose-reinforced rubber composites and the way forward with this technology. Full article

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39 pages, 77196 KiB

Open AccessArticle

The Tensile Behaviour of Highly Filled High-Density Polyethylene Quaternary Composites: Weld-Line Effects, DIC Curiosities and Shifted Deformation Mechanisms

by David Viljoen, Matthieu Fischer, Ines Kühnert and Johan Labuschagné

Polymers 2021, 13(4), 527; https://doi.org/10.3390/polym13040527 - 10 Feb 2021

Cited by 8 | Viewed by 2776

Abstract

The interactive effects between additives and weld lines, which are frequent injection-moulding defects, were studied in high-density polyethylene (HDPE) and compared to weld-line-free reference samples. These materials were formulated around a D- and I-optimal experimental design, based on a quadratic Scheffé polynomial model, [...] Read more.

The interactive effects between additives and weld lines, which are frequent injection-moulding defects, were studied in high-density polyethylene (HDPE) and compared to weld-line-free reference samples. These materials were formulated around a D- and I-optimal experimental design, based on a quadratic Scheffé polynomial model, with up to 60 wt% calcium carbonate, masterbatched carbon black and a stabiliser package. Where reasonable and appropriate, the behaviours of the systems were modelled using statistical techniques, for a better understanding of the underlying trends. The characterisations were performed through the use of conventional tensile testing, digital image correlation (DIC) and scanning electron microscopy (SEM). A range of complex interactive effects were found during conventional tensile testing, with DIC used to better understand and explain these effects. SEM is used to better understand the failure mechanics of some of these systems through fractography, particularly regarding particle effects. A measure is introduced to quantify the deviation of the pre-yield deformation curve from the ideal elastic case. Novel analysis of DIC results is proposed, through the use of combined time-series plots and measures quantifying the extent and localisation of peak deformation. Through this, it could be found that strong shifts in the deformation mechanisms occur as a function of formulation and the presence/absence of weld lines. Primarily, changes are noted in the onset of continuous inter- and intralamellar slip and cavitation/fibrillation, seen through the onset of localised deformation and stress-whitening. Full article

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15 pages, 11411 KiB

Open AccessArticle

Thermomechanical Analysis of Isora Nanofibril Incorporated Polyethylene Nanocomposites

by Cintil Jose, Chin Han Chan, Tan Winie, Blessy Joseph, Abhimanyu Tharayil, Hanna J Maria, Tatiana Volova, Francesco Paolo La Mantia, Didier Rouxel, Marco Morreale, David Laroze, Lovely Mathew and Sabu Thomas

Polymers 2021, 13(2), 299; https://doi.org/10.3390/polym13020299 - 19 Jan 2021

Cited by 9 | Viewed by 2501

Abstract

The research on cellulose fiber-reinforced nanocomposites has increased by an unprecedented magnitude over the past few years due to its wide application range and low production cost. However, the incompatibility between cellulose and most thermoplastics has raised significant challenges in composite fabrication. This [...] Read more.

The research on cellulose fiber-reinforced nanocomposites has increased by an unprecedented magnitude over the past few years due to its wide application range and low production cost. However, the incompatibility between cellulose and most thermoplastics has raised significant challenges in composite fabrication. This paper addresses the behavior of plasma-modified polyethylene (PE) reinforced with cellulose nanofibers extracted from isora plants (i.e., isora nanofibrils (INFs)). The crystallization kinetics of PE–INF composites were explained using the Avrami model. The effect of cellulose nanofillers on tuning the physiochemical properties of the nanocomposite was also explored in this work. The increase in mechanical properties was due to the uniform dispersion of fillers in the PE. The investigation on viscoelastic properties confirmed good filler–matrix interactions, facilitating the stress transfer. Full article

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2020

Jump to: 2023, 2022, 2021, 2018, 2017

17 pages, 2056 KiB

Open AccessArticle

Dispersion of Graphite Nanoplates in Polypropylene by Melt Mixing: The Effects of Hydrodynamic Stresses and Residence Time

by Luís Lima Ferrás, Célio Fernandes, Denis Semyonov, João Miguel Nóbrega and José António Covas

Polymers 2021, 13(1), 102; https://doi.org/10.3390/polym13010102 - 29 Dec 2020

Cited by 3 | Viewed by 2274

Abstract

This work combines experimental and numerical (computational fluid dynamics) data to better understand the kinetics of the dispersion of graphite nanoplates in a polypropylene melt, using a mixing device that consists of a series of stacked rings with an equal outer diameter and [...] Read more.

This work combines experimental and numerical (computational fluid dynamics) data to better understand the kinetics of the dispersion of graphite nanoplates in a polypropylene melt, using a mixing device that consists of a series of stacked rings with an equal outer diameter and alternating larger and smaller inner diameters, thereby creating a series of converging/diverging flows. Numerical simulation of the flow assuming both inelastic and viscoelastic responses predicted the velocity, streamlines, flow type and shear and normal stress fields for the mixer. Experimental and computed data were combined to determine the trade-off between the local degree of dispersion of the PP/GnP nanocomposite, measured as area ratio, and the absolute average value of the hydrodynamic stresses multiplied by the local cumulative residence time. A strong quasi-linear relationship between the evolution of dispersion measured experimentally and the computational data was obtained. Theory was used to interpret experimental data, and the results obtained confirmed the hypotheses previously put forward by various authors that the dispersion of solid agglomerates requires not only sufficiently high hydrodynamic stresses, but also that these act during sufficient time. Based on these considerations, it was estimated that the cohesive strength of the GnP agglomerates is in the range of 5–50 kPa. Full article

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17 pages, 2670 KiB

Open AccessArticle

Effect of Filler Synergy and Cast Film Extrusion Parameters on Extrudability and Direction-Dependent Conductivity of PVDF/Carbon Nanotube/Carbon Black Composites

by Beate Krause, Karina Kunz, Bernd Kretzschmar, Ines Kühnert and Petra Pötschke

Polymers 2020, 12(12), 2992; https://doi.org/10.3390/polym12122992 - 15 Dec 2020

Cited by 9 | Viewed by 3126

Abstract

In the present study, melt-mixed composites based of poly (vinylidene fluoride) (PVDF) and fillers with different aspect ratios (carbon nanotubes (CNTs), carbon black (CB)) and their mixtures in composites were investigated whereby compression-molded plates were compared with melt-extruded films. The processing-related orientation of [...] Read more.

In the present study, melt-mixed composites based of poly (vinylidene fluoride) (PVDF) and fillers with different aspect ratios (carbon nanotubes (CNTs), carbon black (CB)) and their mixtures in composites were investigated whereby compression-molded plates were compared with melt-extruded films. The processing-related orientation of CNTs with a high aspect ratio leads to direction-dependent electrical and mechanical properties, which can be reduced by using mixed filler systems with the low aspect ratio CB. An upscaling of melt mixing from small scale to laboratory scale was carried out. From extruded materials, films were prepared down to a thickness of 50 µm by cast film extrusion under variation of the processing parameters. By combining CB and CNTs in PVDF, especially the electrical conductivity through the film could be increased compared to PVDF/CNT composites due to additional contact points in the sample thickness. The alignment of the fillers in the two directions within the films was deduced from the differences in electrical and mechanical film properties, which showed higher values in the extrusion direction than perpendicular to it. Full article

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21 pages, 8559 KiB

Open AccessArticle

Effect of Iron-Oxide Nanoparticles Impregnated Bacterial Cellulose on Overall Properties of Alginate/Casein Hydrogels: Potential Injectable Biomaterial for Wound Healing Applications

by Rahul Patwa, Oyunchimeg Zandraa, Zdenka Capáková, Nabanita Saha and Petr Sáha

Polymers 2020, 12(11), 2690; https://doi.org/10.3390/polym12112690 - 14 Nov 2020

Cited by 49 | Viewed by 5372

Abstract

In this study we report the preparation of novel multicomponent hydrogels as potential biomaterials for injectable hydrogels comprised of alginate, casein and bacterial cellulose impregnated with iron nanoparticles (BCF). These hydrogels demonstrated amide cross-linking of alginate–casein, ionic cross-linking of alginate and supramolecular interaction [...] Read more.

In this study we report the preparation of novel multicomponent hydrogels as potential biomaterials for injectable hydrogels comprised of alginate, casein and bacterial cellulose impregnated with iron nanoparticles (BCF). These hydrogels demonstrated amide cross-linking of alginate–casein, ionic cross-linking of alginate and supramolecular interaction due to incorporation of BCF. Incorporation of BCF into the hydrogels based on natural biopolymers was done to reinforce the hydrogels and impart magnetic properties critical for targeted drug delivery. This study aimed to improve overall properties of alginate/casein hydrogels by varying the BCF loading. The physico-chemical properties of gels were characterized via FTIR, XRD, DSC, TGA, VSM and mechanical compression. In addition, swelling, drug release, antibacterial activity and cytotoxicity studies were also conducted on these hydrogels. The results indicated that incorporation of BCF in alginate/casein hydrogels led to mechanically stronger gels with magnetic properties, increased porosity and hence increased swelling. A porous structure, which is essential for migration of cells and biomolecule transportation, was confirmed from microscopic analysis. The porous internal structure promoted cell viability, which was confirmed through MTT assay of fibroblasts. Moreover, a hydrogel can be useful for the delivery of essential drugs or biomolecules in a sustained manner for longer durations. These hydrogels are porous, cell viable and possess mechanical properties that match closely to the native tissue. Collectively, these hybrid alginate–casein hydrogels laden with BCF can be fabricated by a facile approach for potential wound healing applications. Full article

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16 pages, 5941 KiB

Open AccessArticle

Effects of Accelerated Weathering on Degradation Behavior of Basalt Fiber Reinforced Polymer Nanocomposites

by Ummu Raihanah Hashim, Aidah Jumahat, Mohammad Jawaid, Rudi Dungani and Salman Alamery

Polymers 2020, 12(11), 2621; https://doi.org/10.3390/polym12112621 - 06 Nov 2020

Cited by 12 | Viewed by 2483

Abstract

This work aims to give insight on the effect of accelerated weathering, i.e., the combination of ultraviolet (UV) exposure and water spraying, on the visual and mechanical properties of basalt fiber reinforced polymer (BFRP) composites. The solvent exchange method, sonication and high shear [...] Read more.

This work aims to give insight on the effect of accelerated weathering, i.e., the combination of ultraviolet (UV) exposure and water spraying, on the visual and mechanical properties of basalt fiber reinforced polymer (BFRP) composites. The solvent exchange method, sonication and high shear milling technique were used to prepare the nanocomposite laminates. Three types of laminates were fabricated, i.e., unmodified BFRP, nanosilica modified BFRP and graphene nanoplatelet (GNP) modified BFRP composites with the total fiber loading of 45 wt.%. Glass fiber reinforced polymer (GFRP) laminate was also prepared for performance comparison purposes between the natural and synthetic fibers. The laminates were exposed to UV with a total weathering condition of 504 h using a Quantum-UV accelerated weathering tester. The weathering condition cycle was set at 8 h 60 °C UV exposure and 4 h 50 °C condensation. The discoloration visual inspection on the tested specimen was observed under the optical microscope. The obtained results showed that the UV exposure and water absorption caused severe discoloration of the laminates due to photo-oxidation reaction. The effect of weathering conditions on tensile and flexural properties of unmodified BFRP composites indicated that the UV exposure and water absorption caused reduction by 12% in tensile strength and by 7% in flexural strength. It is also found that the reduction in tensile and flexural properties of nanomodified BFRP composites was smaller than the unmodified system. It concluded from this work, that the mineral based composites (i.e., BFRP) has high potential for structural applications owing to its better properties than synthetic based composites (i.e., GFRP). Full article

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19 pages, 10282 KiB

Open AccessArticle

Key Role of the Dispersion of Carbon Nanotubes (CNTs) within Epoxy Networks on their Ability to Release

by Maxime Pras, Jean-François Gérard, Luana Golanski, Guilhem Quintard and Jannick Duchet-Rumeau

Polymers 2020, 12(11), 2530; https://doi.org/10.3390/polym12112530 - 29 Oct 2020

Cited by 14 | Viewed by 2699

Abstract

Carbon nanotube (CNT)-reinforced nanocomposites represent a unique opportunity in terms of designing advanced materials with mechanical reinforcement and improvements in the electrical and thermal conductivities. However, the toxic effects of these composites on human health have been studied, and very soon, some regulations [...] Read more.

Carbon nanotube (CNT)-reinforced nanocomposites represent a unique opportunity in terms of designing advanced materials with mechanical reinforcement and improvements in the electrical and thermal conductivities. However, the toxic effects of these composites on human health have been studied, and very soon, some regulations on CNTs and on composites based on CNTs will be enacted. That is why the release of CNTs during the nanocomposite lifecycle must be controlled. As the releasing depends on the interfacial strength that is stronger between CNTs and polymers compared to CNTs in a CNT agglomerate, two dispersion states—one poorly dispersed versus another well dispersed—are generated and finely described. So, the main aim of this study is to check if the CNT dispersion state has an influence on the CNT releasing potential in the nanocomposite. To well tailor and characterize the CNT dispersion state in the polymer matrix, electronic microscopies (SEM and TEM) and also rheological analysis are carried out to identify whether CNTs are isolated, in bundles, or in agglomerates. When the dispersion state is known and controlled, its influence on the polymerization kinetic and on mechanical properties is discussed. It appears clearly that in the case of a good dispersion state, strong interfaces are generated, linking the isolated nanotubes with the polymer, whereas the CNT cohesion in an agglomerate seems much more weak, and it does not provide any improvement to the polymer matrix. Raman spectroscopy is relevant to analyze the interfacial properties and allows the relationship with the releasing ability of nanocomposites; i.e., CNTs poorly dispersed in the matrix are more readily released when compared to well-dispersed nanocomposites. The tribological tests confirm from released particles granulometry and observations that a CNT dispersion state sufficiently achieved in the nanocomposite avoids single CNT releasing under those solicitations. Full article

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23 pages, 6366 KiB

Open AccessFeature PaperArticle

Mechanical and Functional Properties of Novel Biobased Poly(decylene-2,5-furanoate)/Carbon Nanotubes Nanocomposite Films

by Giulia Fredi, Andrea Dorigato, Mauro Bortolotti, Alessandro Pegoretti and Dimitrios N. Bikiaris

Polymers 2020, 12(11), 2459; https://doi.org/10.3390/polym12112459 - 23 Oct 2020

Cited by 14 | Viewed by 2634

Abstract

The present work investigates the microstructural, thermo-mechanical, and electrical properties of a promising, but still not thoroughly studied, biobased polymer, i.e., poly(decylene furanoate) (PDeF), and its performance when multi-walled carbon nanotubes (CNTs) are added. After sample preparation by solution mixing and film casting, [...] Read more.

The present work investigates the microstructural, thermo-mechanical, and electrical properties of a promising, but still not thoroughly studied, biobased polymer, i.e., poly(decylene furanoate) (PDeF), and its performance when multi-walled carbon nanotubes (CNTs) are added. After sample preparation by solution mixing and film casting, the microstructural investigation evidences that the fracture surface becomes smoother and more homogeneous with a small fraction of CNTs, and that the production process is suitable to achieve good disentanglement and dispersion of CNTs within the matrix, although some aggregates are still observable. CNTs act as nucleating agents for PDeF crystals, as evidenced by differential scanning calorimetry, as the crystallinity degree increases from 43.2% of neat PDeF to 55.0% with a CNT content of 2 phr, while the crystallization temperature increases from 68.4 °C of PDeF to 91.7 °C of PDeF-CNT-2. A similar trend in crystallinity is confirmed by X-ray diffraction, after detailed Rietveld analysis with a three-phase model. CNTs also remarkably improve the mechanical performance of the bioderived polymer, as the elastic modulus increases up to 123% and the stress at break up to 131%. The strain at break also increases by +71% when a small amount of 0.25 phr of CNTs are added, which is probably the consequence of a more homogeneous microstructure. The long-term mechanical performance is also improved upon CNT addition, as the creep compliance decreases considerably, which was observed for both the elastic and the viscoelastic component. Finally, the films become electrically dissipative for a CNT content of 1 phr and conductive for a CNT amount of 2 phr. This study contributes to highlight the properties of bioderived furan-based polymer PDeF and evidences the potential of CNTs as a promising nanofiller for this matrix. Full article

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22 pages, 12372 KiB

Open AccessArticle

Tribological Performance of Nylon Composites with Nanoadditives for Self-Lubrication Purposes

by Isabel Clavería, Sofía Gimeno, Ignacio Miguel, Gemma Mendoza, Aleida Lostalé, Ángel Fernández, Pere Castell and Daniel Elduque

Polymers 2020, 12(10), 2253; https://doi.org/10.3390/polym12102253 - 30 Sep 2020

Cited by 10 | Viewed by 2894

Abstract

A systematic study comparing the wear behaviour of composites with nylon matrix (PA66, PA46, PA12) and different nanoadditives and reinforcing additives (graphite, graphene, MoS₂ and ZrO₂) has been carried out in order to achieve a proper self-lubricant material for bearing [...] Read more.

A systematic study comparing the wear behaviour of composites with nylon matrix (PA66, PA46, PA12) and different nanoadditives and reinforcing additives (graphite, graphene, MoS₂ and ZrO₂) has been carried out in order to achieve a proper self-lubricant material for bearing cages. The wear characterisation was done using pin-on-disc tests, SEM and EDX analysis. The results show that better outcomes are obtained for composites based on PA12. The addition of ZrO₂ offers negative values of wear due to the metallic particle transference from the counterface to the polymeric pin. Full article

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15 pages, 6120 KiB

Open AccessArticle

Surface Modification of Carbon Microspheres with Guanidine Phosphate and Its Application as a Flame Retardant in PET

by Shan Jiang, Cheng Ji, Dan Zha, Yonghong Ding, Dun Wu and Qiang Yu

Polymers 2020, 12(8), 1689; https://doi.org/10.3390/polym12081689 - 29 Jul 2020

Cited by 9 | Viewed by 2191

Abstract

Composites based on polyethylene terephthalate (PET) and surface-modified carbon microspheres (CMSs) were prepared by melt mixing. The surface modification of CMSs was conducted with low-temperature plasma technology first, and a phosphorus-nitrogen flame retardant, guanidine phosphate (GDP), was then grafted onto CMSs. The modification [...] Read more.

Composites based on polyethylene terephthalate (PET) and surface-modified carbon microspheres (CMSs) were prepared by melt mixing. The surface modification of CMSs was conducted with low-temperature plasma technology first, and a phosphorus-nitrogen flame retardant, guanidine phosphate (GDP), was then grafted onto CMSs. The modification of CMSs was done to improve both the filler dispersity in the PET matrix and the flame-retardant performance of composites. The obtained CMSs-GDP was characterized by FTIR spectra and a scanning electron microscope (SEM). The grafting ratio was characterized and calculated by thermal gravimetric analysis (TGA). The grain size analysis was used to describe the dispersity of CMSs. The mechanical properties of the PET/CMSs-GDP composite were measured using a universal testing machine. The PET/CMSs-GDP composite can achieve a limiting oxygen index (LOI) value of 32.4% and a vertical burning test (UL94) V-0 rating at 3% CMSs-GDP loading. Full article

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12 pages, 3833 KiB

Open AccessArticle

l-Arginine Grafted Poly(Glycerol Sebacate) Materials: An Antimicrobial Material for Wound Dressing

by Chia-Chun Wang, Ting-Yu Shih, Yi-Ting Hsieh, Jie-Len Huang and Jane Wang

Polymers 2020, 12(7), 1457; https://doi.org/10.3390/polym12071457 - 29 Jun 2020

Cited by 8 | Viewed by 3275

Abstract

This study focuses on the development and evaluation of a novel wound dressing material. l-arginine grafted poly(glycerol sebacate) materials (PGS-g-Arg) are developed by chemical conjugation of l-arginine on poly(glycerol sebacate) chains and the mechanical property, water vapor transmission rate, antimicrobial functions [...] Read more.

This study focuses on the development and evaluation of a novel wound dressing material. l-arginine grafted poly(glycerol sebacate) materials (PGS-g-Arg) are developed by chemical conjugation of l-arginine on poly(glycerol sebacate) chains and the mechanical property, water vapor transmission rate, antimicrobial functions and biocompatibility are investigated. At various l-arginine grafting ratio, the mechanical properties are tunable. It was found that between 7–13% l-arginine grafting ratios, the tensile strengths of PGS-g-Arg were similar to that of natural skin. These materials are shown with a low water vapor transmission rate, 6.1 to 10.3 g/m²/h, which may form a barrier and assist in the closure of wounds. Inhibition in the growth of Pseudomonas aeruginosa and Staphylococcus aureus was observed on PGS-g-Arg, and a series of experiments were conducted to confirm its biocompatibility. In summary, l -arginine grafted poly(glycerol sebacate) may offer a novel option for wound dressing. Full article

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2018

Jump to: 2023, 2022, 2021, 2020, 2017

14 pages, 3809 KiB

Open AccessArticle

Effects of Particle Size and Surface Chemistry on the Dispersion of Graphite Nanoplates in Polypropylene Composites

by Raquel M. Santos, Sacha T. Mould, Petr Formánek, Maria C. Paiva and José A. Covas

Polymers 2018, 10(2), 222; https://doi.org/10.3390/polym10020222 - 24 Feb 2018

Cited by 24 | Viewed by 5102

Abstract

Carbon nanoparticles tend to form agglomerates with considerable cohesive strength, depending on particle morphology and chemistry, thus presenting different dispersion challenges. The present work studies the dispersion of three types of graphite nanoplates (GnP) with different flake sizes and bulk densities in a [...] Read more.

Carbon nanoparticles tend to form agglomerates with considerable cohesive strength, depending on particle morphology and chemistry, thus presenting different dispersion challenges. The present work studies the dispersion of three types of graphite nanoplates (GnP) with different flake sizes and bulk densities in a polypropylene melt, using a prototype extensional mixer under comparable hydrodynamic stresses. The nanoparticles were also chemically functionalized by covalent bonding polymer molecules to their surface, and the dispersion of the functionalized GnP was studied. The effects of stress relaxation on dispersion were also analyzed. Samples were removed along the mixer length, and characterized by microscopy and dielectric spectroscopy. A lower dispersion rate was observed for GnP with larger surface area and higher bulk density. Significant re-agglomeration was observed for all materials when the deformation rate was reduced. The polypropylene-functionalized GnP, characterized by increased compatibility with the polymer matrix, showed similar dispersion effects, albeit presenting slightly higher dispersion levels. All the composites exhibit dielectric behavior, however, the alternate current (AC) conductivity is systematically higher for the composites with larger flake GnP. Full article

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12 pages, 5165 KiB

Open AccessArticle

Transparent Low Electrostatic Charge Films Based on Carbon Nanotubes and Polypropylene. Homopolymer Cast Films

by Zoe Vineth Quiñones-Jurado, Miguel Ángel Waldo-Mendoza, José Manuel Mata-Padilla, Pablo González-Morones, Juan Guillermo Martínez-Colunga, Florentino Soriano-Corral, Víctor Javier Cruz-Delgado, Ronald Francis Ziolo and Carlos Alberto Avila-Orta

Polymers 2018, 10(1), 55; https://doi.org/10.3390/polym10010055 - 09 Jan 2018

Cited by 6 | Viewed by 3445

Abstract

Use of multi-wall carbon nanotubes (MWCNTs) in external layers (A-layers) of ABA-trilayer polypropylene films was investigated, with the purpose of determining intrinsic and extrinsic factors that could lead to antistatic behavior of transparent films. The incorporation of 0.01, 0.1, and 1 wt % [...] Read more.

Use of multi-wall carbon nanotubes (MWCNTs) in external layers (A-layers) of ABA-trilayer polypropylene films was investigated, with the purpose of determining intrinsic and extrinsic factors that could lead to antistatic behavior of transparent films. The incorporation of 0.01, 0.1, and 1 wt % of MWCTNs in the A-layers was done by dilution through the masterbatch method. Masterbatches were fabricated using isotactic polypropylene (iPP) with different melt flow indexes 2.5, 34, and 1200 g/10 min, and using different ultrasound assist methods. It was found that films containing MWCNTs show surface electrical resistivity of 10¹² and 10¹⁶ Ω/sq, regardless of the iPP melt flow index (MFI) and masterbatch fabrication method. However, electrostatic charge was found to depend upon the iPP MFI, the ultrasound assist method and MWCNT concentration. A percolation electron transport mechanism was determined most likely responsible for this behavior. Optical properties for films containing MWCNTs do not show significant differences compared to the reference film at MWCNT concentrations below 0.1 wt %. However, an enhancement in brightness was observed, and it was attributed to ordered iPP molecules wrapping the MWCNTs. Bright transparent films with low electrostatic charge were obtained even for MWCNTs concentrations as low as 0.01 wt %. Full article

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2017

Jump to: 2023, 2022, 2021, 2020, 2018

6582 KiB

Open AccessArticle

Reprocessing of PLA/Graphene Nanoplatelets Nanocomposites

by Luigi Botta, Roberto Scaffaro, Fiorenza Sutera and Maria Chiara Mistretta

Polymers 2018, 10(1), 18; https://doi.org/10.3390/polym10010018 - 24 Dec 2017

Cited by 73 | Viewed by 8058

Abstract

This work reports a study on the effect of multiple reprocessing on the properties of poly(lactic acid) (PLA) filled with graphene nanoplatelets (GnP) compared to the melt reprocessed neat polymeric matrix. In particular, morphological, X-Ray Diffraction and Micro-Raman analyses, intrinsic viscosity measurements, thermal, [...] Read more.

This work reports a study on the effect of multiple reprocessing on the properties of poly(lactic acid) (PLA) filled with graphene nanoplatelets (GnP) compared to the melt reprocessed neat polymeric matrix. In particular, morphological, X-Ray Diffraction and Micro-Raman analyses, intrinsic viscosity measurements, thermal, rheological and mechanical tests were carried out on materials reprocessed up five times by means of a single screw extruder. The results indicated that the presence of GnP decreased the degradation rate as a function of the reprocessing cycles in comparison with the neat PLA that, on the contrary, showed a more drastic reduction of the molecular weight. Moreover, the reprocessing improved the particle dispersion and reduced the presence of GnP aggregates. Full article

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2185 KiB

Open AccessReview

Spectroscopic Techniques for the Characterization of Polymer Nanocomposites: A Review

by Liliane Bokobza

Polymers 2018, 10(1), 7; https://doi.org/10.3390/polym10010007 - 22 Dec 2017

Cited by 41 | Viewed by 9414

Abstract

Due to the growing interest in nanocomposites, a molecular characterization of these materials is essential for the understanding of their properties and for the development of new materials. Spectroscopic techniques that bring information at a molecular level are unavoidable when characterizing polymers, fillers [...] Read more.

Due to the growing interest in nanocomposites, a molecular characterization of these materials is essential for the understanding of their properties and for the development of new materials. Spectroscopic techniques that bring information at a molecular level are unavoidable when characterizing polymers, fillers and composites. Selected examples of the application of fluorescence, solid-state nuclear magnetic resonance (NMR), infrared and Raman spectroscopies, illustrate the potential of these techniques for the analysis of the filler surface, the evaluation of the state of filler dispersion in the host matrix, the extent of interaction between the polymer and the filler particles or the dynamics of polymer chains at the polymer–filler interface. Full article

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11547 KiB

Open AccessArticle

Morphology, Nucleation, and Isothermal Crystallization Kinetics of Poly(ε-caprolactone) Mixed with a Polycarbonate/MWCNTs Masterbatch

by Thandi P. Gumede, Adriaan S. Luyt, Mohammad K. Hassan, Ricardo A. Pérez-Camargo, Agnieszka Tercjak and Alejandro J. Müller

Polymers 2017, 9(12), 709; https://doi.org/10.3390/polym9120709 - 13 Dec 2017

Cited by 22 | Viewed by 6694

Abstract

In this study, nanocomposites were prepared by melt blending poly (ε-caprolactone) (PCL) with a (polycarbonate (PC)/multi-wall carbon nanotubes (MWCNTs)) masterbatch in a twin-screw extruder. The nanocomposites contained 0.5, 1.0, 2.0, and 4.0 wt % MWCNTs. Even though PCL and PC have been reported [...] Read more.

In this study, nanocomposites were prepared by melt blending poly (ε-caprolactone) (PCL) with a (polycarbonate (PC)/multi-wall carbon nanotubes (MWCNTs)) masterbatch in a twin-screw extruder. The nanocomposites contained 0.5, 1.0, 2.0, and 4.0 wt % MWCNTs. Even though PCL and PC have been reported to be miscible, our DSC (Differential Scanning Calorimetry), SAXS (Small Angle X-ray Scattering), and WAXS (Wide Angle X-ray Scattering) results showed partial miscibility, where two phases were formed (PC-rich and PCL-rich phases). In the PC-rich phase, the small amount of PCL chains included within this phase plasticized the PC component and the PC-rich phase was therefore able to crystallize. In contrast, in the PCL-rich phase the amount of PC chains present generates changes in the glass transition temperature of the PCL phase that were much smaller than those predicted by the Fox equation. The presence of two phases was corroborated by SEM, TEM, and AFM observations where a fair number of MWCNTs diffused from the PC-rich phase to the PCL-rich phase, even though there were some MWCNTs agglomerates confined to PC-rich droplets. Standard DSC measurements demonstrated that the MWCNTs nucleation effects are saturated at a 1 wt % MWCNT concentration on the PCL-rich phase. This is consistent with the dielectric percolation threshold, which was found to be between 0.5 and 1 wt % MWCNTs. However, the nucleating efficiency was lower than literature reports for PCL/MWCNTs, due to limited phase mixing between the PC-rich and the PCL-rich phases. Isothermal crystallization experiments performed by DSC showed an increase in the overall crystallization kinetics of PCL with increases in MWCNTs as a result of their nucleating effect. Nevertheless, the crystallinity degree of the nanocomposite containing 4 wt % MWCNTs decreased by about 15% in comparison to neat PCL. This was attributed to the presence of the PC-rich phase, which was able to crystallize in view of the plasticization effect of the PCL component, since as the MWCNT content increases, the PC content in the blend also increases. The thermal conductivities (i.e., 4 wt % MWCNTs) were enhanced by 20% in comparison to the neat material. The nanocomposites prepared in this work could be employed in applications were electrical conductivity is required, as well as lightweight and tailored mechanical properties. Full article

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4115 KiB

Open AccessReview

Microporous Hyper-Crosslinked Polystyrenes and Nanocomposites with High Adsorption Properties: A Review

by Rachele Castaldo, Gennaro Gentile, Maurizio Avella, Cosimo Carfagna and Veronica Ambrogi

Polymers 2017, 9(12), 651; https://doi.org/10.3390/polym9120651 - 28 Nov 2017

Cited by 71 | Viewed by 10530

Abstract

Hyper-crosslinked (HCL) polystyrenes show outstanding properties, such as high specific surface area and adsorption capability. Several researches have been recently focused on tailoring their performance for specific applications, such as gas adsorption and separation, energy storage, air and water purification processes, and catalysis. [...] Read more.

Hyper-crosslinked (HCL) polystyrenes show outstanding properties, such as high specific surface area and adsorption capability. Several researches have been recently focused on tailoring their performance for specific applications, such as gas adsorption and separation, energy storage, air and water purification processes, and catalysis. In this review, main strategies for the realization of HCL polystyrene-based materials with advanced properties are reported, including a summary of the synthetic routes that are adopted for their realization and the chemical modification approaches that are used to impart them specific functionalities. Moreover, the most up to date results on the synthesis of HCL polystyrene-based nanocomposites that are realized by embedding these high surface area polymers with metal, metal oxide, and carbon-based nanofillers are discussed in detail, underlining the high potential applicability of these systems in different fields. Full article

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3056 KiB

Open AccessReview

Generation of Polymer Nanocomposites through Shear-Driven Aggregation of Binary Colloids

by Xinxin Sheng, Li Zhang and Hua Wu

Polymers 2017, 9(11), 619; https://doi.org/10.3390/polym9110619 - 15 Nov 2017

Cited by 1 | Viewed by 6043

Abstract

Design of polymer nanocomposites has been an intense research topic in recent decades because hybrid nanomaterials are widely used in many fields. Throughout their development, there has often been a challenging issue how one can uniformly distribute nanoparticles (NPs) in a polymer matrix, [...] Read more.

Design of polymer nanocomposites has been an intense research topic in recent decades because hybrid nanomaterials are widely used in many fields. Throughout their development, there has often been a challenging issue how one can uniformly distribute nanoparticles (NPs) in a polymer matrix, avoiding their agglomeration. In this short review, we first introduce the theory of colloidal aggregation/gelation purely based on intense shear forces. Then, we illustrate a methodology for preparing polymer nanocomposites where the NPs (as fillers) are uniformly and randomly distributed inside a matrix of polymer NPs, based on intense shear-driven aggregation of binary colloids, without using any additives. Its feasibility has been demonstrated using two stable binary colloids composed of (1) poly-methyl methacrylate fillers and polystyrene NPs, and (2) graphene oxide sheets (fillers) and poly-vinylidene fluoride NPs. The mechanism leading to capturing and distribution of the fillers inside the polymer NP matrix has been illustrated, and the advantages of the proposed methodology compared with the other common methods are also discussed. Full article

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4359 KiB

Open AccessArticle

Effect of the GO Reduction Method on the Dielectric Properties, Electrical Conductivity and Crystalline Behavior of PEO/rGO Nanocomposites

by Asish Malas, Avanish Bharati, Olivier Verkinderen, Bart Goderis, Paula Moldenaers and Ruth Cardinaels

Polymers 2017, 9(11), 613; https://doi.org/10.3390/polym9110613 - 14 Nov 2017

Cited by 62 | Viewed by 5625

Abstract

The effect of the reduction method to prepare reduced graphene oxide (rGO) on the melt linear viscoelastic properties, electrical conductivity, polymer matrix crystalline behavior and dielectric properties of PEO-rGO nanocomposites was investigated. Reduction was performed chemically with either sodium borohydride (NaBH₄) [...] Read more.

The effect of the reduction method to prepare reduced graphene oxide (rGO) on the melt linear viscoelastic properties, electrical conductivity, polymer matrix crystalline behavior and dielectric properties of PEO-rGO nanocomposites was investigated. Reduction was performed chemically with either sodium borohydride (NaBH₄) or hydrazine monohydrate (N₂H₄·H₂O) or both reduction agents consecutively as well as thermally at 1000 °C. The different reduction methods resulted in exfoliated rGO sheets with different types and amounts of remaining functional groups, as indicated by FT-IR, Raman, TGA and XRD characterization. Moreover, their electrical conductivity ranged between 10⁻⁴ and 10⁻¹ S/cm, with the consecutive use of both chemical reduction agents being far superior. PEO nanocomposites with filler loadings of 0.5 wt %, 1 wt % and 2 wt % were prepared by solvent mixing. The rGO fillers affected the melt linear viscoelastic and crystalline behavior of the PEO matrix and resulted in nanocomposites with a substantially increased electrical conductivity. Despite the wide variability in filler conductivity, the effects on the polymer nanocomposite properties were less distinctive. A correlation was obtained between the reduction of the mobility of the polymer chains (evaluated by the glass transition temperature) and the dielectric strength of the interfacial polarisation originating from the effective entrapment of GO/rGO filler charges at the interface with the less conductive PEO. Thus, favorable interactions of the polar PEO with the filler led to reduced mobility of the PEO chains and thereby a more effective entrapment of the filler charges at the PEO interface. Full article

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5702 KiB

Open AccessArticle

Atomistic Molecular Dynamics Simulations of the Initial Crystallization Stage in an SWCNT-Polyetherimide Nanocomposite

by Victor M. Nazarychev, Sergey V. Larin, Alexey V. Lyulin, Theo Dingemans, Jose M. Kenny and Sergey V. Lyulin

Polymers 2017, 9(10), 548; https://doi.org/10.3390/polym9100548 - 24 Oct 2017

Cited by 18 | Viewed by 5503

Abstract

Crystallization of all-aromatic heterocyclic polymers typically results in an improvement of their thermo-mechanical properties. Nucleation agents may be used to promote crystallization, and it is well known that the incorporation of nanoparticles, and in particular carbon-based nanofillers, may induce or accelerate crystallization through [...] Read more.

Crystallization of all-aromatic heterocyclic polymers typically results in an improvement of their thermo-mechanical properties. Nucleation agents may be used to promote crystallization, and it is well known that the incorporation of nanoparticles, and in particular carbon-based nanofillers, may induce or accelerate crystallization through nucleation. The present study addresses the structural properties of polyetherimide-based nanocomposites and the initial stages of polyetherimide crystallization as a result of single-walled carbon nanotube (SWCNT) incorporation. We selected two amorphous thermoplastic polyetherimides ODPA-P3 and aBPDA-P3 based on 3,3′,4,4′-oxydiphthalic dianhydride (ODPA), 2,3′,3,4′-biphenyltetracarboxylic dianhydride (aBPDA) and diamine 1,4-bis[4-(4-aminophenoxy)phenoxy]benzene (P3) and simulated the onset of crystallization in the presence of SWCNTs using atomistic molecular dynamics. For ODPA-P3, we found that the planar phthalimide and phenylene moieties show pronounced ordering near the CNT (carbon nanotube) surface, which can be regarded as the initial stage of crystallization. We will discuss two possible mechanisms for ODPA-P3 crystallization in the presence of SWCNTs: the spatial confinement caused by the CNTs and π–π interactions at the CNT-polymer matrix interface. Based on our simulation results, we propose that ODPA-P3 crystallization is most likely initiated by favorable π–π interactions between the carbon nanofiller surface and the planar ODPA-P3 phthalimide and phenylene moieties. Full article

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5926 KiB

Open AccessArticle

Polyimide Aerogels Cross-Linked with Aminated Ag Nanowires: Mechanically Strong and Tough

by Tianyi Zhang, Yan Zhao and Kai Wang

Polymers 2017, 9(10), 530; https://doi.org/10.3390/polym9100530 - 19 Oct 2017

Cited by 19 | Viewed by 7558

Abstract

In this study, polyimide (PI)/Ag nanowire (AgNW) nanocomposite aerogels with extremely high mechanical performance have been fabricated utilizing amine-modified AgNWs as mechanical nanoreinforcement particulates and crosslinking agents. Initially, AgNWs were fabricated and surface modified by p-aminothiophenol (PATP), then the aminated AgNWs were [...] Read more.

In this study, polyimide (PI)/Ag nanowire (AgNW) nanocomposite aerogels with extremely high mechanical performance have been fabricated utilizing amine-modified AgNWs as mechanical nanoreinforcement particulates and crosslinking agents. Initially, AgNWs were fabricated and surface modified by p-aminothiophenol (PATP), then the aminated AgNWs were dispersed into polyamide acid solution and aerogels were prepared by supercritical CO₂ drying. Raman and X-ray photoelectron spectroscopy (XPS) spectrometry were carried out on A-AgNWs (aminated Ag nanowires) to prove the successful modification. This functional nanoparticle greatly enhanced the strength and toughness of aerogels without evident increase in densities. Comparing to pure PI aerogels, samples with 2.0 wt % of A-AgNWs had a 148% increase in compression strength and 223% increase in Young’s modulus, which equates to 2.41 and 27.66 MPa, respectively. Simultaneously, the tensile test indicated that aerogels with 2.0 wt % of A-AgNWs had a breaking energy of 40.18 J/m³, which is 112% higher than pure PI aerogels. The results presented herein demonstrate that aminated AgNWs are an innovative cross-linker for PI aerogels and can improve their strength and toughness. These aerogels have excellent potential as high-duty, lightweight porous materials in many areas of application. Full article

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5165 KiB

Open AccessArticle

Morphology, Crystallization and Thermal Behaviors of PLA-Based Composites: Wonderful Effects of Hybrid GO/PEG via Dynamic Impregnating

by Shikui Jia, Demei Yu, Yan Zhu, Zhong Wang, Ligui Chen and Lei Fu

Polymers 2017, 9(10), 528; https://doi.org/10.3390/polym9100528 - 19 Oct 2017

Cited by 145 | Viewed by 8824

Abstract

In this paper, a dynamic impregnating device, which can generate supersonic vibration with the vacuum-adsorbing field, was used to prepare the hybrid graphene oxide (GO)/polyethylene glycol (PEG). Interestingly, the hybrid GO/PEG under dynamic impregnating and/or internal mixing was introduced into poly-(lactic acid) (PLA) [...] Read more.

In this paper, a dynamic impregnating device, which can generate supersonic vibration with the vacuum-adsorbing field, was used to prepare the hybrid graphene oxide (GO)/polyethylene glycol (PEG). Interestingly, the hybrid GO/PEG under dynamic impregnating and/or internal mixing was introduced into poly-(lactic acid) (PLA) matrix via melting-compounding, respectively. On one hand, compared with the internal mixing, the hybrid GO/PEG with the different component ratio using dynamic impregnation had a better dispersed morphology in the PLA matrix. On the other hand, compared with the high molecular weight (M_w) of PEG, the hybrid GO/PEG with low M_w of PEG had better an exfoliated morphology and significantly improved the heat distortion temperature (HDT) of the PLA matrix. Binding energies results indicate that low M_w of PEG with GO has excellent compatibility. Dispersed morphologies of the hybrid GO/PEG show that the dynamic impregnating had stronger blending capacity than the internal mixing and obviously improved the exfoliated morphology of GO in the PLA. Crystallization behaviors indicate that the hybrid GO/PEG with the low M_w of PEG based on dynamic impregnating effectively enhanced the crystallinity of PLA, and the cold crystallization character of PLA disappeared in the melting process. Moreover, the storage modulus and loss factor of the PLA-based composites were also investigated and their HDT was improved with the introduction of hybrid GO/PEG. Furthermore, a physical model for the dispersed morphology of the hybrid GO/PEG in the PLA matrix was established. Overall, the unique blending technique of hybrid GO/PEG via dynamic impregnating is an effective approach to enhance the property range of PLA and is suitable for many industrial applications. Full article

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Open AccessReview

Polymer Nanocomposites via Click Chemistry Reactions

by Mehmet Arslan and Mehmet Atilla Tasdelen

Polymers 2017, 9(10), 499; https://doi.org/10.3390/polym9100499 - 11 Oct 2017

Cited by 43 | Viewed by 13153

Abstract

The emerging areas of polymer nanocomposites, as some are already in use in industrial applications and daily commodities, have the potential of offering new technologies with all manner of prominent capabilities. The incorporation of nanomaterials into polymeric matrix provides significant improvements, such as [...] Read more.

The emerging areas of polymer nanocomposites, as some are already in use in industrial applications and daily commodities, have the potential of offering new technologies with all manner of prominent capabilities. The incorporation of nanomaterials into polymeric matrix provides significant improvements, such as higher mechanical, thermal or electrical properties. In these materials, interface/interphase of components play a crucial role bringing additional features on the resulting nanocomposites. Among the various preparation strategies of such materials, an appealing strategy relies on the use of click chemistry concept as a multi-purpose toolbox for both fabrication and modulation of the material characteristics. This review aims to deliver new insights to the researchers of the field by noticing effective click chemistry-based methodologies on the preparation of polymer nanocomposites and their key applications such as optic, biomedical, coatings and sensor. Full article

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Open AccessArticle

Polymer Blending as a Novel Approach for Tuning the SPR Peaks of Silver Nanoparticles

by Shujahadeen B. Aziz, Rebar T. Abdulwahid, Mariwan A. Rasheed, Omed Gh. Abdullah and Hameed M. Ahmed

Polymers 2017, 9(10), 486; https://doi.org/10.3390/polym9100486 - 04 Oct 2017

Cited by 101 | Viewed by 6175

Abstract

In the present work, a novel method is exhibited for tuning the surface plasmon resonance (SPR) peaks of silver nanoparticles based on chitosan-Poly(vinyl alcohol) blend polymer nanocomposites. Silver nanoparticles were synthesized by in situ method through the chitosan host polymer. The absence of [...] Read more.

In the present work, a novel method is exhibited for tuning the surface plasmon resonance (SPR) peaks of silver nanoparticles based on chitosan-Poly(vinyl alcohol) blend polymer nanocomposites. Silver nanoparticles were synthesized by in situ method through the chitosan host polymer. The absence of crystalline peaks of PVA in the blend system indicated the occurrence of miscibility between CS and PVA polymers. The UV–vis spectra of CS:AgNt samples shows SPR bands with weak intensity. Obvious tuning in SPR peaks of silver nanoparticles occurred when different amounts of PVA polymer incorporated to the CS:AgNt system. The appearance of distinguishable crystalline peaks of Ag° nanoparticles at 2θ = 38.6° and 2θ = 44.2° in the blend system reveals the role of polymer blending in the enhancement of SPR peaks of silver nanoparticles. Silver nanoparticles synthesized in this work with enhanced SPR peaks are important in various applications and areas such as optoelectronic devices. The TEM images show dispersed silver nanoparticles. The dielectric constant of PVA is higher than that of chitosan. The result of dielectric constant study validates the Mie model which reveals the fact that the dielectric constant of the surrounding material has a great effect on the SPR peak intensity of nanoparticles. Full article

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5624 KiB

Open AccessArticle

Effects of Covalent Functionalization of MWCNTs on the Thermal Properties and Non-Isothermal Crystallization Behaviors of PPS Composites

by Myounguk Kim, Jungmin Lee, Hyun-gyoo Roh, Dahyun Kim, Juhee Byeon and Jongshin Park

Polymers 2017, 9(10), 460; https://doi.org/10.3390/polym9100460 - 21 Sep 2017

Cited by 13 | Viewed by 5047

Abstract

In this study, a PPS/MWCNTs composite was prepared with poly(phenylene sulfide) (PPS), as well as pristine and covalent functionalized multi-walled carbon nanotubes (MWCNTs) via melt-blending techniques. Moreover, the dispersion of the MWCNTs on the PPS matrix was improved by covalent functionalization as can [...] Read more.

In this study, a PPS/MWCNTs composite was prepared with poly(phenylene sulfide) (PPS), as well as pristine and covalent functionalized multi-walled carbon nanotubes (MWCNTs) via melt-blending techniques. Moreover, the dispersion of the MWCNTs on the PPS matrix was improved by covalent functionalization as can be seen from a Field-Emission Scanning Electron Microscope (FE-SEM) images. The thermal properties of the PPS/MWCNTs composites were characterized using a thermal conductivity analyzer, and a differential scanning calorimeter (DSC). To analyze the crystallization behavior of polymers under conditions similar with those in industry, the non-isothermal crystallization behaviors of the PPS/MWCNTs composites were confirmed using various kinetic equations, such as the modified Avrami equation and Avrami-Ozawa combined equation. The crystallization rate of PPS/1 wt % pristine MWCNTs composite (PPSP1) was faster because of the intrinsic nucleation effect of the MWCNTs. However, the crystallization rates of the composites containing covalently-functionalized MWCNTs were slower than PPSP1 because of the destruction of the MWCNTs graphitic structure via covalent functionalization. Furthermore, the activation energies calculated by Kissinger’s method were consistently decreased by covalent functionalization. Full article

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Open AccessArticle

Effect of the Grafting Reaction of Aluminum Nitride on the Multi-Walled Carbon Nanotubes on the Thermal Properties of the Poly(phenylene sulfide) Composites

by Myounguk Kim, Sunmin Park and Jongshin Park

Polymers 2017, 9(9), 452; https://doi.org/10.3390/polym9090452 - 15 Sep 2017

Cited by 11 | Viewed by 6218

Abstract

In this study, the PPS/MWCNTs/AlN composite was prepared with poly(phenylene sulfide) (PPS), covalent functionalized multi-walled carbon nanotubes (fMWCNTs), and aluminum nitride (AlN) via melt-blending techniques. The AlN is a fascinating non-oxidizing ceramic material having the highest thermal conductivity among the ceramic materials. In [...] Read more.

In this study, the PPS/MWCNTs/AlN composite was prepared with poly(phenylene sulfide) (PPS), covalent functionalized multi-walled carbon nanotubes (fMWCNTs), and aluminum nitride (AlN) via melt-blending techniques. The AlN is a fascinating non-oxidizing ceramic material having the highest thermal conductivity among the ceramic materials. In order to introduce the functional groups on the surface of the AlN particles, a silane coupling agent was used as it is able to graft with the functional groups on the covalent functionalized MWCNTs. The silanization reaction of the AlN was confirmed qualitatively and quantitatively by FT-IR (Fourier Transform Infrared Spectroscopy), and XPS (X-ray Photoelectron Spectroscopy). The grafting reaction of the AlN particles on the MWCNTs was confirmed using UV–Vis (Ultraviolet-Visible Spectroscopy), FE-SEM (Field-Emission Scanning Electron Microscopy) and FE-TEM (Field-Emission Transmission Electron Microscopy) images. The grafting reaction was accomplished by observing the change of the transmittance, the morphology of the AlN particle bonded to the MWCNTs. For the morphological changes of the fractured surface of the PPS/MWCNTs/AlN composites by FE-SEM, the hybrid filler was homogeneously dispersed on the PPS matrix when the AlN particle was grafted on the MWCNTs. The homogeneous distribution of the hybrid filler acts as a heat transfer path, which led the higher thermal properties, such as thermal conductivity, thermal resistance, and melting temperature than those of not grafted MWCNTs. Full article

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2837 KiB

Open AccessReview

Effective Assembly of Nano-Ceramic Materials for High and Anisotropic Thermal Conductivity in a Polymer Composite

by Haeleen Hong, Jong Uk Kim and Tae-il Kim

Polymers 2017, 9(9), 413; https://doi.org/10.3390/polym9090413 - 05 Sep 2017

Cited by 72 | Viewed by 13541

Abstract

Recently, anisotropic heat dissipation and its management have drawn attention as a promising technique for highly integrated electrical devices. Among many potentially challenging materials such as carbon nanotube, graphene, metal particles, and inorganic ceramics commonly used for high thermally conductive fillers in a [...] Read more.

Recently, anisotropic heat dissipation and its management have drawn attention as a promising technique for highly integrated electrical devices. Among many potentially challenging materials such as carbon nanotube, graphene, metal particles, and inorganic ceramics commonly used for high thermally conductive fillers in a composite form, nanoscale ceramic fillers are considered ideal candidates due to their thermal conductivity, electrical insulation, and low thermal expansion coefficient. However, enhancing the thermal conductivity of a randomly dispersed ceramic-polymer composite is limited by its discontinuous filler contact and thermal expansion coefficient mismatch. Thus, recent research has focused on how to assemble and generate highly networked filler contacts to make effective pathways for heat flow, with minimized concentration of the filler in the composite. In this review, we will introduce several essential strategies to assemble fillers with a two- or three-dimensional networked composite for highly enhanced anisotropic heat dissipation. Moreover, this review elucidates filler alignment effects compared to randomly dispersed ceramic composites. Full article

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8445 KiB

Open AccessArticle

Wax Confinement with Carbon Nanotubes for Phase Changing Epoxy Blends

by Giulia Fredi, Andrea Dorigato, Luca Fambri and Alessandro Pegoretti

Polymers 2017, 9(9), 405; https://doi.org/10.3390/polym9090405 - 31 Aug 2017

Cited by 68 | Viewed by 5368

Abstract

A paraffin wax was shape stabilized with 10 wt % of carbon nanotubes (CNTs) and dispersed in various concentrations in an epoxy resin to develop a novel blend with thermal energy storage capabilities. Thermogravimetric analysis showed that CNTs improve the thermal stability of [...] Read more.

A paraffin wax was shape stabilized with 10 wt % of carbon nanotubes (CNTs) and dispersed in various concentrations in an epoxy resin to develop a novel blend with thermal energy storage capabilities. Thermogravimetric analysis showed that CNTs improve the thermal stability of paraffin, while differential scanning calorimetry showed that the paraffin kept its ability to melt and crystallize, with enthalpy values almost proportional to the paraffin fraction. In contrast, a noticeable loss of enthalpy was observed for epoxy/wax blends without CNTs, which was mainly attributed to the partial exudation of paraffin out of the epoxy matrix during the curing phase. Dynamic mechanical thermal analysis contributed to elucidate the effects of the melting of the paraffin phase on the viscoelastic properties of the epoxy blends. Flexural elastic modulus and strength of the blends decreased with the wax/CNT content according to a rule of mixtures, while flexural strain at break values deviate positively from it. These results show the potentialities of the investigated epoxy blends for the development of multifunctional structural composites. Full article

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9082 KiB

Open AccessArticle

Interfacially-Located Nanoparticles Anticipate the Onset of Co-Continuity in Immiscible Polymer Blends

by Martina Salzano de Luna, Andrea Causa and Giovanni Filippone

Polymers 2017, 9(9), 393; https://doi.org/10.3390/polym9090393 - 25 Aug 2017

Cited by 5 | Viewed by 5257

Abstract

The addition of nanoparticles has recently emerged as a clever tool to manipulate the microstructure and, through it, the macroscopic properties of immiscible polymer blends. Despite the huge number of studies in this field, the underlying mechanisms of most of the nanoparticle-induced effects [...] Read more.

The addition of nanoparticles has recently emerged as a clever tool to manipulate the microstructure and, through it, the macroscopic properties of immiscible polymer blends. Despite the huge number of studies in this field, the underlying mechanisms of most of the nanoparticle-induced effects on the blend microstructure remain poorly understood. Among others, the origin of effect of nanoparticles on the transition from distributed (drop-in-matrix) to co-continuous morphology is still controversial. Here we address this issue through a systematic study on a model blend of polystyrene (PS) and poly(methyl methacrylate) (PMMA) filled with small amounts of nanoparticles (organo-modified clay) selectively located at the polymer–polymer interface. Extraction experiments with selective solvents prove that the nanoparticles significantly anticipate the onset of co-continuity with respect to the unfilled blend. Morphological analyses reveal that such an effect is a consequence of the interconnection of nanoparticle-coated polymer domains. Such “ginger-like” clusters get into contact at low content due to their irregular shape, thus anticipating the onset of co-continuity. Full article

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9599 KiB

Open AccessFeature PaperArticle

The Distribution of Nanoclay Particles at the Interface and Their Influence on the Microstructure Development and Rheological Properties of Reactively Processed Biodegradable Polylactide/Poly(butylene succinate) Blend Nanocomposites

by Reza Salehiyan, Suprakas Sinha Ray, Jayita Bandyopadhyay and Vincent Ojijo

Polymers 2017, 9(8), 350; https://doi.org/10.3390/polym9080350 - 09 Aug 2017

Cited by 38 | Viewed by 5657

Abstract

The present work investigates the distribution of nanoclay particles at the interface and their influence on the microstructure development and non-linear rheological properties of reactively processed biodegradable polylactide/poly(butylene succinate) blend nanocomposites. Two types of organoclays, one is more hydrophilic (Cloisite^®30B (C30B)) [...] Read more.

The present work investigates the distribution of nanoclay particles at the interface and their influence on the microstructure development and non-linear rheological properties of reactively processed biodegradable polylactide/poly(butylene succinate) blend nanocomposites. Two types of organoclays, one is more hydrophilic (Cloisite^®30B (C30B)) and another one is more hydrophobic (Betsopa^TM (BET)), were used at different concentrations. Surface and transmission electron microscopies were respectively used to study the blend morphology evolution and for probing the dispersion and distribution of nanoclay platelets within the blend matrix and at the interface. The results suggested that both organoclays tended to localize at the interface between the blend’s two phases and encapsulate the dispersed poly(butylene succinate) phase, thereby suppressing coalescence. Using small angle X-ray scattering the probability of finding neighboring nanoclay particles in the blend matrix was calculated using the Generalized Indirect Fourier Transformation technique. Fourier Transform-rheology was utilized for quantifying nonlinear rheological responses and for correlating the extent of dispersion as well as the blend morphological evolution, for different organoclay loadings. The rheological responses were in good agreement with the X-ray scattering and electron microscopic results. It was revealed that C30B nanoparticles were more efficient in stabilizing the morphologies by evenly distributing at the interface. Nonlinear coefficient from FT-rheology was found to be more pronounced in case of blends filled with C30B, indicating better dispersion of C30B compare with BET which was in agreement with the SAXS results. Full article

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8460 KiB

Open AccessArticle

Increased Surface Roughness in Polydimethylsiloxane Films by Physical and Chemical Methods

by Jorge Nicolás Cabrera, Mariano M. Ruiz, Mirta Fascio, Norma D’Accorso, Rosica Mincheva, Philippe Dubois, Leonardo Lizarraga and R. Martín Negri

Polymers 2017, 9(8), 331; https://doi.org/10.3390/polym9080331 - 02 Aug 2017

Cited by 33 | Viewed by 8971

Abstract

Two methods, the first physical and the other chemical, were investigated to modify the surface roughness of polydimethylsiloxane (PDMS) films. The physical method consisted of dispersing multi-walled carbon nanotubes (MWCNTs) and magnetic cobalt ferrites (CoFe₂O₄) prior to thermal cross-linking, [...] Read more.

Two methods, the first physical and the other chemical, were investigated to modify the surface roughness of polydimethylsiloxane (PDMS) films. The physical method consisted of dispersing multi-walled carbon nanotubes (MWCNTs) and magnetic cobalt ferrites (CoFe₂O₄) prior to thermal cross-linking, and curing the composite system in the presence of a uniform magnetic field H. The chemical method was based on exposing the films to bromine vapours and then UV-irradiating. The characterizing techniques included scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, optical microscopy, atomic force microscopy (AFM) and magnetic force microscopy (MFM). The surface roughness was quantitatively analyzed by AFM. In the physical method, the random dispersion of MWCNTs (1% w/w) and magnetic nanoparticles (2% w/w) generated a roughness increase of about 200% (with respect to PDMS films without any treatment), but that change was 400% for films cured in the presence of H perpendicular to the surface. SEM, AFM and MFM showed that the magnetic particles always remained attached to the carbon nanotubes, and the effect on the roughness was interpreted as being due to a rupture of dispersion randomness and a possible induction of structuring in the direction of H. In the chemical method, the increase in roughness was even greater (1000%). Wells were generated with surface areas that were close to 100 μm² and depths of up to 500 nm. The observations of AFM images and FTIR spectra were in agreement with the hypothesis of etching by Br radicals generated by UV on the polymer chains. Both methods induced important changes in the surface roughness (the chemical method generated the greatest changes due to the formation of surface wells), which are of great importance in superficial technological processes. Full article

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2349 KiB

Open AccessArticle

Biodegradation of Halloysite Nanotubes-Polyester Nanocomposites Exposed to Short Term Seawater Immersion

by Mohd Shahneel Saharudin, Jiacheng Wei, Islam Shyha and Fawad Inam

Polymers 2017, 9(8), 314; https://doi.org/10.3390/polym9080314 - 28 Jul 2017

Cited by 5 | Viewed by 4945

Abstract

Halloysite nanotubes (HNTs)-polyester nanocomposites with four different concentrations were produced using solution casting technique and the biodegradation effect of short-term seawater exposure (120 h) was studied. Monolithic polyester was observed to have the highest seawater absorption with 1.37%. At 0.3 wt % HNTs [...] Read more.

Halloysite nanotubes (HNTs)-polyester nanocomposites with four different concentrations were produced using solution casting technique and the biodegradation effect of short-term seawater exposure (120 h) was studied. Monolithic polyester was observed to have the highest seawater absorption with 1.37%. At 0.3 wt % HNTs reinforcement, the seawater absorption dropped significantly to the lowest value of 0.77% due to increase of liquid diffusion path. For samples tested in dry conditions, the T_g, storage modulus, tensile properties and flexural properties were improved. The highest improvement of T_g was from 79.3 to 82.4 °C (increase 3.1 °C) in the case of 0.3 wt % HNTs. This can be associated with the exfoliated HNTs particles, which restrict the mobility of polymer chains and thus raised the T_g. After seawater exposure, the T_g, storage modulus, tensile properties and flexural properties of polyester and its nanocomposites were decreased. The Young’s modulus of 0.3 wt % HNTs-polyester dropped 20% while monolithic polyester dropped up to 24% compared to their values in dry condition. Apart from that, 29% flexural modulus reduction was observed, which was 18% higher than monolithic polyester. In contrast, fracture toughness and surface roughness increased due to plasticization effect. The presence of various microbial communities caused gradual biodegradation on the microstructure of the polyester matrix as also evidently shown by SEM images. Full article

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940 KiB

Open AccessArticle

Photooxidation Behavior of a LDPE/Clay Nanocomposite Monitored through Creep Measurements

by Francesco Paolo La Mantia, Mario Biondo, Maria Chiara Mistretta, Fiorenza Sutera and Marco Morreale

Polymers 2017, 9(8), 308; https://doi.org/10.3390/polym9080308 - 26 Jul 2017

Cited by 2 | Viewed by 3713

Abstract

Creep behavior of polymer nanocomposites has not been extensively investigated so far, especially when its effects are combined with those due to photooxidation, which are usually studied in completely independent ways. In this work, the photooxidation behavior of a low density polyethylene/organomodified clay [...] Read more.

Creep behavior of polymer nanocomposites has not been extensively investigated so far, especially when its effects are combined with those due to photooxidation, which are usually studied in completely independent ways. In this work, the photooxidation behavior of a low density polyethylene/organomodified clay nanocomposite system was monitored by measuring the creep curves obtained while subjecting the sample to the combined action of temperature, tensile stress, and UV radiation. The creep curves of the irradiated samples were found to be lower than those of the non-irradiated ones and progressively diverging, because of the formation of branching and cross-linking due to photooxidation. This was further proved by the decrease of the melt index and the increase of the intrinsic viscosity; at the same time, the formation of carbonyl groups was observed. This behavior was more observable in the nanocomposite sample, because of its faster photooxidation kinetics. Full article

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9601 KiB

Open AccessArticle

PES/POSS Soluble Veils as Advanced Modifiers for Multifunctional Fiber Reinforced Composites

by Gianluca Cicala, Ignazio Blanco, Alberta Latteri, Giulia Ognibene, Francesco Agatino Bottino and Maria Elena Fragalà

Polymers 2017, 9(7), 281; https://doi.org/10.3390/polym9070281 - 13 Jul 2017

Cited by 19 | Viewed by 6150

Abstract

Novel polyhedral oligomeric silsesquioxanes (POSS)-filled thermoplastic electrospun veils were used to tailor the properties of the interlaminar region of epoxy-based composites. The veils were designed to be soluble upon curing in the epoxy matrix, so that POSS could be released within the interlaminar [...] Read more.

Novel polyhedral oligomeric silsesquioxanes (POSS)-filled thermoplastic electrospun veils were used to tailor the properties of the interlaminar region of epoxy-based composites. The veils were designed to be soluble upon curing in the epoxy matrix, so that POSS could be released within the interlaminar region. Three different POSS contents, varying from 1 to 10 wt %, were tested while the percentage of coPolyethersulphone (coPES) dissolved in the epoxy resin was kept to a fixed value of 10 wt %. Good quality veils could be obtained at up to 10 wt % of POSS addition, with the nanofibers’ diameters varying from 861 nm for the coPES to 428 nm upon POSS addition. The feasibility of the soluble veils to disperse POSS in the interlaminar region was proved, and the effect of POSS on phase morphology and viscoelastic properties studied. POSS was demonstrated to significantly affect the morphology and viscoelastic properties of epoxy composites, especially for the percentages 1% and 5%, which enabled the composites to avoid POSS segregates occurring. A dynamic mechanical analysis showed a significant improvement to the storage modulus, and a shift of more than 30 °C due to the POSS cages hindering the motion of the molecular chains and network junctions. Full article

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8876 KiB

Open AccessArticle

Structure of Composite Based on Polyheteroarylene Matrix and ZrO₂ Nanostars Investigated by Quantitative Nanomechanical Mapping

by Maria P. Sokolova, Michael A. Smirnov, Alexander N. Bugrov, Pavel Geydt, Elena N. Popova, Erkki Lahderanta, Valentin M. Svetlichnyi and Alexander M. Toikka

Polymers 2017, 9(7), 268; https://doi.org/10.3390/polym9070268 - 06 Jul 2017

Cited by 10 | Viewed by 4823

Abstract

It is known that structure of the interface between inorganic nanoparticles and polymers significantly influences properties of a polymer–inorganic composite. At the same time, amount of experimental researches on the structure and properties of material near the inorganic-polymer interface is low. In this [...] Read more.

It is known that structure of the interface between inorganic nanoparticles and polymers significantly influences properties of a polymer–inorganic composite. At the same time, amount of experimental researches on the structure and properties of material near the inorganic-polymer interface is low. In this work, we report for the first time the investigation of nanomechanical properties and maps of adhesion of material near the inorganic-polymer interface for the polyheteroarylene nanocomposites based on semi-crystalline poly[4,4′-bis (4″-aminophenoxy)diphenyl]imide 1,3-bis (3′,4-dicarboxyphenoxy) benzene, modified by ZrO₂ nanostars. Experiments were conducted using quantitative nanomechanical mapping (QNM) mode of atomic force microscopy (AFM) at the surface areas where holes were formed after falling out of inorganic particles. It was found that adhesion of AFM cantilever to the polymer surface is higher inside the hole than outside. This can be attributed to the presence of polar groups near ZrO₂ nanoparticle. QNM measurements revealed that polymer matrix has increased rigidity in the vicinity of the nanoparticles. Influence of ZrO₂ nanoparticles on the structure and thermal properties of semi-crystalline polyheteroarylene matrix was studied with wide-angle X-ray scattering, scanning electron microscopy, and differential scanning calorimetry. Full article

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21923 KiB

Open AccessArticle

Morphology Development and Mechanical Properties Variation during Cold-Drawing of Polyethylene-Clay Nanocomposite Fibers

by Bartolomeo Coppola, Paola Scarfato, Loredana Incarnato and Luciano Di Maio

Polymers 2017, 9(6), 235; https://doi.org/10.3390/polym9060235 - 20 Jun 2017

Cited by 25 | Viewed by 6759

Abstract

In this work, the influence of composition and cold-drawing on nano- and micro-scale morphology and tensile mechanical properties of PE/organoclay nanocomposite fibers was investigated. Nanocomposites were prepared by melt compounding in a twin-screw extruder, using a maleic anhydride grafted linear low density polyethylene [...] Read more.

In this work, the influence of composition and cold-drawing on nano- and micro-scale morphology and tensile mechanical properties of PE/organoclay nanocomposite fibers was investigated. Nanocomposites were prepared by melt compounding in a twin-screw extruder, using a maleic anhydride grafted linear low density polyethylene (LLDPE–g–MA) and an organomodified montmorillonite (Dellite 67G) at three different loadings (3, 5 and 10 wt %). Fibers were produced by a single-screw extruder and drawn at five draw ratios (DRs): 7.25, 10, 13.5, 16 and 19. All nanocomposites, characterized by XRD, SEM, TEM, and FT-IR techniques, showed an intercalated/exfoliated morphology. The study evidenced that the nanoclay presence significantly increases both elastic modulus (up to +115% for fibers containing 10 wt % of D67G) and drawability of as-spun nanocomposite fibers. Moreover, at fixed nanocomposite composition, the cold-drawing process increases fibers elastic modulus and tensile strength at increasing DRs. However, at high DRs, “face-to-edge” rearrangement phenomena of clay layers (i.e., clay layers tend to rotate and touch each other) arise in fibers at high nanoclay loadings. Finally, nanocomposite fibers show a lower diameter reduction during drawing, with respect to the plain system, and surface feature of adjustable roughness by controlling the composition and the drawing conditions. Full article

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Graphical abstract

4488 KiB

Open AccessArticle

Effect of Interfacial Polarization and Water Absorption on the Dielectric Properties of Epoxy-Nanocomposites

by Philipp Marx, Andrea J. Wanner, Zucong Zhang, Huifei Jin, Ioannis-Alexandros Tsekmes, Johan J. Smit, Wolfgang Kern and Frank Wiesbrock

Polymers 2017, 9(6), 195; https://doi.org/10.3390/polym9060195 - 28 May 2017

Cited by 20 | Viewed by 7472

Abstract

Five types of nanofillers, namely, silica, surface-silylated silica, alumina, surface-silylated alumina, and boron nitride, were tested in this study. Nanocomposites composed of an epoxy/amine resin and one of the five types of nanoparticles were tested as dielectrics with a focus on (i) the [...] Read more.

Five types of nanofillers, namely, silica, surface-silylated silica, alumina, surface-silylated alumina, and boron nitride, were tested in this study. Nanocomposites composed of an epoxy/amine resin and one of the five types of nanoparticles were tested as dielectrics with a focus on (i) the surface functionalization of the nanoparticles and (ii) the water absorption by the materials. The dispersability of the nanoparticles in the resin correlated with the composition (OH content) of their surfaces. The interfacial polarization of the thoroughly dried samples was found to increase at lowered frequencies and increased temperatures. The β relaxation, unlike the interfacial polarization, was not significantly increased at elevated temperatures (below the glass-transition temperature). Upon the absorption of water under ambient conditions, the interfacial polarization increased significantly, and the insulating properties decreased or even deteriorated. This effect was most pronounced in the nanocomposite containing silica, and occurred as well in the nanocomposites containing silylated silica or non-functionalized alumina. The alternating current (AC) breakdown strength of all specimens was in the range of 30 to 35 kV·mm⁻¹. In direct current (DC) breakdown tests, the epoxy resin exhibited the lowest strength of 110 kV·mm⁻¹; the nanocomposite containing surface-silylated alumina had a strength of 170 kV·mm⁻¹. In summary, water absorption had the most relevant impact on the dielectric properties of nanocomposites containing nanoparticles, the surfaces of which interacted with the water molecules. Nanocomposites containing silylated alumina particles or boron nitride showed the best dielectric properties in this study. Full article

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7449 KiB

Open AccessArticle

Intensification of Electrochemical Performance of AA7075 Aluminum Alloys Using Rare Earth Functionalized Water-Based Polymer Coatings

by Atzin C. Ferrel-Álvarez, Miguel A. Domínguez-Crespo, Aidé M. Torres-Huerta, Hongbo Cong, Silvia B. Brachetti-Sibaja and Ana B. López-Oyama

Polymers 2017, 9(5), 178; https://doi.org/10.3390/polym9050178 - 18 May 2017

Cited by 12 | Viewed by 5798

Abstract

This work reports the effect of different amounts of ceria nanoparticles on UV resistance and barrier properties of water-based polyurethane (WPU) on glass and AA7075 aluminum alloy substrates. Hybrid coatings were synthesized from an aliphatic WPU–HDI (1,6-hexamethylene di-isocyanate) and cerium oxide nanoparticles (CeO [...] Read more.

This work reports the effect of different amounts of ceria nanoparticles on UV resistance and barrier properties of water-based polyurethane (WPU) on glass and AA7075 aluminum alloy substrates. Hybrid coatings were synthesized from an aliphatic WPU–HDI (1,6-hexamethylene di-isocyanate) and cerium oxide nanoparticles (CeO₂) with an average particle size distribution of about 25 nm. Different nanoceria amounts (1, 3 and 5 wt %), mixing times (30, 60 and 120 min) and methods to disperse the nanostructures into the polymer matrix (magnetic stirring and sonication) were evaluated. Initially, the dispersion of CeO₂ nanoparticles embedded in the polymer matrix and displacement in the corrosion potential (E_corr) were analyzed by confocal scanning laser microscopy (CLSM) and open circuit potential (E_ocp) measurements. According to this behavior, the dispersion and water ratio required during the polymerization process were established. Coated samples obtained after the second stage were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and optical light microscopy. In addition, optical measurements on glass substrates were evaluated with UV-vis spectroscopy. The effect of the synthesis parameters on the corrosion behavior of WPU–CeO₂/AA7075 systems was investigated with E_ocp and electrochemical impedance spectroscopy (EIS) in a 3 wt % NaCl solution. In addition, the films were subjected to 180 h of accelerated weathering. The results show that the combination of specific nanoceria addition with the optimal synthesis parameters enhances optical transparence of WPU as well as barrier properties. From these, the coated specimens prepared with 3 wt % of ceria content and sonicated for 30 min showed a highly dispersed system, which results in a high charge transfer resistance. The observed properties in clear coats deposited on metallic substrates suggested an improvement in the appearance and less deterioration in UV exposure in comparison with pure WPU, enhancing the protective properties of the AA7075 aluminum alloy when exposed to a corrosive medium. Full article

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