Polymers

13 pages, 3244 KiB

Open AccessArticle

Simultaneous Enhancement of Strength and Toughness of PLA Induced by Miscibility Variation with PVA

by Yanping Liu^1,2

, Hanghang Wei^1,2, Zhen Wang³, Qian Li^1,2,* and Nan Tian^4,*

¹ School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou 450001, China

² National Centre for International Joint Research of Micro-nano Molding Technology, Zhengzhou University, Zhengzhou 450001, China

³ National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002, China

⁴ MOE Key Laboratory of Space Applied Physics and Chemistry, Shanxi Key Laboratory of Macromolecular Science and Technology, School of Science, Northwestern Polytechnical University, Xi’an 710072, China

Polymers 2018, 10(10), 1178; https://doi.org/10.3390/polym10101178 - 22 Oct 2018

Cited by 35 | Viewed by 6690

Abstract

The mechanical properties of poly (lactic acid) (PLA) nanofibers with 0%, 5%, 10%, and 20% (w/w) poly (vinyl alcohol) (PVA) were investigated at the macro- and microscale. The macro-mechanical properties for the fiber membrane revealed that both the modulus [...] Read more.

The mechanical properties of poly (lactic acid) (PLA) nanofibers with 0%, 5%, 10%, and 20% (w/w) poly (vinyl alcohol) (PVA) were investigated at the macro- and microscale. The macro-mechanical properties for the fiber membrane revealed that both the modulus and fracture strain could be improved by 100% and 70%, respectively, with a PVA content of 5%. The variation in modulus and fracture strain versus the diameter of a single electrospun fiber presented two opposite trends, while simultaneous enhancement was observed when the content of PVA was 5% and 10%. With a diameter of 1 μm, the strength and toughness of the L95V5 and L90V10 fibers were enhanced to over 3 and 2 times that of pure PLA, respectively. The structural evolution of electrospun nanofiber was analyzed by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Although PLA and PVA were still miscible in the concentration range used, the latter could crystallize independently after electrospinning. According to the crystallization behavior of the nanofibers, a double network formed by PLA and PVA—one microcrystal/ordered structure and one amorphous structure—is proposed to contribute to the simultaneous enhancement of strength and toughness, which provides a promising method for preparing biodegradable material with high performance. Full article

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17 pages, 5014 KiB

Open AccessArticle

Diels–Alder-Crosslinked Polymers Derived from Jatropha Oil

by Muhammad Iqbal^1,2

, Remco Arjen Knigge², Hero Jan Heeres², Antonius A. Broekhuis² and Francesco Picchioni^2,*

¹ Department of Chemistry, Institut Teknologi Bandung, Jalan Ganesha No. 10, 40132 Bandung, Indonesia

² ENgineering and TEchnology Institute Groningen (ENTEG), Chemical Product Engineering, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands

Polymers 2018, 10(10), 1177; https://doi.org/10.3390/polym10101177 - 22 Oct 2018

Cited by 8 | Viewed by 5266

Abstract

Methyl oleate, methyl linoleate, and jatropha oil were fully epoxidized using in situ-generated performic acid. The epoxidized compounds were further reacted with furfurylamine in a solvent-free reaction to obtain furan-functionalized fatty esters which, then, functioned as oligomers for a network preparation. Thermoreversible crosslinking [...] Read more.

Methyl oleate, methyl linoleate, and jatropha oil were fully epoxidized using in situ-generated performic acid. The epoxidized compounds were further reacted with furfurylamine in a solvent-free reaction to obtain furan-functionalized fatty esters which, then, functioned as oligomers for a network preparation. Thermoreversible crosslinking was obtained through a (retro) Diels–Alder reaction with bismaleimide, resulting in the formation of a brittle network for furan-functionalized methyl linoleate and jatropha oil. The furan-functionalized fatty esters were mixed with alternating (1,4)-polyketone reacted with furfurylamine (PK-Furan) for testing the mechanical and self-healing properties with DMTA and DSC, respectively. Full self-healing properties were found, and faster thermoreversibility kinetics were observed, compared to PK-Furan. Full article

(This article belongs to the Special Issue Bio-Based Resins and Crosslinked Polymers from Renewable Resources)

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11 pages, 1751 KiB

Open AccessArticle

Effects of Extractives on Dimensional Stability, Dynamic Mechanical Properties, Creep, and Stress Relaxation of Rice Straw/High-Density Polyethylene Composites

by Huanbo Wang, Fazhi Lin, Pingping Qiu and Tian Liu^*

Key Laboratory of Bio-Based Material Science and Technology (Ministry of Education), College of Material Science and Engineering, Northeast Forestry University, 26 Hexing Road, Harbin 150040, China

Polymers 2018, 10(10), 1176; https://doi.org/10.3390/polym10101176 - 22 Oct 2018

Cited by 14 | Viewed by 4347

Abstract

The removal of rice straw extractives increases the interphase adhesion between rice straw and the high-density polyethylene (HDPE) matrix, while eradicating the inner defects of rice straw/HDPE composites. This study investigated the effect of rice straw extractives removal on the dimensional stability (water [...] Read more.

The removal of rice straw extractives increases the interphase adhesion between rice straw and the high-density polyethylene (HDPE) matrix, while eradicating the inner defects of rice straw/HDPE composites. This study investigated the effect of rice straw extractives removal on the dimensional stability (water uptake and thermal expansion), dynamic mechanical properties, creep, and stress relaxation of rice straw/HDPE composites. Cold water (CW), hot water (HW), and 1% alkaline solution (AL) extraction methods were utilized to remove rice straw extractives. Extracted and unextracted rice straws were mixed with HDPE, maleated polyethylene (MAPE), and Polyethylene wax to prepare composites via extrusion. Removal of rice straw extractives significantly improved the dimensional stability, dynamic mechanical properties, and creep and stress relaxation of rice straw/HDPE composites, with the exception of the thickness swelling of the AL/HDPE and the thermal expansion of the rice straw/HDPE composites. HW/HDPE exhibited the best comprehensive performance. Full article

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12 pages, 30529 KiB

Open AccessArticle

Design and Optimization of a Hyper-Branched Polyimide Proton Exchange Membrane with Ultra-High Methanol-Permeation Resistivity for Direct Methanol Fuel Cells Applications

by Liying Ma¹, Guoxiao Xu², Shuai Li², Jiao Ma¹, Jing Li^2,* and Weiwei Cai^2,*

¹ School of Chemistry and Materials Science, Guizhou Normal University, 116 Baoshan North Road, Guiyang 550001, China

² Sustainable Energy Laboratory, Faculty of Materials Science and Chemistry, China University of Geosciences Wuhan, 388 Lumo RD, Wuhan 430074, China

Polymers 2018, 10(10), 1175; https://doi.org/10.3390/polym10101175 - 22 Oct 2018

Cited by 11 | Viewed by 3832

Abstract

A hyper-branched sulfonated polyimide (s-PI) was synthesized successfully and composited with polyvinylidene fluoride (PVDF) to achieve ultra-high methanol-permeation resistive for direct methanol fuel cell application. The optimized s-PI-PVDF composite membrane exhibited methanol resistivity low to 1.80 × 10⁻⁸ cm [...] Read more.

A hyper-branched sulfonated polyimide (s-PI) was synthesized successfully and composited with polyvinylidene fluoride (PVDF) to achieve ultra-high methanol-permeation resistive for direct methanol fuel cell application. The optimized s-PI-PVDF composite membrane exhibited methanol resistivity low to 1.80 × 10⁻⁸ cm²/s, two orders of magnitude lower than the value of the commercial Nafion 117 membrane (60 × 10⁻⁷ cm²/s). At the same time, the tensile strength of the composite membrane is 22 MPa, which is comparable to the value of the Nafion 117 membrane. Therefore, the composite membrane is promising for application in direct methanol fuel cell. Full article

(This article belongs to the Special Issue Polymers for Modern and Advanced Engineering Applications)

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18 pages, 8397 KiB

Open AccessArticle

The New Generation from Biomembrane with Green Technologies for Wastewater Treatment

by Ahmed Mohamed El-hadi^1,2,*

and Hatem Rashad Alamri³

¹ Department of Physics, Faculty of Applied Science, Umm Al-Qura University, Al-Abidiyya, P.O. Box 13174, Makkah 21955, Saudi Arabia

² Department of Basic Science, Higher Institute of Engineering and Technology, El Arish, North Sinai 9004, Egypt

³ Physics Department, Jamoum University College, Umm Al-Qura University, Makkah 21955, Saudi Arabia

Polymers 2018, 10(10), 1174; https://doi.org/10.3390/polym10101174 - 22 Oct 2018

Cited by 18 | Viewed by 4983

Abstract

A biopolymer of polylactic acid (PLLA)/polypropylene carbonate (PPC)/poly (3-hydroxybutrate) (PHB)/triethyl citrate (TEC) blends was prepared by the solution-casting method at different proportions. The thermal characteristics were studied by differential scanning calorimetry (DSC) and thermogravimetry (TG). PHB and TEC were added to improve the [...] Read more.

A biopolymer of polylactic acid (PLLA)/polypropylene carbonate (PPC)/poly (3-hydroxybutrate) (PHB)/triethyl citrate (TEC) blends was prepared by the solution-casting method at different proportions. The thermal characteristics were studied by differential scanning calorimetry (DSC) and thermogravimetry (TG). PHB and TEC were added to improve the interfacial adhesion, crystallization behavior, and mechanical properties of the immiscible blend from PLLA and PPC (20%). The addition of more than 20% of PPC as an amorphous part hindered the crystallization of PLLA. PPC, PHB, and TEC also interacted with the PLLA matrix, which reduced the glass transition temperature (T_g), the cold crystallization temperature (T_cc), and the melting point (T_m) to about 53, 57 and 15 °C, respectively. The T_g shifted from 60 to 7 °C; therefore, the elongation at break improved from 6% (pure PLLA) to 285% (PLLA blends). In this article, biomembranes of PLLA with additives were developed and made by an electrospinning process. The new generation from biopolymer membranes can be used to absorb suspended pollutants in the water, which helps in the purification of drinking water in the household. Full article

(This article belongs to the Special Issue Polymer for Separation)

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9 pages, 974 KiB

Open AccessArticle

Reversible Assembly of Terpyridine Incorporated Norbornene-Based Polymer via a Ring-Opening Metathesis Polymerization and Its Self-Healing Property

by Jookyeong Lee, Hwi Hyun Moon, Keewook Paeng^* and Changsik Song^*

Department of Chemistry, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do 16419, Korea

Polymers 2018, 10(10), 1173; https://doi.org/10.3390/polym10101173 - 22 Oct 2018

Cited by 11 | Viewed by 5251

Abstract

We induced a terpyridine moiety into a norbornene-based polymer to demonstrate its self-healing property, without an external stimulus, such as light, heat, or healing agent, using metal–ligand interactions. We synthesized terpyridine incorporated norbornene-based polymers using a ring-opening metathesis polymerization. The sol state of [...] Read more.

We induced a terpyridine moiety into a norbornene-based polymer to demonstrate its self-healing property, without an external stimulus, such as light, heat, or healing agent, using metal–ligand interactions. We synthesized terpyridine incorporated norbornene-based polymers using a ring-opening metathesis polymerization. The sol state of diluted polymer solutions was converted into supramolecular assembled gels, through the addition of transition metal ions (Ni²⁺, Co²⁺, Fe²⁺, and Zn²⁺). In particular, a supramolecular complex gel with Zn²⁺, which is a metal with a lower binding affinity, demonstrated fast self-healing properties, without any additional external stimuli, and its mechanical properties were completely recovered. Full article

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16 pages, 4285 KiB

Open AccessArticle

Preparation and Characterization of Potato Starch Film with Various Size of Nano-SiO₂

by Rongfei Zhang, Xiangyou Wang^* and Meng Cheng

Department of Food Science and Engineering, Shandong University of Technology, Zibo 255000, China

Polymers 2018, 10(10), 1172; https://doi.org/10.3390/polym10101172 - 22 Oct 2018

Cited by 119 | Viewed by 8969

Abstract

The various sizes (15, 30, 80, and 100 nm) of nano-SiO₂/potato starch films were synthesized and characterized. The gas permeability, antibacterial properties, and mechanical properties of the films were evaluated to their potential for application as food packaging materials. Results indicated [...] Read more.

The various sizes (15, 30, 80, and 100 nm) of nano-SiO₂/potato starch films were synthesized and characterized. The gas permeability, antibacterial properties, and mechanical properties of the films were evaluated to their potential for application as food packaging materials. Results indicated that the 100 nm nano-SiO₂ was well dispersed in the starch matrix, which induced an active group on the surface of 100 nm nano-SiO₂ adequately combined with starch macromolecule. The water resistance and mechanical properties of the films were improved with the addition of nano-SiO₂. Notably, resistance to ultraviolet and thermal aging was also enhanced. The nano-SiO₂/potato starch films were more efficient against Escherichia coli (E. coli) than Staphylococcus aureus (S. aureus). Remarkable preservation properties of the films packaging the white mushrooms were obtained, with those of the 100 nm films considered superior. This study can significantly guide the rational choice of the nano-SiO₂ size to meet the packaging requirements of various agricultural products. Full article

(This article belongs to the Collection Polysaccharides)

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13 pages, 1907 KiB

Open AccessArticle

Grafting Halloysite Nanotubes with Amino or Carboxyl Groups onto Carbon Fiber Surface for Excellent Interfacial Properties of Silicone Resin Composites

by Xiandong Zhang and Guangshun Wu^*

School of Chemistry and Materials Science, Ludong University, Yantai 264025, China

Polymers 2018, 10(10), 1171; https://doi.org/10.3390/polym10101171 - 22 Oct 2018

Cited by 32 | Viewed by 5337

Abstract

The quality of interphase in carbon fibers (CFs) composites makes a key contribution to overall performance of composites. Here, we achieved for the first time the chemical grafting of halloysite nanotubes (HNTs) with amino or carboxyl groups onto the CFs surface aiming to [...] Read more.

The quality of interphase in carbon fibers (CFs) composites makes a key contribution to overall performance of composites. Here, we achieved for the first time the chemical grafting of halloysite nanotubes (HNTs) with amino or carboxyl groups onto the CFs surface aiming to increase composites interfacial strength. HNTs were grafted using 3-aminopropyltriethoxysilane (APS) followed by succinic anhydride treatment, and HNTs with amino groups (HNT–NH₂) or carboxyl groups (HNT–COOH) were separately introduced into the interphase of composites. Functional groups of HNTs and fiber surface structures were characterized, which confirmed the modification success. The wettability between the modified CFs and resin have been enhanced obviously based on the improved fiber polarity and enhanced surface roughness by the introduced two functionalized HNTs with the uniform distributions onto fiber surface. Moreover, interfacial properties and anti-hydrothermal aging behaviors of modified methylphenylsilicone resin (MPSR) composites were improved significantly, especially for HNT–COOH grafting. In addition, the interfacial reinforcement mechanisms for untreated and modified CF composites are discussed and compared. Full article

(This article belongs to the Special Issue Polymer Clay Nano-composites)

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16 pages, 5308 KiB

Open AccessArticle

Synthesis and Characterization of Isosorbide-Based Polyurethanes Exhibiting Low Cytotoxicity Towards HaCaT Human Skin Cells

by Barbara S. Gregorí Valdés^1,2, Clara S. B. Gomes³

, Pedro T. Gomes^3,*

, José R. Ascenso^3,*, Hermínio P. Diogo³, Lídia M. Gonçalves²

, Rui Galhano dos Santos¹

, Helena M. Ribeiro²

and João C. Bordado^1,*

¹ CERENA, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

² Research Institute for Medicine and Pharmaceutical Science (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal

³ Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

Polymers 2018, 10(10), 1170; https://doi.org/10.3390/polym10101170 - 20 Oct 2018

Cited by 22 | Viewed by 8105

Abstract

The synthesis of four samples of new polyurethanes was evaluated by changing the ratio of the diol monomers used, poly(propylene glycol) (PPG) and D-isosorbide, in the presence of aliphatic isocyanates such as the isophorone diisocyanate (IPDI) and 4,4′-methylenebis(cyclohexyl isocyanate) (HMDI). The thermal properties [...] Read more.

The synthesis of four samples of new polyurethanes was evaluated by changing the ratio of the diol monomers used, poly(propylene glycol) (PPG) and D-isosorbide, in the presence of aliphatic isocyanates such as the isophorone diisocyanate (IPDI) and 4,4′-methylenebis(cyclohexyl isocyanate) (HMDI). The thermal properties of the four polymers obtained were determined by DSC, exhibiting T_g values in the range 55–70 °C, and their molecular structure characterized by FTIR, ¹H, and ¹³C NMR spectroscopies. The diffusion coefficients of these polymers in solution were measured by the Pulse Gradient Spin Echo (PGSE) NMR method, enabling the calculation of the corresponding hydrodynamic radii in diluted solution (1.62–2.65 nm). The molecular weights were determined by GPC/SEC and compared with the values determined by a quantitative ¹³C NMR analysis. Finally, the biocompatibility of the polyurethanes was assessed using the HaCaT keratinocyte cell line by the MTT reduction assay method showing values superior to 70% cell viability. Full article

(This article belongs to the Special Issue Functional Polyurethanes – In Memory of Prof. József Karger-Kocsis)

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19 pages, 11329 KiB

Open AccessArticle

High-Performance PEDOT:PSS/Hexamethylene Diisocyanate-Functionalized Graphene Oxide Nanocomposites: Preparation and Properties

by José Antonio Luceño Sánchez¹

, Rafael Peña Capilla² and Ana Maria Díez-Pascual^1,*

¹ Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Faculty of Biology, Environmental Sciences and Chemistry, Alcalá University, 28871 Madrid, Spain

² Department of Signal Theory and Communication, Alcalá University, 28805 Madrid, Spain

Polymers 2018, 10(10), 1169; https://doi.org/10.3390/polym10101169 - 20 Oct 2018

Cited by 43 | Viewed by 6708

Abstract

Graphene oxide (GO) has emerged as an ideal filler to reinforce polymeric matrices owing to its large specific surface area, transparency, flexibility, and very high mechanical strength. Nonetheless, functionalization is required to improve its solubility in common solvents and expand its practical uses. [...] Read more.

Graphene oxide (GO) has emerged as an ideal filler to reinforce polymeric matrices owing to its large specific surface area, transparency, flexibility, and very high mechanical strength. Nonetheless, functionalization is required to improve its solubility in common solvents and expand its practical uses. In this work, hexamethylene diisocyanate (HDI)-functionalized GO (HDI-GO) has been used as filler of a conductive polymer matrix, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The nanocomposites have been prepared via a simple solution casting method, and have been characterized by scanning electron microscopy (SEM), UV–Vis and Raman spectroscopies, X-ray diffraction (XRD), thermogravimetric analysis (TGA), tensile tests, and four-point probe measurements to get information about how the HDI-GO functionalization degree (FD) and the HDI-GO concentration in the nanocomposite influence the final properties. SEM analysis showed a very homogenous dispersion of the HDI-GO nanosheets with the highest FD within the matrix, and the Raman spectra revealed the existence of very strong HDI-GO-PEDOT:PSS interactions. A gradual improvement in thermal stability was found with increasing HDI-GO concentration, with only a small loss in transparency. A reduction in the sheet resistance of PEDOT:PSS was found at low HDI-GO contents, whilst increasing moderately at the highest loading tested. The nanocomposites showed a good combination of stiffness, strength, ductility, and toughness. The optimum balance of properties was attained for samples incorporating 2 and 5 wt % HDI-GO with the highest FD. These solution-processed nanocomposites show considerably improved performance compared to conventional PEDOT:PSS nanocomposites filled with raw GO, and are highly suitable for applications in various fields, including flexible electronics, thermoelectric devices, and solar energy applications. Full article

(This article belongs to the Special Issue Applications of Graphene and Fullerene Nanocomposites)

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15 pages, 4471 KiB

Open AccessArticle

Hydrothermal Synthesis of Cellulose Nanocrystal-Grafted-Acrylic Acid Aerogels with Superabsorbent Properties

by Xuehua Liu¹, Rue Yang², Mingcong Xu¹, Chunhui Ma¹, Wei Li^1,2,3,*

, Yu Yin¹, Qiongtao Huang², Yiqiang Wu³, Jian Li¹ and Shouxin Liu^1,*

¹ Key Laboratory of Bio-Based Material Science and Technology of Ministry of Education, Northeast Forestry University, Hexing Road 26, Harbin 150040, China

² Post-Doctoral Research Center, Yihua Lifestyle Technology Co., Ltd., Shantou 515834, China

³ School of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, Hunan, China

Polymers 2018, 10(10), 1168; https://doi.org/10.3390/polym10101168 - 19 Oct 2018

Cited by 25 | Viewed by 5940

Abstract

In this work, we applied a fast and simple method to synthesize cellulose nanocrystal (CNC) aerogels, via a hydrothermal strategy followed by freeze drying. The characteristics and morphology of the obtained CNC-g-AA aerogels were affected by the hydrothermal treatment time, volume of added [...] Read more.

In this work, we applied a fast and simple method to synthesize cellulose nanocrystal (CNC) aerogels, via a hydrothermal strategy followed by freeze drying. The characteristics and morphology of the obtained CNC-g-AA aerogels were affected by the hydrothermal treatment time, volume of added AA (acrylic acid), and the mass fraction of the CNCs. The formation mechanism of the aerogels involved free radical graft copolymerization of AA and CNCs with the cross-linker N,N′-methylene bis(acrylamide) (MBA) during the hydrothermal process. The swelling ratio of the CNC-g-AA aerogels was as high as 495:1, which is considerably greater than that of other polysaccharide-g-AA aerogels systems. Moreover, the CNC-g-AA aerogels exhibited an excellent methyl blue (MB) adsorption capacity and the ability to undergo rapid desorption/regeneration. The maximum adsorption capacity of the CNC-g-AA aerogels for MB was greater than 400 mg/g. Excellent regeneration performance further indicates the promise of our CNC-g-AA aerogels as an adsorbent for applications in environmental remediation. Full article

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15 pages, 5435 KiB

Open AccessArticle

Mass-Production and Characterizations of Polyvinyl Alcohol/Sodium Alginate/Graphene Porous Nanofiber Membranes Using Needleless Dynamic Linear Electrospinning

by Ting-Ting Li^1,2

, Mengxue Yan¹, Wenting Xu¹, Bing-Chiuan Shiu³, Ching-Wen Lou^1,4,5,6,* and Jia-Horng Lin^{1,3,5,6,7,8,*}

¹ Innovation Platform of Intelligent and Energy-Saving Textiles, School of Textiles, Tianjin Polytechnic University, Tianjin 300387, China

² Tianjin and Education Ministry Key Laboratory of Advanced Textile Composite Materials, Tianjin Polytechnic University, Tianjin 300387, China

³ Laboratory of Fiber Application and Manufacturing, Department of Fiber and Composite Materials, Feng Chia University, Taichung 40724, Taiwan

⁴ Department of Bioinformatics and Medical Engineering, Asia University, Taichung 41354, Taiwan

⁵ Department of Chemical Engineering and Materials, Ocean College, Minjiang University, Fuzhou 350108, China

⁶ College of Textile and Clothing, Qingdao University, Qingdao 266071, China

⁷ School of Chinese Medicine, China Medical University, Taichung 40402, Taiwan

⁸ Department of Fashion Design, Asia University, Taichung 41354, Taiwan

Polymers 2018, 10(10), 1167; https://doi.org/10.3390/polym10101167 - 19 Oct 2018

Cited by 27 | Viewed by 4980

Abstract

The aim of this study was to investigate the feasibility of large-scale preparation of porous polyvinyl alcohol/sodium alginate/graphene (Gr) (Gr-AP) nanofiber membranes using a copper wire needleless dynamic linear electrode electrospinning machine. Furthermore, the effects of Gr concentrations (0, 0.0375, 0.075, 0.25, 0.5, [...] Read more.

The aim of this study was to investigate the feasibility of large-scale preparation of porous polyvinyl alcohol/sodium alginate/graphene (Gr) (Gr-AP) nanofiber membranes using a copper wire needleless dynamic linear electrode electrospinning machine. Furthermore, the effects of Gr concentrations (0, 0.0375, 0.075, 0.25, 0.5, and 0.75 wt.%) on the morphology, electrical, hydrophilicity and thermal properties were evaluated. Results indicate that the dynamic linear electrospun Gr-AP membranes have a high yield of 1.25 g/h and are composed of porous finer nanofibers with a diameter of 141 ± 31 nm. Gr improved the morphology, homogeneity, hydrophobicity and thermal stability of Gr-AP nanofiber membranes. The critical conductive threshold is 0.075 wt.% for Gr, which provides the nanofiber membranes with an even distribution of diameter, an optimal conductivity, good hydrophilicity, appropriate specific surface area and optimal thermal stability. Therefore, needleless dynamic linear electrospinning is beneficial to produce high quality Gr-AP porous nanofiber membranes, and the optimal parameters can be used in artificial nerve conduits and serve as a valuable reference for mass production of nanofiber membranes. Full article

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22 pages, 50821 KiB

Open AccessArticle

Fire Phenomena of Rigid Polyurethane Foams

by Martin Günther¹, Alessandra Lorenzetti² and Bernhard Schartel^2,*

¹ Bundesanstalt für Materialforschung und-prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany

² Department of Industrial Engineering, Padova University, v. F. Marzolo 9, 35131 Padua, Italy

Polymers 2018, 10(10), 1166; https://doi.org/10.3390/polym10101166 - 19 Oct 2018

Cited by 77 | Viewed by 9845

Abstract

Rigid polyurethane foams (RPUFs) typically exhibit low thermal inertia, resulting in short ignition times and rapid flame spread. In this study, the fire phenomena of RPUFs were investigated using a multi-methodological approach to gain detailed insight into the fire behaviour of pentane- and [...] Read more.

Rigid polyurethane foams (RPUFs) typically exhibit low thermal inertia, resulting in short ignition times and rapid flame spread. In this study, the fire phenomena of RPUFs were investigated using a multi-methodological approach to gain detailed insight into the fire behaviour of pentane- and water-blown polyurethane (PUR) as well as pentane-blown polyisocyanurate polyurethane (PIR) foams with densities ranging from 30 to 100 kg/m³. Thermophysical properties were studied using thermogravimetry (TG); flammability and fire behaviour were investigated by means of the limiting oxygen index (LOI) and a cone calorimeter. Temperature development in burning cone calorimeter specimens was monitored with thermocouples inside the foam samples and visual investigation of quenched specimens’ cross sections gave insight into the morphological changes during burning. A comprehensive investigation is presented, illuminating the processes taking place during foam combustion. Cone calorimeter tests revealed that in-depth absorption of radiation is a significant factor in estimating the time to ignition. Cross sections examined with an electron scanning microscope (SEM) revealed a pyrolysis front with an intact foam structure underneath, and temperature measurement inside burning specimens indicated that, as foam density increased, their burning behaviour shifted towards that of solid materials. The superior fire performance of PIR foams was found to be based on the cellular structure, which is retained in the residue to some extent. Full article

(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)

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17 pages, 2805 KiB

Open AccessArticle

Anionic Polymer Brushes for Biomimetic Calcium Phosphate Mineralization—A Surface with Application Potential in Biomaterials

by Tobias Mai¹, Karol Wolski²

, Agnieszka Puciul-Malinowska², Alexey Kopyshev³, Ralph Gräf⁴, Michael Bruns⁵

, Szczepan Zapotoczny^2,*

and Andreas Taubert^1,*

¹ Institute of Chemistry, University of Potsdam, D-14476 Potsdam, Germany

² Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland

³ Institute of Physics and Astronomy, University of Potsdam, D-14476 Potsdam, Germany

⁴ Institute of Biochemistry and Biology, University of Potsdam, D-14476 Potsdam, Germany

⁵ Institute for Applied Materials and Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology, D-76344 Eggenstein-Leopoldshafen, Germany

Polymers 2018, 10(10), 1165; https://doi.org/10.3390/polym10101165 - 18 Oct 2018

Cited by 17 | Viewed by 6814

Abstract

This article describes the synthesis of anionic polymer brushes and their mineralization with calcium phosphate. The brushes are based on poly(3-sulfopropyl methacrylate potassium salt) providing a highly charged polymer brush surface. Homogeneous brushes with reproducible thicknesses are obtained via surface-initiated atom transfer radical [...] Read more.

This article describes the synthesis of anionic polymer brushes and their mineralization with calcium phosphate. The brushes are based on poly(3-sulfopropyl methacrylate potassium salt) providing a highly charged polymer brush surface. Homogeneous brushes with reproducible thicknesses are obtained via surface-initiated atom transfer radical polymerization. Mineralization with doubly concentrated simulated body fluid yields polymer/inorganic hybrid films containing AB-Type carbonated hydroxyapatite (CHAP), a material resembling the inorganic component of bone. Moreover, growth experiments using Dictyostelium discoideum amoebae demonstrate that the mineral-free and the mineral-containing polymer brushes have a good biocompatibility suggesting their use as biocompatible surfaces in implantology or related fields. Full article

(This article belongs to the Special Issue Hybrid Adhesive and Coatings for Medical Applications)

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14 pages, 3626 KiB

Open AccessArticle

Preparation of Microparticles Capable of Glucose-Induced Insulin Release under Physiological Conditions

by Kentaro Yoshida^1,*, Kazuma Awaji², Seira Shimizu², Miku Iwasaki², Yuki Oide², Megumi Ito², Takenori Dairaku¹, Tetsuya Ono¹, Yoshitomo Kashiwagi¹ and Katsuhiko Sato²

¹ School of Pharmaceutical Sciences, Ohu University 31-1 Misumido, Tomita-Machi, Koriyama, Fukushima 963-8611, Japan

² Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan

Polymers 2018, 10(10), 1164; https://doi.org/10.3390/polym10101164 - 18 Oct 2018

Cited by 13 | Viewed by 4428

Abstract

Hydrogen peroxide (H₂O₂)-sensitive layer-by-layer films were prepared based on combining phenyl boronic acid (PBA)-modified poly(allylamine) (PAH) with shikimic acid (SA)-modified-PAH through boronate ester bonds. These PBA-PAH/SA-PAH multilayer films could be prepared in aqueous solutions at pH 7.4 and 9.0 [...] Read more.

Hydrogen peroxide (H₂O₂)-sensitive layer-by-layer films were prepared based on combining phenyl boronic acid (PBA)-modified poly(allylamine) (PAH) with shikimic acid (SA)-modified-PAH through boronate ester bonds. These PBA-PAH/SA-PAH multilayer films could be prepared in aqueous solutions at pH 7.4 and 9.0 in the presence of NaCl. It is believed that the electrostatic repulsion between the SA-PAH and PBA-PAH was diminished and the formation of ester bonds between the SA and PBA was promoted in the presence of NaCl. These films readily decomposed in the presence of H₂O₂ because the boronate ester bonds were cleaved by an oxidation reaction. In addition, SA-PAH/PBA-PAH multilayer films combined with glucose oxidase (GOx) were decomposed in the presence of glucose because GOx catalyzes the oxidation of D-glucose to generate H₂O₂. The surfaces of CaCO₃ microparticles were coated with PAH/GOx/(SA-PAH/PBA-PAH)₅ films that absorbed insulin. A 1 mg quantity of these particles released up to 10 μg insulin in the presence 10 mM glucose under physiological conditions. Full article

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12 pages, 7155 KiB

Open AccessArticle

Preparation and Characterization of Hot Melt Copolyester (PBTI) Ultrafine Particles and Their Effect on the Anti-Pilling Performance of Polyester/Cotton Fabrics

by Zhichao Huang^* and Wenxing Chen^*

Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, China

Polymers 2018, 10(10), 1163; https://doi.org/10.3390/polym10101163 - 18 Oct 2018

Cited by 8 | Viewed by 4524

Abstract

An ultrafine particle aqueous-phase system of hot melt copolyester was prepared by an inverse emulsion–precipitation method. Laser particle size analysis showed that the diameter of the obtained copolyester particles was mostly distributed between 20 and 100 nm. The structure of the copolymer was [...] Read more.

An ultrafine particle aqueous-phase system of hot melt copolyester was prepared by an inverse emulsion–precipitation method. Laser particle size analysis showed that the diameter of the obtained copolyester particles was mostly distributed between 20 and 100 nm. The structure of the copolymer was characterized by FT–IR and ¹H-NMR, and the melting point of the particles was determined to be 125 °C, as measured by differential scanning calorimetry (DSC). Intrinsic viscosity analysis showed that the particle intrinsic viscosity decreased by 6.73% compared with that of the original copolyester. Polyester/cotton woven fabrics were padded with the ultrafine copolyester particles at different concentrations, and the corresponding SEM showed that the fibers were well bonded to each other. The pilling test results showed that these ultrafine copolyester granules improved the pilling performance of the polyester/cotton woven fabrics to a grade of 4.5–5. Full article

(This article belongs to the Special Issue Polymer Processing for Enhancing Textile Application)

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11 pages, 1295 KiB

Open AccessArticle

Lignin Phenol Formaldehyde Resoles Using Base-Catalysed Depolymerized Kraft Lignin

by Pia Solt^1,2,*, Björn Rößiger³, Johannes Konnerth²

and Hendrikus W. G. Van Herwijnen¹

¹ Wood K plus-Competence Center of Wood Composites and Wood Chemistry, Kompetenzzentrum Holz GmbH, Altenberger Str. 69, A-4040 Linz, Austria

² Department of Material Science and Process Engineering, Institute of Wood Technology and Renewable Materials, BOKU-University of Natural Resources and Life Sciences-Vienna, Konrad Lorenz Str. 24, A-3430 Tulln, Austria

³ Fraunhofer Center for Chemical-Biotechnological Processes CBP, 06237 Leuna, Germany

Polymers 2018, 10(10), 1162; https://doi.org/10.3390/polym10101162 - 17 Oct 2018

Cited by 53 | Viewed by 13173

Abstract

Lignin phenol formaldehyde (LPF) resols were produced using depolymerized lignin fractions at various levels of phenol substitution (50 to 70 wt %). To produce monomeric-rich (BCD-oil) and oligomeric (BCD-oligomers) bio-based phenolic compounds, softwood kraft lignin was base-catalysed degraded. These base-catalysed depolymerized (BCD) building [...] Read more.

Lignin phenol formaldehyde (LPF) resols were produced using depolymerized lignin fractions at various levels of phenol substitution (50 to 70 wt %). To produce monomeric-rich (BCD-oil) and oligomeric (BCD-oligomers) bio-based phenolic compounds, softwood kraft lignin was base-catalysed degraded. These base-catalysed depolymerized (BCD) building blocks were further used to substitute phenol in the synthesis of phenolic resins and were characterized in detail (such as viscosity, free formaldehyde and phenol content, chemical composition, curing and bonding behaviour). The adhesive properties were compared to a phenol formaldehyde (PF) reference resin and a LPF with untreated kraft lignin. The resins synthesized with the two depolymerized lignin types differ significantly from each other with increasing phenol substitution. While with LPF-BCD-oligomers the viscosity increases and the bonding strength is not effected by increasing lignin content in the resin, a reduction of these properties could be observed with LPF-BCD-oil. Furthermore, LPF-BCD-oil showed similar curing behaviour and ultimate strength as the reference LPF. Adhesive bonds made using LPF-BCD-oligomers exhibited similar strength to those made using PF. Compared to the reference resins, it has been demonstrated that modified renewable lignin based phenolic components can be an equally performing alternative to phenol even for high degrees of substitution of 70%. Full article

(This article belongs to the Special Issue Bio-Based Resins and Crosslinked Polymers from Renewable Resources)

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9 pages, 1167 KiB

Open AccessCommunication

Selective Polymer Distributed Bragg Reflector Vapor Sensors

by Paola Lova

Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Genova, Via Dodecaneso 31, 16146 Genova, Italy

Polymers 2018, 10(10), 1161; https://doi.org/10.3390/polym10101161 - 17 Oct 2018

Cited by 31 | Viewed by 5145

Abstract

We report on Flory–Huggins photonic sensors for the selective detection of volatile organic compounds without the use of any chemical functionalization. For this purpose, we employed periodic multilayers made of inert cellulose acetate alternated to active polystyrene films whose free volume was modified [...] Read more.

We report on Flory–Huggins photonic sensors for the selective detection of volatile organic compounds without the use of any chemical functionalization. For this purpose, we employed periodic multilayers made of inert cellulose acetate alternated to active polystyrene films whose free volume was modified with silanized ZnO nanoparticles. The simple UV-visible (UV-vis) dynamic optical response of such polymer distributed Bragg reflectors during exposure to vapors of benzene, toluene, o-dichlorobenzene, and carbon tetrachloride allows their detection and recognition based on different chemico–physical affinity with the active polymer medium. Full article

(This article belongs to the Special Issue Biomimicry through Molecular Imprinting: From Polymer Design to Devices)

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18 pages, 13756 KiB

Open AccessArticle

Effects of Nano-CaCO₃ Content on the Crystallization, Mechanical Properties, and Cell Structure of PP Nanocomposites in Microcellular Injection Molding

by Huajie Mao^1,2,3, Bo He^1,2,3, Wei Guo^2,3,4,*, Lin Hua^2,3,4 and Qing Yang^2,3,4

¹ School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China

² Hubei Key Laboratory of Advanced Technology for Automotive Components, Wuhan University of Technology, Wuhan 430070, China

³ Hubei Collaborative Innovation Center for Automotive Components Technology, Wuhan 430070, China

⁴ School of Automotive Engineering, Wuhan University of Technology, Wuhan 430070, China

Polymers 2018, 10(10), 1160; https://doi.org/10.3390/polym10101160 - 17 Oct 2018

Cited by 55 | Viewed by 6688

Abstract

Using supercritical nitrogen as the physical foaming agent, microcellular polypropylene (PP) nanocomposites were prepared in microcellular injection molding. The main purpose of this work is to study effects of content of nano-CaCO₃ on the crystallization, mechanical properties, and cell structure of PP [...] Read more.

Using supercritical nitrogen as the physical foaming agent, microcellular polypropylene (PP) nanocomposites were prepared in microcellular injection molding. The main purpose of this work is to study effects of content of nano-CaCO₃ on the crystallization, mechanical properties, and cell structure of PP nanocomposites in microcellular injection molding. The results show that adding nano-CaCO₃ to PP could improve its mechanical properties and cell structure. The thermal stability and crystallinity enhances with increase of nano-CaCO₃. As a bubble nucleating agent, adding nano-CaCO₃ to PP improves the cell structure in both the parallel sections and vertical sections. The mechanical properties increase first and then decrease with increase of nano-CaCO₃. The mechanical properties are affected by the cell structure, as well. The mechanical properties and cell structure are optimum when the content of nano-CaCO₃ is 6 wt %. Full article

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19 pages, 5078 KiB

Open AccessArticle

Soy Protein-Based Composite Hydrogels: Physico-Chemical Characterization and In Vitro Cytocompatibility

by Samira Tansaz^1,*, Raminder Singh^2,3, Iwona Cicha² and Aldo R. Boccaccini^1,*

¹ Institute of Biomaterials, Department of Materials Science and Engineering, University of Erlangen-Nuremberg, 91058 Erlangen, Germany

² Section of Experimental Oncology and Nanomedicine, ENT-Department, University Hospital Erlangen University of Erlangen-Nuremberg, 91054 Erlangen, Germany

³ Department of Cardiology and Angiology, University Hospital Erlangen, University of Erlangen-Nuremberg, 91054 Erlangen, Germany

Polymers 2018, 10(10), 1159; https://doi.org/10.3390/polym10101159 - 17 Oct 2018

Cited by 20 | Viewed by 5192

Abstract

Novel composite hydrogels based on the combination of alginate (Alg), soy protein isolate (SPI) and bioactive glass (BG) nanoparticles were developed for soft tissue engineering. Human umbilical vein endothelial cells (HUVEC) and normal human dermal fibroblasts were cultivated on hydrogels for 7, 14 [...] Read more.

Novel composite hydrogels based on the combination of alginate (Alg), soy protein isolate (SPI) and bioactive glass (BG) nanoparticles were developed for soft tissue engineering. Human umbilical vein endothelial cells (HUVEC) and normal human dermal fibroblasts were cultivated on hydrogels for 7, 14 and 21 days. Cell morphology was visualized using fluorescent staining at Days 7 and 14 for fibroblast cells and Days 14 and 21 for HUVEC. Metabolic activity of cells was analyzed using a colorimetric assay (water soluble tetrazolium (WST) assay). Compared to pure Alg, Alg/SPI and Alg/SPI/BG provided superior surfaces for both types of cells, supporting their attachment, growth, spreading and metabolic activity. Fibroblasts showed better colonization and growth on Alg/SPI/BG hydrogels compared to Alg/SPI hydrogels. The results indicate that such novel composite hydrogels might find applications in soft tissue regeneration. Full article

(This article belongs to the Special Issue Polymer Scaffolds for Biomedical Application)

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11 pages, 2029 KiB

Open AccessArticle

Influence of Ethylene Oxide Content in Nonionic Surfactant to the Hydrolysis of Reactive Dye in Silicone Non-Aqueous Dyeing System

by Jiping Wang^1,2, Yongbo Zhang^1,2, Huashu Dou³ and Liujun Pei^1,2,3,*

¹ Engineering Research Center for Eco-Dyeing and Finishing of Textiles, Zhejiang Sci-Tech University, Hangzhou 310018, China

² National Base for International Science & Technology Cooperation in Textiles and Consumer-Goods Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China

³ Key Laboratory of Fluid Transmission Technology of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China

Polymers 2018, 10(10), 1158; https://doi.org/10.3390/polym10101158 - 17 Oct 2018

Cited by 15 | Viewed by 6886

Abstract

Silicone reverse dyeing technology provides an important means of saving water and salts-free in the textile dyeing industry. The interactions between dyes and surfactants may influence the hydrolysis of dye during dyeing. In this investigation, the effect of ethylene oxide content in nonionic [...] Read more.

Silicone reverse dyeing technology provides an important means of saving water and salts-free in the textile dyeing industry. The interactions between dyes and surfactants may influence the hydrolysis of dye during dyeing. In this investigation, the effect of ethylene oxide content in nonionic surfactant on the hydrolytic reaction of reactive dye was firstly investigated in a siloxane reverse emulsion dyeing system. Compared with no surfactants, the hydrolytic reaction of vinyl sulfone reactive dye was a slowdown when some nonionic surfactants were used during dyeing. Usually, the hydrophobic groups in nonionic surfactants were dodecyl chains but their polar head groups were different. The hydrolytic reaction of vinyl sulfone dye showed that the longer of EO (ethylene oxide) chains, the faster the hydrolytic reaction of vinyl sulfone dye. From the absorption spectrum of dye, it could be concluded that more of dyes would be solubilized into the formed micelles, and dye-surfactant complexes were adhered to the surface of micelles if the molecular structure of surfactant had a shorter EO chains. Furthermore, the intramolecular or intermolecular hydrogen bond could be formed between dye and surfactant, which would further influence the hydrolytic reaction of vinyl sulfone dye. However, the solubility of surfactant in siloxane non-aqueous media would decrease with the increase of EO chains. Meanwhile, the dispersion of dye was enhanced as well as the hydrolytic reaction of dye. From this investigation, some surfactant can be used to improve the fixation of reactive dye during dyeing. Furthermore, washing times after dyeing and the ecological problems can be decreased. Full article

(This article belongs to the Special Issue Polymer Processing for Enhancing Textile Application)

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14 pages, 2033 KiB

Open AccessArticle

Effects of Hydrothermal Pretreatment on the Structural Characteristics of Organosolv Lignin from Triarrhena lutarioriparia

by Tianying Chen¹, Zhiwen Li¹, Xueming Zhang¹

, Douyong Min², Yuying Wu¹, Jialong Wen^1,*

and Tongqi Yuan¹

¹ Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China

² Guangxi Key Laboratory of Clean Pulp and Papermaking and Pollution Control, Nanning 530004, China

Polymers 2018, 10(10), 1157; https://doi.org/10.3390/polym10101157 - 16 Oct 2018

Cited by 22 | Viewed by 4747

Abstract

The effects of hydrothermal pretreatment (170–180 °C, 30–60 min) on the structural characteristics of enzymatic and extracted lignin from Triarrhena lutarioriparia (TL) during the integrated delignification process have been comprehensively investigated. Ion chromatography and NMR characterization showed that liquid products after [...] Read more.

The effects of hydrothermal pretreatment (170–180 °C, 30–60 min) on the structural characteristics of enzymatic and extracted lignin from Triarrhena lutarioriparia (TL) during the integrated delignification process have been comprehensively investigated. Ion chromatography and NMR characterization showed that liquid products after mild hydrothermal process (170 °C, 30 min) were mainly composed of xylooligosaccharide (XOS) with different degrees of polymerization (DP ≥ 2). In addition, the structural changes of lignin during hydrothermal pretreatment and organic acid delignification process have been demonstrated by quantitative 2D heteronuclear single quantum coherence (2D-HSQC) and ³¹P-NMR techniques. Results showed that the structural changes of lignin (e.g., cleavage of β-O-4 linkages) induced by the hydrothermal pretreatment will facilitate the subsequent organic acid delignification process, and acetylated lignin could be obtained with a considerable yield, which can be used in lignin-based composite and candidate feedstock for catalytic upgrading of lignin. In short, the proposed process facilitates the producing of XOS and acetylated lignin for lignin valorization. Full article

(This article belongs to the Special Issue Lignin Polymers: Structures, Reactions and Applications)

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26 pages, 3264 KiB

Open AccessArticle

Slip Spring-Based Mesoscopic Simulations of Polymer Networks: Methodology and the Corresponding Computational Code

by Grigorios Megariotis¹, Georgios G. Vogiatzis², Aristotelis P. Sgouros¹

and Doros N. Theodorou^1,*

¹ School of Chemical Engineering, National Technical University of Athens (NTUA), 9 Heroon Polytechniou Street, Zografou Campus, GR-15780 Athens, Greece

² Polymer Technology, Department of Mechanical Engineering, Eindhoven University of Technology, PO BOX 513, 5600MB Eindhoven, The Netherlands

Polymers 2018, 10(10), 1156; https://doi.org/10.3390/polym10101156 - 16 Oct 2018

Cited by 27 | Viewed by 7818

Abstract

In previous work by the authors, a new methodology was developed for Brownian dynamics/kinetic Monte Carlo (BD/kMC) simulations of polymer melts. In this study, this methodology is extended for dynamical simulations of crosslinked polymer networks in a coarse-grained representation, wherein chains are modeled [...] Read more.

In previous work by the authors, a new methodology was developed for Brownian dynamics/kinetic Monte Carlo (BD/kMC) simulations of polymer melts. In this study, this methodology is extended for dynamical simulations of crosslinked polymer networks in a coarse-grained representation, wherein chains are modeled as sequences of beads, each bead encompassing a few Kuhn segments. In addition, the C++ code embodying these simulations, entitled Engine for Mesoscopic Simulations for Polymer Networks (EMSIPON) is described in detail. A crosslinked network of cis-1,4-polyisoprene is chosen as a test system. From the thermodynamic point of view, the system is fully described by a Helmholtz energy consisting of three explicit contributions: entropic springs, slip springs and non-bonded interactions. Entanglements between subchains in the network are represented by slip springs. The ends of the slip springs undergo thermally activated hops between adjacent beads along the chain backbones, which are tracked by kinetic Monte Carlo simulation. In addition, creation/destruction processes are included for the slip springs at dangling subchain ends. The Helmholtz energy of non-bonded interactions is derived from the Sanchez–Lacombe equation of state. The isothermal compressibility of the polymer network is predicted from equilibrium density fluctuations in very good agreement with the underlying equation of state and with experiment. Moreover, the methodology and the corresponding C++ code are applied to simulate elongational deformations of polymer rubbers. The shear stress relaxation modulus is predicted from equilibrium simulations of several microseconds of physical time in the undeformed state, as well as from stress-strain curves of the crosslinked polymer networks under deformation. Full article

(This article belongs to the Special Issue Theory and Simulations of Entangled Polymers)

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32 pages, 5896 KiB

Open AccessArticle

The Continuum Approach to the Description of Semi-Crystalline Polymers Deformation Regimes: The Role of Dynamic and Translational Defects

by Yurii V. Grinyaev^1,*, Nadezhda V. Chertova¹, Evgeny V. Shilko^1,2

and Sergey G. Psakhie¹

¹ Institute of Strength Physics and Materials Science SB RAS, pr. Akademicheskii 2/4, 634055 Tomsk, Russia

² Physical Faculty, National Research Tomsk State University, 36 Lenin ave., 634050 Tomsk, Russia

Polymers 2018, 10(10), 1155; https://doi.org/10.3390/polym10101155 - 16 Oct 2018

Cited by 7 | Viewed by 7265

Abstract

This paper presents a new approach to describe the mechanical behavior of semi-crystalline polymers, the plastic deformation of which is determined by their two-phase structure. To describe the plastic behavior of semi-crystalline polymers, a two-phase model is used. In the framework of this [...] Read more.

This paper presents a new approach to describe the mechanical behavior of semi-crystalline polymers, the plastic deformation of which is determined by their two-phase structure. To describe the plastic behavior of semi-crystalline polymers, a two-phase model is used. In the framework of this model, one phase is in a hard (crystalline) state, and the other in a soft (amorphous) state. The two-phase material is modeled by a single-phase homogeneous continuum based on the approximation of the effective medium. It is assumed that two infinitely close material points of the continuum are connected in series by elastic and viscous bonds, which corresponds to the Maxwell model. It is shown that, in this case, the Maxwell continuum is a pseudo-Euclidean space. Generalizing the definition of defects from a three-dimensional space to a four-dimensional pseudo-Euclidean space, we obtained a dynamic system of nonlinear, interrelated equations to describe the behavior of translational-type defects in the solid phase and dynamic defects in the amorphous phase. As an example of an application for these equations, the phenomenon of creep under uniaxial loading is considered. It is shown that the formalism of the proposed two-phase model makes it possible to describe creep phenomenon regularities, which correspond to both the aging theory and the flow theory. Full article

(This article belongs to the Special Issue Mechanical Behavior of Polymers)

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13 pages, 2488 KiB

Open AccessArticle

Effects of Calcium Alginate Submicroparticles on Seed Germination and Seedling Growth of Wheat (Triticum aestivum L.)

by Jinxia He^1,2,†, Ruixin Li^1,3,†, Xue Sun¹, Wenxia Wang¹, Jianen Hu^2,*, Hongguo Xie^1,* and Heng Yin^1,*

¹ Liaoning Provincial Key Laboratory of Carbohydrates, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China

² School of Food Science and Engineering, Dalian Ocean University, Dalian 116023, China

³ School of Environment Science and Engineering, Dalian Maritime University, Dalian 116026, China

^† Jinxia He and Ruixin Li contributed equally to this work.

Polymers 2018, 10(10), 1154; https://doi.org/10.3390/polym10101154 - 16 Oct 2018

Cited by 19 | Viewed by 4783

Abstract

Calcium alginate (CaAlg) submicroparticles have a potential application in agricultural delivery systems. This study investigated the effects of CaAlg submicroparticles on seed germination and seedling growth of wheat. CaAlg submicroparticles with a Z-average diameter of around 250.4 nm and a measured zeta potential [...] Read more.

Calcium alginate (CaAlg) submicroparticles have a potential application in agricultural delivery systems. This study investigated the effects of CaAlg submicroparticles on seed germination and seedling growth of wheat. CaAlg submicroparticles with a Z-average diameter of around 250.4 nm and a measured zeta potential value of about −25.4 mV were prepared and characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS). After this, the effects of the concentration of CaAlg submicroparticles (10–500 μg/mL) on germination percentage, seedling length, the number of adventitious roots, chlorophyll content and soluble protein content were evaluated. The results demonstrated a significant increase in the level of germination percentage (9.0%), seedling index (50.3%), adventitious roots (27.5%), seedling length (17.0%), chlorophyll (8.7%) and soluble protein contents (4.5%) at a concentration of 100 μg/mL. However, an inhibitory effect was observed at a concentration of 500 μg/mL. The SEM examination showed that CaAlg submicroparticles could be successfully adsorbed onto the surface of the wheat seed. Further studies proved that CaAlg submicroparticles at a concentration of 100 μg/mL promoted the expression of indole-3-acetic acid (IAA)-related genes (YUCCA9, AUX1, ARF and UGT) in wheat, which resulted in an increase of 69% and 21% in IAA concentration in wheat roots and shoots, respectively. Full article

(This article belongs to the Special Issue Polysaccharides)

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11 pages, 4267 KiB

Open AccessArticle

Mechanisms of the Complex Thermo-Mechanical Behavior of Polymer Glass Across a Wide Range of Temperature Variations

by Weidong Liu and Liangchi Zhang^*

Laboratory for Precision and Nano Processing Technologies, School of Mechanical and Manufacturing Engineering, The University of New South Wales, New South Wales 2052, Australia

Polymers 2018, 10(10), 1153; https://doi.org/10.3390/polym10101153 - 16 Oct 2018

Cited by 9 | Viewed by 4240

Abstract

This paper aims to explore the mechanisms of the complex thermo-mechanical behavior of polymer glass across a wide range of temperature variations. To this end, the free vibration frequency spectrum of simply supported poly(methyl methacrylate) (PMMA) beams was thoroughly investigated with the aid [...] Read more.

This paper aims to explore the mechanisms of the complex thermo-mechanical behavior of polymer glass across a wide range of temperature variations. To this end, the free vibration frequency spectrum of simply supported poly(methyl methacrylate) (PMMA) beams was thoroughly investigated with the aid of the impulse excitation technique. It was found that the amplitude ratio of the multiple peaks in the frequency spectrum is a strongly dependent on temperature, and that the peaks correspond to the multiple vibrational modes of the molecular network of PMMA. At a low temperature, the vibration is dominated by the overall microstructure of PMMA. With increasing the temperature, however, the contribution of the sub-microstructures is retarded by β relaxation. Above 80 °C, the vibration is fully dominated by the microstructure after relaxation. The relaxation time at the transition temperature is of the same order of the vibration period, confirming the contribution of β relaxation. These findings provide a precise method for establishing reliable physical-based constitutive models of polymer glass. Full article

(This article belongs to the Special Issue Mechanical Behavior of Polymers)

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11 pages, 3056 KiB

Open AccessArticle

Recycled Carbon Fiber-Supported Polyaniline/Manganese Dioxide Prepared via One-Step Electrodeposition for Flexible Supercapacitor Integrated Electrodes

by Xiaoning Wang, Hongli Wei, Wei Du^*, Xueqin Sun, Litao Kang, Yuping Zhang, Xiangjin Zhao and Fuyi Jiang

School of Environment and Material Engineering, Yantai University, Yantai 264005, China

Polymers 2018, 10(10), 1152; https://doi.org/10.3390/polym10101152 - 16 Oct 2018

Cited by 18 | Viewed by 5201

Abstract

The exploration of multifunctional electrode materials has been a hotspot for the development of high-performance supercapacitors. We have used carbon fiber plates recovered from construction waste to prepare high-quality flexible carbon fiber materials by pyrolysis of epoxy resin. The as-prepared recycled carbon fiber [...] Read more.

The exploration of multifunctional electrode materials has been a hotspot for the development of high-performance supercapacitors. We have used carbon fiber plates recovered from construction waste to prepare high-quality flexible carbon fiber materials by pyrolysis of epoxy resin. The as-prepared recycled carbon fiber has a diameter of 8 μm and is the perfect substrate material for flexible electrode materials. Furthermore, polyaniline and manganese dioxide are uniformly deposited on the recycled carbon fiber by one-step electrodeposition to form an active film. The recycled carbon fiber/polyaniline/MnO₂ composite shows an excellent specific capacitance of 475.1 F·g⁻¹ and capacitance retention of 86.1% after 5000 GCD cycles at 1 A·g⁻¹ in 1 M Na₂SO₄ electrolyte. The composites optimized for electrodeposition time have more electroactive sites, faster ions and electron transfer, structural stability and higher conductivity, endowing the composites promising application prospect. Full article

(This article belongs to the Special Issue Polymers for Energy Applications)

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10 pages, 3820 KiB

Open AccessArticle

Facile Route for Bio-Phenol Siloxane Synthesis via Heterogeneous Catalytic Method and its Autonomic Antibacterial Property

by Xiaoyan Pang¹, Xin Ge¹, Jianye Ji¹, Weijie Liang²

, Xunjun Chen¹

and Jianfang Ge^1,*

¹ College of Chemistry and Chemical Engineering, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China

² School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, China

Polymers 2018, 10(10), 1151; https://doi.org/10.3390/polym10101151 - 16 Oct 2018

Cited by 8 | Viewed by 3859

Abstract

Eugenol, used as bio-phenol, was designed to replace the hydrogen atom of hydrogenterminated siloxane by hydrosilylation reaction under the presence of alumina-supported platinum catalyst (Pt-Al₂O₃), silica-supported platinum catalyst (Pt-SiO₂) and carbon nanotube-supported platinum catalyst (Pt-CNT), respectively. The [...] Read more.

Eugenol, used as bio-phenol, was designed to replace the hydrogen atom of hydrogenterminated siloxane by hydrosilylation reaction under the presence of alumina-supported platinum catalyst (Pt-Al₂O₃), silica-supported platinum catalyst (Pt-SiO₂) and carbon nanotube-supported platinum catalyst (Pt-CNT), respectively. The catalytic activities of these three platinum catalysts were measured by nuclear magnetic resonance hydrogen spectrometer (¹H NMR). The properties of bio-phenol siloxane were characterized by Fourier transform infrared spectrometer (FT–IR), UV-visible spectrophotometer (UV) and thermogravimeter (TGA), and its antibacterial property against Escherichia coli was also studied. The results showed that the catalytic activity of the catalyst Pt-CNT was preferable. When the catalyst concentration was 100 ppm, the reaction temperature was 80 °C and reaction time was 6 h, the reactant conversion rate reached 97%. After modification with bio-phenol, the thermal stability of the obtained bio-phenol siloxane was improved. For bio-phenol siloxane, when the ratio of weight loss reached 98%, the pyrolysis temperature was raised to 663 °C which was 60 °C higher than hydrogenterminated siloxane. Meanwhile, its autonomic antibacterial property against Escherichia coli was improved significantly. Full article

(This article belongs to the Collection Silicon-Containing Polymeric Materials)

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13 pages, 2117 KiB

Open AccessArticle

A Phenolphthalein-Dummy Template Molecularly Imprinted Polymer for Highly Selective Extraction and Clean-Up of Bisphenol A in Complex Biological, Environmental and Food Samples

by Jiajia Yang^1,†

, Yun Li^2,†, Chaonan Huang^2,3, Yanna Jiao⁴ and Jiping Chen^2,*

¹ College of Materials Science and Engineering, Hebei University of Engineering, 199 South Guangming Street, Handan 056038, China

² CAS Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China

³ University of Chinese Academy of Sciences, Beijing 100049, China

⁴ Inspection and Quarantine Technology Centre, Hunan Entry-Exit Inspection and Quarantine Bureau, Changsha 410004, China

^† These authors contributed equally to this work.

Polymers 2018, 10(10), 1150; https://doi.org/10.3390/polym10101150 - 15 Oct 2018

Cited by 35 | Viewed by 4953

Abstract

A molecularly imprinted polymer (MIP) for highly selective solid-phase extraction (SPE) of bisphenol A (BPA) was prepared using phenolphthalein (PP) as the novel dummy template by bulk polymerization. A particle diameter distribution of 40–60 μm, a specific surface area of 359.8 m² [...] Read more.

A molecularly imprinted polymer (MIP) for highly selective solid-phase extraction (SPE) of bisphenol A (BPA) was prepared using phenolphthalein (PP) as the novel dummy template by bulk polymerization. A particle diameter distribution of 40–60 μm, a specific surface area of 359.8 m²·g⁻¹, and a total pore volume of 0.730 cm³·g⁻¹ for the prepared PP-imprinted polymer (PPMIP) were obtained. Good selectivity and specific adsorption capacity for BPA of the prepared PPMIP were also demonstrated by the chromatographic evaluation and sorption experiments. The PPMIP as a SPE sorbent was evaluated for the selective extraction and clean-up of BPA from complex biological, environmental, and food samples. Meanwhile, an accurate and sensitive analytical method based on the PPMIP-SPE purification procedure coupled with high performance liquid chromatography-diode array detector (HPLC-DAD) detection has been successfully developed for the rapid determination of BPA from these samples, with detection limits of 1.3 ng·mL⁻¹ for bovine serum and milk, 2.6 ng·mL⁻¹ for human urine and edible oil, 5.2 ng·mL⁻¹ for soybean sauce, and 1.3 ng·g⁻¹ for sediment. The BPA recoveries at two different spiking levels were in the range of 82.1–106.9%, with relative standard deviation (RSD) values below 7.7%. Full article

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18 pages, 2418 KiB

Open AccessArticle

Novel Kinetic Models of Xylan Dissolution and Degradation during Ethanol Based Auto-Catalyzed Organosolv Pretreatment of Bamboo

by Jing Liu¹, Zhenggang Gong¹, Guangxu Yang¹, Lihui Chen¹, Liulian Huang¹, Yonghui Zhou^2,* and Xiaolin Luo^1,*

¹ College of Materials Engineering, Fujian Agriculture and Forestry University, Fuzhou 350002, China

² Department of Civil and Environmental Engineering, Brunel University London, Kingston Lane, Uxbridge UB8 3PH, UK

Polymers 2018, 10(10), 1149; https://doi.org/10.3390/polym10101149 - 15 Oct 2018

Cited by 12 | Viewed by 3999

Abstract

Due to the invalidity of traditional models, pretreatment conditions dependent parameter of susceptible dissolution degree of xylan (d_X) was introduced into the kinetic models. After the introduction of d_X, the dissolution of xylan, and the formation of xylo-oligosaccharides and [...] Read more.

Due to the invalidity of traditional models, pretreatment conditions dependent parameter of susceptible dissolution degree of xylan (d_X) was introduced into the kinetic models. After the introduction of d_X, the dissolution of xylan, and the formation of xylo-oligosaccharides and xylose during ethanol based auto-catalyzed organosolv (EACO) pretreatments of bamboo were well predicted by the pseudo first-order kinetic models (R² > 97%). The parameter of d_X was verified to be a variable dependent of EACO pretreatment conditions (such as solvent content in pretreatment liquor and pretreatment temperature). Based on the established kinetic models of xylan dissolution, the dissolution of glucan and the formation of degradation products (furfural and acetic acid) could also be empirically modeled (R² > 97%). In addition, the relationship between xylan and lignin removal can provide guidance for alleviating the depositions of lignin or pseudo-lignin. The parameter of d_X derived novel kinetic models can not only be used to reveal the multi-step reaction mechanisms of xylan, but also control the final removal of main components in bamboo during EACO pretreatments, indicating scientific and practical significance for governing the biorefinery of woody biomass. Full article

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Polymers, Volume 10, Issue 10 (October 2018) – 133 articles

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