Dear Colleagues,

A polymer composite is a material system composed of two or more macro/micro/nano constituents of different shapes, properties or chemical compositions, at least one of which is a polymer. The design of multifunctional and tunable polymer-based composite materials is an emerging area of research with a wide range of applications in the aerospace industry, the automotive industry, the home appliance industry, the sporting goods industry, as well as the booming biomedical device/biomaterial industry. Polymer composite materials can be classified according to matrix materials (synthetic polymers, biopolymers, inorganic and organic fillers, etc.) and reinforcement geometries (particles, fibers, gels, films, layers, foams, mixtures, etc.). In addition, the polymer composite can be a multiphase material with a significant proportion of each phase or a blended material system with a continuous phase that greatly enhances the physical, chemical or biological properties of the material matrix. By optimizing molecular interfaces between different components, polymer-based composite materials can also encompass a range of functions, such as thermal stability at different temperatures, elasticity to support diverse structures, electrical sensitivity in variable sensors, and optical properties for advanced fiberglass technology. In this Special Issue, we will highlight the latest developments in these advanced polymer composite materials, including their design, synthesis, characterization, manufacturing, and modeling, as well as their various applications. Both research and review articles are welcome.

Dr. Xiao Hu
Prof. Dr. Francesco Trotta
Guest Editors

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Research

Jump to: Review

23 pages, 4233 KiB  

Open AccessArticle

The Impact of Composition and Morphology on Ionic Conductivity of Silk/Cellulose Bio-Composites Fabricated from Ionic Liquid and Varying Percentages of Coagulation Agents

by Bailey Blessing, Cory Trout, Abneris Morales, Karleena Rybacki, Stacy A. Love, Guillaume Lamoureux, Sean M. O’Malley, Xiao Hu and David Salas-de la Cruz

Int. J. Mol. Sci. 2020, 21(13), 4695; https://doi.org/10.3390/ijms21134695 - 30 Jun 2020

Cited by 18 | Viewed by 2650

Abstract

Blended biocomposites created from the electrostatic and hydrophobic interactions between polysaccharides and structural proteins exhibit useful and unique properties. However, engineering these biopolymers into applicable forms is challenging due to the coupling of the material’s physicochemical properties to its morphology, and the undertaking [...] Read more.

Blended biocomposites created from the electrostatic and hydrophobic interactions between polysaccharides and structural proteins exhibit useful and unique properties. However, engineering these biopolymers into applicable forms is challenging due to the coupling of the material’s physicochemical properties to its morphology, and the undertaking that comes with controlling this. In this particular study, numerous properties of the Bombyx mori silk and microcrystalline cellulose biocomposites blended using ionic liquid and regenerated with various coagulation agents were investigated. Specifically, the relationship between the composition of polysaccharide-protein bio-electrolyte membranes and the resulting morphology and ionic conductivity is explored using numerous characterization techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray scattering, atomic force microscopy (AFM) based nanoindentation, and dielectric relaxation spectroscopy (DRS). The results revealed that when silk is the dominating component in the biocomposite, the ionic conductivity is higher, which also correlates with higher β-sheet content. However, when cellulose becomes the dominating component in the biocomposite, this relationship is not observed; instead, cellulose semicrystallinity and mechanical properties dominate the ionic conduction. Full article

(This article belongs to the Special Issue Advanced Polymer Composite Materials)

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15 pages, 4902 KiB  

Open AccessArticle

A Mild Method for Preparation of Highly Selective Magnetic Biochar Microspheres

by Tao Zhao, Rongqi Chen and Junping Wang

Int. J. Mol. Sci. 2020, 21(11), 3752; https://doi.org/10.3390/ijms21113752 - 26 May 2020

Cited by 11 | Viewed by 2633

Abstract

We report the use of biochar and Fe₃O₄ nanoparticles as co-stabilizers for oil-in-water (o/w) Pickering emulsion. The emulsion is subsequently used to prepare magnetic tetracycline-imprinted biochar composite microspheres (MMIPMs) with good uniformity and high selectivity. The MMIPMs were characterized by [...] Read more.

We report the use of biochar and Fe₃O₄ nanoparticles as co-stabilizers for oil-in-water (o/w) Pickering emulsion. The emulsion is subsequently used to prepare magnetic tetracycline-imprinted biochar composite microspheres (MMIPMs) with good uniformity and high selectivity. The MMIPMs were characterized by scanning electron microscopy (SEM), Brunner-Emmet-Teller (BET) measurements, Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and thermogravimetry analysis (TGA). The adsorption properties of tetracycline to the MMIPMs were investigated using different adsorption experiments including adsorption kinetic experiment, equilibrium binding experiment, selectivity evaluation and competitive adsorption tests. The theoretical maximum adsorption capacity of the MMIPMs (15.45 mg g⁻¹) was greater than that of the raw biochar (2.10 mg g⁻¹) and non-imprinted biochar composite microspheres (3.39 mg g⁻¹) for tetracycline. Further, the MMIPMs were used as adsorbent for magnetic solid phase extraction (SPE) for the extraction of tetracycline present in drinking water, milk, fish and chicken samples. Under optimal conditions, the results showed good recovery yield ranging from 88.41% to 106.29% with a relative standard deviation (RSD) ranging from 0.35% to 6.83%, respectively. Full article

(This article belongs to the Special Issue Advanced Polymer Composite Materials)

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18 pages, 3406 KiB  

Open AccessArticle

Enhancement of Biomimetic Enzymatic Mineralization of Gellan Gum Polysaccharide Hydrogels by Plant-Derived Gallotannins

by Timothy E. L. Douglas, Julia K. Keppler, Marta Vandrovcová, Martin Plencner, Jana Beranová, Michelle Feuereisen, Bogdan V. Parakhonskiy, Yulia Svenskaya, Vsevolod Atkin, Anna Ivanova, Patrick Ricquier, Lieve Balcaen, Frank Vanhaecke, Andreas Schieber, Lucie Bačáková and Andre G. Skirtach

Int. J. Mol. Sci. 2020, 21(7), 2315; https://doi.org/10.3390/ijms21072315 - 27 Mar 2020

Cited by 11 | Viewed by 3397

Abstract

Mineralization of hydrogel biomaterials with calcium phosphate (CaP) is considered advantageous for bone regeneration. Mineralization can be both induced by the enzyme alkaline phosphatase (ALP) and promoted by calcium-binding biomolecules, such as plant-derived polyphenols. In this study, ALP-loaded gellan gum (GG) hydrogels were [...] Read more.

Mineralization of hydrogel biomaterials with calcium phosphate (CaP) is considered advantageous for bone regeneration. Mineralization can be both induced by the enzyme alkaline phosphatase (ALP) and promoted by calcium-binding biomolecules, such as plant-derived polyphenols. In this study, ALP-loaded gellan gum (GG) hydrogels were enriched with gallotannins, a subclass of polyphenols. Five preparations were compared, namely three tannic acids of differing molecular weight (MW), pentagalloyl glucose (PGG), and a gallotannin-rich extract from mango kernel (Mangifera indica L.). Certain gallotannin preparations promoted mineralization to a greater degree than others. The various gallotannin preparations bound differently to ALP and influenced the size of aggregates of ALP, which may be related to ability to promote mineralization. Human osteoblast-like Saos-2 cells grew in eluate from mineralized hydrogels. Gallotannin incorporation impeded cell growth on hydrogels and did not impart antibacterial activity. In conclusion, gallotannin incorporation aided mineralization but reduced cytocompatibility. Full article

(This article belongs to the Special Issue Advanced Polymer Composite Materials)

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18 pages, 7726 KiB  

Open AccessArticle

Solvent Dependence of the Rheological Properties in Hydrogel Magnetorheological Plastomer

by Norhiwani Mohd Hapipi, Saiful Amri Mazlan, U. Ubaidillah, Siti Aishah Abdul Aziz, Muntaz Hana Ahmad Khairi, Nur Azmah Nordin and Nurhazimah Nazmi

Int. J. Mol. Sci. 2020, 21(5), 1793; https://doi.org/10.3390/ijms21051793 - 05 Mar 2020

Cited by 10 | Viewed by 2863

Abstract

Chemically crosslinked hydrogel magnetorheological (MR) plastomer (MRP) embedded with carbonyl iron particles (CIPs) exhibits excellent magnetic performance (MR effect) in the presence of external stimuli especially magnetic field. However, oxidation and desiccation in hydrogel MRP due to a large amount of water content [...] Read more.

Chemically crosslinked hydrogel magnetorheological (MR) plastomer (MRP) embedded with carbonyl iron particles (CIPs) exhibits excellent magnetic performance (MR effect) in the presence of external stimuli especially magnetic field. However, oxidation and desiccation in hydrogel MRP due to a large amount of water content as a dispersing phase would limit its usage for long-term applications, especially in industrial engineering. In this study, different solvents such as dimethyl sulfoxide (DMSO) are also used to prepare polyvinyl alcohol (PVA) hydrogel MRP. Thus, to understand the dynamic viscoelastic properties of hydrogel MRP, three different samples with different solvents: water, DMSO, and their binary mixtures (DMSO/water) were prepared and systematically carried out using the oscillatory shear. The outcomes demonstrate that the PVA hydrogel MRP prepared from precursor gel with water shows the highest MR effect of 15,544% among the PVA hydrogel MRPs. However, the samples exhibit less stability and tend to oxidise after a month. Meanwhile, the samples with binary mixtures (DMSO/water) show an acceptable MR effect of 11,024% with good stability and no CIPs oxidation. Otherwise, the sample with DMSO has the lowest MR effect of 7049% and less stable compared to the binary solvent samples. This confirms that the utilisation of DMSO as a new solvent affects the rheological properties and stability of the samples. Full article

(This article belongs to the Special Issue Advanced Polymer Composite Materials)

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19 pages, 13138 KiB  

Open AccessArticle

Light Weight, Easy Formable and Non-Toxic Polymer-Based Composites for Hard X-ray Shielding: A Theoretical and Experimental Study

by Mattia Lopresti, Gabriele Alberto, Simone Cantamessa, Giorgio Cantino, Eleonora Conterosito, Luca Palin and Marco Milanesio

Int. J. Mol. Sci. 2020, 21(3), 833; https://doi.org/10.3390/ijms21030833 - 28 Jan 2020

Cited by 16 | Viewed by 4657

Abstract

Composite lightweight materials for X-ray shielding applications were studied and developed with the goal of replacing traditional screens made of lead and steel, with innovative materials with similar shielding properties, but lighter, more easily formed and workable, with lower impact on the environment [...] Read more.

Composite lightweight materials for X-ray shielding applications were studied and developed with the goal of replacing traditional screens made of lead and steel, with innovative materials with similar shielding properties, but lighter, more easily formed and workable, with lower impact on the environment and reduced toxicity for human health. New epoxy based composites additivated with barium sulfate and bismuth oxide were designed through simulations performed with softwares based on Geant4. Then, they were prepared and characterized using different techniques starting from digital radiography in order to test the radiopacity of the composites, in comparison with traditional materials. The lower environmental impact and toxicity of these innovative screens were quantified by Life Cycle Assessment (LCA) calculation based on the ecoinvent database, within the openLCA framework. Optimized mixtures are (i) 20% epoxy/60% bismuth oxide/20% barite, which guarantees the best performance in X-ray shielding, largely overcoming steel, but higher in costs and a weight reduction of circa 60%; (ii) 20% epoxy/40% bismuth oxide/40% barite which has slightly lower performances in shielding, but it is lighter and cheaper than the first one and (iii) the 20% epoxy/20% bismuth oxide/60% barite which is the cheapest material, still maintaining the X-ray shielding of steel. Depending on cost/efficiency request of the specific application (industrial radiography, aerospace, medical analysis), the final user can choose among the proposed solutions. Full article

(This article belongs to the Special Issue Advanced Polymer Composite Materials)

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14 pages, 8410 KiB  

Open AccessArticle

Reflectance According to Cell Size, Foaming Ratio and Refractive Index of Microcellular Foamed Amorphous Polymer

by Sung Woon Cha, Soo-hyun Cho, Joo Seong Sohn, Youngjae Ryu and Jeonghun Ahn

Int. J. Mol. Sci. 2019, 20(23), 6068; https://doi.org/10.3390/ijms20236068 - 02 Dec 2019

Cited by 12 | Viewed by 3953

Abstract

Microcellular foamed plastic has a cell size of approximately 0.1 to 10 microns inside a foamed polymer and a cell density in the range of 10⁹ to 10¹⁵ cells/cm³. Typically, the formation of numerous uniform cells inside a polymer [...] Read more.

Microcellular foamed plastic has a cell size of approximately 0.1 to 10 microns inside a foamed polymer and a cell density in the range of 10⁹ to 10¹⁵ cells/cm³. Typically, the formation of numerous uniform cells inside a polymer can be effectively used for various purposes, such as lightweight materials, insulation and sound absorbing materials. However, it has recently been reported that these dense cell structures, which are induced through microcellular foaming, can affect the light passing through the medium, which affects the haze and permeability and causes the diffused reflection of light to achieve high diffuse reflectivity. In this study, the effects of cell size, foaming ratio and refractive index on the optical performance were investigated by applying the microcellular foaming process to three types of amorphous polymer materials. Thus, this study experimentally confirmed that the advantages of porous materials can be implemented as optical properties by providing a high specific surface area as a small and uniform cell formed by inducing a high foaming ratio through a microcellular foaming process. Full article

(This article belongs to the Special Issue Advanced Polymer Composite Materials)

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12 pages, 1838 KiB  

Open AccessArticle

Effect of Long-Term Brushing on Deflection, Maximum Load, and Wear of Stainless Steel Wires and Conventional and Spot Bonded Fiber-Reinforced Composites

by Andrea Scribante, Pekka Vallittu, Lippo V. J. Lassila, Annalisa Viola, Paola Tessera, Paola Gandini and Maria Francesca Sfondrini

Int. J. Mol. Sci. 2019, 20(23), 6043; https://doi.org/10.3390/ijms20236043 - 30 Nov 2019

Cited by 15 | Viewed by 2411

Abstract

Fiber-reinforced composite (FRC) retainers are an aesthetic alternative to conventional Stainless Steel splints. They are generally used with a full bonded technique, but some studies demonstrated that they could be managed with a spot bonding technique to significantly decrease their rigidity. In order [...] Read more.

Fiber-reinforced composite (FRC) retainers are an aesthetic alternative to conventional Stainless Steel splints. They are generally used with a full bonded technique, but some studies demonstrated that they could be managed with a spot bonding technique to significantly decrease their rigidity. In order to propose this FRC spot bonding technique for clinical use, the aim of this study was to evaluate mechanical properties and surface wear of fibers left uncovered. Tests were made by simulating tooth brushing, comparing FRC spot bonding technique splints with stainless steel and FRC traditional technique splints. Specimens were tested both at 0.1 mm of deflection and at maximum load, showing higher values of rigidity for the FRC full bonded technique. After tooth brushing, no significant reduction in values at 0.1 mm deflection was reported, while we found a similar reduction in these values for the Stainless Steel and FRC spot bonding technique at maximum load, and no significant variation for the FRC full bonded technique. SEM images after tooth brushing showed wear for FRC fibers left uncovered, while no relevant wear signs in metal and conventional FRC fibers were noticed. Results showed that FRC spot bonding technique has advantages in mechanical properties when compared to the FRC traditional full bonding technique, also after tooth brushing. However, the surface wear after tooth brushing in the FRC spot bonding technique is considerable and other tests must be performed before promoting this technique for routine clinical use. Full article

(This article belongs to the Special Issue Advanced Polymer Composite Materials)

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15 pages, 3166 KiB  

Open AccessArticle

Designing Microparticle-Impregnated Polyelectrolyte Composite: The Combination of ATRP, Fast Azidation, and Click Reaction Using a Single-Catalyst, Single-Pot Strategy

by Ranjit De, Minhyuk Jung and Hohjai Lee

Int. J. Mol. Sci. 2019, 20(22), 5582; https://doi.org/10.3390/ijms20225582 - 08 Nov 2019

Cited by 6 | Viewed by 3117

Abstract

Polystyrene microparticles were covalently impregnated into the networks of functional polyelectrolyte chains designed via a tandem run of three reactions: (i) synthesis of water-soluble polyelectrolyte, (ii) fast azidation and (iii) a ‘click’ reaction, using the single-catalyst, single-pot strategy at room temperature in mild [...] Read more.

Polystyrene microparticles were covalently impregnated into the networks of functional polyelectrolyte chains designed via a tandem run of three reactions: (i) synthesis of water-soluble polyelectrolyte, (ii) fast azidation and (iii) a ‘click’ reaction, using the single-catalyst, single-pot strategy at room temperature in mild aqueous media. The model polyelectrolyte sodium polystyrenesulfonate (NaPSS) was synthesized via the well-controlled atom transfer radical polymerization (ATRP) whose halogen living-end was transformed to azide and subsequently coupled with an alkyne carboxylic acid through a ‘click’ reaction using the same ATRP catalyst, throughout. Halogen to azide transformation was fast and followed the radical pathway, which was explained through a plausible mechanism. Finally, the success of microparticle impregnation into the NaPSS network was evaluated through Kaiser assay and imaging. This versatile synthetic procedure, having a reduced number of discrete reaction steps and eliminated intermediate work-ups, has established a fast and simple pathway to design functional polymers required to fabricate stable polymer-particle composites where the particles are impregnated covalently and controllably. Full article

(This article belongs to the Special Issue Advanced Polymer Composite Materials)

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17 pages, 3106 KiB  

Open AccessArticle

Fabrication of Surfactant-Dispersed HiPco Single-Walled Carbon Nanotube-Based Alginate Hydrogel Composites as Cellular Products

by Fabian Alvarez-Primo, Shweta Anil Kumar, Felicia S. Manciu and Binata Joddar

Int. J. Mol. Sci. 2019, 20(19), 4802; https://doi.org/10.3390/ijms20194802 - 27 Sep 2019

Cited by 14 | Viewed by 3635

Abstract

In this study, we designed, synthesized, and characterized ultrahigh purity single-walled carbon nanotube (SWCNT)-alginate hydrogel composites. Among the parameters of importance in the formation of an alginate-based hydrogel composite with single-walled carbon nanotubes, are their varying degrees of purity, their particulate agglomeration and [...] Read more.

In this study, we designed, synthesized, and characterized ultrahigh purity single-walled carbon nanotube (SWCNT)-alginate hydrogel composites. Among the parameters of importance in the formation of an alginate-based hydrogel composite with single-walled carbon nanotubes, are their varying degrees of purity, their particulate agglomeration and their dose-dependent correlation to cell viability, all of which have an impact on the resultant composite’s efficiency and effectiveness towards cell-therapy. To promote their homogenous dispersion by preventing agglomeration of the SWCNT, three different surfactants-sodium dodecyl sulfate (SDS-anionic), cetyltrimethylammonium bromide (CTAB-cationic), and Pluronic F108 (nonionic)-were utilized. After mixing of the SWCNT-surfactant with alginate, the mixtures were cross-linked using divalent calcium ions and characterized using Raman spectroscopy. Rheometric analysis showed an increase in complex viscosity, loss, and storage moduli of the SWCNT composite gels in comparison with pure alginate gels. Scanning electron microscopy revealed the presence of a well-distributed porous structure, and all SWCNT-gel composites depicted enhanced electrical conductivity with respect to alginate gels. To characterize their biocompatibility, cardiomyocytes were cultured atop these SWCNT-gels. Results comprehensively implied that Pluronic F108 was most efficient in preventing agglomeration of the SWCNTs in the alginate matrix, leading to a stable scaffold formation without posing any toxicity to the cells. Full article

(This article belongs to the Special Issue Advanced Polymer Composite Materials)

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Review

Jump to: Research

23 pages, 4180 KiB  

Open AccessReview

Recent Advances in Electrospun Sustainable Composites for Biomedical, Environmental, Energy, and Packaging Applications

by Hao Liu, Christopher R. Gough, Qianqian Deng, Zhenggui Gu, Fang Wang and Xiao Hu

Int. J. Mol. Sci. 2020, 21(11), 4019; https://doi.org/10.3390/ijms21114019 - 04 Jun 2020

Cited by 55 | Viewed by 5321

Abstract

Electrospinning has gained constant enthusiasm and wide interest as a novel sustainable material processing technique due to its ease of operation and wide adaptability for fabricating eco-friendly fibers on a nanoscale. In addition, the device working parameters, spinning solution properties, and the environmental [...] Read more.

Electrospinning has gained constant enthusiasm and wide interest as a novel sustainable material processing technique due to its ease of operation and wide adaptability for fabricating eco-friendly fibers on a nanoscale. In addition, the device working parameters, spinning solution properties, and the environmental factors can have a significant effect on the fibers’ morphology during electrospinning. This review summarizes the newly developed principles and influence factors for electrospinning technology in the past five years, including these factors’ interactions with the electrospinning mechanism as well as its most recent applications of electrospun natural or sustainable composite materials in biology, environmental protection, energy, and food packaging materials. Full article

(This article belongs to the Special Issue Advanced Polymer Composite Materials)

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