EVA Matrix Research Articles

Flexible poly (ethylene-co-vinyl acetate)/copper oxide nanocomposites: A promising avenue for energy storage applications

The use of metal oxide nanoparticles in polymeric materials to improve optical properties, dielectric constant, mechanical strength, and electrical conductivity has generated significant interest in fabricating flexible optoelectronic and energy storage devices. Herein, copper oxide (CuO) nanoparticle-reinforced poly (ethylene-co-vinyl acetate) (EVA) nanocomposites were prepared using a solvent-free two roll mill mixing method. Fourier transform infrared (FTIR) analysis reveals the distinct absorption peaks of CuO in the EVA matrix. The addition of CuO nanoparticles improved the crystallinity of EVA, as confirmed by X-ray diffraction (XRD). The addition of CuO to EVA led to an increase in the refractive index and a decrease in bandgap energy, as well as a broadening and intensification of UV–visible absorption, indicating strong interactions between CuO nanoparticles and the EVA matrix. Field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) revealed a homogeneous dispersion of CuO nanoparticles throughout the EVA matrix. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) demonstrated that the incorporation of CuO nanoparticles into EVA significantly enhanced its thermal properties. The electrical characteristics studies showed that the AC conductivity and dielectric constant of EVA increased significantly with increasing temperatures and CuO nanoparticle loading levels. EVA containing 5 wt% CuO exhibited the highest conductivity and the lowest activation energy. CuO nanoparticle reinforcement significantly enhanced the tensile, tear, and impact strength of EVA while reducing elongation at break up to a particular concentration. The nanocomposites containing 5 wt% CuO exhibited the highest tensile, tear resistance, and impact strengths, outperforming virgin EVA by 85 %, 103.6 %, and 83.16 %, respectively. These findings suggest that EVA/CuO nanocomposites are promising candidates for flexible dielectric materials.

Flame Retardancy and Properties of Thermoplastic Vulcanizates from Dibutyl Phosphate-Bound Natural Rubber/Ethylene Vinyl Acetate Blends

ABSTRACT Dibutyl phosphate-bound epoxidized natural rubber (DBNR) was synthesized from natural rubber latex via epoxidation using a 20 mol% intermediate. Successful formation of epoxidized natural rubber (ENR-20) and DBNR was confirmed by FTIR analysis. Thermoplastic vulcanizates (TPVs) were prepared by dynamically vulcanizing blends of DBNR and ethylene-vinyl acetate copolymer (EVA). The 50/50 DBNR/EVA TPV exhibited higher mixing torque during vulcanization, indicative of increased shear stress, shear rate, and tensile strength. This was attributed to finer dispersion of vulcanized rubber domains in the EVA matrix, leading to enhanced interfacial adhesion. Elongation at break decreased with increasing EVA content, while hardness and tension set increased, suggesting reduced elasticity at higher EVA proportions. Under heat aging, TPVs experienced degradation of mechanical properties and increased tension set, indicating loss of elastomeric behavior. Significantly, DBNR exhibited a low burning rate of 0.2 mm/s, imparting inherent flame retardancy. The burning rate of DBNR/EVA TPVs decreased with increasing DBNR content, demonstrating improved flame retardancy. Overall, DBNR/EVA TPVs exhibited favorable mechanical properties and flame retardancy, making them suitable for applications requiring flame-retardant elastomeric materials.

Effect of cage and ladder configuration of polyphenyl silsesquioxane on mechanical performance and flame retardancy of ethylene–vinyl acetate composites

Improving the flame retardancy of ethylene–vinyl acetate copolymer (EVA) while maintaining its mechanical properties is critical for EVA applications. Polyhedral oligomeric silsesquioxane (POSS) can be a molecular structure designed to improve the flame retardancy of polymers while minimizing damage to the mechanical properties of polymers. In this study, two types of POSS with the same chemical structure but different spatial structures, which are named cage octaphenyl POSS (OPS) and ladder polyphenyl silsesquioxane (PPSQ) are prepared. The miscibility and dispersibility of these two types of POSS in the EVA matrix and their effects on mechanical properties, dielectric properties, and fire behaviors are also investigated. Compared to OPS-based EVA composite, the PPSQ with ladder structure has good miscibility and dispersion state in EVA matrix, obtaining better toughness, dielectric properties, and flame retardancy under cone calorimeter test. However, OPS-based EVA composite obtains superior flame retardancy than that of PPSQ-based EVA composite under small fire test (limiting oxygen index and UL-94 vertical burning tests). The mechanism of these two separate flame-retardant performances under various scenarios is explored. A novel flame-retardant model is proposed, as well as a new understanding of the role of POSS in EVA combustion. This study provides powerful guidance for obtaining EVA composites with excellent flame retardant and mechanical properties.

A Macroscopic Interpretation of the Correlation between Electrical Percolation and Mechanical Properties of Poly-(Ethylene Vinyl Acetate)/Zn Composites.

Elastic composites were prepared using a procedure involving hot plates and zinc powder that was directly dispersed into an EVA matrix. The correlation between the zinc content and the conductive properties of the material was studied via impedance spectroscopy, the thermal properties of the material were studied via differential calorimetry and the mechanical properties of the composites were studied via tensile strength curves, representing an important advancement in the characterization of this type of composite material. The composites' tensile strength and elongation at break decrease with the addition of filler since zinc particles act as stress-concentrating centres, while the composites' hardness and Young's modulus increase because of an increase in the stiffness of the material. The AC perturbation across the EVA/Zn composites was characterized using an RC parallel equivalent circuit that allowed us to easily measure their resistivity (ρp) and permittivity (εp). The dependence of these electrical magnitudes on the zinc content is correlated with their mechanical properties across the characteristic time constant τp = ρp·εp of this equivalent circuit. The dependence of the mechanical and electrical magnitudes on the zinc content is consistent with the formation of percolation clusters. The addition of graphite particles increases their potential performance. Three possible mechanisms for the electrical transport of the ac-perturbation across the EVA/Zn composites have been identified. Chemical corrosion in acid media causes the loss of zinc surface particles, but their bulk physical properties practically remain constant.

Non-covalently functionalized black phosphorene to efficient flame retardant EVA with improved mechanical properties

The development of flame-retardant polymer materials play a vital role in reducing fire hazards and protecting both lives and property. Black phosphorus (BP) is an extremely promising flame retardant since its synergistic flame retardancy with different modifiers. Nevertheless, the issue of unven dispersion within the polymer matrix has severely restricted its practical applications. Herein, BP nanosheets functionalized with ionic liquid (IL-BP) were prepared and then compounding with EVA to improve the mechanical and the flame-retardant properties of EVA matrix. The results demonstrated enhanced compatibility of IL-BP nanosheets within the EVA matrix, leading to the 1.5 %IL-BP/EVA composite displayed a 25 % and 9.6 % increase in tensile strength and elongation at break, respectively. Remarkably, the flammability test results demonstrated that the 1.5 %IL-BP/EVA sample featured a significant decrease of 18.1 % and 21.5 % in total heat release (THR) and peak heat release rate (PHRR), respectively. Meanwhile, the composite also achieved a V-0 rating in UL-94 test and demonstrated superior resistance to melt dripping. The flame-retardant mechanisms of IL-BP/EVA composites in both gas phase and condensed phase were studied. This work provides a promising strategy to design synergetic flame retardants that simultaneously enhanced the fire safety and mechanical properties of EVA.

Dicyanopyridine derivatives: One-pot preparation, ACQ-to-AIE transformation, light-conversion quality and photostability

Low cost and strong fluorescence emission are two important guarantees for luminogens used as light conversion agents. By one-pot multicomponent approach and inexpensive starting materials, three dicyanopyridine (DP) derivatives named as DCP (2-amino-6-methoxy-4-phenylpyridine-3,5-dicarbonitrile), DCO (2-amino-6-methoxy-4-(4-methoxyphenyl) pyridine-3,5-dicarbonitrile) and DCC (2-amino-4-(4-cyanophenyl)-6-methoxypyridine-3,5-dicarbonitrile) were designed and synthesized.Meanwhile, the ACQ-to-AIE transformation was successfully realized by altering substituent groups rather than traditional rotor–stator theory. Based on crystal analysis and theoretical calculations, the ACQ-to-AIE transformation is attributed to the tunable stacking modes and intermolecular weak interactions. Owing to matched fluorescence emission, low lost, high yield, and AIE activity, DCC is used as light conversion agents and doped in EVA matrix. The light conversion quality confirms that DCC can not only convert ultraviolet light, but also significantly improve the transmittance of 25 %/40 % EVA, whose photosynthetic photon flux density at 400–500 nm and 600–700 nm increased to 30.67 %/30.21 % and 25.37 %/37.82 % of the blank film, respectively. After 20 h of UV irradiation (365 nm, 40 W), the fluorescence intensities of DCC films can maintain 92 % of the initial values, indicating good photostability in the doping films. This work not only provides an excellent and low-cost light conversion agent, but also has important significance for ACQ-to-AIE transformation of luminogens.

Investigation on the physicochemical properties of poly (ethylene-co-vinyl acetate)/mesoporous silica nanocomposites: Effects of content and surface functionalization

In this study, poly (ethylene-co-vinyl acetate)/mesoporous silica EVA/SBA-15 nanocomposites, containing 0.5, 1.5, and 2.5 wt% of unfunctionalized and functionalized SBA-15 were prepared by melt blending in an internal mixer. Mesoporous silica was synthesized through the sol-gel method and modified by hexadecyltrimethoxysilane (HDTMS). Several characterizations were performed; including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical properties, dynamic mechanical analysis (DMA), and dielectric study to characterize the physicochemical properties of elaborated materials. The results revealed the successful synthesis and functionalization of mesoporous silica, as confirmed by the FTIR and SEM. The crystallinity of the nanocomposites decreased and the elastic modulus increased with the incorporation of the mesoporous silica. Measurement of tensile properties shows that the tensile strength of the nanocomposite content of 1.5 wt% F-SBA-15 is 17.2% is higher as compared to pure EVA. DMA analysis validates the improvement in mechanical properties of the EVA/SBA-15 samples. SEM images displayed well-dispersed F-SBA-15 nanoparticles and enhanced interfacial adhesion between the phases. TGA indicates the enhancement of the thermal stability of nanocomposites as compared with the pure EVA matrix. The surface functionalization presented an approach to preparing nanocomposites with enhanced thermal stability and a low dielectric constant.

Synergistic effect of modified anhydrous magnesium carbonate and hexaphenoxycyclotriphosphazene on flame retardancy of ethylene-vinyl acetate copolymer.

Ethylene-vinyl acetate copolymer (EVA) is widely used in various applications; however, its flammability limits its application in wire and cable industries. In this study, 3-methacryloxypropyltrimethoxysilane (KH570) was successfully grafted onto the surface of anhydrous magnesium carbonate (AMC) by alkali activation treatment. The KH570 modified AMC (AMC@KH570) was then introduced into the EVA matrix along with hexaphenoxycyclotriphosphazene (HPCTP) to assess their effects on the flame retardancy and mechanical properties of EVA composites. The results illustrate a significant synergistic effect in enhancing the flame retardancy of EVA composites by using AMC@KH570 and HPCTP, and the limiting oxygen index (LOI) and vertical burning test (UL-94) of EVA filled with 5 wt% HPCTP and 45 wt% AMC@KH570 (mAMC/H-45-5) reached 27.6% and V-0, respectively. The flame retardant mechanism was investigated by thermogravimetric/infrared (TG-IR) spectroscopy and residual carbon composition analysis. The results show that the thermal decomposition of AMC@KH570 and HPCTP consists of gas dilution, free radical quenching, and catalytic carbonization. Furthermore, KH570 works as a bridge to improve the compatibility of AMC and EVA matrix, which offsets the mechanical loss of EVA to some extent. The present research provides a new path to modify AMC and fabricate EVA composites with excellent flame retardant properties.

Rheological analysis of peroxide radical-induced modification of microalgae-based polymer composite

In this study, the effect of peroxide radical-induced chemical modification on microalgae (Chlorella sp. HS2)/ polymer (ethylene-vinyl acetate, EVA) composite is investigated based on rheological and mechanical measurements, morphological observations, FT-IR, and gel tests. Generation of macromolecular clusters throughout the composite according to gelation of HS2/EVA, reflecting in linear viscoelasticity of composite. Rheological analysis characterizes the gelation kinetics of crosslinking or grafting reaction of dicumyl peroxide (DCP) radicals to HS2 and EVA matrix by identifying the gel time (tg) and gelation fractal dimension (df). DCP radicals require tg of 440 s for EVA while it delays to 1200s for HS2/EVA. The fractal dimension (df) of EVA/HS2/DCP is 2.37, decreasing from 2.42 for EVA/DCP, meaning that the reaction between radical and HS2 retard the growth of macromolecular clusters throughout the composite by gelation. The addition of HS2 significantly affects the gelation kinetics of radicals, delaying the gelation as well as its growth. Correspondingly, when DCP radicals have sufficient reaction time (> 1200 s) to induce grafting, both the tensile strength and modulus of EVA/HS2/DCP composite are significantly improved, meaning that the grafting reaction of DCP radicals between HS2 and EVA coherently improves the interfacial interaction and mechanical tensile properties. This study suggests a radical reaction as a method to improve the mechanical performance of a microalgae-based polymer composite by inducing interfacial bonding between microalgae and polymer. It will increase the potential of microalgae as a promising biomass filler for the fabrication of eco-friendly polymer composite.

High-efficient flame retardant ethylene-vinyl acetate composites by incorporating monomolecular IFR and its pyrolysis behavior

Highly efficient flame retardant and excellent mechanical performance was critical for the application of ethylene vinyl acetate copolymer (EVA) composites. Herein, a monomolecular intumescent flame retardant poly(piperazine methylphosphonic acid pentaerythritol ester) defined as PPMPPE was incorporated into the EVA matrix, and the flame retardancy, mechanical performance of EVA composites were investigated. When 21 wt% PPMPPE was incorporated, the limiting oxygen index (LOI) of 1.6 mm EVA/PPMPPE composites was increased from 18.2 % for neat EVA to 27.5 %, and it achieved UL-94 V-0 grate during vertical burning tests. Meanwhile, the cone calorimetry tests indicated that the peak value of heat release rate and total heat release of FR-EVA composites were obviously reduced by 41.1 % and 27 % compared to neat EVA. The analysis of flame-retarded mechanism for EVA/PPMPPE indicated that PPMPPE facilitated the decomposition of EVA and formed an expanding char layer, and it possessed barrier effect in condensed phase. In addition, the PPMPPE could exert free radicals quenching effect and in gaseous phase. Therefore, the PPMPPE endowed the EVA matrix with good flame-retardant efficiency. Meanwhile, the mechanical performance of EVA/21 wt% PPMPPE composites was well maintained, and its tensile strength and elongation at break decreased by 21.9 % and 14.4 %, respectively. This research work provided a feasibility approach for producing EVA composites with excellent flame-retardant and mechanical performance.

Nonisothermal crystallization kinetic behavior of pure ethylene-Vinyl acetate copolymers and ethylene-Vinyl acetate copolymer/nitrile rubber thermoplastic vulcanizate

Thermoplastic vulcanizate (TPV) made from the ethylene-vinyl acetate copolymer (EVA)/nitrile rubber (NBR) blend was fabricated using the dynamic vulcanization method. Differential scanning calorimetry (DSC) was utilized to analyze the nonisothermal crystallization kinetics of both pure EVA and EVA/NBR TPV. The nonisothermal crystallization mechanism was evaluated using the Avrami method modified by Jeziorny, the Ozawa method and the Mo method. The results demonstrate that the nonisothermal crystallization of both pure EVA and EVA/NBR TPV can be adequately described by the Avrami method modified by Jeziorny and the Mo method, while the Ozawa method is not applicable. By elevating the cooling rate, there was a reduction in the crystallization temperature and t1/2 for both pure EVA and EVA/NBR TPV, while the degree of crystallization increased. At the same cooling rate, the crystallization temperature of the EVA/NBR TPV was found to be higher than that of the pure EVA, suggesting that the presence of NBR facilitated the nucleation of the EVA matrix within the EVA/NBR TPV. Moreover, a steric hindrance effect existed in the NBR phase of EVA/NBR TPV at the same cooling rate, resulting in a larger t1/2 compared to that of the pure EVA, indicating hindered crystal growth.

Constructing Fe2O3 particles uniformly grown on graphene oxide as additives for ethylene vinyl acetate copolymer thermal stability, thermal conductivity and anti‐static performance enhancement

AbstractEthylene‐vinyl acetate copolymer (EVA) has been widely used for packaging materials for decades. However, EVA was highly restricted due to the poor thermal stability and anti‐static performance. For enhancing thermal stability and anti‐static performances, a large number of additives were added to EVA, which seriously prejudice the processability and mechanical properties of the polymer. To address this problem, N‐doped reduced graphene oxide@Fe2O3 (RGF) was constructed as a heat and electronic conduction actor in EVA matrix in this work. As as‐prepared RGF composites shown, Fe2O3 particles well dispersed on the surface of RGO sheets, forming a point‐plane three‐dimensional structure. Therefore, the thermal conductivity and volume resistivity of the EVA composites reached 0.58 W/mK and 1.7 × 1010 ohm∙cm at 1.0 wt.% of RGF addition, which shows 284% folds increasement and 7 orders of magnitude decrement than neat EVA. Moreover, the storage modulus and thermal stability of EVA composites at 180°C were also improved. In sum, all those enhancements were attributed to the Fe2O3 particles well dispersed on RGO sheets, and amino groups from RGF provided mass of hydrogen bonds with EVA chains which provide more sites and path for heat and electronic conduction. In this work, RGF composites and its synthesis strategy show potential promising in the highly effective thermal and electrical exchange materials.

Construction of a multi-scale microporous structure in EVA matrix toward passive cooling roofs

Global warming has brought tremendous attention to developing passive cooling materials. Due to the high performance of solar reflection, heat insulation and infrared radiation, constructing porous structures in polymeric matrix has emerged as a promising technique to fabricate passive cooling materials. This work herein demonstrated a multi-scale microporous structure in ethylene-vinyl acetate copolymer (EVA) matrix via chemical foaming and chemical etching. It was found that pore size and shape depended upon the addition and removal of inorganic particles CaCO3. In chemical foaming system, by reflecting 76.9% NIR light and transmitting heat through the atmosphere in the long-wave infrared, the cellular EVA/CaCO3 composites (40% porosity, 13.84 μm avg. pore size)-covered device exhibited a final temperature of 31.6 °C after solar simulation for 1 h with the intensity of ∼594 W/m2. To further enhance the cooling effect, the CaCO3 particles in cellular EVA/CaCO3 composites were removed via 20% HCl solution etching to minimize the pore structure. Higher heat insulation with thermal conductivity of 0.148 Wm−1K−1 accompanied by 65.5% NIR irradiance and 0.84 thermal emittance made the excellent cooling property with a final temperature of 30.6 °C (lower than all EVA/CaCO3 composites-covered device) realize after chemical etching. Furthermore, the prepared porous EVA materials possessed good tensile properties and are of potential value in the field of passively cooled roofs.

Fabrication of Novel Polymer Composites from Leather Waste Fibers and Recycled Poly(Ethylene-Vinyl-Acetate) for Value-Added Products

This investigation was focused on evaluating the utilization of Leather-waste, i.e., “Leather Shavings”, to develop “Poly(ethylene-vinyl-acetate)” (EVA) based “polymer matrix composites”. Composites with the highest ratio of 1:1 were developed using a rolling-mill, which was then subjected to hot-press molding for value-added applications, notably in the “floor-covering”, “structural”, “footwear”, and “transportation domain”. The specimens were examined for evaluating the “physico-mechanical characteristics” such as, “Compressive and Tensile, strength, Abrasion-resistance, Density, tear-resistance, hardness, adhesion-strength, compression, and resilience, damping, and water absorption” as per standard advanced testing techniques. Raising the leather-fiber fraction in the composites culminated in considerable enhancement in “physico-mechanical characteristics” including “modulus”, and a decline in “tensile-strain” at “fracture-breakage”. The thermo-analytic methods, viz. TGA and DSC studies have evidenced that substantial enhancement of thermo-stability (up to 211.1–213.81 °C) has been observed in the newly developed PMCs. Additionally, the DSC study showed that solid leather fibers lose water at an endothermic transition temperature of around 100 °C, are thermo-stable at around 211 degrees centigrade, and begin to degrade at 332.56-degree centigrade for neat recycled EVA samples and begin to degrade collagen at 318.47-degree centigrade for “leather shavings/recycled EVA polymer composite samples”, respectively. Additionally, the “glass transition temperature” (Tg) of the manufactured composites was determined to be between −16 and 30 °C. Furthermore, SEM and EDAX analysis have been used to investigate the morphological characteristics of the developed composites. Micrograph outcomes have confirmed the excellent “uniformity, compatibility, stability and better-bonding” of leather-fibers within the base matrix. Additionally, the “Attenuated-total-reflection” (ATR-FTIR) was carried out to test the “physicochemical chemical-bonding”, “molecular-structure”, and “functional-groups” of the “base matrix”, and its “composites” further affirm the “recycled EVA matrix” contained additives remain within the polymeric-matrix. An “X-ray diffraction study” was also conducted to identify the “chemical-constituents” or “phases” involved throughout the “crystal-structures” of the base matrix and PMCs. Additionally, AFM analysis has also been utilized to explore the “interfacial adhesion properties” of mechanically tested specimens of fabricated polymeric composite surfaces, their “surface topography mapping”, and “phase-imaging analysis” of polymer composites that have leather-shavings fibers.

The effect of inorganic particles on the breakdown strength and mechanical properties ofEVA‐based composites

AbstractEthylene‐vinyl acetate (EVA) copolymer was melt‐blended with different inorganic particles, such as alumina trihydrate (ATH), montmorillonite‐based organoclay (CLO15A) and organophilic silica (R202) to produce (nano)composites with outstanding electrical breakdown strength. The composites loaded with different amount of particles were characterized by dielectric, rheological, morphological and mechanical properties. The addition of the particles resulted in an increase of electrical breakdown strength, whose results depend on the nature and amount of filler. The addition of 1%–5% of ATH resulted in an increase of 50% of this property. Similar results were observed for the composites loaded with 7% of CLO15A and R202. All composites displayed low values of dielectric constant and dielectric loss, which is interesting for insulator applications. The presence of the filler did not exert great influence on the rheological properties of the composites, thus keeping the good processability of EVA matrix. Finally, the composites containing the organoclay presented the best mechanical response.

3D-Printed EVA Devices for Antiviral Delivery and Herpes Virus Control in Genital Infection.

Herpes viruses are widespread in the human population and can cause many different diseases. Genital herpes is common and can increase the risk of HIV infection and neonatal herpes. Acyclovir is the most used drug for herpes treatment; however, it presents some disadvantages due to its poor oral bioavailability. In this study, some ethylene vinyl acetate devices with different acyclovir amounts (0, 10, and 20 wt.%) were manufactured by fused filament fabrication in two different geometries, an intrauterine device, and an intravaginal ring. Thermal analyses suggested that the crystallinity of EVA decreased up to 8% for the sample loaded with 20 wt.% of acyclovir. DSC, SEM, and FTIR analyses confirmed that the drug was successfully incorporated into the EVA matrix. Moreover, the drug release tests suggested a burst release during the first 24 h followed by a slower release rate sustained up to 80 days. Biological assays showed the biocompatibility of the EVA/ACV device, as well as a 99% reduction in vitro replication of HSV-1. Finally, the EVA presented a suitable performance for 3D printing manufacturing that can contribute to developing personalized solutions for long-term herpes treatment.

Dispersion of unfractionated CO2-derived protein-rich microalgae (Chlorella sp. HS2) for ecofriendly polymer composite fabrication

This study investigates unfractionated protein-rich microalgae (Chlorella sp. HS2) (HS2) as a new CO2-derived biomass filler resource with which to develop an ecofriendly microalgae-based polymer composite. Unfractionated HS2 is mixed with poly(ethylene-vinyl acetate) (EVA) over wide range of concentrations ranging from 10 to 70 wt%. The dispersion of HS2 is analyzed based on morphological, rheological and mechanical measurements. Protein-rich HS2 has hydrophilic-hydrophobic surface due to the existence of chemical functional groups (CO, N-H) caused by high protein content (51% protein), predicting compatibility with EVA with polar functional (CO). Due to this compatibility, with 10–30 wt% of HS2, the composite shows a homogeneous micrometer-scale dispersion of HS2 in the EVA matrix (avg. diameter (Davg) ~ 7 µm). The composite maintains the dispersion of the HS2 without significant coalescence or network formation up to 50 wt% of HS2 (Davg ~ 10 µm). Correspondingly, the storage modulus (G′ at 0.1 rad/s) of the composite increases linearly until the HS2 content reaches 40 wt%, after which it increases exponentially with an increase in the HS2 content. An EVA composite with 10–20 wt% HS2 shows increased ductility (from 1700% to 2000% elongation at break with 10 wt% HS2) without a decrease in the tensile strength due to the homogeneous dispersion. Even with higher concentration of HS2, the composite maintains its ductile behavior and retains its synergistic effect with EVA (~ 500% elongation at break with 70 wt% HS2). The compatibility of HS2 with EVA and their hydrophilic surface delay agglomeration or percolation formation of HS2 cells in a polymer. This study suggests that protein-rich HS2 is a promising biomass filler that disperses in a polymer to the micrometer scale without additional chemical treatment.

Morphological and ferroelectric characterizations of porous poly (ethylene‐co‐vinyl acetate) copolymer films prepared by coextrusion and pressing methods for pseudo‐piezoelectric effect

A piezoelectric porous film is designed to convert daily human activities and acoustic vibrations into usable electrical energy. Copolymers are one of the materials used for harvesting this wasted energy by creating the pseudo piezoelectric effect. One of the important steps to obtain a good piezoelectric response is to produce a homogeneous dispersion of the cells/voids with a good distribution. Several production methods were used. In this work, the effect of porosity-processing on the morphology as well as piezoelectric properties of Porous Poly (ethylene-co-vinyl acetate) Copolymer were studied. Two different foam-processing methods, coextrusion process and multilayer hot-pressing method were used. The morphologic characterization was obtained using SEM. Coextrusion process gives a good dispersion of the cells/voids withinthe EVA matrix rather than multilayer hot-pressing, irregular cells/voids were obtained with a random distribution. The 160–320 μm film thicknesses ranging elaborated by coextrusion using 1% and 2% chemical foaming agent lead to a porous thin films with a porosity of 37% and 65% respectively. The porosity percentage effect on our EVA thin films produced by coextrusion process on piezoelectric coefficient d33 and remanent polarization Pr were studied too. The results showed that d33 and Pr increases with increasing the porosity of our films reaching 4.7 pC/N and 2.21 C/cm2 respectively for a 65% EVA film.

Carbon nanomaterials as additives to ethylene vinyl acetate copolymer foams for sport footwear applications

AbstractEthylene vinyl acetate (EVA) copolymer foams with addition of 1.0, 2.5, and 5 wt% of carbon nanomaterials (graphene, graphene oxide, carbon nanotubes, and multiwalled carbon nanotubes) were fabricated. Properties of these foams were compared with reference sample (no additives) and samples containing carbon black. The following properties of these samples were examined: density, compressive stress (50% compression), impact behavior, thermal conductivity, and hydrophobicity. The morphology was studied using scanning electron microscopy. The samples were additionally characterized using thermal gravimetric analysis and differential scanning calorimetry. Increasing weight percentage of carbon‐based additives led to foam structure with lower porosity and higher density. Samples with a higher degree of cross‐linking were less dense (~10%) as compared to the reference sample and also displayed better mechanical and thermal properties. Increasing weight percentages of additives led to higher compressive strength and higher energy absorption. Samples with 5 wt% of additives and increased quantity of cross‐linking agent exhibited great mechanical properties. Despite their lower density, these samples had higher values of compressive stress, 10%–15% higher than those of the reference sample, and higher energy return properties. All samples follow the trend of increasing values of compressive strength with the increase in density, for some samples, this correlation has quasi linear character. The obtained results show that EVA foams with the addition of carbon black, graphene, carbon nanotubes, and multiwalled carbon nanotubes have properties desirable in high‐performance materials for sport footwear soles. Multiwalled carbon nanotube additives could be incorporated at low weight percentages and low degree of crosslinking into EVA matrix to achieve lower density and enhanced energy repulsion and cushioning effects.

Reduced graphene oxide/PdNi/poly(ethylene-co-vinyl acetate) nanocomposites for electromagnetic interference shielding

Ternary nanocomposites comprising of a conducting carbon structure, a magnetic component, and a polymer matrix are of current scientific interest in electromagnetic interference (EMI) shielding applications. In the present work, we explore the utility of reduced graphene oxide (RGO)/PdNi/poly(ethylene-co-vinyl acetate) (EVA) ternary nanocomposites in such applications. The nanocomposites with 0–5 wt % RGO/PdNi filler content in EVA matrices are prepared by a combination of modified Hummer's, reflux, and solution mixing methods. Microscopic imaging, and diffraction and spectroscopic measurements assure the correct size, crystallinity and phases, and desirable magnetic nature of the nanocomposites. The abilities of EM wave reflection and absorption in 2–8 GHz (S-band + C-band) range are found to increase incrementally with increasing filler content. Nanocomposites with 1 and 5 wt % filler content exhibit ∼ 12–30 dB shielding efficiencies (SE's), with maxima in S- and C-band, respectively. An analysis of the electrical conductivity, dielectric permittivity and magnetic permeability suggests that there is a scope to enhance the SE further by varying the Pd:Ni and RGO:alloy ratios. Mechanical and thermal characterisations reveal that the nanocomposites desirably have both the mechanical strength and the thermal stability better than the EVA matrix. Thus, the RGO/PdNi/EVA nanocomposites are found to have a potential in EMI shielding applications.