Influence of Matrix Polarity on the Properties of Ethylene Vinyl Acetate–Carbon Nanofiller Nanocomposites

A series of ethylene vinyl acetate (EVA) nanocomposites using four kinds of EVA with 40, 50, 60, and 70 wt% vinyl acetate (VA) contents and three different carbon-based nanofillers—expanded graphite (EG), multi-walled carbon nanotube (MWCNT), and carbon nanofiber (CNF) have been prepared via solution blending. The influence of the matrix polarity and the nature of nanofillers on the morphology and properties of EVA nanocomposites have been investigated. It is observed that the sample with lowest vinyl acetate content exhibits highest mechanical properties. However, the enhancement in mechanical properties with the incorporation of various nanofillers is the highest for EVA with high VA content. This trend has been followed in both dynamic mechanical properties and thermal conductivity of the nanocomposites. EVA copolymer undergoes a transition from partial to complete amorphousness between 40 and 50 wt% VA content, and this changes the dispersion of the nanofillers. The high VA-containing polymers show more affinity toward fillers due to the large free volume available and allow easy dispersion of nanofillers in the amorphous rubbery phase, as confirmed from the morphological studies. The thermal stability of the nanocomposites is also influenced by the type of nanofiller.     

Vinyl acetate content and electron beam irradiation directed alteration of structure,morphology, and associated properties of EVA/EPDM blends

A series of ethylene vinyl acetate/ethylene–propylene diene elastomer (EVA/EPDM) blends with four types of EVAs with various vinyl acetate (VA) content, are prepared without and with crosslinker, trimethylol propane triacrylate (TMPTA). These are irradiated by electron beam (EB). As the VA content increases, the gel content, i.e., degree of crosslinking of EVA/EPDM blends, is increased. With increase in VA content, the modulus and tensile strength are decreased but elongation at break is increased due to increase in amorphousness. On EB irradiation, modulus and tensile strengths are increased but at the cost of elongation at break. Crystallinities of all blends are decreased with increase in VA and EB crosslinking. The thermal stability of EVA/EPDM blend is decreased with increase in VA content but increased after EB irradiation. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) show that with increase in VA content the miscibility of two polymers keeps on increasing, which even become more after EB irradiation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43468.     

Influence of Polymer Type and Structure on Polymer Modified Asphalt Concrete Mix

Two low‐density polyethylene (LDPE) resins and two ethyl vinyl acetate (EVA) polymers were used to modify asphalt binder, and then mixed with asphalt concrete according to Marshall Method of mix design (ASTM D 1559). Effect of weight average molecular weight (M_w) of LDPE and vinyl acetate (VA) content of EVA was studied by performing Marshall Stability, moisture susceptibility (AASHTO T 283‐89), resilient modulus (M_R) and permanent deformation (rutting) tests. EVA with low VA content showed lower stability loss in Marshall Stability test and improved resistance in moisture susceptibility test in comparison to hot mix asphalt concrete mix (HMA) and other polymer modified asphalt concrete mixes (PMAMs). Higher M_R and better rutting resistance were observed for PMAMs than that of HMA. This elastic behaviour of modified asphalt correlates very well with the M_R and rutting resistance properties of PMAM.     

Toughening effects of ethylene–vinyl acetate copolymers with different vinyl acetate content and viscosity on nylon 1010 blends

Nylon 1010 blends with ethylene–vinyl acetate copolymer (EVA) and maleated ethylene–vinyl acetate (EVA‐g‐MAH) were prepared through melt blending. The vinyl acetate (VA) content and viscosity of EVA significantly affected the notched impact strength of nylon/EVA/EVA‐g‐MAH (80/15/5) blends. The nylon/EVA/EVA‐g‐MAH blends with high notched impact strength (over 60 kJ/m²) were obtained when the VA content in EVA ranged from 28 to 60 wt%. The effect of VA content on the notched impact strength of blends was related to the glass transition temperature for EVA with high VA content and crystallinity for EVA with low VA content. For nylon blends with EVA with the same VA content, low viscosity of EVA led to high notched impact strength. Fracture morphology of nylon/EVA/EVA‐g‐MAH (80/15/5) blends showed that blends with ductile fracture behavior usually had large matrix plastic deformation, which was the main energy dissipation mechanism. A relationship between the notched impact strength and the morphology of nylon/EVA/EVA‐g‐MAH (80/15/5) blends was well correlated by the interparticle distance model. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Multtphase Materials with Lignin. III. Polyblends with Ethylene-Vinyl Acetate Copolymers

Abstract

Organosolv lignin (OSL) from red oak, and its corresponding hydroxypropyl lignin (HPL) derivative, were blended in the melt with polyethylene and with ethylene-vinyl acetate (EVA) copolymer, and injection molded. Lignin (derivative) content and vinyl acetate (VA) content both served as process variables. All mixtures produced immiscible blends, both by scanning electron microscopy and dynamic mechanical analysis. However, the compatibility of the two polymers increased with VA content. Both lignin products proved to be effective modulus builders, but. HPI, was more effective than OSL at VA contents above 20%. Modulus increased roughly in accordance with the rule of mixing. Inferior tensile strength properties were observed with the EVA copolymer if VA content was below 10%, and superior characteristics were noted in materials containing more than 25% VA and between 5 and 20% HPL.     

Influence of the vinyl acetate content and the tackifier nature on the rheological,thermal, and adhesion properties of EVA adhesives

Three ethylene vinyl acetate (EVA) copolymers with different vinyl acetate (VA) contents (28-40 wt%) were mixed with rosin ester and polyterpene resin tackifiers in a 1 : 1 (weight/weight) ratio. The rheological and thermal properties of the tackifiers were determined and the use of rheological measurements as a precise way to measure the softening point of the tackifiers is proposed. The glass transition temperature of the tackifiers was obtained from the second heating run, after the thermal history of the tackifiers was removed. The addition of the rosin ester to EVA produced a compatible mixture, whereas for the terpene resin a less compatible mixture was obtained. The increase in the VAamount decreased the crystallinity of EVAand both the storage and the loss moduli also decreased, but the peel strength and the immediate adhesion were increased. The immediate adhesion of EVA/tackifier blends was affected by both the compatibility and the rheological properties of the blends. In fact, a relationship between the mechanical storage modulus (E^t′) - obtained from DMTA experiments - of the adhesives and the immediate adhesion to thin rubber substrates was obtained. The adhesives containing the T tackifier showed higher moduli than those containing the G tackifier, and therefore higher peel strength values were obtained. An increase in the VA content increased the flexibility of the adhesives and thus a decrease in peel strength was obtained.     

Gamma radiation aging of EVA/EPDM blends: Effect of vinyl acetate (VA) content and radiation dose on the alteration in mechanical,thermal, and morphological behavior

A series of ethylene vinyl acetate (EVA)/ethylene‐propylene diene elastomer (EPDM) blends (50/50 ratio) with four types of EVAs were prepared using brabender type batch mixer followed by compression molding. All compression‐molded samples were exposed to gamma radiation at 500, 1000, and 1500 kGy doses and were subjected to mechanical, compression set, thermal and morphological test. The % retention in tensile strength, elongation, and hardness were found higher for higher vinyl acetate (VA) containing radiation aged EVA/EPDM blends. The compression set value was decreased with increase of VA content. The thermal degradation kinetics of high VA containing irradiated blend (EVA40/EPDM) (EVA40 is 40%VA containing EVA) was found slower than those of lower VA containing blend (EVA18/EPDM). The surface morphology for EVA18/EPDM sample was transformed into more irregular one with more cracks and fragmented segments by aging at 1500 kGy dose while surface for EVA40/EPDM sample was found comparatively smooth, fine, and continuous with very few cracks and fragmented parts at similar dose. Thus, from the measured properties and morphology, it was revealed that the degree of degradation of blends kept on decreasing with increase in VA content. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46216.     

Kinetic features of the nonisothermal oxidative degradation of ethylene vinyl acetate copolymers

Thermogravimetric analysis was used for a comparative investigation of the thermooxidative decomposition of ethylene vinyl acetate (EVA) copolymers with different vinyl acetate (VA) group contents. There were two stages of mass loss in this process. It was revealed that the apparent activation energies were correlated with the content of VA groups in the EVA copolymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1958–1961, 2004     

Effect of vinyl acetate content on the photovoltaic-encapsulation performance of ethylene vinyl acetate under accelerated ultra-violet aging

The vinyl acetate (VA) content in ethylene vinyl acetate (EVA) can significantly affect its performance as an encapsulant in photovoltaic modules under field conditions. EVA films of varying VA content (18, 24, 33, and 40%) have been prepared using twin screw extruder with the necessary additives and subsequently cured at 150 °C. All the EVA films have been subjected to UV radiation at a wavelength of 340 nm for 1000 and 2000 h to simulate accelerated field aging. The effects of accelerated aging on the gel content, mechanical properties, transmittance, Fourier transform infra-red (FTIR) spectra, thermal stability, degree of crystallinity, and yellowness have been studied. The observations made in this study of UV aging up to 2000 h suggests that the optimum range of VA content in EVA should be between 18 and 33% by weight. VA content beyond 40% degrades almost all properties needed for an encapsulate material after aging of only 2000 h. VA content of around 18% is the most stable under UV aging conditions but has a slightly lower value of transmittance for the unaged sample although the difference in transmittance between different specimens decreases with UV aging. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48268.     

Influence of the polarity of ethylene–vinyl acetate copolymers on the morphology and mechanical properties of their uncompatibilised blends with polystyrene

Rubber‐toughened polystyrene has been extensively studied and is a well‐established technology. However, the use of thermoplastic elastomers to toughen polystyrene (PS) is new and has the potential for further investigations. In the present study, three EVAs (ethylene–vinyl acetate copolymers) with identical melt flow indices (MFIs), of ～2.5 dgmin^?1, but different vinyl acetate (VA) contents, of 9.3 wt% (EVA760), 18.0 wt% (EVA460) and 28.0 wt% (EVA265), were melt blended with PS at 180 °C, and various ASTM test pieces were injection moulded at 200 °C. The polarity of the dispersed phase (ie EVA), has a significant effect on the mechanical properties of the blends. Both mechanical and rheological studies reveal that the uncompatibilised PS/EVA265 blends exhibit some degree of compatibility when the amount of EVA265 is lower than 30 wt%. These results indicate that EVA265 with the highest VA content is the most effective impact modifier for PS. The results clearly show that increasing the VA content in EVA increases the polarity of the dispersed phase, approaching that of the matrix (ie PS) and subsequently improving the compatibility between the two phases in terms of interfacial adhesion. © 2002 Society of Chemical Industry     

Corona discharge treatment of EVAs with different vinyl acetate contents

Four ethylene vinyl acetate (EVA) co-polymers with different vinyl acetate (VA) contents (9–20 wt%) were treated with corona discharge to improve their adhesion to polychloroprene (PCP) adhesive. The thermal properties of the EVAs decreased as their VA content increased, caused by a decrease in crystallinity. The elastic and viscous moduli of the EVAs decreased and the temperature and modulus at the cross-over between these moduli decreased with increasing VA content. Contact-angle measurements (water), infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to analyse the surface modifications produced in the corona-discharge-treated EVAs. The corona discharge treatment produced improved wettability and created roughness and oxygen moieties on the EVA surfaces. The higher the VA content and the higher the corona energy, the more significant modifications were produced on the EVA surface. The VA content also affected the T-peel strength values of treated EVA/polychloroprene + isocyanate adhesive joints, as the values increased with increasing VA content. Mixed failure modes (interfacial + cohesive failure in the EVA) were obtained in the adhesive joints produced with corona discharge treated EVAs containing more than 9 wt% VA. The accelerated ageing of the joints did not affect the T-peel strength values, but the locus of failure in most cases became fully cohesive in the EVA, likely due to the higher extent of curing of the adhesive.     

Ultrasonic disassociation of EVA random copolymer in dilute solutions

Ultrasonic disassociation of the ethylene–vinyl acetate (EVA) random copolymer in 1,2‐dichloroethane (DCE), cyclohexane (CYH), and their solvent mixtures was investigated using viscometry and dynamic laser light scattering (DLLS). It was found that the disassociation of the EVA aggregates in solutions increases with increasing the time and intensity of ultrasonic shearing and approaches invariant finally. This phenomenon is especially marked for the EVA copolymer with low vinyl acetate (VA) content in the polar solvent of DCE at higher concentration and lower temperature. This is attributed to disassociation of the ethylene segment of the EVA random copolymer in dilute solutions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2798–2802, 2001     

Improved adhesion of EVAs with different vinyl acetate contents treated with sulphuric acid

Four ethylene vinyl acetate copolymers (EVAs) containing 9, 12, 18 and 20 wt% vinyl acetate (VA) were treated with concentrated sulphuric acid to improve their adhesion to polychloroprene (PCP) adhesive. The tensile strength and Young's modulus of EVAs decreased as the VA content increased, due to the reduction in crystallinity of the polyethylene blocks in the copolymer. The modifications produced in the EVAs by treatment with sulphuric acid were followed using contact angle measurements (water, 25 °C), ATR-IR spectroscopy and scanning electron microscopy (SEM). Adhesive-bond strength was obtained by T-peel tests on treated EVA/polychloroprene adhesive joints. The vinyl acetate content in the EVA affected the extent, but not the nature, of the surface modification produced by treatment with sulphuric acid. The treatment produced both sulfonation and oxidation on the EVA surfaces. The higher the vinyl acetate content in the EVA, the more significant the modifications produced. Increased T-peel strengths of EVA/polychloroprene adhesive + 5 wt% polyisocyanate joints were obtained and a mixed failure (adhesion failure + cohesive failure in the adhesive) was produced. It was found that, to be effective, the treatment of EVAs must be carried out with 96 wt% sulphuric acid.     

Effect of hot air aging on properties of EPDM/SmBO3/EVA and EPDM/ATO/EVA composites

Ethylene–propylene–diene rubber (EPDM)/samarium borate (SmBO₃)/ethylene‐vinyl acetate (EVA) copolymer and EPDM/antimony‐doped tin oxide (ATO)/EVA composites are aged at 150°C for different intervals. Surface modification is used to improve filler to matrix interphase. The main aim is to investigate the effect of filler type and vinyl acetate (VA) content in EVA on stability of EPDM composites. It is found that acidic ATO particles can lower pH level of EPDM composites and then promote the degradation of acetic acid during aging. Moreover, when VA content exceeds 14 wt %, the instable VA content causes more acetic acids escape during aging. With the increasing of aging time, EPDM/SmBO₃ control and EPDM/SmBO₃/EVA composites tend to become darker while EPDM/ATO and EPDM/ATO/EVA composites would become yellow. And the color change is correlated well with the variation of carbonyl index. The chemical crosslink points prevent crystals in EVA from melting at aging temperature (150°C), and the variation of crosslink density influences the crystallinity during aging. The tendency of tensile strength is well consistent with that of swelling ratios, and electric properties are correlated with increased polar groups and crystallinity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Melt grafting of poly(ethylene‐vinyl acetate) copolymer with maleic anhydride

Poly(ethylene‐vinyl acetate) (EVA) copolymer was melt grafted with maleic anhydride (MAH) in a twin screw extruder in the presence of peroxide. It is confirmed that MAH has been melt grafted on the backbone of EVA by FTIR using the method of hydrolysis. The NMR analysis suggests that the grafting reaction occurs on the tertiary carbon of main chain of EVA other than the methyl moiety of vinyl acetate (VA) group. The incorporation of VA groups onto the matrix shows a competitive effect on the grafting. The existence of VA groups promotes the extent of MAH graft onto EVA; nevertheless, it also weakens the crystallizability of main chain. When the content of peroxide initiator is 0.1 wt % based on the polymer matrix, the grafting degree increases with increasing the concentration of monomer. When the peroxide content is higher than 0.1 wt %, side reactions such as crosslinking or disproportionation will be introduced into this system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 841–846, 2006     

Preparation and characterization of ethylene‐vinyl acetate nanocomposites: enhanced flame retardant

Ethylene‐vinyl acetate (EVA) nanocomposites with enhanced flame retardance were prepared by the sol–gel process in the melt. Two EVAs with different vinyl acetate (VA) contents and aluminium isopropoxide were used as organic and inorganic phases. The nanocomposites were prepared in a batch mixer under constant processing conditions and were analysed by several characterization techniques. Aluminium isopropoxide presented low activation energy, which allows the synthesis of the nanoparticles without a post step treatment. The reaction mechanism is proposed. Nanocomposites with smaller and well dispersed metal nanoparticles were produced with an EVA with higher VA content. EVA nanocomposites achieve the requirements for 94 V‐0 classification. © 2013 Society of Chemical Industry     

Use of pyrolyzed oil shale as filler in poly(ethylene‐co‐vinyl acetate) with different vinyl acetate contents

Pyrolyzed oil shale (POS) obtained from the pyrolysis of bituminous rock was used as filler in poly(ethylene‐co‐vinyl acetate) (EVA). The effects of the VA content of EVA and the particle size of POS on the mechanical properties were investigated. The composites were prepared in a rotor mixer at 180°C with a concentration of POS of up to 30 wt %. The stress–strain plots of the compression‐molded composites are similar to the EVA (18% VA content) behavior for low concentrations (1–5 wt %) of POS with a particle size lower than 270 mesh. It was observed that decreasing the POS particle size and increasing the VA content of EVA produced better compatibility between the polymer and filler. The mechanical properties, differential scanning calorimetry, and dynamic mechanical analysis also demonstrated the compatibility between EVA and POS under the increase of the VA content in the EVA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1544–1555, 2002; DOI 10.1002/app.10494     

电子束辐照交联PVC/EVA共混物的研究

以丙烯酸酯类多官能团不饱和单体为交联敏化剂，采用电子束对聚氯乙烯(PVC)与乙烯—酸酸乙烯共聚物(EVA)的共混物进行辐照交联。研究了VA质量分数、交联敏化剂种类及用量、辐照剂量、EVA用量对共混物凝胶质量分数、力学性能以及热延伸性能的影响。结果表明：EVA共聚物能促进PVC的辐照交联，增加共混体系的凝胶质量分数，改善其力学及热延伸性能；EVA共聚物中VA质量分数增大，共混体系的凝胶质量分数增大，力学及热延伸性能改善更明显。     

EVA-PVA binder system for polymer derived mullite made by material extrusion based additive manufacturing

Low processing temperature of preceramic polymers (PCPs) makes them attractive for material extrusion based additive manufacturing (MEX-AM), earlier called fused deposition modeling (FDM). Fabrication of bulk polymer derived ceramics is challenging due to gas evolution during crosslinking leading to pores and cracks in final product. Mixture of ethylene vinyl acetate (EVA) and polyvinyl alcohol (PVA) was successfully used to generate open porosity before crosslinking step. For 3D printing, a pellet extruder was used and a PVA binder content of 50 vol% was essential for succcessful solvent debinding process in water. The effect of PVA content and different EVA grades on printability and debinding behavior was studied. EVA with a lower melt flow index (MFI) showed better compatibility with PVA additive in terms of mixing and printing. EVA with higher vinyl acetate content seems to be more favorable for later thermal debinding processes because of its higher gas permeability.     

Viscoelastic and adhesion properties of hot-melts made with blends of ethylene-co-n-butyl acrylate (EBA) and ethylene-co-vinyl acetate (EVA) copolymers

Several hot-melts (HMAs) were prepared by using blends of ethylene-co-n-butyl acrylate (EBA) and ethylene-co-vinyl acetate (EVA) copolymers - EBA/EVA. HMAs were prepared with mixtures of EVA copolymers with 18 (EVA18) and 27 (EVA27) wt% vinyl acetate contents and EBA copolymer with 27 wt% n-butyl acrylate, polyterpene resin and mixture of microcrystalline and Fischer-Tropsch waxes. HMAs made with EBA/EVA blends showed lower viscosities and reduced shear thinning than the ones made with EBA or EVA due to differences in compatibility, but both the set time and the open time were not affected as they depended mainly on the wax nature and amount. The increase of the vinyl acetate (VA) content in EVA copolymer reduced the crystallinity of the EBA/EVA blends. Even EBA copolymer was more compatible with EVA27 than with EVA18 (the α- and β-transitions shown in DMTA plots were closer) and the compatibility did not vary with the EBA content in the blends. The addition of polyterpene resin and the mixture of waxes decreased the compatibility of the EBA/EVA blends, the higher compatibility was observed for the HMAs made with only one copolymer. The tack of the HMAs depended on their EBA/EVA contents, EBA/EVA27 HMAs showed broader temperature interval with higher tack, while the tack of EBA/EVA18 HMAs blend decreased and the temperature interval with tack was shortened and shifted to lower temperatures. Adhesion to polypropylene film was improved in HMAs made with 75 wt% EBA/25 wt% EVA18 and 50–75 wt% EBA/50-25 wt% EVA27. The adhesion to aluminum film of EBA or EVA hot melts was improved only in the joints made with EBA/EVA 27 HMAs, more noticeably when they contained higher EBA content.