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.     

Development of new thermoplastic elastomers from blends of polyethylene and ethylene–vinyl acetate copolymer by electron‐beam technology

Electron beam‐initiated crosslinking of films prepared from a blend of low‐density polyethylene (LDPE) and ethylene–vinyl acetate (EVA) containing 45% vinyl acetate, with ditrimethylol propane tetraacrylate (DTMPTA), was carried out over a range of radiation doses (20–500 kGy), concentration of DTMPTA (1–5 parts by weight), and blend compositions. The gel fraction of the films increases with increase in the irradiation dose, DTMPTA level, and EVA content of the blends. The mechanical and dynamic mechanical properties of the films are also changed with the above variables. Reprocessibility studies revealed that the blends irradiated at 50 kGy and below are thermoplastic elastomers with a low permanent set. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1877–1889, 2001     

Studies on dynamic and static crosslinking of ethylene vinyl acetate and ethylene propylene diene tercopolymer blends

The effect of blend ratio on the crosslinking characteristics of ethylene vinyl acetate and ethylene propylene diene tercopolymer (EVA‐EPDM) blends was studied by differential scanning calorimetry and a torque rheometer (Rheocord‐90). The activation energy decreases with an increase in EVA content in the blend. The cure rate increases whereas the optimum cure time and energy consumption for curing decrease with an increase in the EVA/EPDM ratio. The dynamic curing obtained by the torque rheometer is very fast compared to the static curing obtained by differential scanning calorimetry. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2756–2763, 1999     

Effect of electron beam irradiation and vinyl acetate content on the physicochemical properties of LDPE/EVA blends

The radiation‐induced crosslinking, compatibility, and surface modification of low density polyethylene/ethylene vinyl acetate blends (LDPE/EVA) were investigated. The structural and physical properties were characterized in terms of gel content, hot set, mechanical properties, contact angle, and surface free energy. The highest crosslink density was obtained at 20 wt % of EVA. Gel content of LDPE/EVA blends was increased with increasing irradiation dose, vinyl acetate (VA), and EVA contents. The hot set results are consistent with the gel content data. Mechanical testing showed that the tensile strength of samples increased with increasing irradiation dose up to 180 kGy, whereas the elongation at break was decreased with increasing irradiation dose. Contact angle measurements showed that the surface hydrophillicity of LDPE blend was increased with increasing irradiation dose and contents of both VA and EVA. The surface free energy was greatly dependent on irradiation dose and content of both VA and EVA. The total surface free energies of different LDPE formulations were in the range 17.25–32.51 mN/m, in which the polar (^pσ) and disperse (^dσ_s) values were within the range 16.52–26.6 and 0.9–5.91 mN/m, respectively. In conclusion, electron beam irradiation and blending LDPE with EVA improved the wettability or adhesion properties of LDPE/EVA blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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     

iPP/HDPE blends. II. Modification with EPDM and EVA

Past work has shown that addition of high-density polyethylene (HDPE) to polypropylene (PP) resulted in a significant reduction in the elongation at break and in the gate-region impact strength of injection molded articles. In this study, we report on the compatibilization of these blends with ethylene/propylene/diene monomer (EPDM) or ethylene/vinyl acetate (EVA) copolymers. EPDM is effective at improving the impact strength and gate puncture resistance of a 90/10 PP/HDPE blend. EVA, on the other hand, is effective at improving the impact strength and the elongation at break of this material. It was also found that EVA is a better impact modifier for PP than is EPDM. DSC analysis indicated that EPDM, when blended with PP, caused a significant reduction in the degree of crystallinity of the PP. This was not observed in the case of EVA/PP blends. Further, our results indicate that care must be taken in designating a particular material as a better compatibilizer than some other material. It is crucial that conditions be attached to the label compatibilizer, indicating in particular the desired mechanical properties of the blend. © 1996 John Wiley & Sons, Inc.     

Effect of layered silicate on EPDM/EVA blend nanocomposite: Dynamic mechanical,thermal, and swelling properties

Polymer blend nanocomposites have been developed by solution method using ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA‐45) copolymer, and organically modified layered silicate. Morphological investigation made by wide‐angle X‐ray diffraction and transmission electron microscopic analysis indicates intercalated structure of EPDM/EVA nanocomposites with partial disorder. Scanning electron microscopic studies exhibit the phase behavior of EPDM/EVA blend nanocomposites. Dynamic mechanical thermal analysis shows a significant increase in storage modulus in the rubbery plateau. The decrease in damping (tan δ) value and enhanced glass‐transition temperature (T_g) demonstrate the reinforcing effect of layered silicate in the EPDM/EVA blend matrix. The tensile modulus of these nanocomposites also showed a significant improvement with the filler content. The main chain scission of EPDM/EVA blend nanocomposites compared with the neat EPDM/EVA blend showed substantial improvement in thermal stability in nitrogen, whereas a sizeable increase is observed in air. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

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     

EVA–EPDM blends as cable insulant

Base materials for heat-resistant cable insulant have been developed from blends of ethylene vinyl acetate (EVA) copolymer containing 28% VA and ethylene propylene diene (EPDM) rubber. Different electrical, mechanical, and thermal properties of these blends have been studied extensively. Aging under different conditions has also been studied. The chemical and mechanical stability of these compositions has been assessed at the actual temperature range of application. Dielectric properties have been determined against varying temperature. These blends may be used as insulating materials having a temperature rating around 90–130°C, which is above the temperature rating (85–90°C) of heat-resistant insulation based on EPDM. © 1994 John Wiley & Sons, Inc.     

Studies on anticorrosive properties of thermally sprayable EVA and EVAl coating

Application of polymeric coatings is one of the methods for protection of mild steel against corrosion. In the present work, blends of different grades of ethylene vinyl acetate (EVA) with varying vinyl acetate (VAc) content viz. 18%, 28%, 40% and hydrolyzed EVA i.e., ethylene vinyl alcohol (EVAl) with low density polyethylene (PE) have been used as binder for development of anticorrosive coating. The blend compositions were characterized using differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and melt flow index (MFI) techniques for determination of melting point, degradation temperature and flow behavior respectively. The blend compositions were applied on grit blasted mild steel specimens by flame spray technique and the coated specimens were evaluated for their resistance to corrosion in salt spray, humidity and seawater. EVA/PE based compositions showed superior resistance to corrosion compared to EVAl/PE based compositions in all exposure conditions after 8 weeks. The corrosion resistance of blend compositions was also studied by electrochemical impedance spectroscopy (EIS) technique. The results indicate that EVA/PE coatings have better resistance to corrosion than EVAl/PE coatings.     

Morphology,rheological, crystallization behavior,and mechanical properties of poly(L‐lactide)/ethylene‐co‐vinyl acetate blends with different VA contents

Poly(L‐lactide)/ethylene‐co‐vinyl acetate (PLLA/EVA) blends with different contents of Vinyl Acetate (VA) in EVA phase were prepared through melt blending process. Although the composition of the blends was invariant (70/30), different phase morphologies were observed, namely, sea‐island morphologies for the blends with VA contents of 7.5, 18, and 28 wt %, whereas approximate co‐continuous morphology for the blend with VA content of 40 wt % was observed. The interfacial interaction between PLLA and EVA was visualized by Fourier transform infrared and rheological measurements. The nonisothermal and isothermal crystallization behaviors of the blends were investigated by wide angle X‐ray diffraction, Differential scanning calorimetry, and polarization optical microscope. Post‐thermal treatment was applied to improve the crystalline structure of PLLA. The results show that all the samples are mainly in amorphous state during the injection molding process. However, annealing promotes the second crystallization of PLLA matrix, leading to the improvement of the crystalline structure. Especially, the effect of annealing on crystalline structure of PLLA matrix is greatly dependent on the VA content of EVA. As expected, addition of EVA results in the improvement of the ductility and fracture toughness of the blends. The decreased tensile modulus and tensile strength can be enhanced through annealing process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Ethylene vinyl acetate/ethylene propylene diene terpolymer‐blend‐layered double hydroxide nanocomposites

Ethylene vinyl acetate (EVA‐45)/ethylene propylene diene terpolymer (EPDM) blend‐layered double hydroxide (LDH) nanocomposites have been prepared by solution blending of 1:1 weight ratio of EVA and EPDM with varying amounts of organo LDH (DS‐LDH). X‐ray diffraction and transmission electron microscopy analysis suggest the formation of partially exfoliated EVA/EPDM/DS‐LDH nanocomposites. Measurement of mechanical properties of the nanocomposites (3 wt% DS‐LDH content) show that the improvement in tensile strength and elongation at break are 35 and 12% higher than neat EVA/EPDM blends. Dynamic mechanical thermal analysis also shows that the storage modulus of the nanocomposites at glass transition temperature is higher compared to the pure blend. Such improvements in mechanical properties have been correlated in terms of fracture behavior of the nanocomposites using scanning electron microscopy analysis. Thermal stability of the prepared nanocomposites is substantially higher compared to neat EVA/EPDM blend, confirming the formation of high‐performance polymer nanocomposites. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Effect of ionizing irradiation on the thermal blend of waste low density polyethylene/ethylene vinyl acetate/bitumen for some industrial applications

The effect of gamma irradiation on the properties of waste low density polyethylene/ethylene vinyl acetate/bitumen blend was investigated. The variation in tensile strength, elongation at break, hardness and compression set (%) of the prepared blends confirmed the impact of gamma irradiation on the blend microstructure. The best mechanical properties were reported at an integral irradiation dose of 75 kGy at a weight composition ratio of bitumen:EVA:waste LDPE blend, 1:1:1. The influence of ionizing irradiation on the thermal stability and compatibility of the prepared blends, solubility and scanning electron micrographs were investigated. The results suggest that EVA content plays a detrimental role in the ultimate specifications via irradiation. The study offers an elastic product thanks to the controllable radiation crosslinking of EVA beside the introduction of the waste LDPE and bitumen as a possible means of recycling for a likely implementation in expansion joint systems of the concrete moulds.     

Comparison Properties of Natural Rubber (SMR L)/Ethylene Vinyl Acetate (EVA) Copolymer Blends and Epoxidized Natural Rubber (ENR-50)/Ethylene Vinyl Acetate (EVA) Copolymer Blends

Mixing torque, morphology, tensile properties and swelling studies of natural rubber/ethylene vinyl acetate copolymer blends were studied. Two series of unvulcanized blends, natural rubber/ethylene vinyl acetate (SMRL/EVA) copolymer blend and epoxidized natural rubber (50% epoxidation)/ethylene vinyl acetate (ENR-50/EVA) copolymer blend were prepared. Blends were prepared using a laboratory internal mixer, Haake Rheomix polydrive with rotor speed of 50 rpm at 120°C. Results indicated that mixing torque value and stabilization torque value in ENR-50 blends are lower than SMRL blends. The process efficiency of ENR-50/EVA blends is better due to less viscous nature of the blend compared to SMRL/EVA blends as indicated in stabilization torque graph. Tensile properties like tensile strength, M100 (modulus at 100% elongation) and E _b (elongation at break) increase with increasing EVA fraction in the blend. At the similar blend composition, ENR-50 blend shows better tensile properties than SMRL blends. In oil resistance test, swelling percentage increased with immersion time and rubber composition. At a similar immersion time, ENR-50 blends exhibit better oil resistance compared to SMRL blends. Scanning electron microscopy (SEM) of tensile fractured surface indicated that EVA/ENR-50 blends need higher energy to cause catastrophic failure compared to EVA/SMRL blends. In etched cryogenically fractured surface, size and distribution of holes due to extraction of rubber phase by methyl ethyl ketone (MEK) were studied and holes became bigger as rubber composition increased due to coalescence of rubber particle.     

Combined effect of VA content and pH level of filler on properties of EPDM/SmBO3 and EPDM/ATO composites reinforced by three types of EVA

This study investigates the interaction of vinyl acetic (VA) content of ethylene‐vinyl acetate (EVA), pH level of Samarium borate (SmBO₃), and Sb‐doped SnO₂ (ATO) on reinforcement of peroxide‐cured ethylene‐propylene‐diene rubber (EPDM)/SmBO₃ and EPDM/ATO composites. It was found that EVA could both reinforce mechanical properties of EPDM, and enhance fluidity of gum during processing. During vulcanization, the interaction of VA groups and pH value of filler particles can influence the crosslink density of EPDM composites. In alkaline EPDM/SmBO₃/EVA, VA groups could hydrolyze to produce polyvinyl alcohol and reduce pH level of medium by consuming OH⁻. When dispersed in acidic EPDM/ATO/EVA, VA groups could generate polyunsaturated bonds and acetic acid during vulcanization. The double bonds could react with dicumyl peroxide (DCP) and then boost crosslink efficiency of EPDM composites. Moreover, acetic acid and reduction of pH value could make DCP decompose into ions, and lower crosslink density of EPDM composites. In addition to the contribution of crosslink density, EVA could crystallize in EPDM composites to reinforce EPDM composites. Electric properties of EPDM were also affected. Surface and volume resistivity of EPDM composites decreased with the rise of VA content. As for EPDM/SmBO₃/EVA composites, the growth of VA groups could boost dielectric constant and loss, decrease dielectric strength, due to the enhancement of polarity and reduction of crosslink density. In terms of EPDM/ATO/EVA composites, the EPDM/ATO/EVA14 possesses the highest dielectric constant and loss, and the lowest dielectric strength, because of the competing effect of VA content and crosslink density. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

相容剂及硫化体系对EPDM/LDPE热塑性弹性体性能的影响

采用两种不同硫化体系通过动态硫化工艺制备EPDM/LDPE热塑性弹性体(TPE),并采用EVA对体系进行相容.结果表明:随着EVA用量的增大,EPDM/LDPE共混物的剪切粘度逐渐减小,加工流动性提高;与硫黄硫化EPDM/LDPE TPE相比,过氧化物硫化EPDM/LDPE TPE的物理性能较差,耐热性能较好;当EVA用量为18份时,EPDM/LDPE TPE的综合性能较好.     

The observation of PP/EVA blends in which isotactic PP was preradiated with different radiation absorbed doses

Isotactic polypropylene (PP) was preradiated by γ ray with different absorbed doses and subsequently blended with ethylene‐vinyl acetate (EVA) co‐polymer to prepare PP/EVA blends. The average molecular weight (M_n) of isotactic PP decreased with the increasing radiation absorbed dose, which indicated that high energy radiation of γ ray broke the isotactic long PP chains into shorter ones. The melt flow rate results evidenced that the processing ability of PP/EVA blends was continuously promoted with the increasing absorbed dose. The β crystal was obtained in the PP/EVA blends by the radiation method. The onset temperatures and peaks of crystallization of PP/EVA blends decreased slightly with the increasing radiation absorbed dose, while high energy radiation was inclined to enhance the crystallinity of PP/EVA blends. The Fourier transform infrared spectroscopy (FTIR) tests confirmed an interesting phenomenon that PP tended to move to the surface of the PP/EVA blends with the increasing radiation absorbed dose. Mechanical tests proved that the PP/EVA blends remained a comparative stable mechanical property under the absorbed dose of 30 kGy. The experimental results indicated that PP/EVA blend was a potential candidate for industrial applying. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45057.     

Synthesis of silane‐grafted ethylene vinyl acetate copolymer and its application to compatibilize the blend of ethylene‐propylene‐diene copolymer and silicone rubber

Vinyltrimethoxysilane‐grafted ethylene vinyl acetate copolymer (EVA‐g‐VTMS) was synthesized and applied to compatibilize ethylene‐propylene‐diene copolymer (EPDM)/methyl vinyl silicone rubber (MVQ) blends. The silane‐grafting was successfully proved by differential scanning calorimetry, FTIR spectroscopy and XPS spectroscopy. The additive amount of the compatibilizer (EVA‐g‐VTMS) was optimized to be 10 phr (parts per hundred of rubber in weight) based on analysis of scanning electron microscopy, mechanical properties, aging properties, dynamic mechanical properties, rheological properties and thermal properties. Compared with the blend without EVA‐g‐VTMS, results show that the blend with 10 phr of EVA‐g‐VTMS exhibits the finest morphology. Tensile strength, elongation at break, modulus at 100% elongation, tear strength and TE index increase by 82.5%, 16.9%, 60.0%, 40.9%, and 41.9%, respectively. Dynamic mechanical analysis reveals storage modulus increase and glass transition temperatures of EPDM and MVQ move closer to each other. Rheological analysis shows a decrease in complex modulus and complex viscosity, and the processibility of the blend was improved. Furthermore, thermogravimetric analysis shows enhancement of thermal stability. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers     

The Effect of Epoxidized Natural Rubber (ENR-50) or Polyethylene Acrylic Acid (PEA) as Compatibilizer on Properties of Ethylene Vinyl Acetate (EVA)/Natural Rubber (SMR L) Blends

The effect of epoxidized natural rubber (ENR) or polyethylene acrylic acid (PEA) as a compatibilizer on properties of ethylene vinyl acetate (EVA)/natural rubber (SMR L) blends was studied. 5 wt.% of compatibilizer was employed in EVA/SMR L blend and the effect of compatibilizer on tensile properties, thermal properties, swelling resistance, and morphological properties were investigated. Blends were prepared by using a laboratory scale of internal mixer at 120°C with 50 rpm of rotor speed. Tensile properties, thermal properties, thermo-oxidative aging resistance, and oil swell resistance were determined according to related ASTM standards. The compatibility of EVA/SMR L blends with 5 wt.% of compatibilizer addition or without compatibilizing agent was compared. The EVA/SMR L blend with compatibilizer shows substantially improvement in tensile properties compared to the EVA/SMR L blend without compatibilizer. Compatibilization had reduced interfacial tension and domain size of ethylene vinyl acetate (EVA)/natural rubber (SMR L) blends.     

Photodegradation of some poly(vinyl chloride) (PVC) blends: PVC/ethylene-vinyl acetate (EVA) copolymers and PVC/butadiene-acrylonitrile (NBR) copolymers

Poly(vinyl chloride) (PVC) and its blends with polybutadiene-acrylonitrile (NBR) (containing 21.7 weight-percent acrylonitrile (AN), a heterogeneous two-phase system; and containing 41.6 weight-percent of AN, a homogeneous one-phase system) and with polyethylene-vinyl acetate (EVA) (containing 45 weight-percent of vinyl acetate (VA), a heterogenous two-phase system; and containing 65 weight-percent VA, a homogeneous one-phase system) were UV-irradiated (at 3500 Å UV-light (solar spectrum)). After UV irradiation the kinetics measurements were made of the formation of hydroperoxy (OOH) and carbonyl (CO) groups and the changes of mechanical properties: tensile strength, elongation to break, and impact energy. As a result of the photooxidative degradation of PVC blends, decreases of mechanical properties were observed. The effects are more severe in PVC/NBR blends, which contain unsaturated bonds (polybutadiene segments) than in the case of PVC/EVA. The phase structure plays an evident role on the UV degradation only of PVC/NBR blends. The photostability of PVC blends can be slightly improved by introducing Tinuvin P or Ni-chelates photostabilizers.