Blends Of Ethylene-vinyl Acetate Copolymer Research Articles

Adhesion Properties of Polyethylene and Ethylene-Vinyl Acetate Copolymer Blend with Acrylate Copolymers of Ethylene

Adhesion Properties of Polyethylene and Ethylene-Vinyl Acetate Copolymer Blend with Acrylate Copolymers of Ethylene

Performance of ethylene vinyl acetate waste (EVA-w) when incorporated into expanded EVA foam for footwear

Ethylene vinyl acetate copolymer blends (EVA-B), with vinyl acetate set at 19 % and 28 % by weight (wt%), were mixed with EVA waste (EVA-w), (a reticulated and micronized ethylene vinyl acetate copolymer) from injection branches and defective midsoles. The EVA-B/EVA-w composites were prepared with 15, 25, and 35 per hundred rubber (phr) EVA-w using a Banbury mixer to mix all components. Afterwards, the mixture was submitted to compression molding to obtain expanded EVA-B/EVA-w composite plates. A standard compound, provided by a Brazilian footwear industry (EVA-ref), was used as reference for thermal and mechanical property comparisons. During the thermal analysis, when increasing the EVA-w content, a delay in the deacetylation of the EVA-B composites in relation to the EVA-ref was observed. There was also an increase in the maximum degradation rate temperature and a reduction in loss of mass in the first decomposition event. In the second event, the maximum temperature did not vary in the composites with EVA-w added as compared to the EVA-ref. The residue content increased at 600 °C, indicating that EVA-w acts as a filler for EVA-B. The mechanical properties evaluated were hardness, tension at break, elongation at break, tear strength, compression set, and shrinkage. Addition of EVA-w to the composites (comparing 15 phr–35 phr) increased tear strength properties by 4 %, (EVA-w acts as a nucleation cell agent, increasing the EVA foam cell density). However, shrinkage increased by roughly 35 % above the specifications for footwear applications. Hardness increased by 5 %, tensile strength increased by 10 %, and elongation at break decreased by roughly 4 %. The compression set property increased by nearly 5 % with the EVA-w content (due to decreasing matrix elongation). Thus, EVA-w acts as a reinforcement filler for EVA-B. A statistical study based on composite performance indices for the mechanical properties, and a cost analysis was performed. Except for the average linear shrinkage (35 phr EVA-w composite), all other studied composites met the mechanical property specifications for sports shoe midsoles. The best combination for process performance and cost analysis was for the EVA-w composite at 25 phr.

Mechanical Properties of Bio-Composites Based on Polymer Blends of Ethylene-Vinyl Acetate Copolymer and Polyethylene with Natural Fillers

Highly filled bio-composites based on ethylene-vinyl acetate copolymer (EVA) with cellulose and wood flour were prepared in the previous parts of the study. The aim of this work was to dilute them with a polyethylene (PE), to prepare new bio-composites with lower EVA content and to investigate the effect of EVA/PE ratio on the mechanical properties. It was shown that melt flow index (MFI) and elongation at break increased additively with an increase of EVA content in the composition, but yield strength had an inverse tendency. The obtained results are extremely useful for choosing the right composition for the industrial implementation.

Rheological studies of SBS/EVA blends modified with bio-based cashew nut shell liquid

Research on bio-plasticizers is a topic of strategic interest in polymer blends. A bio-plasticizer, cashew nut shell liquid (CNSL), was studied in blends of ethylene-vinyl acetate copolymer (EVA) and styrene-butadiene-styrene copolymer (SBS). In the literature does not report the addition of plasticizers to SBS/EVA blend. Statistical analyses showed that there was a significant difference in mechanical properties (tension at break, hardness and elongation at break) vs. the unplasticized blend. The minimum CNSL concentration required for a statistical difference was 10 phr. The Carreau-Yasuda rheological model was used to obtain rheological parameters in these blends. The plasticizing influence of CNSL was confirmed by rheology. The effects of CNSL on creep and recovery were evaluated for the SBS/EBA blends. Burger´s model explained well SBS/EVA creep compliance. Moreover, its parameters (Newtonian dashpots and Hookean springs) were evaluated as a function of the CNSL concentrations. The bio-plasticizer concentration influenced significant correlations among the rheological creep-recovery tests, thus enabling a considerable increase in the elastic phase. Experimental creep-recovery data and curve fit were in good agreement.

Poly(lactic acid)/ethylene vinyl acetate copolymer blend composites with wood flour and wollastonite: Physical properties, morphology, and biodegradability

In the present study, poly(lactic acid) (PLA), a biodegradable plastic, was melt‐blended with five weight percentages (10–50 wt%) of ethylene vinyl acetate (EVA) copolymer, a non‐biodegradable plastic, having a vinyl acetate content of 19 wt% and a melt flow index of 530 g/10 min, on a twin screw extruder, followed by an injection molding. The blends at 10 and 20 wt% EVA revealed a noticeably increased impact strength and strain at break over the pure PLA, and the blend at 10 wt% EVA exhibited the highest impact strength and strain at break. The 90/10 (wt%/wt%) PLA/EVA blend was then selected for preparing either single or hybrid composite with wood flour (WF) and wollastonite (WT). The filler loading was fixed at 30 parts by weight per hundred of resin throughout the experiment, and the WF/WT weight ratios were 30/0, 20/10, 15/15, 10/20, and 0/30. The prepared composites were examined for their mechanical and thermal properties, melt flow index, flammability, water uptake, and biodegradability as a function of composition. All the composites showed a filler‐dose‐dependent decrease in the impact strength and strain at break, but an increase in the tensile and flexural modulus (optimal at 0/30 WF/WT) and tensile and flexural strength (optimal at 30/0 WF/WT) as compared with the neat 90/10 (wt%/wt%) PLA/EVA blend. In addition, the melt flow index, char residue, anti‐dripping ability, water uptake, and biodegradability of the composites were also higher than those of the neat blend. J. VINYL ADDIT. TECHNOL., 25:313–327, 2019. © 2019 Society of Plastics Engineers

Effect of dynamic crosslinking on phase morphology and mechanical properties of polyamide 6,12/ethylene vinyl acetate copolymer blends

The dynamic crosslinking of polyamide 6,12 and ethylene vinyl acetate (PA6,12/EVA) blends in the mixing chamber of a torque rheometer was investigated. EVA was selectively crosslinked within the PA6,12 phase through free radical reactions using dycumil peroxide. The degree of EVA crosslinking in the PA12,6/EVA materials was estimated based on the gel content (insoluble EVA fraction). The PA6,12/EVA phase morphology was investigated by scanning electron microscopy. The mechanical properties were investigated by determining the tensile strength and hardness. The half-life time (t1/2) for homolytic scission of the dcumil peroxide (DCP) was ~6s, and this time is longer than the dispersion time of the DCP in the blends. The addition of DCP resulted in increased torque values due to specific crosslinking in the EVA phase. For the pure EVA and its blends with PA6,12 the stabilized torque values increased proportionally with the amount of DCP in the system, due to a higher degree of crosslinking of the elastomeric phase. The gel content of the dynamically crosslinked blends increased with the amount of DCP incorporated until 4 phr. At 1 phr the gel content value was 2.6wt.%, while at 4 phr it was 17wt.%. For the polymer blend with 8 phr of DCP a lubricating effect contributed to reducing the gel content. The dynamically crosslinked blends, regardless of the amount of DCP added, showed a reduction in the mechanical properties, which is related to the morphological features of the system due to the low mechanical fragmentation during melt processing. http://dx.doi.org/10.18226/23185279.v3iss1p23

Non-isothermal crystallization behavior of poly(vinylidene fluoride)/ethylene–vinyl acetate copolymer blends

Non-isothermal crystallization behavior of poly(vinylidene fluoride) (PVDF) and ethylene–vinyl acetate (EVA) copolymer and their binary blends with different blending ratios were investigated by the use of differential scanning calorimetry (DSC). With the increasing cooling rates, PVDF, EVA and their binary blends showed wide crystallization temperature range and high crystalline enthalpy. Jeziorny and Mo’s models were applied to calculate non-isothermal crystallization kinetics parameters of neat PVDF, EVA and their binary blends. By Jeziorny method, the crystallization process of neat PVDF, EVA and PVDF/EVA = 7/3 blend can be divided into two parts: primary and secondary crystallization processes. The Avrami exponent n 1 indicated that the primary crystallization process was a mixture model of three-dimensional and two-dimensional space extensions. In comparison, PVDF/EVA = 5/5 and PVDF/EVA = 3/7 blends showed a single crystallization process. Through Mo’s analysis, faster cooling rate was demanded to reach higher relative crystallinity. Crystallization rate coefficient (CRC) was used to describe the effect of crystallization rates on the interaction between PVDF and EVA. CRC reached a maximum value when the mass ratio of PVDF and EVA was 7/3. The maximum CRC values of PVDF system and EVA system were 98.1 and 179.9 h−1, respectively. The activation energy was closely related to the extent of conversion and the neat samples had a maximum value of crystallization activation energy. This was consistent with the observation for the parameters from Jeziorny analysis and could be correlated to the heterogeneous nucleation.

Role of clay in compatibilization of immiscible high melt strength polypropylene and ethylene vinyl acetate copolymer blends

AbstractThe compatibilization efficiency of organically modified layered silicates (clay) was studied for immiscible high melt strength polypropylene/ethyl vinyl acetate (EVA) blends for the first time. The size of the dispersed EVA phase in the polypropylene matrix decreased with addition of small amounts of clay (cloisite 20A) to the blend. Scanning electron micrographs (SEM) show an efficient mixing of polymers in the presence of clay. The X‐ray diffraction (XRD) and transmission electron microscopy patterns demonstrate that silicate layers are well dispersed within the phases and are also present at the interphase. This results in substantial size reduction of the dispersed phase. The blends show a drastic increase in mechanical properties with the addition of clay. Differential scanning calorimetry thermo grams further help in understanding blend miscibility in the presence of clay as denoted by the change in the melting range of the components and the crystallization behavior of the components. The dynamic rheology tests reveal a emulsion‐like behavior for the blend system as denoted by the presence of a curvature or kink at lower frequencies, which further increases for the system with clay particles due to decrease in size of the dispersed phase. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers

Thermal and mechanical properties of poly(methyl methacrylate) and ethylene vinyl acetate copolymer blends

AbstractA series of poly(methyl methacrylate) (PMMA) blends have been prepared with different compositions viz., 5, 10, 15, and 20 wt % ethylene vinyl acetate (EVA) copolymer by melt blending method in Haake Rheocord. The effect of different compositions of EVA on the physico‐mechanical and thermal properties of PMMA and EVA copolymer blends have been studied. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) has been employed to investigate the phase behavior of PMMA/EVA blends from the point of view of component specific interactions, molecular motions and morphology. The resulting morphologies of the various blends also studied by optical microscope. The DSC analysis indicates the phase separation between the PMMA matrix and EVA domains. The impact strength analysis revealed a substantial increase in impact strength from 19 to 32 J/m. The TGA analysis reveals the reduction in onset of thermal degradation temperature of PMMA with increase in EVA component of the blend. The optical microscope photographs have demonstrated the PMMA/EVA system had a microphase separated structure consisting of dispersed EVA domains within a continuous PMMA matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Morphology and fracture behaviour of poly(vinyl chloride)/ethylene-vinyl acetate copolymer blends

Poly (vinyl chloride) (PVC)/ethylene-vinyl acetate copolymer (EVA) blends were prepared to investigate the effect of EVA content on the phase morphology and fracture behaviour, evaluated by means of the essential work of fracture method (EWF). The results clearly showed the prominent influence of phase transformation on fracture toughness of the blends. At low EVA content (<7 phr), EVA was dispersed in the PVC matrix as separated small particles, and with increase in EVA content increasing the number of EVA particles increased, resulting in diminished distance between the dispersed particles and an increase in specific essential work of fracture ( w e ). The enhanced w e values were attributed to the increase of specific essential work of fracture in the necking and tearing stage ( w e , n ), although the specific EWF before yielding ( w e , y ) decreased. When EVA content was up to 9 phr, the EVA particles were observed to adhere to each other and formed a coherent phase, which caused sharp decrease of w e as the result of simultaneous decrease of w e , y and w e , n . On the other hand, the specific plastic work, βw p , was barely affected by the increase of EVA content.

Tailoring viscoelastic and mechanical properties of the foamed blends of EVA and various ethylene‐styrene interpolymers

AbstractFoamed materials (EVA/ESI) have been prepared from blends of ethylene‐vinyl acetate copolymer (EVA) and ethylene‐styrene interpolymers (ESI) in the presence of various amounts of dicumyl peroxide (DCP). Four ESIs of different compositions were employed in this study; their styrene contents ranged from 30 to 73 wt% and their Tg ranged from −2 to 33°C. It has been found that microcellular morphology, degree of crosslinking and expansion ratio were strongly affected by the DCP concentration and the type of ESI employed. A minimum degree of crosslinking was required for making good foams and the same degree of crosslinking could be achieved by employing a smaller amount of DCP for an EVA/ESI blend having a higher styrene content. In contrast to other EVA blends, such as EVA/LDPE, these EVA/ESI blends exhibited no existence of any optimum DCP concentration, and the α glass transition temperatures of the foams varied with the ESI type, covering a wide span from 0°C to 37°C. Therefore, it was possible to tailor the Tg of an EVA/ESI blend by choosing an appropriate type of ESI. Furthermore, by correctly tailoring the Tg, the EVA/ESI foam could be made into a rubbery material with a custom‐designed damping factor. Tensile strength and modulus of the EVA/ESI foams increased generally with an increase in the styrene content, with the exception that ESIs with very low styrene content will confer on the blend a high modulus at small strain and a large elongation at break.

Dynamic mechanical analysis of polyethylene and ethylene vinylacetate copolymer blends irradiated by electron beam

AbstractDynamic mechanical properties of nonirradiated and irradiated blends of polyethylene (PE) and ethylene vinylacetate (EVA) copolymer have been determined. Effect of addition of EVA and radiational crosslinking on loss and storage modulus, tan δ, and transition temperatures were determined. Increase in transition temperatures on exposure to radiation and decrease in transition temperatures with addition of EVA is observed. Peak broadening is observed on exposure to radiation. Values of the storage modulus increase while that of loss modulus and tan δ decrease on crosslinking. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2429–2434, 2002

The effect of mercapto‐modified ethylene–vinyl acetate (EVA) on curing parameters, mechanical properties, and thermal properties of vulcanized styrene–butadiene rubber (SBR)/EVA blends

AbstractThe effect of EVA functionalized with mercapto groups (EVALSH) on the compatibilization of SBR and EVA copolymer blends was investigated in vulcanized systems based on sulfur or dicumyl peroxide (DCP). The presence of EVALSH resulted in an improvement of the tensile properties, indicating the reactive compatibilizing effect of this compound. The best mechanical performance was achieved with the sulfur‐curing system for both compatibilized and noncompatibilized blends. The blend systems were also analyzed by scanning electron microscopy, differential scanning calorimetry, and dynamic‐mechanical analysis. The crystallinity of the EVA phase was significantly affected by the presence of the EVALSH, whereas no substantial change was detected on the damping properties or the glass transition temperature of the SBR phase. Considering the aging properties, the presence of EVALSH increases the thermal stability of the blends vulcanized with DCP. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 239–249, 2002

Electron beam modification of thermoplastic elastomeric blends made from polyolefins

Thermoplastic elastomeric films have been prepared from blends of ethylene vinylacetate copolymer (EVA) with low-density polyethylene (LDPE), high-density polyethylene (HDPE) and polypropylene (PP) by electron beam modification in presence of radiation sensitizer. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) have been used to evaluate the structural changes of these blends. Scanning electron microscopy (SEM) indicates the morphological features of the blends. Significant improvements of mechanical, dynamic mechanical and set properties have been obtained by electron beam modification of the blends of EVA with LDPE and HDPE. However, in the case of EVA/PP, degradation of the PP phase has been observed. The effects of ditrimethylol propane tetraacrylate (DTMPTA) as radiation sensitizer have also been evaluated from the mechanical and dynamic mechanical properties.

Heat shrinkability of electron-beam-modified thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer and polyethylene

The heat shrinkability of electron-beam-irradiated thermoplastic elastomeric films from blends of ethylene–vinylacetate copolymer (EVA) and low-density polyethylene (LDPE) has been investigated in this paper. The effects of temperature, time and extent of stretching and shrinkage temperature and time have been reported. Based on the above data, the optimized conditions in terms of high heat shrinkage and low amnesia rating have been evaluated. Influence of radiation doses (0–500 kGy), multifunctional sensitizer levels (ditrimethylol propane tetraacrylate, DTMPTA), and blend proportions on heat shrinkability has been explained with the help of gel fraction and X-ray data. With the increase in radiation dose, gel fraction increases, which in turn gives rise to low values of heat shrinkage and amnesia rating. At a constant radiation dose and blend ratio, percent heat shrinkage is found to decrease with increase in DTMPTA level. Gel content increases with the increase in EVA content of the blend at a constant radiation dose and monomer level, giving rise to decrease in heat shrinkability. Heat shrinkage increases with the increase in percent crystallinity, although the amnesia rating follows the reverse trend.

Melt Rheology and Morphology of Nitrile Rubber and Ethylene-Vinyl Acetate Copolymer Blends

The melt Theological behavior of nitrile rubber (NBR)/ethylene-vinyl acetate (EVA) copolymer blends was studied with special reference to the effect of the blend ratio, cross-linking systems, and shear rate using a capillary rheometer. At a given shear stress at 90°C, the viscosities of the blends vary slightly with composition. The effect of cross-linking systems [viz., sulfur (S), peroxide (DCP) and mixed (S+DCP) systems] on the viscosity of NBR/EVA blends is negligible. The melt viscosity of the blends decreases with increasing shear rate, showing pseudoplastic behavior. The flow behavior index values also support the pseudoplastic nature of these blends. Various theoretical models were used to predict the melt viscosity of the blends. Parameters such as die swell, principal normal stress difference, recoverable shear strain, and shear modulus were calculated to characterize the melt elasticity of these blends. The melt elasticity of the system was increased by the addition of NBR to EVA. The extrudate deformation at different shear rates was also studied. It was observed that as the shear rate increases, the extrudate surface exhibits a higher degree of deformation. The morphology of the extrudates of the blends at different shear rates has been examined by a scanning electron microscope. The morphology was found to be dependent on the blend ratio and shear rate.

Fourier transform IR study of acid—base interactions: Blends of ethylene—vinylacetate copolymer and terpene-phenol resins

Specific interactions in binary blends of ethylene-vinylacetate copolymer (EVA) with various low molecular weight terpene-phenol tackifying resins (TPR) were systematically investigated, as a function of the composition of the blend and of the electron-acceptor ability of the resin, using attenuated total reflection Fourier transform IR (ATR-FTi.r.) spectroscopy. Molecular acid—base complexes (according to Lewis' electron acceptor—donor concepts) were evidenced between TPR hydroxyl groups and EVA carbonyl groups. Quantitative information on the fraction of acid—base bonded entities, the enthalpy and the equilibrium constant of pair formation were obtained. It appears that the amorphous phases of such polymer blends remain thermodynamically miscible whatever the composition of the blend and the resin acidity. On the contrary, a crystalline transition of the EVA copolymer is observed, depending on the blend composition and resin acidity. This transition is discussed in terms of enthalpy and entropy considerations based on FTi.r. and differential scanning calorimetry (DSC) investigations. Fundamental results are then summarized in order to predict the melting enthalpy of a polymer blend.

Viscoelastic Properties of Silica-Filled Natural Rubber and Ethylene-Vinyl Acetate Copolymer Blend

Abstract The viscoelastic properties such as storage modulus (E′), loss modulus (E”) and damping (tan δ) of unfilled and silica-filled blends of natural rubber (NR) and ethylene-vinyl acetate copolymer (EVA) have been evaluated. The blends were crosslinked by a mixed system consisting of accelerated sulfur and peroxide. The tan δ values of unfilled blends showed two transitions corresponding to EVA and NR phases. This indicated that the blends are immiscible. The damping curves of EVA and EVA-rich blends possess three distinct regions: a rubbery plateau, a melt transition, and a viscous plateau. It is seen that the addition of silica decreased the tan δ values of the samples substantially except that of NR, where a slight increase in tan δ values can be observed at high temperatures. The sharp decrease in tan δ in filled EVA and EVA-rich blends is associated with the decrease in crystallinity of the EVA phase due to the presence of filler. Addition of silica filler increased the storage and loss modulus o...

Melt rheology and elasticity of natural rubber—ethylene–vinyl acetate copolymer blends

AbstractThe melt rheology of blends of natural rubber (NR) and ethylene–vinyl acetate copolymer (EVA) has been studied with reference to the effects of blend ratio, cross‐linking systems, shear stress, and temperature. When EVA formed the dispersed phase, the viscosity of the blends was found to be a nonadditive function of the viscosities of the component polymers at lower shear region, i.e., a positive deviation was observed. This behavior has been explained based on structural buildup of dispersed EVA domains in the continuous NR matrix. The effect of the addition of silica filler on the flow characteristics of the blends has been investigated. The melt elasticity parameters such as die swell, principal normal stress difference, recoverable shear strain, and elastic shear modulus of NR–EVA blends were also evaluated. © 1993 John Wiley &amp; Sons, Inc.

Improved interaction effected by maleic anhydride‐grafted polypropylene in PRP triblock polymer–EVA blend

AbstractThe role of anhydride‐grafted polypropylene in the ethylene–propylene triblock polymer and ethylene–vinyl acetate copolymer blend has been studied. Maleic anhydride grafted onto polypropylene interacts with polymer components in the blend and also improves the dispersion of the rubber phase in the plastic matrix. Improved interaction is reflected in the ultimate properties of the blend. Blends with good impact resistance and low‐temperature brittleness may be obtained by optimizing the modifier concentration. Composition with good low‐temperature brittleness is achieved by lowering the glass transition temperature of the plastic phase by adding a low concentration of modifier. Impact strength of the studied blend does not depend only on the reactive maleic anhydride content but also on the type of modifier. Generally, an increase in interfacial surface area improves impact strength. © 1993 John Wiley &amp; Sons, Inc.