Ethylene Vinyl Acetate Blends Research Articles

Investigation into Paraffin Wax and Ethylene Vinyl Acetate Blends for Use as a Carrier Vehicle in Ceramic Injection Molding

ABSTRACTAn experimental study into paraffin wax and ethylene vinyl acetate-28 blends has been undertaken to investigate the potential for their use as carrier vehicles for ceramic injection molding applications. Carrier systems are critical for the fabrication of this type of molded component, making their properties at all stages of the process of great importance. Paraffin wax and ethylene vinyl acetate-28, in most circumstances, combine to form stable homogeneous blends, which experience relatively small changes in the melting and solidification phase transition behavior. However, these blends exhibit notable viscosity shifts and flexural strength performance changes with increasing ethylene vinyl acetate-28 content. The melt flow behavior of the blends at shear rates of 100 s−1 varies from 0.01 Pa.s for paraffin wax to 10 Pa.s for the composition by weight of 50% paraffin wax and 50% ethylene vinyl acetate-28, which suggests the upper viscosity limit for successful carrier systems. All paraffin wax/ethylene vinyl acetate-28 blends experience shear thinning behavior with increasing shear rate, which can be modeled with reasonable accuracy using the Cross and Carreau models. Increasing the ethylene vinyl acetate-28 content in a blend causes the initiation of shear thinning at progressively lower shear rates and also forms a blend with an increasing elastic character at typical injection temperature. Yield stress is not developed for blends containing less than 50 wt% ethylene vinyl acetate-28. The addition of ethylene vinyl acetate-28 significantly alters the mechanical properties of the blends, modifying the brittle nature of paraffin wax to develop increasing flexible and plastic properties. Although with less than 25 wt% ethylene vinyl acetate-28 in a blend fracture failure still results, greater ethylene vinyl acetate-28 content represses the failure mechanisms, developing the increasing degrees of plastic deformation.

Effect of PE-g-MA compatibilizer on the structure and performance of HDPE/EVA blend membranes fabricated via TIPS method

Neat and compatibilized high density polyethylene and ethylene vinyl acetate blend membranes were fabricated via thermally induced phase separation method. ATR-FTIR results confirmed that existence of PE-g-MA as compatibilizer keeps EVA molecules in the bulk of the membrane. Phase behavior studies showed that addition of compatibilizer improves the compatibility of the blend; therefore any cloud point was observed. Leafy structure obtained by SEM images also confirmed that a solid–liquid phase separation was occurred for all ranges of blending ratios. Pure water flux (PWF) and porosity analyses showed that compatibilized HDPE/EVA blend membrane with EVA content of 10wt.%, exhibits the best results in which PWF increases more than 2.8 folds in comparison with both neat blend and pure membranes.The results show that the tensile strength as well as elongation at breaks for compatiblized blend membrane is improved. The fouling behavior of compatiblized blend membranes with optimum composition of EVA in BSA protein filtration showed that maximum flux recovery of 71%, which was 18% and 86% higher than that of neat blend and pure HDPE membranes, respectively. Addition of compatibilizer decreased the portion of irreversible fouling ratio and increased the portion of reversible fouling ratio.

Thermal and mechanical properties of blends of LDPE and EVA crosslinked by electron beam radiation

Low density polyethylene (LDPE) blends with different percentages of ethylene vinyl acetate (EVA) irradiated with 10 MeV electron beam in the range of 50–250 kGy at room temperature. The effect of irradiation and EVA content on the mechanical and thermal properties of LDPE was studied. It was revealed that for all blends increasing the applied dose up to 150 kGy would result in decrease in the specific heat capacity ( c p ) and thermal conductivity ( k ) of LDPE and then raised slightly with further increased in radiation doses. The gel content showed that under the irradiation, the crosslinking density at each irradiation dose depends almost on the amorphous portions of the LDPE/EVA. The mechanical properties of LDPE/EVA blends were found to be influenced by the electron beam irradiation and EVA content. It can be deduced that the mechanical properties of LDPE are improved by blending with EVA and irradiated by electron beam. Fourier transform infrared (FTIR) spectroscopy was used to characterize the structure of LDPE. Result indicates small variation in crystalline content, which could be increased or decreased on the formation of important bond groups.

Properties of ethylene–vinyl acetate filled with metal hydroxide

In this study, the properties of ethylene–vinyl acetate (EVA) and EVA filled with aluminum (aluminum trihydrate; ATH) and magnesium hydroxide (MH) as halogen-free flame-retardant materials were studied. Scanning electron microscopic analysis revealed that MH in EVA matrix is platy in structure, considerably broad size distribution and well homogeneously distributed, whereas ATH particles are smaller and much more homogeneous in size. Addition of ATH or MH to EVA had an impressive affection on the thermal aging and flame tests but impaired the blend mechanical properties. This research explored that in comparison with ATH, addition of MH to EVA blends was more efficient and suitable in all mechanical, thermal, and flammability tests.

Interactions of montmorillonite and electron beam irradiation in enhancing the properties of alumina trihydrate–added polyethylene and ethylene vinyl acetate blends

This study aims at investigating the effects of electron beam irradiation on the montmorillonite and alumina trihydrate–added low-density polyethylene and ethylene vinyl acetate blends. The mechanical, flammability and electrical resistivity of the montmorillonite and alumina trihydrate–added low-density polyethylene and ethylene vinyl acetate blends were investigated. The addition of montmorillonite provided the reinforcing effect to the alumina trihydrate–added low-density polyethylene and ethylene vinyl acetate, whereby the tensile strength of 150 kGy and 250 kGy irradiated samples gradually increased with increasing of montmorillonite composition (i.e. 5 phr to 20 phr). Furthermore, the addition of montmorillonite into low-density polyethylene and ethylene vinyl acetate blends increased the limiting oxygen index and thermal decomposition temperatures of samples, thus improving the flame retardancy and thermal stability. The increasing of montmorillonite and irradiation dosage promoted the char formation during combustion. Besides, the increasing of montmorillonite loading levels gradually decreased the surface and volume resistivities of the polymer blends. The high irradiation dosages (i.e. 150 kGy and 250 kGy) were found to slightly decrease the electrical resistivity of the alumina trihydrate–added low-density polyethylene and ethylene vinyl acetate blends especially at high loading of montmorillonite. The irradiation effect improved the mobility of montmorillonite ions in polymer matrix, subsequently causing the reduction of the electrical resistivity of the polymer blends. The storage capacity of electrical charges of samples was slightly declined with the increasing of montmorillonite loading levels and irradiation dosages as shown by the dielectric constant results. The dielectric loss tangent of samples slightly increased at the increasing of montmorillonite loading level. However, the dielectric loss tangent was declined with increasing of irradiation dosages.

Investigation of nano-size montmorillonite on electron beam irradiated flame retardant polyethylene and ethylene vinyl acetate blends

This study aims at investigating the effects of montmorillonite (MMT) and electron beam irradiation on alumina trihydrate (ATH) added low density polyethylene and ethylene vinyl acetate (LDPE–EVA) blends. The nano-size MMT was used to improve the flammability and mechanical properties of the ATH added LDPE–EVA blends. The samples were irradiated at the dosage range 0–250kGy using electron beam accelerator. The limiting oxygen index test (LOI) revealed that the incorporation of MMT into ATH added LDPE–EVA blends could improve the flammability up to 28.4LOI%. The application of irradiation effect also improved the flame retardancy of the blends for ∼2LOI% compared to un-irradiated samples. The addition of MMT loading levels from 10 to 20phr exhibited reinforcing effect for 10.3–14.6% in tensile strength. On the other hand, the increasing of MMT loading levels has gradually decreased the surface and volume resistance of ATH added LDPE–EVA blends. The increase in irradiation dosages from 0 to 150kGy was found to slightly decrease the surface and volume resistivity of the ATH added LDPE–EVA samples especially at high loading of MMT. The enhancement of mobility of MMT ionic in polymer matrix could lead to the reduction of the surface and volume resistivity. Consequently, this study has demonstrated that addition of MMT and electron beam irradiation to ATH added LDPE–EVA blends have resulted better flammability, mechanical and electrical properties of ATH added LDPE–EVA blends.

Effects of montmorillonite on the electron beam irradiated alumina trihydrate added polyethylene and ethylene vinyl acetate nanocomposite

AbstractThis study aims at investigating the effects of montmorillonite (MMT) nanocomposite on the electron beam irradiated alumina trihydrate flame retardant added polyethylene and ethylene vinyl acetate blends (FRLE). The addition of MMT into FRLE blends has increased the limiting oxygen index (LOI%), which corresponds the improvement of flame resistivity, whereas increasing amount of MMT and irradiation dosage were found moderately influenced LOI% of the blends. However, incorporation of MMT has shown reinforcing effect to the FRLE, where the tensile strength for the samples subjected to 150 and 250 kGy irradiation have increased for 10.7 and 27%, respectively. In addition, increasing loading level of MMT and irradiation dosage caused inferior effects to the surface and volume resistivity of FRLE as high as four folds. This is due to the enhancement of transportability of MMT ionic in polymer matrix that caused the reduction of resistivity of FRLE. POLYM. COMPOS., 33:1883–1892, 2012. © 2012 Society of Plastics Engineers

Effect of flexibility of ethylene vinyl acetate and crystallization of polypropylene on the mechanical properties of i‐PP/EVA blends

AbstractPolymer blend technology has been widely used for the past several years for the modification or enhancement of mechanical properties of polymers to obtain an overall balance of properties over those of the constituents. Despite its interesting mechanical and thermal properties, the impact strength of polypropylene leaves wide scope for improvement. A series of blends of ethylene vinyl acetate (EVA) copolymer with an impact grade of isotactic polypropylene (i‐PP) were prepared by single screw extrusion at 0–0.32 volume fraction of the dispersed phase. The mechanical properties such as tensile behavior, elongation‐at‐break, and impact strength of these blends systems as well as crystallinity were evaluated. Crystallinity data have been used in greater depth to support the mechanical properties. Differential scanning calorimetry studies conducted to study the modification in crystallinity of the crystalline component, i‐PP, of the blend revealed that the rubber component of the blend enhanced the crystallinity of i‐PP phase by providing sites for nucleation. Tensile modulus and strength decreased while the impact strength and breaking elongation enhanced with blending elastomer concentration. The improved properties of these PP/EVA blends are encouraging for carrying out further work on this system (composites) and suggest potential high impact strength applications for PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A study of the recycling and stability of flexographic photopolymer plates

AbstractFlexographic photopolymer plates have a wide range of commercial applications despite the fact that recycling of such materials is difficult. In consequence, there is a large bulk of leftover material around the world. In this research, the photopolymer plate waste products, identified as styrene‐butadiene rubber (SBR)/polyester are blended into common polypropylene (PP) and ethylenevinylacetate (EVA) resins at different loading percentages. PP and EVA are used as the polymer matrix and the recovered styrene‐butadiene rubber (SBR) material as the filler. Evaluation of the mechanical, spectroscopic, thermal and chemical properties, as well as morphology, is done by means of scanning electron microscopy (SEM). Mechanical results show that elongation strongly depends on the matrix polymer: the greater the amount of solid‐sheet photopolymer (SSP), the smaller the elongation. No specific interactions were detected; however, thermal degradation and transitions were displaced, suggesting some miscibility. More homogeneity is seen for EVA blends, with no significant chemical attack detected. It is possible to reuse these recycled materials in blends with PP and EVA resins. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Influence of Radiation Cross-linking and Nano-filler on the Flammability of Ethylene Vinyl Acetate and Low Density Polyethylene Blends for Wire and Cable Applications

Magnesium hydroxide and huntite hydromagnesite were used in halogen free flame retardant (HFFR) compounds based on blends of ethylene vinyl acetate and low density polyethylene. The effect of both cross-linking with electron beam (EB) and the introduction of nano-filler on flammability were investigated. The developed compounds exhibited an improved oxidation induction temperature. A delay in the beginning of the decomposition of compounds was observed due to barrier effect as demonstrated by the cone calorimeter test. In addition, time to ignition increased with increase of irradiation dose and heat release rate was inhibited due to use of nano-fillers.

An investigation on the correlation between rheology and morphology of nanocomposite foams based on low‐density polyethylene and ethylene vinyl acetate blends

AbstractThis article presents the correlation between rheology and morphology of nanocomposite foams of low‐density polyethylene (LDPE), ethylene vinyl acetate (EVA), and their blends. LDPE/EVA nanocomposites were prepared via melt mixing and then foamed using batch foaming method. To assess the rheological behavior of polymer melts, frequency sweep and creep recovery tests were done. Morphology of the samples was also studied by scanning electron microscopy and X‐ray diffraction. The results showed that with increase in clay content, storage modulus, complex and zero shear viscosities will be increased, which affect the foam morphology. In addition, elasticity plays an important role in foaming process, in a way that samples with more elasticity percentage have the highest cell density and the lowest cell size. POLYM. COMPOS., 31:1808–1816, 2010. © 2010 Society of Plastics Engineers.

Dynamic Mechanical Properties and Weight Optimization of Vibrated Ground Recycled Rubber

The aim in this paper is first and foremost to present an experimental method for measuring the dynamic characteristics of granular rubber. Dynamic measurements on recycled granular rubbers are performed here using dynamic mechanical thermal analysis. The Young’s modulus and loss factor of these materials are estimated by using the frequency—temperature equivalence introduced by Williams—Landel—Ferry. It allows us to describe the dynamic properties over a wide range of frequencies. An increase in the wave speed and a decrease in the loss factor were observed with an increase in the frequency for ground tire rubber (GTR) and compound particles obtained by extrusion of GTR—ethylene vinyl acetate blend. However, for recycled polyurethane particles, the loss factor increases with increasing frequency. Then, we investigate the damping efficiency of granular rubbers introduced into a metallic tube, which was subjected to vibrating bending loads. A numerical model is presented to predict the frequency response for the displacement—force function of the tube—particles system. Model prediction is hence validated through a comparison with experimental results. Second, this paper also aims at calculating the optimum weight of granular material with maximum allowable damping effects on tube subjected to bending vibrations. For this purpose, a technique is proposed from the model developed by optimizing the apparent mass of granular material and the dissipation energy of the tube—particles system. Optimization is achieved by a nondominated storing genetic algorithm (NSAG-II). From the results, this technique can be successfully used to optimize the frequency dependence of wave speed and the loss factor of granular rubber with optimized weight.

Crosslinking Kinetics of Blends of Ethylene Vinyl Acetate and Ground Tire Rubber

The copolymer ethylene vinyl acetate (EVA) and blends of EVA and ground tire rubber (GTR) with different compositions are prepared in the presence and absence of dicumyl peroxide (DCP) as a crosslinking agent. The crosslinking kinetics is investigated through oscillatory disc rheometry (ODR) and differential scanning calorimetry (DSC). The crosslinking kinetics is found to be dependent on the amount of GTR in the EVA/GTR blends; the partially crosslinked GTR phase acts as a physical barrier, slowing down the EVA crosslinking rate. Furthermore, activation energies (Ea) and reaction order (n) values suggest that the crosslinking reactions are not restricted to the EVA bulk, but can also occur to some extent at the EVA/GTR interface.

The effect of HVA-2 on properties of irradiated epoxidized natural rubber (ENR-50), ethylene vinyl acetate (EVA), and ENR-50/EVA blend

ENR-50, EVA, and ENR-50/EVA blend (50/50) containing N, N′- m-phenylene dimaleimide (HVA-2) were prepared by a melt blending process. The samples were irradiated using a 3.0 MeV electron beam machine with doses ranging from 20 to 100 kGy. The influence of a coagent (HAV-2) on the properties of irradiated ENR-50, EVA, and ENR-50/EVA blend was investigated. HVA-2 was found to be more effective in enhancing the irradiation-induced crosslinking in the ENR-50 phase than in EVA. The tensile properties of irradiated ENR-50/EVA blend were improved by the addition of HVA-2. The results of dynamic mechanical analysis revealed that HVA-2 enhances the irradiation-induced crosslinking in ENR-50/EVA blend and also improved the compatibility of the blend.

Flammability characteristics and flame retardant mechanism of phosphate-intercalated hydrotalcite in halogen-free flame retardant EVA blends

The flammability characteristics and flame retardant mechanism of phosphate-intercalated hydrotalcite (MgAl-PO 4) in the halogen-free flame retardant ethylene vinyl acetate (EVA) blends have been studied by X-ray diffraction (XRD), Fourier transfer infrared (FTIR) spectroscopy, cone calorimeter test (CCT), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), limiting oxygen index (LOI) and UL-94 tests. The results show that the hydrotalcite MgAl-PO 4 intercalated by phosphate possesses the enhanced thermal stability and flame retardant properties compared with ordinary carbonate-intercalated hydrotalcite MgAl-CO 3 in the EVA blends. The CCT tests indicate that the heat release rate (HRR) and mass loss rate (MLR) values of the EVA/MgAl-PO 4 samples are much lower than those of the EVA/MgAl-CO 3 samples. The TGA data show that the thermal degradation rates of MgAl-PO 4 and EVA/MgAl-PO 4 samples are much slower and leave more charred residues than those of MgAl-CO 3 and its corresponding EVA blends. The LOI values of EVA/MgAl-PO 4 samples are 2% higher than those of the corresponding EVA/MgAl-CO 3 samples at the range of 40–60 wt% loadings, while the EVA sample with 55 wt% MgAl-PO 4 can reach the UL-94 V-1 rating. The dynamic FTIR spectra reveal that the flame retardant mechanism of MgAl-PO 4 can be ascribed to its catalysis degradation of the EVA resin, which promotes the formation of charred layers with the P–O–P and P–O–C complexes in the condensed phase. The SEM observations give further evidence of this mechanism that the compact charred layers formed from the EVA/MgAl-PO 4 sample effectively protect the underlying polymer from burning.

Characterization of Unvulcanized and Dynamically Vulcanized ENR-50/EVA Blends

Blends of epoxidized natural rubber (ENR-50) and ethylene vinyl acetate (EVA), with varying proportion of the components, were dynamically vulcanized using different cross-linking systems, namely, sulfur and dicumyl peroxide (DCP). Dynamic mechanical properties, tensile properties and morphology of unvulcanized and dynamically vulcanized ENR-50/EVA blends were investigated. Dynamic vulcanization has improved the tensile properties of the blends compared to unvulcanized blends. Dynamic vulcanization also found to improve the compatibility of the blends. Its properties revealed that the entire blends are compatible at all blend ratios. DCP cure system produced a more compatible blend compared to control and sulfur cure system.

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.

Development of thin‐walled halogen‐free cable insulation and halogen‐free fire‐resistant low‐smoke cable‐sheathing compounds based on polyolefin elastomer and ethylene vinyl acetate blends

AbstractThere is a growing interest in the use of polyolefins and their copolymer blends in cable industries. The present investigation deals with the development of thin‐walled halogen‐free cable insulation and thin‐walled halogen‐free fire‐resistant low‐smoke cable sheathing compounds based on polyolefin elastomer (Engage®) and ethylene vinyl acetate (EVA) blends. Blends of Engage (an ethylene octene copolymer) and EVA, varying in proportions, are prepared on a two‐roll mixing mill at an elevated temperature. Physicomechanical, electrical, and the most important flame‐retardant properties of the dicumyl peroxide/triallyl cyanurate cured blends have been basically studied. Properly compounded Engage‐EVA blends are found to be excellent materials in cable industry for insulation as well as for sheathing compounds. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Sorption and diffusion of aromatic solvents through linear low density polyethylene–ethylene vinyl acetate blend membranes

An investigation has been made for understanding the transport behaviour of organic solvents through linear low-density polyethylene (LLDPE)/ethylene vinyl acetate (EVA) blend membranes with special reference to the effects of blend ratio, concentration of cross-linking agent, penetrant size and temperature. Attempts have been made to relate the transport parameter with the morphology of the blend. The various transport parameters such as diffusion coefficient (D), permeation coefficient (P) and sorption coefficients (S) were evaluated at different diffusion conditions. The results were compared with theoretical predictions and found that the diffusion process follows anomolous type behaviour. The blends show dispersed/matrix and co-continuous phase morphologies depending on the composition. Dynamic vulcanization leads to fine and uniform distribution of the dispersed domains with a stable morphology. Among the blends E70 sample shows the maximum solvent uptake and E30 the minimum. The solvent uptake of blend varies with concentration of cross-linking agent. Molecular size of the solvent is a decisive factor in the solvent uptake. The rate of sorption and maximum solvent uptake increase with increase of temperature. Irrespective of the solvents used, the maximum solvent uptake increases with increase of temperature. The observed sorptivity, diffusivity and permeability are associated with cross-link densities of different samples. The D, S and P values increase with increase of EVA content in the blend.

Evolution of the Morphology and Characterization of Compatibilized PBT/EVA Blends Prepared by Reactive Extrusion

AbstractSummary: In this work, the possibility of preparing compatibilized blends of poly(butylene terephthalate) (PBT) and an ethylene vinyl acetate (EVA) copolymer by reactive extrusion in the presence of an ethylene acrylic acid copolymer (EAA) and a bisoxazoline compound (PBO) as compatibilization promoters has been studied. In addition, the evolution of the morphology of the blends under different annealing conditions in the presence and absence of the compatibilizing promoters has been studied. Binary blends of PBT and EVA showed behavior typical of incompatible blends with a gross morphology and bad mechanical performance. The situation was however different for ternary PBT/EVA/EAA and especially for quaternary PBT/EVA/EAA/PBO blends. In the latter case, the morphology was finer, the adhesion improved and the mechanical properties were enhanced, with values almost doubled with respect to those of uncompatibilized blends. These results can be explained by the formation of in situ EAA‐g‐(PBO)PBT copolymers which act as compatibilizers for the blends. While the binary and, to some extent, the ternary blend display coalescence under annealing with rapid coarsening of the morphology, the quaternary compatibilized blends showed the best morphological stability as the particle dimensions remained practically unchanged. This phenomenon was interpreted considering the role of kinetic hindrance played by the compatibilizer formed in situ.SEM micrograph of PBT/EVA/EAA/PBO blend at 5 000×.magnified imageSEM micrograph of PBT/EVA/EAA/PBO blend at 5 000×.