Production of polymeric membranes made of polypropylene,poly(ethylene‐co‐vinyl acetate), and poly(vinyl alcohol)

In this study, we prepared and characterized membranes containing polypropylene, poly(ethylene‐co‐vinyl acetate) (EVA), and poly(vinyl alcohol) (PVA). The production process involved blend extrusion and calendering followed by solvent extraction by toluene and water of the EVA and PVA phases. Morphology studies involving scanning electron microscopy determined the pore size distribution at the surface and in the internal regions of the membrane. The resulting membrane properties were related to the processing variables (extension rate, process temperature, and solvent extraction methods) and blend composition. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3275–3286, 2004     

Processing and properties of an ethylene–vinyl acetate blend foam incorporating ethylene–vinyl acetate and polyurethane waste foams

Waste polyurethane foam (w‐PU) and waste ethylene–vinyl acetate foam (w‐EVA) were used as fillers for the production of an ethylene–vinyl acetate (EVA) blend foam. Two different foaming techniques (single‐stage and heat–chill processes) were used for this purpose. The waste foam concentration was varied up to 30 wt % of the original EVA. The physical, mechanical, and morphological properties of the filled foam were studied. The single‐stage process produced blend foams with a lower density and a greater cell size than the foams obtained by the heat–chill process. The density and compression strength of the blend foam increased as the percentage of w‐PU foam increased. However, for the w‐EVA/EVA blend foams, the addition of w‐EVA foam did not significantly affect the density or compression strength compared to the original EVA foams. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44708.     

Electrical,physicomechanical, and X‐ray studies on ethylene‐vinyl acetate copolymer/polyaniline blends

The conductive blend consisting of ethylene‐vinyl acetate (EVA) and a polyaniline/p‐toluene sulfonic acid (PAn/TSA) complex were prepared by a thermal doping process using a Brabender plasticorder at 150°C. The conductivity, dielectric constant, dissipation factor, mechanical behavior, and structural aspects of these blends were investigated. A higher percentage of the PAn/TSA complex in the EVA matrix resulted in an increase in the electrical properties and a decrease in the mechanical properties like the tensile strength and percentage of elongation. These results were compared with the microcrystalline parameters of the blend obtained from X‐ray profile analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1730–1735, 2002     

Characterization of epoxidized natural rubber/ethylene vinyl acetate (ENR‐50/EVA) blend: Effect of blend ratio

Epoxidized natural rubber/Ethylene vinyl acetate copolymer (ENR‐50/EVA) blends with different ratios were prepared by using a Haake internal mixer. The effect of the blend ratio on the processing, tensile properties (such as tensile strength, elongation at break, Young's modulus and stress–strain behavior), morphology, dynamic mechanical properties, and thermal properties has been investigated. The tensile properties increase with the increase of EVA content, whereas the stabilization torque increases with the increase of ENR‐50 content in the blend. In 40:60 and 50:50 blend of ENR‐50/EVA, both the phases exist as continuous phases, producing a co‐continuous morphology. At these blend ratio, the drastic change in properties were noted, indicating that the phase inversion occurs. The results on dynamic mechanical properties revealed that the blends are compatible. Blending of ENR‐50 and EVA lead to the improvement in thermal stability and 50:50 blend ratios is the most stable blend. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1504–1515, 2006     

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     

Porous composites of hydroxyapatite‐filled poly[ethylene‐co‐(vinyl acetate)] for tissue engineering

A novel porous composite of hydroxyapatite/poly[ethylene‐co‐vinyl acetate)] (HAP/EVA) having better osteointegration was fabricated by gas foaming technique using a non toxic gas blowing agent intended for bone replacement applications. Combined techniques of scanning electronic microscopy (SEM) and X‐ray microcomputed tomography (µCT) analysis showed that the pore size and pore volume of the porous composite decrease with the increase of HAP content. The gravimetric analysis evidenced for good pore interconnectivity within the porous composites. Energy dispersive X‐ray analysis (EDX) studies inveterated the even scattering of Ca ions which in turn indicate the uniform dispersion of HAP particles in the composites. The significant gradation in Ca ion concentration seen in EDX studies is well accordance with the amount of HAP loading in the sample. Mechanical properties of the porous composite having different HAP content were measured to have the compressive strength varying from 1.06 to 2.2 MPa. Non‐cytotoxic character of the material was observed by the cytocompatibility studies. The metabolic activity of L929 cells seeded on the material assessed by [3‐(4,5‐dimethylthiazol)‐2‐yl]‐2,5‐diphenyltertrazolium bromide (MTT) assay was found to be 91.8%. The adhesion and migration of the cells inside the pore walls were visualized by confocal microscopy. Copyright © 2010 Society of Chemical Industry     

Multiple melting and partial miscibility of ethylene‐vinyl acetate copolymer/low density polyethylene blends

Multiple melting behaviors and partial miscibility of ethylene‐vinyl acetate (EVA) copolymer/low density polyethylene (LDPE) binary blend via isothermal crystallization are investigated by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD). Crystallization temperature T (°C) is designed as 30, 50, 70, 80°C with different crystallization times t (min) of 10, 30, 60, 300, 600 min. The increase of crystallization temperature and time can facilitate the growth in lateral crystal size, and also the shift of melting peak, which means the completion of defective secondary crystallization. For blends of various fractions, sequence distribution of ethylene segments results in complex multiple melting behaviors during isothermal crystallization process. Overlapping endothermic peaks and drops of equilibrium melting points of LDPE component extrapolated from Hoffman–Weeks plots clarify the existence of partial miscibility in crystalline region between EVA and LDPE. WAXD results show that variables have no perceptible influence on the predominant existence of orthorhombic crystalline phase structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Fabrication of co‐continuous poly(ε‐caprolactone)/polyglycolide blend scaffolds for tissue engineering

The apparent inability of a single biomaterial to meet all the requirements for tissue engineering scaffolds has led to continual research in novel engineered biomaterials. One method to provide new materials and fine‐tune their properties is via mixing materials. In this study, a biodegradable powder blend of poly(ε‐caprolactone) (PCL), polyglycolide (PGA), and poly(ethylene oxide) (PEO) was prepared and three‐dimensional interconnected porous PCL/PGA scaffolds were fabricated by combining cryomilling and compression molding/polymer leaching techniques. The resultant porous scaffolds exhibited co‐continuous morphologies with ～50% porosity. Mean pore sizes of 24 and 56 μm were achieved by varying milling time. The scaffolds displayed high mechanical properties and water uptake, in addition to a remarkably fast degradation rate. The results demonstrate the potential of this fabrication approach to obtain PCL/PGA blend scaffolds with interconnected porosity. In general, these results provide significant insight into an approach that will lead to the development of new composites and blends in scaffold manufacturing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42471.     

Fabrication of poly(ε‐caprolactone) (PCL)/poly(propylene carbonate) (PPC)/ethylene‐α‐octene block copolymer (OBC) triple shape memory blends with cycling performance by constructing a co‐continuous phase morphology

In this paper, a triple shape memory material was prepared by ultra‐simple melt blending from poly(ε‐caprolactone) (PCL), poly(propylene carbonate) (PPC) and ethylene‐α‐octene block copolymer (OBC). The obtained material possessed a co‐continuous phase morphology and presented an excellent triple shape memory effect (triple‐SME). Theoretical prediction demonstrated that a special continuous phase morphology could be constructed by adjusting the proportions of the blend. Moreover, the results indicated that a close relationship existed between the phase morphology and the triple‐SME of PCL/PPC/OBC. The sample with 35 vol% PPC content contributed to the formation of a continuous phase morphology and exhibited the optimal triple‐SME. Additionally, the sample PCL/PPC/OBC (32.5/35/32.5) showed outstanding structure and performance stability during cycle loading–unloading tests, which evidenced the prominent cycling shape memory property (nearly 100% shape fixing and recovery of temporary shape). Overall, this work could provide an efficient, convenient and recyclable method to obtain high‐performance shape memory materials. © 2020 Society of Chemical Industry     

Porous biodegradable polyester blends of poly(L‐lactic acid) and poly(ε‐caprolactone): physical properties,morphology, and biodegradation

Poly(L ‐lactic acid) (PLLA), poly(ε‐caprolactone) (PCL), and their films without or blended with 50 wt% poly(ethylene glycol) (PEG) were prepared by solution casting. Porous films were obtained by water‐extraction of PEG from solution‐cast phase‐separated PLLA‐blend‐PCL‐blend‐PEG films. The effects of PLLA/PCL ratio on the morphology of the porous films and the effects of PLLA/PCL ratio and pores on the physical properties and biodegradability of the films were investigated. The pore size of the blend films decreased with increasing PLLA/PCL ratio. Polymer blending and pore formation gave biodegradable PLLA‐blend‐PCL materials with a wide variety of tensile properties with Young's modulus in the range of 0.07–1.4 GPa and elongation at break in the range 3–380%. Pore formation markedly increased the PLLA crystallinity of porous films, except for low PLLA/PCL ratio. Polymer blending as well as pore formation enhanced the enzymatic degradation of biodegradable polyester blends. Copyright © 2006 Society of Chemical Industry     

Double‐yielding behavior in injection‐molded polycarbonate/high‐density polyethylene/ethylene–vinyl acetate copolymer blends

A uniaxial tensile test was performed for polycarbonate (PC)/high‐density polyethylene (HDPE)/ethylene–vinyl acetate copolymer (EVA) blends with a fixed EVA content but various PC contents. The double‐yielding phenomenon and its composition dependence, as observed in the PC/HDPE blend, were again detected. EVA did not serve as a successful compatibilizer of PC and HDPE in the PC/HDPE/EVA blend. The incorporation of EVA resulted in a larger size and a more irregular shape of the PC fibers, as indicated in the scanning electron microscope observations; this, consequently, produced a higher serious stress concentration in the blend. This more complicated and instable morphology produced different double‐yielding behaviors in the PC/HDPE/EVA blends compared with the binary one. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Photocrosslinking of halogen‐free flame‐retarded ethylene‐vinyl acetate copolymer by phosphorous‐nitrogen compound NP28

The photoinitiated crosslinking of halogen‐free flame‐retarded ethylene‐vinyl acetate copolymer (EVA) by the phosphorous‐nitrogen compound NP28 in the presence of photoinitiator and crosslinker and characterization of the related properties have been investigated by gel determination, heat extension test, thermogravimetric analysis (TGA), mechanical measurement, and thermal aging test. The photocrosslinking efficiency of EVA/NP28 blend and various factors affecting the crosslinking process, such as photoinitiator, crosslinker, NP28 content, and irradiation temperature, were studied in detail and optimized by comparison of gel content. The results show that the EVA/NP28 blend filled with 28.2 wt % NP28 with a thickness of 1.6 mm is homogeneously photocrosslinked to a gel content of above 80 wt % with 4.8 s UV‐irradiation under optimum conditions. The data from TGA, mechanical measurement, and thermal aging test give evidence that the thermal stability and mechanical properties of photocrosslinked EVA/NP28 blend are much better than those of the unphotocrosslinked one.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Tailoring the morphology and properties of poly(lactic acid)/poly(ethylene)‐co‐(vinyl acetate)/starch blends via reactive compatibilization

Poly(lactic acid)/poly(ethylene‐co‐vinyl acetate)/starch (PLA/EVA/starch) ternary blends were prepared by multi‐step melt processing (reactive extrusion) in the presence of maleic anhydride (MA), benzoyl peroxide and glycerol. The effects of MA and glycerol concentration on the morphology and properties of the PLA/EVA/starch blends were studied using scanning electron microscopy, transmission electron microscopy, atomic force microscopy, the Molau experiment, dynamic mechanical thermal analysis and differential scanning calorimetry etc. The plasticization and compatibilization provided a synergistic effect to these blends accompanied by a significant reduction in starch particle size and an increase in interfacial adhesion. Starch was finely dispersed in the ternary blends with a dimension of 0.5 ? 2 µm. Furthermore, EVA‐coated starch or a starch‐in‐EVA type of morphology was observed for the reactively compatibilized PLA/EVA/starch blends. The EVA with starch gradually changed into a co‐continuous phase with increasing MA concentration. Consequently, the toughness of the blends was improved. Since property stability of starch is an issue, the tensile properties of these blends were measured after different storage times and the blends showed good property stability. Copyright © 2012 Society of Chemical Industry     

Toughening and compatibilization of polypropylene/polyamide‐6 blends with a maleated–grafted ethylene‐co‐vinyl acetate

In this article, maleated–grafted ethylene‐co‐vinyl acetate (EVA‐g‐MA) was used as the interfacial modifier for polypropylene/polyamide‐6 (PP/PA6) blends, and effects of its concentration on the mechanical properties and the morphology of blends were investigated. It was found that the addition of EVA‐g‐MA improved the compatibility between PP and PA6 and resulted in a finer dispersion of dispersed PA6 phase. In comparison with uncompatibilized PP/PA6 blend, a significant reduction in the size of dispersed PA6 domain was observed. Toluene‐etched micrographs confirmed the formation of interfacial copolymers. Mechanical measurement revealed that the addition of EVA‐g‐MA markedly improved the impact toughness of PP/PA6 blend. Fractograph micrographs revealed that matrix shear yielding began to occur when EVA‐g‐MA concentration was increased upto 18 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99:3300–3307, 2006     

Effect of trimethylolpropane triacrylate (TMPTA) on the properties of irradiated epoxidized natural rubber (ENR‐50), ethylene‐(vinyl acetate) copolymer (EVA), and an ENR‐50/EVA blend

The effect of trimethylolpropane triacrylate (TMPTA) monomer on the tensile properties, dynamic mechanical properties, and morphology of irradiated epoxidized natural rubber (ENR‐50), ethylene‐(vinyl acetate) copolymer (EVA), and an ENR‐50/EVA blend was investigated. The ENR‐50, EVA, and ENR‐50/EVA blend were irradiated by using a 3.0‐MeV electron‐beam apparatus at doses ranging from 20 to 100 kGy. The improvement of tensile properties and morphology with irradiation indicated the advantage of having irradiation‐induced crosslinks in these materials. Observation of the properties studied confirmed that TMPTA was efficient in enhancing the irradiation‐induced crosslinking of ENR‐50, EVA, and the ENR‐50/EVA blend. Addition of TMPTA improved the adhesion between the ENR‐50/EVA blend phases by forcing grafting and crosslinking at a higher irradiation dose (100 kGy). J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers.     

Natural rubber/poly(ethylene‐co‐vinyl acetate)‐blend‐based nanocomposites

Natural rubber (NR)/poly(ethylene‐co‐vinyl acetate) (EVA) blend–clay nanocomposites were prepared and characterized. The blend nanocomposites were prepared through the melt mixing of NR/EVA in a ratio of 40/60 with various amounts of organoclay with an internal mixer followed by compression molding. X‐ray diffraction patterns revealed that the nanocomposites formed were intercalated. The formation of the intercalated nanocomposites was also indicated by transmission electron microscopy. Scanning electron microscopy, used to study the fractured surface morphology, showed that the distribution of the organoclay in the polymer matrix was homogeneous. The tensile modulus of the nanocomposites increased with an increase in the organoclay content. However, an increase in the organoclay content up to 5 phr did not affect the tensile strength, but the organoclay reduced this property when it was increased further. This study also indicated that a low silicate content dispersed in the blend matrix was capable of increasing the storage modulus of the material. The addition of the organoclay also increased the decomposition temperature of the NR/EVA blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 353–362, 2006     

Optimization of engineering and solvent resistive behavior of high vinyl acetate content EVA‐modified poly(ethylene‐co‐1‐octene) interpenetrating network blends using taguchi orthogonal array

Process parameters of poly (ethylene‐co‐vinyl acetate) (EVA)‐modified poly (ethylene‐co‐1‐octene) (POE)‐interpenetrating, double network blend was designed through Taguchi L9 orthogonal array as a novel approach for complete optimization of engineering and solvent‐swelling properties. Influence of different factors like EVA and peroxide concentrations, blending temperature, and blending time on gel content, tensile modulus, tensile strength, ultimate elongation were statistically calculated. Results showed good correlation between mathematical and physical inferences. Stress relaxation, hysteresis and other physico‐mechanicals like total elongation, solvent‐swelling, etc., were interestingly depended upon the nature of dominantly crosslinked phase instead of net crosslinking of the network hybrids. Sorption, on the other hand, depended on the hydrophobic‐hydrophilic property of the surfaces. The series of data produced finally helped to select the best process parameters under which a particular POE‐EVA blend composition yielded most balanced physico‐mechanicals. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Poly(ethylene‐co‐vinyl acetate)‐graft‐poly(methyl methacrylate) (EVA‐graft‐PMMA) as a modifier of epoxy resins

Conventional approaches to toughen thermosets are: (1) the polymerization‐induced phase separation of a rubber or a thermoplastic, or (2) the use of a dispersion of preformed particles in the initial formulation. In the present study it is shown that it is possible to combine both techniques by using graft copolymers with one of the blocks being initially immiscible and the other that phase separates during polymerization. This is illustrated by the use of poly(ethylene‐co‐vinyl acetate)‐graft‐poly(methyl methacrylate) (EVA‐graft‐PMMA) as modifier of an epoxy resin. EVA is initially immiscible and PMMA phase separates during polymerization. Blends of an epoxy monomer based on diglycidylether of bisphenol A (DGEBA, 100 parts by weight), piperidine (5 parts by weight), and PMMA (5 parts by weight), showed the typical polymerization‐induced phase separation of PMMA‐rich domains before gelation of the epoxy network. Replacing PMMA by EVA‐graft‐PMMA (5 parts by weight), yielded stable dispersions of EVA blocks, favoured by the initial solubility of PMMA blocks. Phase separation of PMMA blocks in the course of polymerization led to a dispersion of in situ generated biphasic particles (plausibly composed of EVA cores surrounded by PMMA shells), with average diameters varying from 0.3 to 0.6 µm with the cure temperature. This procedure may be used to generate stable dispersions of biphasic particles for toughening purposes. © 2002 Society of Chemical Industry     

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     

Soil burial test for poly(ethylene‐co‐vinyl alcohol)‐graft‐polycaprolactone

The ring‐opening polymerization of ε‐caprolactone was carried out with poly(ethylene‐co‐vinyl alcohol) as a macroinitiator to synthesize poly(ethylene‐co‐vinyl alcohol)‐graft‐polycaprolactone (EVOH‐g‐PCL). A simple low‐density polyethylene (LDPE)/polycaprolactone (PCL) (64/36) blend lost 5.3 wt % of its original weight after 90 days of a soil burial test. However, the elongation at break of the LDPE/PCL blend remained almost invariable even after the solid burial test because the tensile properties depended mostly on the LDPE phase on account of the poor interaction between the continuous LDPE matrix and the dispersed PCL phase. For EVOH‐g‐PCL, the elongation at break decreased drastically as a result of the soil burial test, and the reduction of the elongation at break was more pronounced for EVOH‐g‐PCL with a higher PCL concentration, even though the weight loss of EVOH‐g‐PCL after the soil burial test was as low as 1.2–1.3% and was nearly independent of the PCL concentration. Few holes were observed in EVOH‐g‐PCL when the PCL concentration was less than 26 wt % after an accelerated hydrolysis experiment at 60°C for 7 days in a 0.1M KOH solution. In contrast, the hydrolysis formed small holes in EVOH‐g‐PCL with a PCL concentration of 36 wt %. The LDPE/PCL blend was much better percolated, as a result of the hydrolysis, than EVOH‐g‐PCL with the same PCL concentration; the soil burial test showed the same results. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1064–1071, 2005