Effect of hot air aging on the properties of ethylene‐vinyl acetate copolymer and ethylene‐acrylic acid copolymer blends

The aim of this investigation is to evaluate the effect of hot air aging on properties of ethylene‐vinyl acetate copolymer (EVA, 14 wt % vinyl acetate units), ethylene‐acrylic acid copolymer (EAA, 8 wt % acrylic acid units), and their blends. Attenuated total reflection‐Fourier transform infrared spectroscopy, differential scanning calorimeter (DSC), wide angle X‐ray diffraction, and mechanical tests are employed to investigate the changes of copolymer blends' structures and properties. Increase of carbonyl index derived from ATR measurements with aging time suggests the incorporation of oxygen into the polymeric chain. By DSC measurements, the enthalpy at low temperature endothermic peak (T_m2) of EAA becomes less and disappears after 8 weeks aging, but enthalpy at T_m2 of EVA is not influenced by the hot air aging and remains stable despite of the aging time. For various proportions of EAA and EVA blends, enthalpy at T_m2 decreases as the EAA proportion increases when aging time is 8 weeks; after several weeks of hot air aging, the various blends appear a same new peak just over the aging temperature 70°C which is due to the completion of crystals which are not of thermodynamic equilibrium state. Mechanical tests show that increase of crystallinity and hot air aging deterioration both have influence on the hardness, tensile strength, and elongation at break. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(ethylene‐co‐vinyl acetate) blends with phenoxy

EVA was blended with phenoxy over the whole range of composition using a twin‐screw Brabender. Two‐phase separation caused by EVA crystallization was observed in the EVA‐rich blends and the dispersed domain of EVA was not clearly shown in the phenoxy‐rich blends. Differential scanning calorimetry (DSC) showed that the glass transition temperature (T_g) of EVA was increased by 5–10°C in the EVA‐rich blends but the T_g of phenoxy was superposed over the melting behavior of EVA. X‐ray diffraction measurement indicated that EVA crystallization was restricted in the phenoxy‐rich blends and the EVA crystal structure was influenced by incorporation of phenoxy into the EVA‐rich blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 227–236, 1999     

Combined XPS and contact angle studies of flat and rough ethylene‐vinyl acetate copolymer films

Flat and rough thin films were prepared by dip coating using LDPE, PVAc, and EVA polymers containing 12–40% VA contents. Surface free energy of flat films was determined by measuring contact angles. Surface atomic composition was investigated by XPS at 0° and 60° take‐off angles. XPS results show that hydrophobic PE component was found to enrich at the near‐surface region for all EVA samples for a depth of ～ 5 nm for both flat and rough surfaces, whereas hydrophilic VA component was enriched on the surface when VA < 18% for only at 10 nm depth. The difference between the XPS results of the flat and rough surfaces was not significant for EVA samples except EVA‐33 surface where the atomic oxygen content decreased 15–20% for rough surfaces. Contact angle hysteresis values for the rough samples were much larger than that of the flat samples for LDPE and EVA‐12 surfaces due to the presence of partial trapping of air pockets on these rough surfaces. A good agreement was obtained between surface concentration of atomic oxygen in the 5 nm outermost layer and γ surface free energy component especially for the samples having high VA contents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Physicomechanical,optical, barrier,and wide angle X‐ray scattering studies of filled low density polyethylene films

Series of low density polyethylene (LDPE) films filled with different fillers such as silica, mica, soya protein isolate, potassium permanganate, and alumina were processed using a single screw extruder. The filled LDPE films were characterized for physicomechanical properties like tensile strength, percentage elongation at break, and tear strength, optical properties like percent transmission and haze. The barrier properties such as water vapor transmission rate and oxygen transmission rate of the filled LDPE films have also been reported. Microcrystalline parameters such as crystal size (〈N〉) and lattice distortion (g) of the filled LDPE films obtained using wide angle X‐Ray scattering method have been reported. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2781–2789, 2006     

Thermal and wide angle X‐ray analysis of chemically and radiation‐crosslinked low and high density polyethylenes

Low and high density polyethylenes (PE) were crosslinked by two methods, namely, chemically by use of different amounts of tert‐butyl cumyl peroxide (BCUP) and by irradiation with different doses of electron beam. A comparison between the effects of these two types of crosslinking on crystalline structure, crystallinity, crystallization, and melting behaviors of PE was made by wide angle X‐ray diffraction and DSC techniques. Analysis of the DSC first heating cycle revealed that the chemically induced crosslinking, which took place at melt state, hindered the crystallization process and decreased the degree of crystallinity, as well as the size of crystals. Although the radiation‐induced crosslinking, which took place at solid state, had no significant influence on crystalline region, rather, it only increased the melting temperature to some extent. However, during DSC cooling cycle, the crystallization temperature showed a prominent decrease with increasing irradiation dose. The wide angle X‐ray scattering analysis supported these findings. The crystallinity and crystallite size of chemically crosslinked PE decreased with increasing peroxide content, whereas the irradiation‐crosslinked PE did not show any change in these parameters. As compared with HDPE, LDPE was more prone to crosslinking (more gel content) owing to the presence of tertiary carbon atoms and branching as well as owing to its being more amorphous in nature. HDPE, with its higher crystalline content, showed relatively less tendency toward crosslinking especially by way of irradiation at solid state. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3264–3271, 2006     

Study on the properties of ethylene‐vinyl acetate rubber vulcanizate filled with superfluous magnesium hydroxide/methacrylic acid

Ethylene‐vinyl acetate rubber (EVM) vulcanizates cured by dicumyl peroxide (DCP) with excellent mechanical properties were obtained by adding superfluous magnesium hydroxides (MH)/methacrylic acid (MAA). Different factors such as the DCP content and MH content were investigated to reveal their effects on the properties of the MH/MAA‐filled EVM vulcanizates. The formulation of DCP of 2 phr, MH of 60 phr, and MAA of 5 phr is recommended for the EVM vulcanizates with excellent mechanical properties. The stress relaxation and stress softening behavior of MH/MAA‐filled EVM vulcanizates were studied. The stress relaxation and stress softening became faster and more obvious with increasing MH content. The hot air aging resistance of EVM vulcanizates filled with different fillers such as silica and high abrasion furnace were compared, and the MH/MAA‐filled EVM vulcanizates had the best aging resistance at 40‐phr filler content. The MH/MAA‐filled EVM vulcanizates had excellent flame retardancy due to the high MH content. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Free‐radical grafting of trans‐ethylene‐1,2‐dicarboxylic acid onto molten ethylene‐vinyl acetate copolymer

Distinctive features of free‐radical grafting of trans‐ethylene‐1,2‐dicarboxylic acid (TEDA) onto macromolecules of molten ethylene‐vinyl acetate copolymer (EVA) in the course of reactive extrusion have been investigated along with structure, mechanical characteristics, and high‐elastic properties of molten functionalized products (EVA‐g‐TEDA). It is shown that EVA‐g‐TEDA yield depends on both the peroxide initiator concentration and content of vinyl acetate units in the copolymer molecular structure. At functionalization, acid grafting is accompanied by secondary reactions of macromolecular degradation and crosslinking. With a low‐peroxide initiator concentration (0.1 wt %), degradation prevails; with a higher (0.3 wt %) concentration, crosslinking of macromolecules prevails. It is reported that monomers being grafted attach mostly over secondary carbon atoms in the polymer chain. EVA‐g‐TEDA appears to have a less perfect crystal structure with a lower‐melting temperature and crystallinity as against the starting polymer. The functionalized products display enhanced rigidity and lower deformability in comparison with the initial copolymer. Variations in the swelling ratio and melt strength of EVA‐g‐TEDA depend on the course of competing secondary processes of macromolecular degradation and crosslinking. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

X‐ray diffraction characterization of the structure of zein–Oleic acid films

Wide‐angle (WAXS) and small‐angle X‐ray scattering (SAXS) studies of dry granular zein, zein fibers, zein–oleic acid resin, and zein–oleic acid films are reported. WAXS patterns showed two diffuse rings for these samples indicative of noncrystalline structures. Measured d‐spacings of ∼ 4.6 Å and ∼ 10.5 Å were found for zein–oleic acid resins and films, consistent with the presence of α‐helical segments. The granular zein and zein fibers had ∼ 4.6‐Å and ∼ 9.5‐Å spacings. Neither the films nor the fibers showed evidence of orientation of the molecular axes. SAXS studies of zein–oleic acid films indicated that the structure of the films was affected by preparation method. Biaxially drawn resin films showed periodicities of ∼ 170 Å along the film surface direction and ∼ 135 Å in the thickness direction, while the cast films had weaker intensity periodicities of ca. 80 Å for all beam directions; a weak, diffuse 45‐Å spacing was also observed for both samples. The 170‐Å periodicity was present in the resin before deformation and following uniaxial deformation. No SAXS periodicity was observed for the granular zein or zein fibers. Several structural models are presented for the resin films that are consistent with reports in the literature that zein, in solution, consist of prism‐like particles consisting of four or more molecules. ? 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1267‐1281, 1999     

Preparation and characterization of ethylene vinyl acetate copolymer/montmorillonite nanocomposite

Ethylene vinyl acetate copolymer (EVA) and monmorillonite (MMT) nanocomposites have been investigated as a function of vinyl acetate content and molecular weight of EVA and types of substituted alkyl ammonium of MMT. It is found that vinyl acetate content and type of substituted alkyl ammonium are important factors for the intercalation behaviour of MMT in MMT/EVA nanocomposite. Maleic anhydride grafted high‐density polyethylene was used as a compatibilizer to improve the intercalation behaviour of MMT. X‐ray diffraction and transmission electron microscopy were used to characterize the intercalation/exfoliation behaviour, and mechanical properties were measured. © 2003 Society of Chemical Industry     

Thermal and flame retardant properties of ethylene‐vinyl acetate copolymer/modified multiwalled carbon nanotube composites

The synthesized flame retardant 9,10‐dihydro‐9‐oxa‐10‐phosphaphanthrene‐10‐oxide/vinyl methyl dimethoxysilane (DV) was used to modify multiwalled carbon nanotubes (MWNTs). The results of FTIR, ¹H‐NMR, and TGA measurements show that DV has been covalently grafted onto the surfaces of MWNTs, and the MWNTs‐g‐DV is obtained successfully. Transmission electron microscopy images show that a core‐shell nanostructure appears with MWNTs as the core and the DV thin layers as the shell, and the modified MWNTs with DV can achieve better dispersion than unmodified MWNTs in EVM matrix. Thermogravimetric analysis and cone calorimeter tests indicate that the thermal stability and flame retardant are improved for the presence of the MWNTs in EVM matrix. Moreover, the improvement is more evident for EVM/MWNTs‐g‐DV composite compared to unmodified MWNTs‐based composite, which can be attributed to the better dispersion of the DV‐modified MWNTs and to the chemical structure of the combustion residue. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal and mechanical properties of uncrosslinked and chemically crosslinked polyethylene/ethylene vinyl acetate copolymer blends

Uncrosslinked and chemically crosslinked binary blends of low‐ and high‐density polyethylene (PE), with ethylene vinyl acetate copolymer (EVA), were prepared by a melt‐mixing process using 0–3 wt % tert‐butyl cumyl peroxide (BCUP). The uncrosslinked blends revealed two distinct unchanged melting peaks corresponding to the individual components of the blends, but with a reduced overall degree of crystallinity. The crosslinking further reduced crystallinity, but enhanced compatibility between EVA and polyethylene, with LDPE being more compatible than HDPE. Blended with 20 wt % EVA, the EVA melting peak was almost disappeared after the addition of BCUP, and only the corresponding PE melting point was observed at a lowered temperature. But blended with 40% EVA, two peaks still existed with a slight shift toward lower temperatures. Changes of mechanical properties with blending ratio, crosslinking, and temperature had been dominated by the extent of crystallinity, crosslinking degree, and morphology of the blend. A good correlation was observed between elongation‐at‐break and morphological properties. The blends with higher level of compatibility showed less deviation from the additive rule of mixtures. The deviation became more pronounced for HDPE/EVA blends in the phase inversion region, while an opposite trend was observed for LDPE/EVA blends with co‐continuous morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3261–3270, 2007     

Poly(ethylene‐vinyl co‐vinyl acetate)/clay nanocomposites: Mechanical,morphology, and thermal behavior

Nanocomposites of ethylene‐vinyl acetate copolymer (EVAL) with Dellite organoclay were prepared in a laboratory extruder. The extent of intercalation of the nanocomposites was studied by field emission scanning electron microscopy and X‐ray diffraction. It was established that the organoclay is well dispersed and preferentially embedded in the EVAL phase. Further, the intercalation degree of the organoclay decreased with increasing organoclay content. The mechanical properties of the nanocomposites were studied as a function of clay loading and EVAL type. The nanocomposites exhibited enhanced thermal stability as seen in thermogravimetric studies. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Poly(methyl methacrylate) toughened by ethylene‐vinyl acetate copolymer: Physico‐mechanical,thermal, and chemical properties

Blends of poly(methyl methacrylate) (PMMA) with different composition viz., 5, 10, 15, and 20 wt % of ethylene‐vinyl acetate (EVA) copolymer were prepared by extrusion in a corotating twin screw extruder. These prepared PMMA/EVA blends have been characterized for physicomechanical properties such as density, surface hardness, izod impact strength, tensile strength, tensile elongation, and tensile modulus. The chemical aging and heat aging tests were performed on the blends by exposing them to different chemical environments and to 80°C for 168 h respectively. The influence of chemical aging and heat ageing on the mechanical performance of PMMA/EVA blends has been studied. The PMMA/EVA blends were also characterized for thermal properties such as vicat softening point (VSP) and melt flow index (MFI). That means significant improvement in impact strength of PMMA was noticed after incorporation of EVA into PMMA matrix and it lies in the range 19.1–31.96 J/m. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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     

Morphological control of porous ethylene‐vinyl acetate copolymer membrane obtained from a co‐continuous ethylene‐vinyl acetate copolymer/poly(ϵ‐caprolactone) blend

Ethylene‐vinyl acetate copolymer (EVA)/poly(?‐caprolactone) (PCL) blend (50/50 w/w) with co‐continuous morphology was prepared via melt mixing for fabricating microporous EVA membrane materials through selective solvent extraction. Shear flow and quiescent annealing techniques were employed to control co‐continuous phase size in the EVA/PCL blend, and the time‐ and temperature‐dependent relations of phase size were then evaluated theoretically. Using these techniques, microporous EVA membrane materials with various pore sizes ranging from 2 µm to more than 200 µm were obtained. In contrast to the porous EVA membrane prepared by the traditional way of solvent casting/particulate leaching, the as‐obtained microporous membrane shows a higher level of interconnectivity and much narrower pore size distribution with uniform pore structure. © 2013 Society of Chemical Industry     

Study of heat shrinkability of crosslinked low‐density polyethylene/poly(ethylene vinyl acetate) blends

In this study, the heat‐shrinkage property in polymer was induced by first compounding low‐density polyethylene/poly(ethylene vinyl acetate) (LDPE/EVA) blends with various amounts of peroxide in a twin‐screw extruder at about 130°C. The resulting granules were molded to shape and chemically crosslinked by compression molding. A process of heating–stretching–cooling was then performed on the samples while on a tensile machine. Shrinkability and effective parameters were also investigated using thermal mechanical analysis. The results showed that the gel fraction was higher for the sample of higher EVA content with the same amount of dicumyl peroxide (DCP). A decrease in the melting point and heat of fusion (ΔH_f), as determined from DSC, was observed with an increase in the DCP content. Studies on the heat shrinkability of the samples showed that samples stretched above the melting point had a higher shrinkage temperature than those stretched around the crystal transition temperature. The results showed that by increasing the peroxide content, the shrinkage temperature was decreased. These could be attributed to the formation of new spherulites as well as changes in the amount and the size of crystals. Furthermore, in samples elongated at 120°C (above the melting point), the rate of stretching had no effect on the shrinkage temperature. The results showed that the extent of strain had no effect on the temperature of shrinkage, but rather on the ultimate shrinkage value. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1389–1395, 2004     

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     

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     

Structure–shrinkability correlation in polymer blends of ethylene vinyl acetate and chlorosulfonated polyethylene

Heat shrinkability, which is a collective property of polymers, is being utilized in various applications, mainly in the field of encapsulation. Elastic memory is introduced into the system in the form of an elastomeric phase. Here the blends of ethylene vinyl acetate and chlorosulfonated rubber were studied with reference to their shrinkability. It was found that an increase in the elastomer content increased the shrinkage and an increase in cure time also increased the shrinkage. It was seen that high temperature (H‐T) stretched samples showed higher shrinkage than the low (room) temperature (R‐T) stretched one. Generally, the crystallinity of the H‐T stretched sample was higher than that of the low temperature stretched sample, which was again higher than that of the original unstretched sample; but for the low elastomer content blend the crystallinity of the R‐T stretched sample was found to be greater than the corresponding H‐T stretched one. The H‐T differential scanning calorimetry showed that an increase in the CSM content caused the stability toward oxygen to increase. The first decomposition temperatures were found to be higher and the second decomposition temperatures appeared to be lower for the H‐T shrunk sample than the corresponding unstretched sample. The rate of degradation appeared to be enhanced initially, then after 50% decomposition the rate started going down compared to the usual unstretched sample. From SEM it was seen that the H‐T stretched sample was more elongated than the R‐T stretched one. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 707–715, 2000     

Recent developments in polymer applications of synchrotron small‐angle X‐ray scattering

Synchrotron radiation facilities have been established and become very familiar in the polymer community not only from academic but also industrial viewpoints. It is not so unusual now to conduct simultaneous measurements of small‐angle X‐ray scattering (SAXS) with other techniques such as wide‐angle X‐ray scattering, stress–strain, light scattering, and so forth. New techniques have also been established and have become more familiar in recent years. In this review, recent developments in polymer applications of synchrotron SAXS are summarized. Instrumental developments and progress in data analyses are reviewed from the following aspects: ultra‐small‐angle X‐ray scattering, anomalous SAXS, X‐ray photon correlation spectroscopy, new types of simultaneous measurements, grazing‐incidence SAXS, new trends in nanoparticle analyses and industrial applications. © 2016 Society of Chemical Industry