Correlation between the morphology and dynamic mechanical properties of ethylene vinyl acetate/linear low‐density polyethylene blends: Effects of the blend ratio and compatibilization

The effects of the blend composition and compatibilization on the morphology of linear low‐density polyethylene (LLDPE)/ethylene vinyl acetate (EVA) blends were studied. The blends showed dispersed/matrix and cocontinuous phase morphologies that depended on the composition. The blends had a cocontinuous morphology at an EVA concentration of 40–60%. The addition of the compatibilizer first decreased the domain size of the dispersed phase, which then leveled off. Two types of compatibilizers were added to the polymer/polymer interface: linear low‐density polyethylene‐g‐maleic anhydride and LLDPE‐g phenolic resin. Noolandi's theory was in agreement with the experimental data. The conformation of the compatibilizer at the blend interface could be predicted by the calculation of the area occupied by the compatibilizer molecule at the interface. The effects of the blend ratio and compatibilization on the dynamic mechanical properties of the blends were analyzed from ?60°C to +35°C. The experiments were performed over a series of frequencies. The area under the curve of the loss modulus versus the temperature was higher than the values obtained by group contribution analysis. The loss tangent curve showed a peak corresponding to the glass transition of EVA, indicating the incompatibility of the blend system. The damping characteristics of the blends increased with increasing EVA content because of the decrease in the crystalline volume of the system. Attempts were made to correlate the observed viscoelastic properties of the blends with the morphology. Various composite models were used to model the dynamic mechanical data. Compatibilization increased the storage modulus of the system because of the fine dispersion of EVA domains in the LLDPE matrix, which provided increased interfacial interaction. Better compatibilization was effected at a 0.5–1% loading of the compatibilizer. This was in full agreement with the dynamic mechanical spectroscopy data. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4526–4538, 2006     

Melt rheology of HDPE/EVA blends: The effects of blend ratio,compatibilization, and dynamic vulcanization

The melt rheological behavior of high‐density polyethylene (HDPE)/ethylene vinyl acetate (EVA) blends has been examined with reference to the effect of blend ratio, shear stress, and temperature. The HDPE/EVA blends exhibit pseudoplastic behavior, and the observed rheological behavior of the blends was correlated with the extrudate morphology. The experimental values of the viscosity were compared with the theoretical models. The effect of maleic‐ and phenolic‐modified PE compatibilizers on the viscosity of H₇₀ blend was analyzed and found that compatibilization did not significantly increase the viscosity. The effect of dynamic vulcanization and temperature on the viscosity was also analyzed. The activation energy of the system decreased with increase in EVA content in the system. The phase continuity and phase inversion points of the blends were theoretically predicted and compared with the experimental values. The melt flow index (MFI) values of the blends were also determined and found that the MFI values decreased with increase in EVA content in the system. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Melt rheology and morphology of LLDPE/EVA blends: Effect of blend ratio,compatibilization, and dynamic crosslinking

The melt rheological properties of linear low‐density polyethylene (LLDPE)/ethylene vinyl acetate (EVA) blends were investigated with special reference to the effect of blend ratio, temperature, shear rate, compatibilization, and dynamic vulcanization. The melt viscosity of the blends determined with a capillary rheometer is found to decrease with an increase of shear rate, which is an indication of pseudoplastic behavior. The viscosity of the blend was found to be a nonadditive function of the viscosities of the component polymers. A negative deviation was observed because of the interlayer slip between the polar EVA and the nonpolar LLDPE phases. The melt viscosity of these blends decreases with the increased concentration of EVA. The morphology of the extrudate of the blends at different shear rates and blend ratios was studied and the size and distribution of the domains were examined by scanning electron microscopy. The morphology was found to depend on shear rate and blend ratio. Compatibilization of the blends with phenolic‐ and maleic‐modified LLDPE increased the melt viscosity at lower wt % of compatibilizer and then leveled off. Dynamic vulcanization is found to increase the melt viscosity at a lower concentration of DCP. The effect of temperature on melt viscosity of the blends was also studied. Finally, attempts were made to correlate the experimental data on melt viscosity and cocontinuity region with different theoretical models. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3210–3225, 2002     

Dynamic rheological,morphology and mechanical properties of compatibilized LLDPE/EMA blends

Blends of linear low density polyethylene (LLDPE) and ethylene-co-methyl acrylate (EMA) having 60/40 composition was studied with and without compatibilizing agent. The compatibilizing agent used was maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA). The LLDPE backbones of the compatibilizer are compatible with LLDPE blend component, whereas the maleic anhydride is affinated with carbonyl groups of EMA. The effectiveness of the compatibilizing agent was evaluated using different techniques like mechanical, thermal, scanning electron microscopy and rheological studies. Best compatibilization effect was found in the blend at a loading of 3 wt% of compatibilizer since at this level of compatibilizer complex viscosity, tensile strength, modulus, elongation at break, impact strength was found to be higher. The increase in the melt viscosity, storage modulus and thermal stability of the compatibilized blends indicated enhanced interactions between the discrete LLDPE and EMA phases induced by the functional compatibilizer.     

Compatibilization Effects of PE-g-MA on Mechanical,Thermal and Swelling Properties of High Density Polyethylene/Natural Rubber/Thermoplastic Tapioca Starch Blends

Effect of polyethylene grafted maleic anhydride (PE-g-MA) on mechanical, thermal and swelling characteristic of high density polyethylene (HDPE)/natural rubber (NR)/thermoplastic tapioca starch (TPS) blends were studied. The measurements from differential scanning calorimetric (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), proved the effectiveness of PE-g-MA as compatibilizer in improving the miscibility between HDPE/NR – TPS blends. A decrement in crystallinity index was found after adding PE-g-MA. It is due to restriction in mobility of the HDPE chains. In the presence of PE-g-MA, the blends have better thermal stability. On top of that, the storage modulus which is reflected to the blend stiffness also increased as indicated the improvement in HDPE/NR – TPS interaction.     

Rheological behavior of polypropylene/novolac blends

The rheological behavior of polypropylene/novolac blends was investigated with special reference to the effects of the blend ratio, compatibilization, and dynamic cure. The polypropylene and all the polypropylene/novolac blends presented evidence of shear‐thinning behavior. The novolac, compatibilizer, and dynamic cure had dramatic effects on the rheological behavior of the polypropylene. Various rheological plots, including plots of the viscosity, storage modulus, loss modulus, and loss angle, Han plots, and Cole–Cole plots, were used to analyze the polypropylene/novolac blends. The results showed that the compatibilization together with the dynamic cure could increase the viscosity and modulus because of the formation of a grafting polymer between the maleic anhydride grafted polypropylene and the curing novolac resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

The effects of blend ratio,compatibilization and dynamic vulcanization on permeation of gases through HDPE/EVA blends

The effects of blend ratio, compatibilization and vulcanization on the permeability of O₂ and N₂ gas through HDPE/EVA blends were analyzed. As the volume fraction of EVA in the blend increases the permeability increases. The variation in permeability is correlated with the phase morphology. Oxygen exhibits a higher permeability than nitrogen because the “kinetic diameter” of N₂ is greater than that of O₂. The O₂/N₂ selectivity of HDPE is higher than that of EVA and as a result the selectivity decreases with increase in EVA content in the system. The O₂ and N₂ permeabilities decrease and O₂/N₂ selectivity increase upon compatibilization and dynamic vulcanization. The experimental gas permeabilities in HDPE/EVA blends are compared with several theoretical models of permeation.     

Influence of coalescence and interfacial tension on the morphology of PP/HDPE compatibilized blends

In this paper, the compatibilization of polypropylene (PP)/high-density polyethylene (HDPE) blend was studied through morphological and interfacial tension analysis. Three types of compatibilizers were tested: ethylene-propylene-diene copolymer (EPDM), ethylene-vinylacetate copolymer (EVA) and styrene-ethylene/butylene-styrene triblock copolymer (SEBS). The morphology of the blends was studied by scanning electron microscopy. The interfacial tension between the components of the blends was evaluated using small amplitude oscillatory shear analysis. Emulsion curves relating the average radius of the dispersed phase and the interfacial tension to the compatibilizer concentration added to the blend were obtained. It was shown that EPDM was more efficient as an emulsifier for PP/HDPE blend than EVA or SEBS. The relative role of interfacial tension reduction and coalescence reduction to particle size reduction was also addressed. It was observed that the role of coalescence reduction is small, mainly for PP/HDPE (90/10) blends compatibilized by EPDM, EVA or SEBS. The results indicated that the role of coalescence reduction to particle size reduction is lower for blends for which interfacial tension between its components is low at compatibilizer saturation.     

Processability and thermal properties of blends of high density polyethylene,poly (ethylene terephthalate), and ethyl vinyl acetate compatibilizer

Because of differences in chemical structure and rheological characteristics, high density polyethylene (HDPE) and poly(ethylene terephthalate) (PET) are incompatible when blended during recycling of PET soft drink bottles. To improve the properties of the blends, ethylene vinyl acetate copolymer (EVA) was used as a compatibilizer. Based on torque rheometer tests, the higher the concentration of PET in the blends, the higher the initial loading torque. Blends of 50% HDPE and 50% PET had the lowest equilibrium torque. Equilibrium torque was highest at 5% EVA. The presence of EVA made only a slight difference in the glass transition temperatures of HDPE/PET blends. Higher EVA content in the blend resulted in a lower melting endotherm. Thermogravimetric analysis showed that thermal stability was independent of EVA content; but the more PET in the blend, the lower the final weight loss.     

On the compatibilization and dynamic vulcanization of polyacetal/ethylene propylene diene terpolymer blends

This study describes an attempt to improve the impact resistance of polyacetal (POM)/ethylene propylene diene terpolymer (EPDM) blends by means of compatibilization and dynamic vulcanization. A commerical copolymer, poly(acrylic acid)-grafted polypropylene (PGP), has been used as a compatibilizer to control the phase morphology of the blend system. Dicumyl peroxide is used to dynamically vulcanize the EPDM elastomer in the blend. At temperatures higher than 185°C, the compatibilizer decreases the viscosity of compatibilized and dynamically vulcanized (cdv) POM/EPDM blends. Impact strength of the cdv blend system increases considerably with a marginal decrease in tensile yield stress and heat deflection temperature as the PGP content increases. The significant increase in impact strength seems to be due to the role of PGP as a linking agent for the binary blends rather than as a third component. Though dynamic mechanical studies do not indicate any compatibility in cdv-POM/EPDM blends, scanning electron microscopy reveals the strong interpenetrating interphase in the compatibilized blend system. Dynamic vulcanization raises elastic recovery and tensile modulus of the blends. Hysteresis energies of the blends increase consistently with the addition of PGP. The crystalline structure of POM is not affected by compatibilization and vulcanization. © 1994 John Wiley & Sons, Inc.     

Toughened polyoxymethylene by polyolefin elastomer and glycidyl methacrylate grafted high‐density polyethylene

Ternary blends of polyoxymethylene (POM), polyolefin elastomer (POE), and glycidyl methacrylate grafted high density polyethylene (GMA‐g‐HDPE) with various component ratios were studied for their mechanical and thermal properties. The size of POE dispersed phase increased with increasing the elastomer content due to the observed agglomeration. The notched impact strength demonstrated a parabolic tendency with increasing the elastomer content and reached the peak value of 10.81 kJ/m² when the elastomer addition was 7.5 wt%. The disappearance of epoxy functional groups in the POM/POE/GMA‐g‐HDPE blends indicated that GMA‐g‐HDPE reacted with the terminal hydroxyl groups of POM and formed a new graft copolymer. Higher thermal stability was observed in the modified POM. Both storage modulus and loss modulus decreased from dynamic mechanical analysis tests while the loss factor increased with increasing the elastomer content. GMA‐g‐HDPE showed good compatibility between the POM matrix and the POE dispersed phase due to the reactive compatibilization of the epoxy groups of GMA and the terminal hydroxyl groups of POM. A POM/POE blend without compatibilizer was researched for comparison, it was found that the properties of P‐7.5(POM/POE 92.5 wt%/7.5 wt%) were worse than those of the blend with the GMA‐g‐HDPE compatibilizer. POLYM. ENG. SCI., 57:1119–1126, 2017. © 2017 Society of Plastics Engineers     

Blends of nylon/acrylonitrile butadiene rubber: Effects of blend ratio,dynamic vulcanization and reactive compatibilization on rheology and extrudate morphology

The melt flow behavior of thermoplastic elastomers from nylon and nitrile rubber (NBR) was studied as a function of blend ratio, dynamic crosslinking, compatibilization and temperature. The morphology of the extrudates, i.e., the size, shape and distribution of the domains, was analyzed. Uncompatibilized and compatibilized blends showed pseudoplastic behavior. The viscosity of the blends showed positive deviation from a linear rule of mixtures. Compatibilization using chlorinated polyethylene (CPE) increased the melt viscosity of the blends. The addition of the compatibilizer decreased the domain size of the dispersed phase, followed by an increase after a critical concentration of the compatibilizer, where the interface was saturated. The influence of dynamic vulcanization on the rheological behavior was also studied. The extrudate morphology depended on blend ratio, compatibilization and shear rate.     

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

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

HDPE-g-MAH对HDPE/PA 11性能的影响

以马来酸酐(MAH)接枝高密度聚乙烯(HDPE)(HDPE-g-MAH)作为相容剂,通过熔融共混法制备了HDPE/聚酰胺11(PA 11)共混物.研究了HDPE-g-MAH对HDPE/PA 11共混物的增容作用以及对共混物性能的影响.结果表明,HDPE-g-MAH对共混体系有明显的增容作用,共混物的拉伸强度和冲击强度得到提高;相容剂的加入,使共混物的结晶温度升高.     

Effect of nanoclay on the morphology and properties of poly(methyl methacrylate)/high‐density polyethylene blends

The effect of nanoclay on the morphology and properties of poly(methyl methacrylate) (PMMA)/high‐density polyethylene (HDPE) blends was studied. A scanning electron microscopy study of the PMMA/HDPE (70/30 w/w) blends with nanoclay indicated a reduction in the average domain sizes of the dispersed HDPE phase and, hence, a better extent of mixing compared to that of the blends without any nanoclay. An X‐ray diffraction study and transmission electron microscopy revealed the localization of intercalated nanoclay in the PMMA matrix of the PMMA/HDPE (70/30 w/w) blend. However, the same effect of clay was not observed in the PMMA/HDPE (30/70 w/w) blend when HDPE became the matrix. In the PMMA/HDPE (30/70 w/w) blend, the addition of nanoclay increased the domain size of the dispersed PMMA domains by preferential location of the clays inside the PMMA domains. The addition of polyethylene‐grafted maleic anhydride in both compositions of the PMMA/HDPE blend effectively reduced the domain size of the disperse phases in the blend. However, the presence of clay increased the tensile strength and storage modulus of the PMMA/HDPE blends in both blend compositions. Thus, in the PMMA/HDPE blend, the clay platelets acted as a effective compatibilizer as long as they were dispersed mainly in the matrix phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of maleic anhydride grafting on nanokaolinclay reinforced polystyrene/high density polyethylene blends

Nanofillers have revolutionized the field of polymer modification. Modification of polymer blends with nanofillers opens up a myriad of opportunities to develop materials of choice. Polystyrene (PS) and high density polyethylene (HDPE) are two widely used standard plastics. To generate high modulus and strength a PS rich blend of PS/HDPE (80/20) was selected and the blend was modified using low cost nanokaolin clay, a 1:1 alumina silicate. The effect of maleic anhydride grafted PS/PE as compatibilizer in this system was studied. The incorporation of the compatibilizer improves the mechanical properties. This can be correlated with better interfacial adhesion as evidenced by scanning electron microscopy. The optimum in these properties was obtained at a compatibilizer concentration of 10–15%. The composites were characterized byX‐ray diffraction, differential scanning calorimetric, and dynamic mechanical analyzer techniques. This study shows that kaolin can be used as potential modifier of PS/HDPE blend. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers     

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     

Improved compatibility of high‐density polyethylene/poly(ethylene terephthalate) blend by the use of blocked isocyanate group

The blocked isocyanate group (BHI) was synthesized to improve the storage stability of HI (2‐hydroxyethyl methacrylate combined with isophorone diisocyanate) and characterized by Fourier transform infrared spectroscopy (FTIR). High‐density polyethylene grafted with the blocked isocyanate group (HDPE‐g‐BHI) was used as a reactive compatibilizer for an immiscible high‐density polyethylene/poly(ethylene terephthalate) (HDPE/PET) blend. A possible reactive compatibilization mechanism is that regenerated isocyanate groups of HDPE functionalized by BHI react with the hydroxyl and carboxyl groups of PET during melt blending. The HDPE‐g‐BHI/PET blend showed the smaller size of a dispersed phase compared to the HDPE/PET blend, indicating improved compatibility between HDPE and PET. This increased compatibility was due to the formation of an in situ graft copolymer, which was confirmed by dynamic mechanical analysis. Differential scanning calorimetry (DSC) analysis represented that there were few changes in the crystallinity for the continuous PET phase of the HDPE‐g‐BHI/PET blends, compared with those of the HDPE/PET blends at the same composition. Tensile strengths and elongations at the break of the HDPE‐g‐BHI/PET blends were greater than those of the HDPE/PET blends. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1017–1024, 2000     

Influence of crosslinking on crystallization,rheological, and mechanical behaviors of high density polyethylene/ethylene‐vinyl acetate copolymer blends

High density polyethylene (HDPE)/ethylene‐vinyl acetate copolymer (EVA) blends with selective crosslinking the EVA phase were prepared and the crystallization, rheological, and mechanical behaviors were studied. Selective crosslinking of EVA component could greatly improve both tensile and impact strengths of the HDPE‐rich blends and influence melting enthalpy at different annealing temperature in successive self‐nucleation and annealing procedure. Dynamic mechanical analysis reveals that glass transition temperatures of both the HDPE and EVA components are lowered upon blending and are raised upon crosslinking. The uncrosslinked HDPE/EVA blends are unstable in the melt and show increment in storage modulus (G′) and decay in loss tangent (tanδ) with annealing time associated with phase coarsening. However, morphology of selectively crosslinked blends in the melt state is highly unstable, characterized by a fast migration of uncrosslinked HDPE component out of the crosslinked EVA phase to the surface resulting in a rapid decay in G′ and an increment in tanδ at the early stage of annealing. POLYM. ENG. SCI., 54:2848–2858, 2014. © 2014 Society of Plastics Engineers     

Viscoelastic,thermal, and morphological analysis of HDPE/EVA/CaCO<Subscript>3</Subscript> ternary blends

High density polyethylene (HDPE), calcium carbonate (CaCO₃), and ethylene vinyl acetate (EVA) ternary reinforced blends were prepared by melt blend technique using a twin screw extruder. The thermal properties of these prepared ternary blends were investigated by differential scanning calorimetry. The effect of EVA loading on the melting temperature (T _m) and the crystallization temperature (T _C) was evaluated. It was found that the expected heterogeneous nucleating effect of CaCO₃ was hindered due to the presence of EVA. The melt viscosities of the ternary reinforced blends were affected by the % loading of CaCO₃, EVA, and vinyl acetate content. Viscoelastic analysis showed that there is a reduction of the storage modulus (G′) with increasing of EVA loading as compared to neat HDPE resin or to HDPE/CACO₃ blends only. The morphology of the composites was characterized by scanning electron microscopy (SEM). The dispersion and interfacial interaction between CaCO₃ with EVA and HDPE matrix were also investigated by SEM. We observed two main types of phase structures; encapsulation of the CaCO₃ by EVA and separate dispersion of the phases. Other properties of ternary HDPE/CaCO₃/EVA reinforced blends were investigated as well using thermal, rheological, and viscoelastic techniques.