Ionomer compatibilised PA6/EVA blends: mechanical properties and morphological characterisation

The compatibilisation of PA6/EVA blends with the addition of an ionomer on the mechanical properties and morphology were studied as a function of ionomer concentration with the primary aim of enhancing the impact strength of PA6 by EVA. The level of EVA was kept at 20%, which formed the dispersed phase, and the ionomer content was varied from 0 to 1.6 wt%. It was found that notched Izod impact strength of PA6/EVA/ionomer blends increased with the incorporation of ionomer to about three times of the value for uncompatibilised PA6/EVA blends. Further, it was observed that on incorporation of the ionomer the tensile strength also increased significantly. Analysis of the tensile data using predictive theories indicated an enhanced interaction of the dispersed phase and the matrix. SEM studies of cryogenically fractured surfaces indicated a decrease in dispersed phase domain size with the addition of the ionomer, while the impact fractured surfaces of PA6/EVA blends indicated extensive deformation with the formation of rumples indicating increased interfacial adhesion as compared to PA6/EVA blends. An attempt has been made to evaluate the compatibilising efficiency of ionomer in PA6/EVA blends.     

Relaxation behavior of polymer blends with complex morphologies: Palierne emulsion model for uncompatibilized and compatibilized PP/PA6 blends

This paper deals with the dynamic rheological behavior of polypropylene/polyamide6 (PP/PA6) uncompatibilized blends and those compatibilized with a maleic anhydride grafted PP (PP/PP-g-MAH/PA6). The terminal relaxation times of the blends predicted by the Palierne emulsion model were compared with those obtained from experimental relaxation time spectra. The Palierne model succeeded well in describing PP/PA6 uncompatibilized blends with relatively low dispersed phase contents (10 wt%) and failed doing so for those of which the dispersed contents were high (30 wt%). It also failed for the compatibilized ones, irrespective of the dispersed phase content (10 or 30 wt%) and whether or not interface relaxation was taken into consideration. In the case of the uncompatibilized blend with high dispersed-phase content, interconnections among inclusions of the dispersed phase were responsible for the failure of the Palierne model. As for the compatiblized blends, in addition to particle interconnections, the existence of emulsion-in-emulsion (EE) structures was another factor responsible for the failure of Palierne model. A methodology was developed to use Palierne emulsion model upon taking into account the effects of the EE structure on the viscosity of the continuous phase and the effective volume fraction of the dispersed phase.     

Influence of microstructure and flexibility of maleated styrene-b-(ethylene-co-butylene)-b-styrene rubber on the mechanical properties of polyamide 12

The present investigation deals with the mechanical and morphological properties of binary polyamide 12/maleic anhydride-grafted styrene-b-(ethylene-co-butylene)-b-styrene rubber (PA12/SEBS-g-MA) blends at varying dispersed phase (SEBS-g-MA) concentrations. Tensile behavior, impact strength and crystallinity of these blend systems were evaluated. Influence of microstructure, dispersed phase particle size, and ligament thickness on the impact toughness of the blend was studied. DSC data indicated an increase in crystallinity of PA12 in the blends. Tensile modulus and strength decreased while impact strength and elongation-at-break increased with the elastomer concentration. The enhanced properties were supported by interphase adhesion between the grafted maleic groups of rubber with polar moiety of polyamide 12. Analysis of the tensile data employing simple theoretical models showed the variation of stress concentration effect with blend composition.     

MORPHOLOGY,CRYSTALLIZATION BEHAVIORS,AND MECHANICAL PROPERTIES OF PA1010/HIPS AND PA1010/HIPS-g-MA BLENDS

The binary blends of polyamide 1010 (PA1010) with the high-impact polystyrene (HIPS)/maleic anhydride (MA) graft copolymer (HIPS-g-MA) and with HIPS were prepared using a wide composition range. Different blend morphologies were observed by scanning electron microscopy according to the nature and content of PA1010 used. Compared with the PA1010/HIPS binary blends, the domain sizes of dispersed-phase particles in PA1010/HIPS-g-MA blends were much smaller than that in PA1010/HIPS blends at the same compositions. It was found that the tensile properties of PA1010/HIPS-g-MA blends were obviously better than that of PA1010/HIPS blends. Wide-angle x-ray diffraction analyses were performed to confirm that the number of hydrogen bonds in the PA1010 phase decreased in the blends of PA1010/HIPS-g-MA. These behaviors could be attributed to the chemical interactions between the two components and good dispersion in PA1010/HIPS-g-MA blends.     

Reactive compatibilizer precursors for LDPE/PA6 blends. II: maleic anhydride grafted polyethylenes

Several home made and commercially available polyethylene (PE) samples grafted with maleic anhydride (MA) (PE-g-MA) were used as compatibilizer precursors (CPs) for the reactive blending of low density PE (LDPE) with polyamide-6 (PA). Scope of the work was to compare the effectiveness of these CPs with that of a number of ethylene-acrylic acid copolymers (EAA), which had been employed in a previous study for the reactive compatibilization of the same blends, and to get a deeper insight into the coupling reactions producing the PA-g-CP copolymers that are thought to act as the true compatibilizers in these systems. To this end, binary CP/LDPE and CP/PA and ternary LDPE/PA/CP blends were prepared with a Brabender mixer and were characterized by DSC, SEM and solvent fractionation. The results show that the PE-g-MA copolymers react more rapidly with PA than the EAA copolymers and that their CP effectiveness depends critically on the microstructure and the molar mass of their PE backbones. In particular, the CPs produced by functionalization of LDPE were shown to be miscible with this blend component and to be scarcely available at the interface where reaction with PA is expected to occur. Conversely, the CPs prepared from the HDPE grades were immiscible with LDPE and showed better CP performance. Whereas the effectiveness of the EAA copolymers studied earlier had been shown to increase with an increase in the concentration of the carboxyl groups, the concentration of the succinic anhydride groups of the PE-g-MA CPs studied in this work was found to play a minor role, at least in the investigated range (0.3-3.0 wt% MA).     

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     

Comparative study of different maleic anhydride grafted compatibilizer precursors towards LDPE/PA6 blends: Morphology and mechanical properties

The study deals with the effectiveness of maleic anhydride grafted styrene-b-ethylene-co-propylene copolymer (SEPMA) as compatibilizer precursor (CP) for blends of low density polyethylene (LDPE) with polyamide-6 (PA). The CP was produced by grafting MA onto SEP in the melt. The specific interactions between the CP and the blends components have been investigated through characterizations of the binary LDPE/CP and PA/CP blends. The compatibilizing efficiency of the MA-grafted SEP, as revealed by the thermal properties and the morphology of the compatibilized blends, has been shown to be excellent. The morphology, as well as the mechanical properties of the compatibilized with SEPMA 75/25 w/w and 25/75 w/w LDPE/PA6 blends have been compared with those of the blends compatibilized with maleic anhydride functionalized HDPE sample (1-HDPE-g-MA) and with a commercial maleic anhydride grafted styrene-b-(ethylene-co-1-butene)-b-styrene copolymer (SEBSMA1). The results show that the strong compatibilizing efficiency of SEPMA is comparable with that of SEBSMA1, while 1-HDPE-g-MA exhibits a slightly lower activity, particularly for the blends, in which PA is the matrix phase.     

Compatibilization and properties of ethylene vinyl acetate copolymer (EVA) and thermoplastic polyurethane (TPU) blend based foam

Ethylene vinyl acetate copolymer/thermoplastic polyurethane (EVA/TPU) blending foams are rarely reported so far because of their poor compatibility, and addition of a compatibilizer to the blend system was our major interest, which can improve interfacial adhesion between the two phases. In this paper, TPU-grafted EVA (EVA-g-TPU), as a compatibilizer, was simply prepared using maleic anhydride-grafted EVA (EVA-g-MAH) and 4,4′ diamino diphenyl methane in the mixing process of TPU and EVA matrix. Fourier transform infrared spectroscopy and differential scanning calorimetry were used to investigate the structures of EVA-g-TPU and the interfacial reaction in the mixing process, and the effect of EVA-g-TPU on compatibilization between the two phases of EVA/TPU blends was investigated using scanning electron microscopy. Finally, EVA/EVA-g-TPU/TPU foams based on the good compatibility of the resin blends were prepared, and the physical properties directly related to the compatibility were investigated as a function of the theoretical quantity (molar mass) of EVA-g-TPU (n _EVA-g-TPU) in the foams. Moreover, the tensile strength, elongation at break, tear strength and compression set were improved by 19.0, 9.3, 43.6 and 7.5 %, respectively. Overall, EVA/EVA-g-TPU/TPU foams with excellent mechanical properties were obtained without sacrificing other important physical properties (lower density etc.) through popular and friendly means in this research.     

Effect of rubber particle size and rubber type on the mechanical properties of glass fiber reinforced, rubber-toughened nylon 6

The effects of rubber type and particle size on the mechanical properties of glass fiber reinforced blends of nylon 6 and EPR/EPR-gMA or SEBS/SEBS-g-MA were investigated; rubber particle size in the two systems could be controlled by varying the ratio of EPR to EPR-g-MA or SEBS to SEBS-g-MA. Unreinforced materials with the highest levels of toughness did not necessarily lead to the highest fracture energy when reinforced with 15 wt% glass fibers. Materials toughened with SEBS/SEBS-gMA, which are tougher in the absence of glass fibers had lower fracture energies when 15 wt% glass fibers are present. In general, smaller rubber particles led to higher fracture energies. Fracture analysis according to a modified essential work of fracture analysis reveals that SEBS/SEBS-g-MA have high values of the dissipative energy density, u_d, in the absence of glass fibers. When 15 wt% glass fibers are added, u_d is essentially zero for all the materials tested. The limiting specific fracture energy, u₀, on the other hand, was higher for both unreinforced and glass fiber reinforced EPR/EPR-g-MA toughened blends than for SEBS/SEBS-g-MA based materials. Transmission electron microscopy observations of fractured specimens indicate that glass fibers decrease the size of the damage zone of rubber toughened nylon 6. Shear yielding was seen in fractured specimens of reinforced nylon 6 blends containing either SEBS/SEBS-g-MA or EPR-g-MA, but the size of this shear yielded zone was larger for EPR/EPR-g-MA. In addition, EPR/EPR-g-MA based materials displayed craze-like deformations, while SEBS-g-MA materials did not exhibit this deformation process.     

Morphology and mechanical properties of polyamide 12/polypropylene blends in presence and absence of reactive compatibiliser

Blends of polyamide 12 (PA12) and isotactic polypropylene (PP) were prepared by melt mixing in an internal mixer in presence and absence of compatibilisers. The compatibiliser used was maleic anhydride functionalised polypropylene (PP-g-MA). Effect of compatibilisation on the blends has been evaluated from the morphological parameters derived from scanning electron micrographs (SEM) of cryogenically fractured and extracted surfaces of the specimens. The uncompatibilised blends showed two-phase unstable morphology due to high interfacial tension and coalescence effects in the absence of favourable interactions at interface between the individual phases. Incompatibility increased as the concentration of dispersed phase in the blend increased. Compatibilisation stabilised the morphology by reducing the particle size as well as interparticle distance and enhancing the interfacial area and interface adhesion. A critical concentration of compatibiliser required for effective compatibilisation (CMC) was observed beyond which there was no net improvement in interfacial properties and was considered as the point of interfacial saturation. Experimental results were compared with the compatibilisation theories of Noolandi and Hong and Leibler and based on the calculated average interfacial area occupied per compatibiliser molecule it was concluded that the molecular state of compatibiliser at interface changed with concentration. It was supported by the rate constant for change in interfacial tension (K) values which experienced a maximum at CMC followed by drastic reduction. Mechanical properties of the uncompatibilised blends showed inferior properties. It was found that compatibilisation significantly improved the mechanical properties. A good correlation has been observed between the mechanical properties and morphological parameters.     

Oil and thermal aging resistance in compatibilized and thermally stabilized chlorinated polyethylene/natural rubber blends

Influences of EPDM-g-MA as a compatibilizer and a phenolic antioxidant on oil and thermal aging resistance in 50/50 CPE/NR blends were investigated. It has been found that EPDM-g-MA could decrease phase size of the blend system, indicating compatibilizing effect. The optimal concentration of EPDM-g-MA is 1 phr. Beyond this concentration, phase size starts to increase. The addition of phenolic antioxidant apparently decreases the phase size in blends. This is probably due to the improvement in a thermal stabilization of NR phase in blends provided by the antioxidant, which leads to a reduction in phase coalescence during blending. In addition, the results of oil and thermal aging resistance are in good agreement with the morphological results, indicating that the oil resistance and thermal aging properties based on relative tensile strength in the 50/50 CPE/NR blends are strongly controlled by the size of the NR dispersed phase in CPE matrix. The smaller the dispersed phase size, the higher the resistance to oil and thermal aging.     

Optimum toughening via a bicontinuous blending: toughening of PPO with SEBS and SEBS-g-maleic anhydride

The poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was toughened by melt extrusion through its blending with a styrene-b-ethylene/butadiene-b-styrene triblock copolymer (SEBS), or with maleic anhydride (MA) grafted SEBS (SEBS-g-MA). Their morphology, mechanical properties, and rheology have been investigated. Transmission electron microscopy revealed that both kinds of blends had an island-sea structure at low concentrations of SEBS or SEBS-g-MA and a bicontinuous one at sufficiently high concentrations. However, the percolation threshold was higher for SEBS than for the SEBS-g-MA. The Izod impact strength of PPO could be significantly improved through its blending with SEBS-g-MA, particularly in a blend with 20 wt% of SEBS-g-MA at which it had a maximum value. The rheological experiments indicated that the incorporation of SEBS increased and that of SEBS-g-MA decreased the melt viscosity of the system.     

Blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 toughened by maleated polystyrene‐based copolymers: Mechanical properties,morphology, and rheology

Poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 (PPO/PA6 30/70) blends were impact modified by addition of three kinds of maleated polystyrene‐based copolymers, i.e., maleated styrene‐ethylene‐butylene‐styrene copolymer (SEBS‐g‐MA), maleated methyl methacrylate‐butadiene‐styrene copolymer (MBS‐g‐MA), and maleated acrylonitrile‐butadiene‐styrene copolymer (ABS‐g‐MA). The mechanical properties, morphology and rheological behavior of the impact modified PPO/PA6 blends were investigated. The selective location of the maleated copolymers in one phase or at interface accounted for the different toughening effects of the maleated copolymer, which is closely related to their molecular structure and composition. SEBS‐g‐MA was uniformly dispersed in PPO phase and greatly toughened PPO/PA6 blends even at low temperature. MBS‐g‐MA particles were mainly dispersed in the PA6 phase and around the PPO phase, resulting in a significant enhancement of the notched Izod impact strength of PPO/PA6 blends from 45 J/m to 281 J/m at the MBS‐g‐MA content of 20 phr. In comparison, the ABS‐g‐MA was mainly dispersed in PA6 phase without much influencing the original mechanical properties of the PPO/PA6 blend. The different molecule structure and selective location of the maleated copolymers in the blends were reflected by the change of rheological behavior as well. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of maleated syndiotactic polystyrene on the morphology,mechanical properties,and crystallization behavior of syndiotactic polystyrene/polyamide 6 blends

The compatibilization of syndiotactic polystyrene (sPS)/polyamide 6 (PA‐6) blends with maleic anhydride grafted syndiotactic polystyrene (sPS‐g‐MA) as a reactive compatibilizer was investigated. The sPS/PA‐6 blends were in situ compatibilized by a reaction between the maleic anhydride (MA) of sPS‐g‐MA and the amine end group of PA‐6. The occurrence of the chemical reaction was substantiated by the disappearance of a characteristic MA peak from the Fourier transform infrared spectrum. Morphology observations showed that the size of the dispersed PA‐6 domains was significantly reduced and that the interfacial adhesion was much improved by the addition of sPS‐g‐MA. As a result of reactive compatibilization, the impact strengths of the sPS/PA‐6 blends increased with an increase in the sPS‐g‐MA content. The crystallization behaviors of the blends were affected by the compatibilization effect of sPS‐g‐MA. A single melting peak of sPS in the noncompatibilized blend was gradually split into two peaks as the amount of the compatibilizer increased. A single crystallization peak of PA‐6 in the noncompatibilized blend became two peaks with the addition of 3 wt % sPS‐g‐MA. The new peak was a result of the fractionation crystallization. As the amount of sPS‐g‐MA increased, the intensity of the new peak increased, and the original peak nearly disappeared. Finally, the crystallization peak of PA‐6 disappeared with 20 wt % sPS‐g‐MA in the blend. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2502–2506, 2003     

Encapsulated phase structure and morphology evolution during quiescent annealing in ternary polymer blends with PA6 as matrix

This work is aim to study the encapsulated morphology development in ternary blends of polyamide 6/high density polyethylene/maleic anhydride‐grafted‐ethylene propylene diene monomer (PA6/HDPE/EPDM‐g‐MA) and polyamide 6/maleic anhydride‐grafted‐high density polyethylene/ethylene propylene diene monomer (PA6/HDPE‐g‐MA/EPDM) through thermodynamically control described by Harkins spreading theory. The phase morphology was confirmed by using scanning electron microscope (SEM) and selective solvent extraction revealed that PA6/HDPE/EPDM‐g‐MA blend having a composition of 70/15/15 vol % is constituted of polyamide 6 matrix with dispersed composite droplets of HDPE subinclusions encapsulated by EPDM‐g‐MA phase, while for PA6/HDPE‐g‐MA/EPDM blend with the same composition is constituted of polyamide 6 matrix with dispersed composite droplets of HDPE‐g‐MA subinclusions encapsulated by EPDM phase. Quiescent annealing test revealed that for PA6/HDPE/EPDM‐g‐MA blend, a perfect core–shell structure with one HDPE particle encapsulated by EPDM‐g‐MA phase was formed during annealing, and for PA6/HDPE‐g‐MA/EPDM blend, a novel complete inverting HDPE‐g‐MA/EPDM core/shell structure was achieved. Moreover, quantitative analysis about coalescent behaviors of HDPE‐g‐MA and HDPE subinclusions during quiescent annealing were investigated by image analysis and the result suggested that the grafted maleic anhydride group in HDPE‐g‐MA, acted as a role of steric repulsion, could suppress coalescence effects, thus leaded to a lower coalescent rate than that of HDPE subinclusions. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39937.     

Recycling of polycarbonate by blending with maleic anhydride grafted ABS

Recycling of used polycarbonate (PC) was conducted via melt blending with maleic anhydride grafted ABS (ABS-g-MA) using a twin-screw extruder. The toughness of waste PC was greatly improved through the modification of ABS-g-MA. The toughening mechanism was explored based on the morphology of the blends. The grafting of MA onto ABS was considered a key factor, which resulted in a special morphology of ABS domains dispersed in PC matrix. At a certain PC/ABS-g-MA weight ratio, the ABS domains connected together forming a network and gave rise to a maximum of the notched impact strength.     

Effect of core‐shell morphology evolution on the rheology,crystallization, and mechanical properties of PA6/EPDM‐g‐MA/HDPE ternary blend

In this article, polyamide 6 (PA6), maleic anhydride grafted ethylene‐propylene‐diene monomer (EPDM‐g‐MA), high‐density polyethylene (HDPE) were simultaneously added into an internal mixer to melt‐mixing for different periods. The relationship between morphology and rheological behaviors, crystallization, mechanical properties of PA6/EPDM‐g‐MA/HDPE blends were studied. The phase morphology observation revealed that PA6/EPDM‐g‐MA/HDPE (70/15/15 wt %) blend is constituted from PA6 matrix in which is dispersed core‐shell droplets of HDPE core encapsulated by EPDM‐g‐MA phase and indicated that the mixing time played a crucial role on the evolution of the core‐shell morphology. Rheological measurement manifested that the complex viscosity and storage modulus of ternary blends were notable higher than the pure polymer blends and binary blends which ascribed different phase morphology. Moreover, the maximum notched impact strength of PA6/EPDM‐g‐MA/HDPE blend was 80.7 KJ/m² and this value was 10–11 times higher than that of pure PA6. Particularly, differential scanning calorimetry results indicated that the bulk crystallization temperature of HDPE (114.6°C) was partly weakened and a new crystallization peak appeared at a lower temperature of around 102.2°C as a result of co‐crystal of HDPE and EPDM‐g‐MA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polystyrene/EVA melt blends compatibilized with EVA-graft-polystyrene

The influence of poly[(ethylene-co-vinyl acetate)-g-polystyrene] (EVA-g-PS) on the mechanical and morphological properties of polystyrene and the blends with EVA copolymers has been investigated. The melt blends have been performed in a twin-screw extruder. The addition of the graft copolymer enhances the mechanical properties and impact resistance of the PS matrix and PS/EVA (90 : 10 wt %) blends. Better results on impact strength and elongation at break have been achieved by using a EVA-g-PS graft copolymer with a higher EVA proportion by weight. This graft copolymer also contains a lower molecular weight of the PS-grafted segments than the PS matrix. Morphological studies by scanning electron microscopy revealed some interfacial adhesion between the components in the compatibilized polymer blends. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2141–2149, 1997     

Elastomer particle morphology in ternary blends of maleated and non-maleated ethylene-based elastomers with polyamides: Role of elastomer phase miscibility

The elastomer particle morphology in ternary blends of maleated and non-maleated ethylene-based elastomers with polyamides has been examined. The elastomers used include an ethylene/propylene copolymer, EPR, with a maleic anhydride (MA) grafted version, EPR-g-MA, and an ethylene/1-octene copolymer, EOR, with maleated versions EOR-g-MA-X% where X is 0.35, 1.6 or 2.5. The polyamides used were nylon 6 and an amorphous polyamide, Zytel 330 from DuPont. The morphology development was explored from both thermodynamic and kinetic points of view where the former refers to miscibility of the elastomers and the latter might include the ratio of the elastomers, the matrix type, the order of mixing, mixing intensity, i.e. the extruder type, and graft structure, etc. Both sources influence the morphology developed. For ternary blends with EPR-g-MA/EPR, the morphology (particle size and distribution) seems to be well controlled via the level of maleation in the rubber phase. The two polyamides generate comparable rubber particle sizes at the same of MA level. For ternary blends with EOR-g-MA/EOR, the morphology strongly depends on the level of MA; the rubber particle size, in general, is much smaller in nylon 6 blends than in Zytel 330 blends. Morphology of ternary blends with EOR-g-MA/EOR is much more complex than that of blends with EPR-g-MA/EPR due to the co-existence of miscibility limits and the kinetic factors. Miscibility of maleated EOR elastomers is examined via transmission electron microscopy (TEM) using a special staining technique; a miscibility boundary, as revealed by TEM, occurs around Δ(%MA)=0.9−1.25 MA%. If the two elastomers are miscible, a unimodal particle size distribution always appears in blends regardless of the kinetic factors; however, if immiscibility prevails, either a unimodal or bimodal particle size distribution may develop depending on the ratio of the elastomers and the matrix type. The order of mixing and the mixing intensity do not seem to change the modality of the size distribution.     

Influence of the polarity of ethylene–vinyl acetate copolymers on the morphology and mechanical properties of their uncompatibilised blends with polystyrene

Rubber‐toughened polystyrene has been extensively studied and is a well‐established technology. However, the use of thermoplastic elastomers to toughen polystyrene (PS) is new and has the potential for further investigations. In the present study, three EVAs (ethylene–vinyl acetate copolymers) with identical melt flow indices (MFIs), of ～2.5 dgmin^?1, but different vinyl acetate (VA) contents, of 9.3 wt% (EVA760), 18.0 wt% (EVA460) and 28.0 wt% (EVA265), were melt blended with PS at 180 °C, and various ASTM test pieces were injection moulded at 200 °C. The polarity of the dispersed phase (ie EVA), has a significant effect on the mechanical properties of the blends. Both mechanical and rheological studies reveal that the uncompatibilised PS/EVA265 blends exhibit some degree of compatibility when the amount of EVA265 is lower than 30 wt%. These results indicate that EVA265 with the highest VA content is the most effective impact modifier for PS. The results clearly show that increasing the VA content in EVA increases the polarity of the dispersed phase, approaching that of the matrix (ie PS) and subsequently improving the compatibility between the two phases in terms of interfacial adhesion. © 2002 Society of Chemical Industry