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     

Effect of EPDM‐g‐MAH on the morphology and properties of PA6/EPDM/HDPE ternary blends

The formation of core‐shell morphology within the dispersed phase was studied for composite droplet polymer‐blend systems comprising a polyamide‐6 matrix, ethylene‐propylene‐diene terpolymer (EPDM) shell and high density polyethylene (HDPE) core. In this article, the effect of EPDM with different molecular weights on the morphology and properties of the blends were studied. To improve the compatibility of the ternary blends, EPDM was modified by grafting with maleic anhydride (EPDM‐g‐MAH). It was found that core‐shell morphology with EPDM‐g‐MAH as shell and HDPE as core and separated dispersion morphology of EPDM‐g‐MAH and HDPE phase were obtained separately in PA6 matrix with different molecular weights of EPDM‐g‐MAH in the blends. DSC measurement indicated that there may be some co‐crystals in the blends due to the formation of core‐shell structure. Mechanical tests showed that PA6/EPDM‐g‐MAH/HDPE ternary blends with the core‐shell morphology exhibited a remarkable rise in the elongation at break. With more perfect core‐shell composite droplets and co‐crystals, the impact strength of the ternary blends could be greatly increased to 51.38 kJ m^?2, almost 10 times higher than that of pure PA6 (5.50 kJ m^?2). POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

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     

Investigation on morphology and mechanical properties of polyamide 6/maleated ethylene‐propylene‐diene rubber/organoclay composites

Maleated ethylene‐propylene‐diene rubber (EPDM‐g‐MA) toughened polyamide 6 (PA6)/organoclay (OMMT) nanocomposites were prepared by melt blending. The role of OMMT in the morphology of the ternary composites and the relationship between the morphology and mechanical properties were investigated by varying the blending sequence. The PA6/EPDM‐g‐MA/OMMT (80/20/4) composites prepared by four different blending sequences presented distinct morphology and mechanical properties. The addition of OMMT could obviously decrease viscosity of the matrix and weaken the interfacial interactions between PA6 and EPDM‐g‐MA when blending EPDM‐g‐MA with a premixed PA6/OMMT nacocomposite, resulting in the increase of rubber particle size. The final mechanical properties are not only determined by the location of OMMT, but also by the interfacial adhesion between PA6 and EPDM‐g‐MA. Having maximum percentage of OMMT platelets in the PA6 matrix and keeping good interfacial adhesion between PA6 and EPDM‐g‐MA are beneficial to impact strength. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

The mechanical and rheological behavior of the PA/TPU blend with POE‐g‐MA modifier

In this research, we attempt to improve the impact strength and the viscosity of PA (polyamide) by blending two elastomers, TPU (thermoplastic polyurethane) and POE‐g‐MA (maleic anhydride‐grafted polyethylene‐octene elastomer), in PA matrix with twin screw extruder. The ratio of blending is 80PA/20TPU and 80PA/20TPU/20POE‐g‐MA (66.66PA/16.67TPU/16.67POE‐g‐MA). Results indicate that POE‐g‐MA improves the low viscosity of PA and TPU during the blending process, and also their compatibility. Thus, the 80PA/20TPU/20POE‐g‐MA blend has better tensile stress and elongation than 80PA/20TPU blend, and furthermore POE‐g‐MA significantly improves the impact strength of PA, even to super‐toughness grade. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of different compatibilizers on the rheological,thermomechanical, and morphological properties of HDPE/LLDPE blend‐based nanocomposites

The influence of two different compatibilizers and their combination (maleic anhydride grafted high density polyethylene, HDPE‐g‐MA; maleic anhydride grafted linear low density polyethylene, LLDPE‐g‐MA; and 50/50 wt % mixture of these compatibilizers) on the rheological, thermomechanical, and morphological properties of HDPE/LLDPE/organoclay blend‐based nanocomposites was evaluated. Nanocomposites were obtained by melt‐intercalation in a torque rheometer in two steps. Masterbatches (compatibilizer/nanoclay 2:1) were obtained and subsequently diluted in the HDPE/LLDPE matrix producing nanocomposites with 2.5 wt % of nanoclay. Wide angle X‐ray diffraction (WAXD), steady‐state rheological properties, and transmission electron microscopy (TEM) were used to determine the influence of different compatibilizer systems on intercalation and/or exfoliation process which occurs preferentially in the amorphous phase, and thermomechanical properties. The LLDPE‐g‐MA with a high melt index (and consequently low viscosity and crystallinity) was an effective compatibilizer for this system. Furthermore, the compatibilized nanocomposites with LLDPE‐g‐MA or mixture of HDPE‐g‐MA and LLDPE‐g‐MA exhibited better nanoclay's dispersion and distribution with stronger interactions between the matrix and the nanoclay. These results indicated that the addition of maleic anhydride grafted polyethylene facilitates both, the exfoliation and/or intercalation of the clays and its adhesion to HDPE/LLDPE blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1726–1735, 2013     

Effect of blending sequence on the morphology and properties of polyamide 6/EPDM‐g‐MA/epoxy blends

The ternary blends of polyamide 6/maleated ethylene‐propylene‐diene rubber/epoxy (PA6/EPDM‐g‐MA/EP) were prepared by a twin‐screw extruder with four different blending sequences. With the variation of blending sequence, the ternary blends presented distinct morphology and mechanical properties because of different interactions induced by various reactive orders. The addition of epoxy could increase the viscosity of the PA6 matrix, but a considerably larger size of the dispersed rubber phase was observed while first preblending PA6 with epoxy followed by blending a premix of PA6/EP with EDPM‐g‐MA, which was attested by rheological behaviors and SEM observations. It was probably ascribed to the fact that the great increase of the interfacial tension between the matrix and rubber phase aroused a great coalescence of rubber particles. The presence of epoxy in the rubber phase reduced the rubber's ability to cavitate so that the toughening efficiency of the EPDM‐g‐MA was decreased. The results of mechanical testing revealed that the optimum blending sequence to achieve balanced mechanical properties is blending PA6, EPDM‐g‐MA, and epoxy simultaneously in which the detrimental reactions might be effectively suppressed. In addition, thermal properties were investigated by TG and DSC, and the results showed that there was no distinct difference. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphological structure and surface properties of maleated ethylene propylene diene monomer/organoclay nanocomposites

The phase morphology and surface properties of some maleated ethylene propylene‐diene/organoclay nanocomposites (EPDM‐g‐MA/OC) were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements. The effect of organoclay and/or compatibilizing agent [maleic anhydride‐grafted polypropylene (PP‐g‐MA)] on the properties of the EPDM‐g‐MA nanocomposites was investigated. The quality and uniformity of nanoclay dispersion were analyzed by SEM and AFM images. The experimental results showed an intercalate structure and biphasic morphology for the binary blends based on EPDM and clay. The surface properties of the studied composites are significantly influenced by the presence of a compatibilizing agent—PP‐g‐MA. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Study on the microstructures and mechanical behaviour of compatibilized polypropylene/polyamide‐6 blends

A series of blends of polypropylene (PP)–polyamide‐6 (PA6) with either reactive polyethylene–octene elastomer (POE) grafted with maleic anhydride (POE‐g‐MA) or with maleated PP (PP‐g‐MA) as compatibilizers were prepared. The microstructures and mechanical properties of the blends were investigated by means of tensile and impact testing and by scanning electron microscopy and transmission electron microscopy. The results indicated that the miscibility of PP–PA6 blends was improved with the addition of POE‐g‐MA and PP‐g‐MA. For the PP/PA6/POE‐g‐MA system, an elastic interfacial POE layer was formed around PA6 particles and the dispersed POE phases were also observed in the PP matrix. Its Izod impact strength was four times that of pure PP matrix, whilst the tensile strength and Young's modulus were almost unchanged. The greatest tensile strength was obtained for PP/PA6/PP‐g‐MA blend, but its Izod impact strength was reduced in comparison with the pure PP matrix. © 2002 Society of Chemical Industry     

Design and properties of a series of high‐temperature thermoplastic elastomeric blends from polyamides and functionalized rubbers

A series of high‐temperature thermoplastic elastomers (TPEs) and thermoplastic vulcanisates (TPVs) were successfully developed based on two different types of heat resistant polyamide (PA) (25 parts by weight)—PA‐12 and PA‐6, in combination with three different functionalized rubbers (75 parts by weight) of varying polarity, e.g., maleic anhydride grafted ethylene propylene diene terpolymer (MA‐g‐EPDM), sulphonated ethylene propylene diene terpolymer, and carboxylated acrylonitrile butadiene rubber, by melt mixing method. These rubbers have low level of unsaturation in its backbone, and the plastics showed high melting range. Thus, the developed TPEs and TPVs were expected to be high temperature resistant. Resol type resin was used for dynamic vulcanization to further increase the high temperature properties of these blends. Interestingly, initial degradation temperature of the prepared blends was much higher (421 °C for MA‐g‐EPDM/PA‐12) than the other reported conventional TPEs and TPVs. Fourier transform infrared analysis described the interactive nature of the TPEs and TPVs, which is responsible for their superior properties. The maximum tensile strength with lowest tension set was observed for the carboxylated acrylonitrile butadiene rubber/PA‐12 TPV. Mild increase in mechanical properties without any degradation was observed after recycling. Dynamic mechanical analysis results showed two distinct glass transition temperatures and indicated the biphasic morphology of the blends, as evident from the scanning electron microscopy. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45353.     

Morphology and properties of nylon 6 and high density polyethylene blends in presence of nanoclay and PE‐g‐MA

In this study, we report the synergistic effect of nanoclay and maleic anhydride grafted polyethylene (PE‐g‐MA) on the morphology and properties of (80/20 w/w) nylon 6/high density polyethylene (HDPE) blend. Polymer blend nanocomposites containing nanoclay with and without compatibilizer (PE‐g‐MA) were prepared by melt mixing, and their morphologies and structures were examined with scanning electron microscopy (SEM) and wide angle X‐ray diffractometer (WAXD) study. The size of phase‐separated domains decreased considerably with increasing content of nanoclay and PE‐g‐MA. WAXD study and transmission electron microscopy (TEM) revealed the presence of exfoliated clay platelets in nylon 6 matrix, as well as, at the interface of the (80/20 w/w) nylon 6/HDPE blend–clay nanocomposites. Addition of PE‐g‐MA in the blend–clay nanocomposites enhanced the exfoliation of clays in nylon 6 matrix and especially at the interface. Thus, exfoliated clay platelets in nylon 6 matrix effectively restricted the coalescence of dispersed HDPE domains while PE‐g‐MA improved the adhesion between the phases at the interface. The use of compatibilizer and nanoclay in polymer blends may lead to a high performance material which combines the advantages of compatibilized polymer blends and the merits of polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Toughening of polyamide 6 with a maleic anhydride functionalized acrylonitrile–butadiene–styrene copolymer

Maleic anhydride functionalized acrylonitrile–butadiene–styrene (ABS‐g‐MA) copolymers were prepared via an emulsion polymerization process. The ABS‐g‐MA copolymers were used to toughen polyamide 6 (PA‐6). Fourier transform infrared results show that the maleic anhydride (MA) grafted onto the polybutadiene phase of acrylonitrile–butadiene–styrene (ABS). Rheological testing identified chemical reactions between PA‐6 and ABS‐g‐MA. Transmission electron microscopy and scanning electron microscopy displayed the compatibilization reactions between MA of ABS‐g‐MA and the amine and/or amide groups of PA‐6 chain ends, which improved the disperse morphology of the ABS‐g‐MA copolymers in the PA‐6 matrix. The blends compatibilized with ABS‐g‐MA exhibited notched impact strengths of more than 900 J/m. A 1 wt % concentration of MA in ABS‐g‐MA appeared sufficient to improve the impact properties and decreased the brittle–ductile transition temperature from 50 to 10°C. Scanning electron microscopy results show that the shear yielding of the PA‐6 matrix was the major toughening mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Toughened poly(trimethylene terephthalate) by blending with a functionalized ethylene–propylene–diene copolymer

A series of blends of poly(trimethylene terephthalate) (PTT) with ethylene–propylene–diene copolymer grafted with maleic anhydride (EPDM‐g‐MA) were prepared in composition by weight 95/5, 90/10, 80/20, and 70/30. Their morphologies, crystallization behavior, and mechanical properties were investigated. Morphology observation shows the well‐dispersed domains of EPDM‐g‐MA in PTT matrix with weight‐average particle size from 0.98 to 3.64 μm when the EPDM‐g‐MA content increases from 5% to 30% (mass fraction) in the blends. The constancy of the crystallinity level indicates that the elastomeric phase does not disturb the crystallization process of PTT. The addition of rubbery EPDM‐g‐MA to PTT matrix increases the notched Izod impact strength, but impairs the tensile strength properties. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Gasoline permeation behavior and mechanical properties of polyamide 6/nanoclay,polyamide 6/PE‐g‐maleic anhydride blend,and polyamide 6/PE‐g‐maleic anhydride/clay nanocomposite

In this article, polyamide 6 (PA6)/clay nanocomposites, PA6/polyethylene grafted maleic anhydride (PE‐g‐MA) blends, and PA6/PE‐g‐MA/clay nanocomposites were prepared and their gasoline permeation behavior and some mechanical properties were investigated. In PA6/clay nanocomposites, cloisite 30B was used as nanoparticles, with weight percentages of 1, 3, and 5. The blends of PA6/PE‐g‐MA were prepared with PE‐g‐MA weight percents of 10, 20, and 30. All samples were prepared via melt mixing technique using a twin screw extruder. The results showed that the lowest gasoline permeation occurred when using 3 wt % of nanoclay in PA6/clay nanocomposites, and 10 wt % of PE‐g‐MA in PA6/PE‐g‐MA blends. Therefore, a sample of PA6/PE‐g‐MA/clay nanocomposite containing 3 wt % of nanoclay and 10 wt % of PE‐g‐MA was prepared and its gasoline permeation behavior was investigated. The results showed that the permeation amount of PA6/PE‐g‐MA/nanoclay was 0.41 g m^?2 day^?1, while this value was 0.46 g m^?2 day^?1 for both of PA6/3wt % clay nanocomposite and PA6/10 wt % PE‐g‐MA blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40150.     

Morphology,thermal behavior,and mechanical properties of PA6/UHMWPE blends with HDPE‐g‐MAH as a compatibilizing agent

A functionalized high‐density polyethylene (HDPE) with maleic anhydride (MAH) was prepared using a reactive extruding method. This copolymer was used as a compatibilizer of blends of polyamide 6 (PA6) and ultrahigh molecular weight polyethylene (UHMWPE). Morphologies were examined by a scanning electron microscope. It was found that the dimension of UHMWPE and HDPE domains in the PA6 matrix decreased dramatically, compared with that of the uncompatibilized blending system. The size of the UHMWPE domains was reduced from 35 μm (PA6/UHMWPE, 80/20) to less than 4 μm (PA6/UHMWPE/HDPE‐g‐MAH, 80/20/20). The tensile strength and Izod impact strength of PA6/UHMWPE/HDPE‐g‐MAH (80/20/20) were 1.5 and 1.6 times as high as those of PA6/UHMWPE (80/20), respectively. This behavior could be attributed to chemical reactions between the anhydride groups of HDPE‐g‐MAH and the terminal amino groups of PA6 in PA6/UHMWPE/HDPE‐g‐MAH blends. Thermal analysis was performed to confirm that the above chemical reactions took place during the blending process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 232–238, 2000     

Synthesis and properties of reactively compatibilized polyester and polyamide blends

The functionalization of poly(butylene terephthalate) (PBT) has been accomplished in a twin screw extruder by grafting maleic anhydride (MA) using a free radical polymerization technique. The resulting PBT‐g‐MA was successfully used as a compatibilizer for the binary blends of polyester (PBT) and polyamide (PA66). Enhanced mechanical properties were achieved for the blend containing a small amount (as low as 2.5 %) of PBT‐g‐MA compared to the binary blend of unmodified PBT with PA66. Loss and storage moduli for blends containing compatibilizer were higher than those of uncompatibilized blends or their respective polymers. The grafting and compatibilization reactions were confirmed using FTIR and ¹³C NMR spectroscopy. The properties of these blends were studied in detail by varying the amount of compatibilizer, and the improved mechanical behaviour was correlated with the morphology with the help of scanning electron microscopy. Morphology studies also revealed the interfacial interaction in the blend containing grafted PBT. The improvement in the properties of these blends can be attributed to the effective interaction of grafted maleic anhydride groups with the amino group in PA66. The results indicate that PBT‐g‐MA acts as an effective compatibilizer for the immiscible blends of PBT and PA66. © 2000 Society of Chemical Industry     

Effect of compatibilization on the properties of HIPS/PA1010 blends

Blends consisting of high‐impact polystyrene (HIPS) as the matrix and polyamide 1010 (PA1010) as the dispersed phase were prepared by mixing. The grafting copolymers of HIPS and maleic anhydride (MA), the compatibilizer precursors of the blends, were synthesized. The contents of the MA in the grafting copolymers are 4.7 wt % and 1.6 wt %, and were assigned as HAM and LMA, respectively. Different blend morphologies were observed by scanning electron microscopy (SEM); the domain size of the PA1010 dispersed phase in the HIPS matrix of compatibilized blends decreased comparing with that of uncompatibilized blends. For the blend with 25 wt % HIPS‐g‐MA component, the T_c of PA1010 shifts towards lower temperature, from 178 to 83°C. It is found that HIPS‐g‐MA used as the third component has profound effect on the mechanical properties of the resulting blends. This behavior has been attributed to the chemical reaction taking place in situ during the mixing between the two components of PA1010 and HIPS‐g‐MA. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 799–806, 2000     

Preparation of the HIPS/MA graft copolymer and its compatibilization in HIPS/PA1010 blends

The graft copolymer of high‐impact polystyrene (HIPS) grafted with maleic anhydride (MA) (HIPS‐g‐MA) was prepared with melt mixing in the presence of a free‐radical initiator. The grafting reaction was confirmed by infrared analyses, and the amount of MA grafted on HIPS was evaluated by a titration method. 1–5% of MA can be grafted on HIPS. HIPS‐g‐MA is miscible with HIPS. Its anhydride group can react with polyamide 1010 (PA1010) during melt mixing of the two components. The compatibility of HIPS‐g‐MA in the HIPS/PA1010 blends was evident. Evidence of reactions in the blends was confirmed in the morphology and mechanical behavior of the blends. A significant reduction in domain size was observed because of the compatibilization of HIPS‐g‐MA in the blends of HIPS and PA1010. The tensile mechanical properties of the prepared blends were investigated, and the fracture surfaces of the blends were examined by means of the scanning electron microscope. The improved adhesion in a 15% HIPS/75% PA1010 blend with 10% HIPS‐g‐MA copolymer was detected. The morphology of fibrillar ligaments formed by PA1010 connecting HIPS particles was observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2017–2025, 1999     

Polyamide 6/maleated ethylene–propylene–diene rubber/organoclay composites with or without glycidyl methacrylate as a compatibilizer

Polyamide 6 (PA6)/maleated ethylene–propylene–diene rubber (EPDM‐g‐MA)/organoclay (OMMT) composites were melt‐compounded through two blending sequences. Glycidyl methacrylate (GMA) was used as a compatibilizer for the ternary composites. The composite prepared through via the premixing of PA6 with OMMT and then further melt blending with EPDM‐g‐MA exhibited higher impact strength than the composite prepared through the simultaneous blending of all the components. However, satisfactorily balanced mechanical properties could be achieved by the addition of GMA through a one‐step blending sequence. The addition of GMA improved the compatibility between PA6 and EPDM‐g‐MA, and this was due to the reactions between PA6, EPDM‐g‐MA, and GMA, as proved by Fourier transform infrared analysis and solubility (Molau) testing. In addition, OMMT acted as a compatibilizer for PA6/EPDM‐g‐MA blends at low contents, but it weakened the interfacial interactions between PA6 and EPDM‐g‐MA at high contents. Both OMMT and GMA retarded the crystallization of PA6. The complex viscosity, storage modulus, and loss modulus of the composites were obviously affected by the addition of OMMT and GMA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical property and morphology comparison between the two blends poly(propylene)/ethylene‐propylene‐diene monomer elastomer and poly(propylene)/maleic anhydride‐g‐ethylene‐propylene‐diene monomer

The comparison of the mechanical properties between poly(propylene)/ethylene‐propylene‐diene monomer elastomer (PP/EPDM) and poly(propylene)/maleic anhydride‐g‐ethylene‐propylene‐diene monomer [PP/MEPDM (MAH‐g‐EPDM)] showed that the latter blend has noticeably higher Izod impact strength but lower Young's modulus than the former one. Phase morphology of the two blends was examined by dynamic mechanical thermal analysis, indicating that the miscibility of PP/MEPDM was inferior to PP/EPDM. The poor miscibility of PP/MEPDM degrades the nucleation effectiveness of the elastomer on PP. The observations of the impact fracture mode of the two blends and the dispersion state of the elastomers, determined by scanning electron microscopy, showed that PP/EPDM fractured in a brittle mode, whereas PP/MEPDM in a ductile one, and that a finer dispersion of MEPDM was found in the blend PP/MEPDM. These observations indicate that the difference in the dispersion state of elastomer between PP/EPDM and PP/MEPDM results in different fracture modes, and thereby affects the toughness of the two blends. The finer dispersion of MEPDM in the blend of PP/MEPDM was attributed to the part cross‐linking of MEPDM resulting from the grafting reaction of EPDM with maleic anhydride (MAH) in the presence of dicumyl peroxide (DCP). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2486–2491, 2002