Ultra‐high molecular weight styrenic block copolymer/TPU blends for automotive applications: Influence of various compatibilizers

Thermoplastic elastomers (TPEs) based on new generation ultrahigh molecular weight styrene‐ethylene‐butylene‐styrene (SEBS) and thermoplastic polyurethane (TPU) are developed and characterized especially for automotive applications. Influence of maleic anhydride grafted styrene‐ethylene‐butylene‐styrene (SEBS‐g‐MA) and maleic anhydride grafted ethylene propylene rubber (EPM‐g‐MA) as compatibilizers has been explored and compared on the blends of SEBS/TPU (60:40). The amount of compatibilizers was varied from 0 to 10 phr. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies revealed the dramatic changes from a nonuniform to finer and uniform dispersed phase morphology. This was reflected in various mechanical properties. SEBS‐g‐MA modified blends showed higher tensile strength. EPM‐g‐MA modified blends also displayed considerable improvement. Elongation at break (EB) was doubled for the entire compatibilized blends. Fourier‐transform infrared spectrometry (FTIR) confirmed the chemical changes in the blends brought about by the interactions between blend components and compatibilizers. Both SEBS‐g‐MA and EPM‐g‐MA had more or less similar effects in dynamic mechanical properties of the blends. Additionally, melt rheological studies have also been pursued through a rubber process analyzer (RPA) to get a better insight.     

Combined effect of compatibilizer and carbon nanotubes on the morphology and electrical conductivity of PP/PS blend

In this work, maleic anhydride grafted styrene–ethylene–butadiene–styrene copolymer (SEBS‐g‐MA) and carbon nanotubes (CNTs) were introduced into the immiscible polypropylene/polystyrene (PP/PS) blend. Among the three polymer components, SEBS‐g‐MA has the strongest affinity to CNTs; thus, it exhibits dual effects to adjust the phase morphology of the blends and the dispersion state of CNTs in the blends. The experimental observations obtained from morphology characterizations using scanning electron microscope and transmission electron microscope confirm the selective localization of CNTs at the interface of the immiscible PP/PS blend. As a consequence, largely decreased percolation threshold is achieved when most of CNTs are selectively localized at the interface region between PP and PS. Copyright © 2014 John Wiley & Sons, Ltd.     

Polyamide 66/EPR‐g‐MA blends: mechanical modeling and kinetic analysis of thermal degradation

The present investigation deals with the mechanical, thermal, and morphological properties of binary nylon 66/maleic anhydride grafted ethylene propylene rubber (EPR‐g‐MA) blends at different dispersed phase (EPR‐g‐MA) concentrations. The effects of EPR‐g‐MA concentration and dispersed particle size on the mechanical properties of the blends were studied. Analysis of the tensile data in terms of various theoretical models revealed the variation of stress concentration effect with blend composition and the improvement of interfacial adhesion between dispersed rubber phase and nylon 66 matrix. The thermal degradation of the blends was analyzed by nonisothermal thermogravimetric analysis (TGA). It was found that the activation energy (E_a) and overall reaction order of thermal degradation decreased with increasing EPR‐g‐MA content. The scanning electron microscopic (SEM) analysis showed a significant decrease in dispersed particle size with increasing EPR‐g‐MA content, which was explained on the basis of the level of chemical interaction (in situ compatibilization) between nylon 66 and EPR‐g‐MA. The surface morphology of the nylon 66/EPR‐g‐MA blends was illustrated by the roughness of atomic force microscopy (AFM) images. Copyright © 2008 John Wiley & Sons, Ltd.     

Poly(lactic acid)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer/sepiolite nanocomposites: Investigation of thermo‐mechanical and morphological properties

In this study, sepiolite nanoclay is used as reinforcing agent for poly(lactic acid) (PLA)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer (SEBS‐g‐MA) 90/10 (w/w) blend. Effects of sepiolite on thermal behavior, morphology, and thermomechanical properties of PLA/SEBS‐g‐MA blend were investigated. Differential scanning calorimetry results showed 7% improvement in crystallinity at 0.5 wt% of sepiolite. The nanocomposite exhibited approximately 36% increase in the tensile modulus and 17% increase in toughness as compared with the blend matrix at 0.5 and 2.5 wt% of sepiolite respectively. Field emission scanning electron microscopy and transmission electron microscopy images exhibited sepiolite‐induced morphological changes and dispersion of sepiolite in both PLA and SEBS‐g‐MA phases. Dynamic mechanical analysis and wide angle X‐ray diffraction present evidences in support of the reinforcing nature of sepiolite and phase interaction between the filler and the matrix. This study confirms that sepiolite can improve tensile modulus and toughness of PLA/SEBS‐g‐MA blend.     

Effects of different types of polyethylene on the morphology and properties of recycled poly(ethylene terephthalate)/polyethylene compatibilized blends

Recycled poly(ethylene terephthalate) (R‐PET) was blended with four types of polyethylene (PE), linear low density polyethylene (LLDPE; LL0209AA, Fs150), low density polyethylene (LDPE; F101‐1), and metallocene‐LLDPE (m‐LLDPE; Fv203) by co‐rotating twin‐screw extruder. Maleic anhydride‐grafted poly(styrene‐ethylene/butyldiene‐styrene) (SEBS‐g‐MA) was added as compatibilizer. R‐PET/PE/SEBS‐g‐MA blends were examined by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and mechanical property testing. The results indicated that the morphology and properties of the blends depended to a great extent on the miscibility between the olefin segments of SEBS‐g‐MA and PE. Due to the proper interaction between SEBS‐g‐MA and LDPE (F101‐1), most SEBS‐g‐MA, located at the interface between two phases of PET and LDPE to increase the interfacial adhesion, lead to better mechanical properties of R‐PET/LDPE (F101‐1) blend. However, both the poor miscibility of SEBS‐g‐MA with LLDPE (LL0209AA) and the excessive miscibility of SEBS‐g‐MA with LLDPE (Fs150) and m‐LLDPE (Fv203) reduced the compatibilization effect of SEBS‐g‐MA. DSC results showed that the interaction between SEBS‐g‐MA and PE obviously affected the crystallization of PET and PE. DMA results indicated that PE had more influence on the movement of SEBS‐g‐MA than PE did. Copyright © 2010 John Wiley & Sons, Ltd.     

The effect of various compatibilizers on thermal,mechanical, and morphological properties of polystyrene/polypropylene blends

The effects of various compatibilizers on thermal, mechanical and morphological properties of 50/50 polypropylene/polystyrene blends were investigated. Various compatibilizers, polystyrene-(ethylene/butylenes/ styrene) (SEBS), ethylene vinyl acetate (EVA), polystyrene-butylene rubber (SBR) and blend of compatibilizers SEBS/PP-g-MAH, EVA/PP-g-MAH, and SBR/PP-g-MAH were used. Differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray scattering, scanning electron microscopy, microhardness, and Izod impact strength were adopted. It was found that the influence of various compatibilizers was appeared on all the properties studied. The properties of the blends compatibilized with SEBS, EVA, and SBR are very distinct from those of blends compatibilized with blend of compatibilizers. Results show that compatibilized blends with the blend of compatibilizers EVA/PP-g-MAH, SBR/PP-g-MAH, and SEBS/PP-g-MAH or SBR were relatively more stable than the uncompatibilized blend and blend compatibilized with SEBS or EVA. The compatibilizer does not only reduce the interfacial tension or increase the phase interfacial adhesion between the immiscible polymers, but greatly affects the degree of crystallinity of blends.

     

Influence of extender oil composition on flowing property,thermal stability,and morphology of styrene‐b‐ethylene‐co‐butylene‐b‐styrene copolymer/polypropylene/oil blends

In this study, a series of styrene‐b‐ethylene‐co‐butylene‐b‐styrene copolymer (SEBS)/polypropylene (PP)/oil blends with different kinds of oil composition was developed through melt blending. The effect of oil with different composition and properties on its phase equilibrium and “redistribution” in multiphasic SEBS elastomer was systematically studied for the first time. Moreover, an integral influencing mechanism of oil composition on the structure and properties of SEBS/PP/oil blends was also put forward. The mineral oil was mainly distributed in ethylene/butylene (EB)/PP phase, which greatly enhanced the processing flowability of SEBS/PP/oil blends. With increasing oil C_N content, a redistribution of oil appeared and excess naphthenic oil (NO) entered the interphase of soft and hard phases. The dynamic mechanical thermal analysis (DMTA) analysis indicated that the polystyrene (PS) phase was plasticized, which also helped to improve the processing fluidity of blends. However, the plasticizing of physical cross‐linking point PS resulted in a decrease in mechanical strength and thermal stability. Small‐angle X‐ray scattering (SAXS) and transmission electron microscope (TEM) results showed that PS phase (45 nm to 55 nm) cylindrically distributed in EB/PP/oil matrix, the excess NO in the interphase enlarged the distance between PS phase and widen the escape channel for oil migration. At over 45% oil C_N content, the electron density difference between soft and hard phases reduced to the minimum, same as T_gPS, indicating a deeper plasticizing effect. The PS phase swelled and exhibited elastic behavior; thus, the force could be uniformly transferred between two phases. Importantly, a recover in strength and thermal stability was observed in O‐5 blend. This work significantly filled the gap of studies in oil‐extended thermoplastic elastomers (TPEs), exhibiting great theoretical guiding significance and application value.     

Evaluation of the SEBS copolymer in the compatibility of PP/ABS blends through mechanical,thermal, thermomechanical properties,and morphology

Polypropylene (PP) blends with acrylonitrile-butadiene-styrene (ABS) were prepared using the styrene-ethylene-butylene-styrene copolymer (SEBS) as a compatibilizing agent. The blends were prepared in a co-rotational twin-screw extruder and injection molded. Torque rheometry, Izod impact strength, tensile strength, heat deflection temperature (HDT), differential scanning calorimetry, thermogravimetry, and scanning electron microscopy properties were investigated. The results showed that there was an increase in the torque of PA6/ABS blends with SEBS addition. The PP/ABS/SEBS (60/25/15%) blend showed significant improvement in impact strength, elongation at break, thermal stability, and HDT compared with neat PP. The elastic modulus and tensile strength have not been significantly reduced. The degree of crystallinity and the crystalline melting temperature increased, indicating a nucleating effect of ABS. The PP/ABS blends compatibilized with 12.5% and 15% SEBS presented morphology with well-distributed fine ABS particles with good interfacial adhesion. As a result, thermal stability has been improved over pure PP and the mechanical properties have been increased, especially impact strength. In general, the addition of the SEBS copolymer as the PP/ABS blend compatibilizer has the advantage of refining the blend's morphology, increasing its toughness and thermal stability, without jeopardizing other PP properties.     

Tailoring of interface of polypropylene/polystyrene/carbon nanofibre composites by polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene

Mechanical and physical properties of polypropylene (PP)/polystyrene (PS) blend, PP/PS/polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) ternary blend and their composites with carbon nanofibers (CNF) were investigated. Composites of ternary blend exhibited superior properties compared to those of binary blends. Mechanical performance of nanocomposites was intimately related to their phase morphology. PP/PS/SEBS/0.1 wt% CNF hybrid composites exhibited excellent impact strength (Four-fold increase compared to PP/PS blend) and ductility (12-fold increase in elongation at break, with respect to PP/PS blend). Moreover, these composites displayed good tensile strength and modulus (15% increase in Young's modulus, compared to PP/PS/SEBS blend) and are suitable for various end-use applications including automobile applications. Although crystallinity of PP phase is decreased by the incorporation of CNF, thermal stability of the composites remained almost unaffected. Contact angle measurements revealed that ternary composites exhibited maximum hydrophobicity.     

Synthesis and characterization of polyethylene‐g‐polystyrene as the compatibilizer for polypropylene/ Polystyrene blends

Polyethylene‐g‐polystyrene (PE‐g‐PS) was synthesized as a compatibilizer for polypropylene/polystyrene­(PP/PS) blends by the living radical polymerization of styrene with polyethylene‐co‐glycidylmethacrylate (PE‐co‐GMA). The compatibilizer effect of PE‐g‐PS on the morphology and thermal properties of PP/PS blends was investigated. The crystalline temperature of PP in PP/PS blends decreased with increasing PE‐g‐PS contents. Morphologies of PP/PE‐g‐PS/PS blends showed much better dispersion of each domain for higher PE‐g‐PS contents. The molecular weight of PS segment in PP/PE‐g‐PS/PS blend was increased by addition of styrene monomer during the post melt blending process where post living radical polymerization reaction proceeded. Copyright © 2003 John Wiley & Sons, Ltd.     

Three‐Dimensional Structure of Olefinic Thermoplastic Elastomer Blends Using Electron Tomography

Summary: The present communication reports the first use of electron tomography in reconstructing the three‐dimensional morphology in thermoplastic elastomer blends. The blends investigated were dynamically vulcanized blends of ethylene‐propylene‐diene (EPDM) rubber/poly(propylene)/oil and polystyrene‐block‐(ethylene‐co‐butylene)‐block‐polystyrene (SEBS)/poly(propylene)/oil. An easy identification of blend morphology could be carried out at blend compositions, where conventional transmission electron microscopic imaging gives misleading information. This technique gives a higher resolution than any other microscopic technique, and is applicable to blends with dispersed as well as co‐continuous morphologies.

Example of a tomographic model of partially co‐continuous SEBS phases in a SEBS/PP/oil thermoplastic blend. Only the contours of the SEBS phase are shown.     

Morphological stability,interfacial tension,and dual-phase continuity in polystyrene-polyethylene blends

The morphological stability of polystyrene high-density polyethylene (PS/PE) blend is investigated in the region of dual-phase continuity. The effect of the addition of a triblock SEBS copolymer to the blends on the stability of these morphologies, is examined. The results show that the morphology of the unmodified blends changes from co-continuous to droplet matrix for PS-rich blends whereas the morphology of a 50/50 blend maintains continuity but coarsened significantly upon annealing at 200°C. In the presence of the copolymer, these morphologies are much more stable. Selective solvent extraction of polystyrene in di-ethyl ether reveals that the level of PS continuity in the 50/50 blend is higher for the unmodified system than for the modified one. Upon annealing, the level of PS continuity significantly increases for the unmodified 50/50 PS/PE blend. The effect of the copolymer content in the blend on the interfacial tension between the two components is also investigated using the breaking thread method. The interfacial tension is found to be reduced from 5.6 to 1.1 mN/m by the addition of 20 parts of the copolymer to the blend. © 1997 John Wiley & Sons, Inc.     

The compatibilization effect of ethylene/styrene interpolymer on polystyrene/polyethylene blends

In this study, ethylene/styrene interpolymer (ESI) was used as compatibilizer for the blends of polystyrene (PS) and low‐density polyethylene (LDPE). The mechanical properties including impact, tensile properties, and morphology of the blends were investigated by means of uniaxial tension, instrumented falling‐weight impact measurements, and scanning electron microscopy. Impact measurements indicated that the impact strength of the blends increases slowly with LDPE content up to 40 wt %; thereafter, it increases sharply with increasing LDPE content. The impact energy of the LDPE‐rich blends exceeded that of pure LDPE, implying that the LDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of ESI. Tensile tests showed that the yield strength of the PS/LDPE/ESI blends decreases considerably with increasing LDPE content. However, the elongation at break of the blends tended to increase significantly with increasing LDPE content. The compatibilization efficiency of ESI and polystyrene‐hydrogenated butadiene‐polystyrene triblock copolymers (SEBS) for PS/LDPE 50/50 was further compared. Mechanical properties show that ESI is more effective to achieve a combination of LDPE toughness and PS rigidity than SEBS. The correlation between the impact property and morphology of the ESI‐compatibilized PS/LDPE blends is discussed. The excellent tensile ductility of the LDPE‐rich blends resulted from shield yielding of the matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2136–2146, 2007     

Effects of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] on the charge distributions of low‐density polyethylene/polystyrene blends

The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004     

Long-Range Processing Correlation and Morphological Fractality of Compatibilized Blends of PS/ HDPE/ SEBS Block Copolymer

Summary: Processing and compatibilization effects of a commercially available styrene/ ethylene-butylene/ styrene (SEBS) compatibilizer on the morphological structure, rheological and mechanical properties of blends of polystyrene (PS) and high density polyethylene (HDPE) were investigated. The rheological behaviour of the blends melt during processing was followed by measuring torque; extrusion capacity output and melts back-pressure in a twin screw extruder. The processing parameters were decreased with the HDPE content. The results show that SEBS compatibilizer can yield compatibilization by substantially reducing torque and increasing the back-pressure. However, the Hurst indices of melt processing parameters are increased with compatibilization. Near-infrared spectra had been described by the Hurst index H_NIR which is then related to HDPE content in the blends. The correlation between the blend compositions, morphological structure, mechanical and rheological properties and processing parameters was established and discussed on base of correlation with the fractal indices obtained from the SEM microphotographs of PS/HDPE/SEBS blends.     

New high impact polystyrene: Use of poly(1‐hexene) and poly(1‐hexene‐co‐hexadiene) as impact modifiers

In this study, polystyrene (PS) was melt blended with different amounts of poly1‐hexene (PH) and poly(1‐hexene‐co‐hexadiene) (COPOLY) and the blends were compared with conventional PS/polybutadiene (PS/PB) one. Scanning electron microscope revealed that the dispersion of PH and COPOLY in PS matrix was more uniform with the appearance of small particles in PS matrix; however, in the case of PS/PB blends, the fracture surface showed nonhomogenous morphology with the appearance of bigger rubber particles. Based on Differential Scanning Calorimetry (DSC) and dynamic mechanical thermal analysis results, T_g of the blends decreased in comparison with it in neat PS. Impact strength of PS/PH and PS/COPOLY blends was considerably higher than that in PS/PB and significantly higher than the value for neat PS. Tensile test showed substantial improvement in stress at yield and better elongation at break for COPOLY containing blend than the samples containing PH and PB rubbers. Also, blending of PS with 10% of the rubbers was considered in the presence of dicumylperoxide as a probable grafting/cross‐linking agent to produce XPS/COPOLY10 and XPS/PB10 samples, respectively. IR results of the nonsoluble solvent extracted gel showed that COPOLY and PB were grafted to PS matrix during melt blending, which caused higher impact strength in the related samples.     

PPO/SEBS-g-MAH共混体系的形态结构与冲击性能

从亚微相态和冲击性能出发 ,对比了采用熔融挤出法制备的PPO/SEBS和PPO/SEBS g MAH两种共混物 .结果表明 ,在本文所研究的弹性体用量范围内 ,PPO/SEBS为“海 岛”型结构 ,而PPO/SEBS g MAH呈现网状结构 ;PPO/SEBS体系无脆韧转变现象 ,PPO/SEBS g MAH体系则在弹性体用量为 10 %～ 15 %时出现明显的脆韧转变 ,缺口冲击强度达到 95 0J/m ,这种超韧现象源于其网状结构的形成 .文中进一步用DSC和毛细管流变仪对共混体系的热性能和流变性能进行了测试 ,探讨了PPO/SEBS g MAH共混物网状结构的形成原因     

Exploring the effect of radiation crosslinking on the physico‐mechanical,dynamic mechanical and dielectric properties of EOC–PDMS blends for cable insulation applications

This work focuses on the effect of electron beam irradiation on the physico‐mechanical, dynamic mechanical and dielectric properties of blends based on ethylene octene copolymer (EOC) and poly dimethyl siloxane (PDMS) rubber. It is found that electron beam irradiation caused considerable improvement in the physico‐mechanical properties; the tensile strength was enhanced by nearly 35% for 70:30 EOC:PDMS blend. Phase morphology of the blends analyzed before irradiation by scanning electron microscopy (SEM) exhibited droplet/matrix morphology with sizes of the PDMS rubber domain varying from 0.55 µm to 0.47 µm as the amount of PDMS rubber decreased from 30 wt% to 10 wt%. This reduction in the PDMS rubber domain has been correlated with the physico‐mechanical properties of the blends. Further, the dynamic mechanical properties and creep behavior of these EOC:PDMS blends before and after irradiation has been studied. It is inferred that the 70:30 blend after radiation crosslinking shows a 17% decrease in the creep compliance, i.e. higher creep resistance compared to neat blends. All the radiation crosslinked blends exhibited lower dielectric constant, lower dielectric loss and higher electrical resistivity as compared to the virgin blends which makes it suitable for cable insulating application. Copyright © 2016 John Wiley & Sons, Ltd.     

Binary and ternary blends of high‐density polyethylene with poly(ethylene terephthalate) and polystyrene based on recycled materials

Binary blends of recycled high‐density polyethylene (R‐HDPE) with poly(ethylene terephthalate) (R‐PET) and recycled polystyrene (R‐PS), as well as the ternary blends, i.e. R‐HDPE/R‐PET/R‐PS, with varying amounts of the constituents were prepared by twin screw extruder. The mechanical, rheological, thermal, and scanning electron microscopy (SEM) analyses were utilized to characterize the samples. The results revealed that both R‐HDPE/R‐PET and R‐HDPE/R‐PS blends show phase inversion but at different compositions. The R‐PET was found to have much higher influence on the properties enhancement of the R‐HDPE compared to R‐PS, but at the phase inverted situation, a significant loss in the tensile strength of R‐HDPE/R‐PET blend was observed due to the weak interaction at this morphological state. However, the ternary blends with higher loading of second phase, namely greater than 50 wt% of R‐PET+R‐PS, demonstrated better mechanical properties than the binary blends with the same content of either R‐PET or R‐PS. Copyright © 2009 John Wiley & Sons, Ltd.     

Structural and mechanical behavior of polypropylene/ maleated styrene‐(ethylene‐co‐butylene)‐styrene/sisal fiber composites prepared by injection molding

Hybrid composites consisting of isotactic poly(propylene) (PP), sisal fiber (SF), and maleic anhydride grafted styrene‐(ethylene‐co‐butylene)‐styrene copolymer (MA‐SEBS) were prepared by melt compounding, followed by injection molding. The melt‐compounding torque behavior, thermal properties, morphology, crystal structure, and mechanical behavior of the PP/MA‐SEBS/SF composites were systematically investigated. The torque test, thermogravimetric analysis, differential scanning calorimetric, and scanning electron microscopic results all indicated that MA‐SEBS was an effective compatibilizer for the PP/SF composites, and there was a synergism between MA‐SEBS and PP/SF in the thermal stability of the PP/MA‐SEBS/SF composites. Wide‐angle X‐ray diffraction analysis indicated that the α form and β form of the PP crystals coexisted in the PP/MA‐SEBS/SF composites. With the incorporation of MA‐SEBS, the relative amount of β‐form PP crystals decreased significantly. Mechanical tests showed that the tensile strength and impact toughness of the PP/SF composites were generally improved by the incorporation of MA‐SEBS. The instrumented drop‐weight dart‐impact test was also used to examine the impact‐fracture behavior of these composites. The results revealed that the maximum impact force (F_max), impact‐fracture energy (E_T), total impact duration (t_r), crack‐initiation time (t_init), and crack‐propagation time (t_prop) of the composites all tended to increase with an increasing MA‐SEBS content. From these results, the incorporation of MA‐SEBS into PP/SF composites can retard both the crack initiation and propagation phases of the impact‐fracture process. These prolonged the crack initiation and propagation time and increased the energy consumption during impact fracture, thereby leading to toughening of PP/MA‐SEBS/SF composites. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1214–1222, 2002