Impact-specific essential work of fracture of maleic anhydride-compatibilized polypropylene/elastomer blends and their composites

Charpy drop-weight-impact and essential work of fracture (EWT) characteristics of maleic anhydride (MA)-compatibilized styrene- ethylene butylene-styrene (SEBS)/ polypropylene (PP) blends and their composites reinforced with short glass fibers (SGFs) were investigated. MA was grafted to either SEBS copolymer (SEBS-g-MA) or PP (PP-g-MA). The mPP blend was prepared by the compounding of 95% PP and 5% PP-g-MA. Drop-weight-impact results revealed that the mPP specimen had an extremely low impact strength. The incorporation of SEBS or SEBS-g-MA elastomers into mPP improved its impact strength dramatically. Similarly, the addition of SEBS was beneficial for enhancing the impact strength of the SGF/SEBS/mPP and SGF/SEBS-g-MA/mPP hybrids. A scanning electron microscopy examination of the fractured surfaces of impact specimens revealed that the glass-fiber surfaces of the SGF/SEBS/mPP and SGF/SEBS-g-MA/mPP hybrids were sheathed completely with deformed matrix material. This was due to strong interfacial bonding between the phase components of the hybrids associated with the MA addition. Impact EWT tests were carried out on single-edge-notched-bending specimens at 3 m s(-1). The results showed that pure PP, mPP, and the composites only exhibited specific essential work. The nonessential work was absent in these specimens under a high-impact-rate loading condition. The addition of SEBS or SEBS-g-NU elastomer to mPP increased both the specific essential and nonessential work of fracture. This implied that elastomer particles contributed to the dissipation of energy at the fracture surface and in the outer plastic zone at a high impact speed of 3 m s(-1). (C) 2002 Wiley Periodicals, Inc.