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Keywords:

  • toughening mechanism;
  • nanocomposite;
  • clay;
  • polymer blend;
  • crazing

Abstract

The toughness of a polypropylene (PP)/ethylene-octene copolymer (EOC)/maleic anhydride-grafted poly(ethylene-co-octene) (EOC-g-MA)/clay nanocomposite and blends of PP/EOC and PP/EOC/EOC-g-MA was investigated using Charpy impact and single-edge-notch tensile (SENT) tests. In order to understand the toughening mechanisms, impact fracture surfaces and damage zones of single-edge-notch samples were studied with scanning electron microscopy and transmission optical microscopy, respectively. It was observed that the addition of EOC-g-MA to PP/EOC blend led to improvements in both impact strength and fracture energy of SENT tests because of the enhanced compatibility of the blend, which resulted from reduced EOC particle size and improved interfacial adhesion, and the decreased crystallinity of PP. The incorporation of clay to PP/EOC/EOC-g-MA blend caused a further increase of the toughness, owing to the greater decrease in the size of elastomer particles, to the presence of clay tactoids inside the elastomer phase and presumably to debonding of clay layers during the low-speed SENT tests. The results of microscopic observations showed that the main toughening mechanism in PP/EOC/EOC-g-MA blend and PP/EOC/EOC-g-MA/clay nanocomposite is crazing. Copyright © 2012 Society of Chemical Industry