Compatibilizing effect of Novolak on toughness, crystallite and morphologyof polyacetal and nitrile-butadiene rubber blends

Compatibilizing effect of novolak on toughness, crystallite, and morphology of polyacetal (POM) and nitrile-butadiene (NBR) blends were investigated, It was found the POM and NBR were immiscible system, and the compatibilizat ion of POM and NBR could be improved by addition of Novolak. As a result, I zod impact strength increased remarkably. The crystallite morphology of the blends under polarized light microscopy demonstrated that the size of sphe rulites of POM was so large as to increase the brittleness of blends. The s ize of spherulites of POM could be sharply reduced by mixing with Novolak, which suggested that the inner stress concentration in blends be diminished . POM/NBR blends exhibited a "sea-island" morphology, where NBR was the dis persed phase "sea" and POM was continuous phase "island". The morphology of POM/NBR/novolak (mass ratio 60/40/5) blends showed that there was not a "s ea-island" structure but a physical elastomer network. The elastomer networ k impeded the growth of craze and promoted the shear deformation of POM mat rix. As a result, a large amount of impact energy could be absorbed and the super-toughness was thus obtained.