Impact modification of PA-6 and PBT by epoxy-functionalized rubbers

Glycidylmethacrylate (GMA) grafted apolar (ethylene/propylene/diene - EPDM) and polar (acrylonitrile/butadiene - NBR) rubbers were melt blended with polyamide-6 (PA-6) and polybutylene terephthalate (PBT). The toughness of the blends containing 5, 10 and 50 wt.% epoxy functionalized rubbers was assessed by various methods (notched Charpy, perforation impact) as a function of temperature (T=23 and −40°C). The notched Charpy tests served to deduce the fracture toughness (K_c) and energy (G_c) data. It was established that EPDM-g-GMA is a slightly better impact modifier than is NBR-g-GMA albeit the latter polar rubber is more compatible with both matrices than the less polar EPDM-g-GMA. This finding was traced to the difference in the glass transition temperature (T_g of NBR is higher than that of EPDM) and to the dispersion of the epoxy functionalized rubbers.