High impact strength and low wear of epoxy modified by a combination of liquid carboxyl terminated poly(butadiene-co-acrylonitrile) rubber and organoclay

Hybrid composites with rubber properties were made from an epoxy modified with either 2.5 phr (parts per hundred) or 15 phr carboxyl terminated poly(butadiene-co-acrylonitrile) (CTBN). Organo-montmorillonite clay added ranged from 0 to 5 phr. Morphology including that of worn surfaces was examined, dynamic mechanical analysis performed and impact resistance determined. Dynamic friction and wear were determined using a pin-on-disc tribometer at dry sliding conditions. Storage modulus of the material containing 2.5 phr CTBN is higher than for 15 phr CTBN, a result of smaller CTBN droplets in the former. All composites have higher values of the Izod impact strength than the neat epoxy resin. Dynamic friction of the hybrids is not influenced by addition of clay whereas the wear resistance depends on the clay concentration. The wear rates at the applied load of 5 N for EP/15-CTBN hybrids are much larger than for EP/2.5-CTBN nanocomposites. This result can be related to the lower glassy storage modulus of EP/15-CTBN as compared to EP/2.5-CTBN. The addition of less than 5 phr clay improves the wear resistance at both 5 and 10 N normal loads. 1 phr clay in the EP/2.5-CTBN matrix is recommended as the optimum composition for improving both mechanical and tribological properties of the epoxy resin.