The effect of molecular composition and heterogeneity on the environmental stress cracking resistance (ESCR) of propylene impact copolymers

The ESCR of three propylene impact copolymers in the presence of isopropanol was investigated and the variation in stress crack resistance was evaluated in terms of polymer characteristics. The effect of removing both soluble and crystalline material from the copolymers on the ESCR was evaluated. The stress crack resistance appears to be dependent on the crystallinity of the materials, but not solely so. The amount and distribution of the rubbery copolymer in these materials appears to play a role as well.