| Abstract: | Moldings of ethylene–propylene block copolymer (block PP) are improved by annealing in their tensile impact strength (TIS) and brittle temperature (Tb). To elucidate the mechanism, the role of the poly(ethylene-co-propylene) (PEP) component was studied, and the component extracted with n-heptane from annealed test pieces was subjected to characterization by a fractionation technique. It is found that recrystallization takes place by annealing in the PP matrix and results in segregation of atactic PP and high molecular weight amorphous PEP from the crystal region to the amorphous region. Furthermore, crystalline PEP also undergoes recrystallization by annealing, increasing the miscibility in the interface of PP and PEP. These phenomena in the solid phase are discussed in connection with the annealing effect related to impact strength. © 1992 John Wiley & Sons, Inc. |
