Nonisothermal crystallization behaviors of a polyolefin terpolymer and its foam

Abstract

Nonisothermal crystallization analysis of a terpolymer and its foam provides some important information about the crystalline structures of these materials. In the present work, a modified version of the Ozawa's method proposed by us was successfully applied to the DSC data for a polypropylene containing terpolymer and its foam at various low cooling rates. The Avrami exponent of the pristine terpolymer was 3.1, which is close to that of iPP, indicating that the crystallites had a spherulite structure. On the other hand, high Avrami exponent values (ca 5.6) were obtained for the foamed terpolymer, indicating that the crystallites had structures resembling a three dimensional solid sheaf. This difference between the pristine and foamed terpolymer samples is attributed to the appearance of the gamma-form in the foamed terpolymer. The observed behavior can be attributed to a large number of nuclei being produced during the foaming process by FIC.