The melting conditions of biaxially oriented polypropylene (BOPP) have a very strong effect on the courses of both non-isothermal and isothermal crystallization from the melt. It has been shown that the crystallization proceeds by two mechanisms. Depending on the melting conditions, both crystallization mechanisms can proceed individually or simultaneously (double crystallization). The high rate mechanism, occurring in non-isothermal crystallization at low undercooling and observed in isothermal crystallization, can be attributed to the ordered structure of the melt preserved after melting, presumably a mesomorphic state. The second component corresponds to crystallization from the isotropic melt. Anomalous crystallization of BOPP samples can be eliminated by energetic heat treatment, by the destruction of ordered structures. As a result of this treatment, the characteristics of crystallization and its quantitative parameters will become similar to those of unoriented polypropylene.
ASJC Scopus subject areas
- Chemical Engineering(all)