Thermal and chemical effects of nucleating agents on α, β, γ-polymorphism of isotactic polypropylene

Abstract

Isotactic polyprpylene (iPP) occurs in several crystalline forms, denoted as f (monoclinic), g (hexagonal), and n (orthorhombic) phases. Hot-stage microscopy, differential scanning calorimetery, and wide-angle X-ray diffraction were used to investigate the influence of thermal treatment and nucleating agents on the morphology of iPP matrices. The tendency of glass fiber (GF) and Kevlar aramid fiber (KF) to induce transcrystallinity in different iPP matrices was evaluated. The f form was present in all iPP specimens treated by different nucleating agents at different crystallization temperatures (Tc). The g and n forms (impure) were found only in iPP specimens that were treated with g -nucleating agent and n - nucleating agent, respectively. Development of transcrystallization was found to depend on the type of fiber used, nucleating agents, and Tc. It was observed that the crystallinity content, obtained by applying different thermal treatments (slow cooling or quenching), gave rise to different morphologies of iPP matrices.