ISOTHERMAL CRYSTALLIZATION OF IPP IN MODEL GLASS-FIBER COMPOSITES

Isothermal crystallization of iPP in model glass-fiber composites is s tudied by DSC, and the basic energetic parameters of crystallization a re determined. Unsized untreated and thermally treated glass fibers ar e used in model composites to determine the role of the surface on nuc leation and crystallization processes. Thermally treated glass fibers are found to exhibit a predominant nucleating effect as compared to un sized untreated ones, and the crystallization proceeds faster, resulti ng in lower values for the halftime of crystallization (10-120 s). The energy of formation of a nuclei of critical dimensions at a given T-c is also lower, and it decreases as the content of the fibers in the c omposite increases. The surface free energy of folding, sigma(e) = 140 x 10(-3) J/m(2), was determined for iPP in the composite containing 5 0% glass fibers, while for pure iPP, sigma(e) = 170 x 10(-3)J/m(2) was found. (C) 1998 John Wiley & Sons, Inc.