Interaction parameters of crystalline/crystalline polypropylene/poly(butene-1) blends: Effect of molecular fractionation

Compatibility of crystalline/crystalline polypropylene (PP)/poly(butene-1) (PB-1) blends was investigated via the method of equilibrium melting temperature depression followed by determining the polymer-polymer interaction parameter (chi) using the Nishi-Wang equation. The composition variation of the equilibrium melting temperatures of blends (T-mb(o)) was determined with the Hoffman-Weeks plot. The T-mb(o) and its variation with the blend composition depended on the crystallization temperature range. The morphological effect of the blend composition was not a contribution factor for the depressions of PP and PB-1 in the blends. The interplay of the dilution effect and molecular fractionation effect of the amorphous component on crystallization of the crystalline component in the blends governed the relation of T-mb(o) with the blend composition. The calculated chi values were negative depending on the blend composition. The negative chi values suggested that PP and PB-1 in the amorphous region were compatible. The composition variation of the chi values was attributed to the molecular fractionation effect during crystallization. (C) 2002 Wiley Periodicals, Inc.