Organic solvent treatment of isotactic polypropylene films, 1. Effects of organic solvent treatment on proton spin-lattice and spin-spin relaxation times

An isotactic polypropylene film was treated with cyclohexane, toluene, 1-chloronaphthalene, and glycerin. The morphological changes were characterized by measurements of weight loss, density, molecular weight, and spin-lattice and spin-spin relaxation times. There is a relatively narrow temperature range at which a sharp increase in weight loss occurs corresponding to the kind of the solvent. The change in density occurs almost linearly with treatment time for all solvents. Molecular weight also increases as the weight loss is increased. There is a considerable increase in T₁ with increasing treatment temperature. T₂ of the amorphous region, T_2a, also increases as the treatment temperature is increased, but some decrease in T_2a is found in the samples treated with toluene and cyclohexane at higher temperatures. The fraction of the rigid region, F_c, increases and that of the mobile one, F_a, decreases with proceeding solvent extraction. The value of F_c is considerably different from the crystallinity calculated from the density in the early stage of the treatment followed by the gradual approach to the value calculated from the density, although some different behaviour was found with the samples treated with cyclohexane.