Hiroshi Sobue

Heat Treatment of Irradiated Polypropylene

IT has been shown by Lawton1,2 that during the high-energy irradiation of a polymer, the main effect produced is either intermolecular cross-linking or degradation of the molecular chain, and radicals produced during irradiation can be trapped in the crystalline regions. Crystalline ‘Marlex-50’, irradiated at 25° C. and then annealed at 150° C., gave more cross-links than ‘Marlex-50’ irradiated at 25° C. and not annealed, but less than that of the polymer irradiated at 150° C. for the same dose of irradiation. We have been able to demonstrate the delayed cross-linking effect by heat treatment of pre-irradiated isotactic polypropylene. We find that many trapped radicals produced during irradiation, which are stable at room temperature (as detected by electron spin resonance measurements), could contribute to delayed cross-linking on annealing the irradiated polymer after irradiation, and a big increase of gel content was observed. On the other hand, materials irradiated at 180° C. (molten state) gave no gel content for high dosage beyond 80 Mrads, indicating that in the molten state degradation of the molecular chain was predominant. The phenomenon is very different from the effect in polyethylene.

Distribution of the Substituents in Heterogeneously Methylated Celluloses

Four methyl celluloses made from cotton linters with dimethyl sulfate and alkali in toluene and one commercial product were hydrolyzed. Unsubstituted, monomethyl, di methyl, and trimethyl glucose in the hydrolyzates were separated by filter paper chro matopile, and the results were compared with the calculated values of Spurlin and the experimental values of other investigators.

Rheological Interpretation of the Mechanism of Crease Recovery of Fiber

In an attempt to interpret the mechanism of creasing and the recovery therefrom, a theoretical study of the visco-elastic behavior of fibers and or filaments has been made. The relationship between crease angle of fiber, temperature, and creasing time is discussed theoretically and experimentally.