Base Hydrolysis of Poly(Ethylene Terephthalate) in Methanolic and Aqueous Solutions

Abstract

Hydrolysis of poly(ethylene terephthalate) fibers (intrinsic viscosity: 0.819 dL/g) using methanolic sodium methoxide was compared to that using aqueous sodium hydroxide. Weight and tenacity loss occurred more rapidly with methanolic NaOCH₃. After the methanolic NaOCH₃ treatment, the surface appeared far rougher, much of which was due to low molecular weight material present on the fibers. Intrinsic viscosity measurements indicated virtually no difference between the two treatments in the small amount of chain cleavage obtained at a given weight loss. Fiber density increased after the reaction with methanolic NaOCH₃, probably due to the presence of the methyl ester end groups formed during the ester interchange reaction, while fiber density was essentially unaffected by treatment in aqueous NaOH. Density decreased after the methanolic NaOCH₃-treated fiber was hydrolyzed with aqueous NaOH. Thermal analysis revealed a small increase in the melting temperature after methanolic NaOCH₃ treatment. The shoulder present in the melting region of this sample was markedly affected by chloroform extraction of low molecular weight products resulting from the reaction. While hydrolysis using methanolic NaOCH₃ was more severe than that using aqueous NaOH, both reactions appeared to be confined to the fiber surface.