Poly(ethylene terephthalate) copolymers with a smaller amount of poly(ethylene glycol)s and poly(butylene glycol)s

Abstract

Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess amount of ethylene glycol with 2–20 mol% of poly(ethylene glycol) (E) or poly(butylene glycol) (B), where the molecular weights ( MW) of E and B are 200–7500 and 1000–3000, respectively. Reduced specific viscosity of copolymer increased with increasing MW and the content of polyglycol comonomer. Temperatures of glass transition ( T g), cold crystallization and melting ( T m) decreased with increasing MW of polyglycol and comonomer content, and their decrease is more remarkable for E-type copolymers than for B-type ones. T m depression of copolymers suggested that these copolymers are block-type at higher comonomer content. T g was decreased below room temperature by the copolymerization, which affected the crystallinity and density of the copolymer films. Water content and dye uptake increased with increasing comonomer content, and their increase is higher for E1000 copolymer film than for B1000 one. Alkali resistance increased for B1000 copolymer film, whereas it decreased remarkably for E1000 one. Tensile properties of drawn (3x) film were remarkably affected by the decrease of the T g of the copolymer, and E1000 5 mol% copolymer film showed high tensile recovery. Shrinkage in boiling water increased for E1000 drawn film, whereas it decreased for B1000 one. Thermal stability increased and then decreased with increasing comonomer content and it was lower for B-type copolymer than for E-type one.