Creep Rupture Properties of Homopolymer, Copolymer, and Terpolymer Based on Poly(oxymethylene)

摘要

Polyacetal copolymers were prepared by cationic ring-opening copolymerizations of 1,3,5-trioxane (TOX) with 1,3-dioxolane (DOX), and polyacetal terpolymers were prepared by terpolymerizations of TOX, DOX, and 2-ethylhexyl glycidyl ether (EHGE). Polyacetal polymers with three different structures such as polyacetal homopolymers, polyacetal copolymers, and polyacetal terpolymers were compared in the mechanical properties and the creep characteristics, and discussed from the view point of the polymer structure. The polyacetal copolymers and the polyacetal terpolymers were determined by H-1-MNR measurement. About 80 mol % of DOX and EHGE amounts in feed were incorporated randomly into the each polymer. From the plots of the degree of crystallinity (X-c) versus the tensile strength, the tensile strength and crystallintiy of the polyacetal homopoymers are higher than those of the polyacetal copolymers and the polyacetal terpolymers. However, the tensile strength does not decrease linearly with a decrease in the crystallinity among the polyacetal polymers with three different structures, the polyacetal homopolymer, the polyacetal copolymers, and the polyacetal terpolymers. Creep rupture was characterized by the activation volume, nu(c) value in Zhurkov's equation, which can be estimated from the slope in the plots of load versus log (rupture time) at 80 degrees C. The polyacetal polymers with higher molecular weight have larger values of the activation volume than those with lower molecular weight. When the activation volume values are compared among the polyacetal polymers with the same molecular weights, they increase in the following order: the polyacetal homopolymers < the polyacetal copolymers < polyacetal terpolymers.