The Principle of Superposition of Time, Temperature and Concentration in Dynamic Properties of Ethylene-Vinyl Acetate Copolymers

Abstract

The dynamic mechanical tests of samples of ethylene-vinyl acetate copolymers with various contents of vinyl acetate monomer (VAc) ranging from 0 to 25.3wt% made at varying temperatures from 5°C to 80°C at frequencies ranging from 1 to 100 cycles/sec., and their dynamic tensile modulus E', E were obtained. These were made the data for examining each sample with respect to its principle of superposition of time and temperature. It was found that the larger the melt index of the sample was the wider was the scatter of these data in it. The shift distance log aT was larger than those given from WLF equation. The values of log aT2 computed from the following equation gave good straight lines on a plot of log aT2 vs. 1/T;logaT=(1-φ)logaT1+φlogaT2where log aT and log aT1 represent respective shift distance obtained from experiment and from WLF equation, and in present trial, φ was assumed to represent volume fraction of crystalline part of each sample. Time-concentration principle was also examined with a convenient assumption that one monomer composition in the copolymer act as a diluent or a low molecular plasticizer. It seemed that the principle of superposing time and concentration was formally applicable to the data of copolymer by regarding the content of one monomer composition as concentration.