Accession Number : AD0612084

Title :   THERMOELASTICITY AND CHAIN CONFIGURATION FOR RUBBER LIKE NETWORK POLYMERS,

Corporate Author : PRINCETON UNIV N J FRICK CHEMICAL LAB

Personal Author(s) : Shen,M. C. ; Tobolsky,A. V.

Report Date : MAR 1965

Pagination or Media Count : 23

Abstract : The retractive force, F, in a stretched rubber network is mainly entropic in origin, but may also arise partially from an energetic contribution F sub e. The problem considered is how to relate the relative energetic contribution F sub e/F to stress-temperature measurements at constant length. An exact equation and several approximate equations are considered and applied to the experimental data. A new approximate relation is derived which differs somewhat from the one that is currently used. According to present theories of rubber elasticity, F sub e/F is related to the temperature dependence of the mean square end-to-end distance of the polymer chain in free space; or equivalently, to the energy difference between rotational isomers of the chain conformations, i.e., trans and gauche configurations. One of the basic tenets of these theories requires that the relative energetic contribution should be independent of elongation. New experimental evidence and data in the literature give a constant value of F sub e/F only in the approximate extension range 1.4 < alpha < 3.0. It is to be hoped that in this range thermoelastic measurements relate directly to the energetics of chain conformation, and that the assumption of the absence of intermolecular interaction remains essentially valid. (Author)

Descriptors :   (*ELASTOMERS, THERMOELASTICITY), (*THERMOELASTICITY, ELASTOMERS), (*POLYMERS, MOLECULAR ISOMERISM), RUBBER, STRESSES, THERMODYNAMICS, ACRYLIC RESINS

Distribution Statement : APPROVED FOR PUBLIC RELEASE