LOW-TEMPERATURE THERMAL-CONDUCTIVITY AND SPECIFIC-HEAT OF ELASTOMERS

The specific heat C and thermal conductivity κ of polybutadiene are characteristic of all non-crystalline materials at temperatures below ≈ K, reflecting the presence of localized excitations. The changes in C and κ with variation in crosslinking suggest that the relaxation times of the localized excitations may vary with crosslink density. Extension of an elastomer does not reveal a change in density of localized excitations as monitored by measuring κ, possibly because other phonon scattering mechanisms mask the effect. For T ≲ 10 K the phonon mean-free-path is independent of the microscopic anisotropy of the elastomer. © 1979.