Lactone polymers. V. Viscoelastic properties of poly-ε-caprolactone and poly-ε-thiocaprolactone

The viscoelastic properties of crystalline poly-ε-caprolactone and poly-ε-thiocaprolactone have been characterized and compared by stress relaxation and dynamic mechanical studies. The glass transition temperature of poly-ε-thiocaprolactone was shown to be -40°C at 1 Hz and appeared to be independent of the degree of crystallinity. The rate of viscoelastic relaxation for each polymer was independent of linear strain rate of a decade range. The density of each polymer over a wide temperature range was used to reduce the individual time-dependent modulus values to an arbitrary reference temperature. This reduction of stress relaxation data to a standard mechanical state obviated the requirement of vertical shift factors for construction of the respective master curves. The distribution of relaxation times was correlated with the glass transition and the crystalline melt temperature range for each polymer.