Investigation of entanglement and intersegmental interactions in lightly crosslinked, non-crystalline elastomers

Stress responses of elastomers show significant dependencies on temperature and rate. This work applies photoelastic observations to elucidate the viscoelastic origin of such temperature and rate effects in non-crystalline elastomers. The experiments involve startup uniaxial stretching, stress relaxation, and loading and unloading (cyclic) at various temperatures and stretching rates. At temperature close to the glass transition temperature, intermolecular stress is identified. Both intrachain and interchain components of stress depend on temperature and applied rate and are transiently elastic on different time scales. Finally, cyclic experiments along with photoelastic measurements show that the hysteresis loop and a permanent set are a result of stress relaxation through disengagement of embedded entanglement and partial structural recovery.