Craze Initiation and Failure in Glassy Poly (ethylene Terephthalate): The Effects of Physical Aging with an Without Exposure to Chemical Environments

摘要

The nonequilibrium nature of the glassy state leads to the time-dependent embrittlement of glassy polymers by a process known as physical aging. Similarly, exposure of glassy polymers to an aggressive chemical environment may also lead to a time-dependent embrittlement process known as environmental stress crackign. In the latter process, the time required for brittle failure to occur as a result of chemical exposure depends on he nature of the polymer, its morphology, and hte chemcial environment. Since both physical aging and environmental stress cracking lead to essentially the same result - brittle failure - the question arises as to whether or not the physical aging process might affect the environmetnal stress cracking process. In this work, we demonstrate the accelerated effects of physical aging on craze initiation in a commercially important engineering thermoplastic, poly(ethylene terephthalate), both with and without exposure to aggressive chemical environments.