Thermal Behavior of Solid Polymers During Fracture

Abstract

The fracture of polymers is inevitably accompanied by thermal events. The sources of the thermal events may be both the deformational processes and the rupture of macromolecules. Pure elastic (brittle) fracture of solids is more the exception than the rule [1]. Normally the appearence of the initial sources of fracture — cracks — results in the local plastic deformation. A considerable part of the work, corresponding to the plastic deformation is transformed into heat and this local heat build-up leads to the local rises in temperature during the crack propagation in solids. Unlike the typical low molecular solids in which the plastic deformation at the tip of the cracks is the main mechanism of the local temperature rises under rupture, in polymers one more source of the rise in temperature is possible which is a direct consequence of the chain structure of macromolecules. A part of a macromolecule stressed almost to its load-bearing capacity represents an extremely powerful source of the elastically stored energy. The scission of any single bond in these adequately long segments of the highly stressed macromolecules is inevitably accompanied with dissipation of all the energy stored in all the other bonds. Therefore, this process can also be a very powerful source of the local rise in temperature.