Creep and fracture kinetics of polymers

The creep kinetics and the fracture kinetics of oriented linear polymer (polypropylene) are compared. The distributions (scatter) of the specimen lives and the steady-state creep rate are studied on series of identical specimens loaded under the same conditions (load, temperature). It is found that the scatter of the specimen lives is significantly larger than the scatter of the creep rates at the same activation energy of fracture (the measure of which is the life) and creep. This finding reflects a localized character of fracture (break) of specimens and a delocalized character (involvement of the entire specimen volume) of creep. It is concluded that the equality of the activation energies of both processes is caused by the elementary acts of fracture of an oriented polymer (breaking of chain molecules), and they open up possibilities for creep acts, i.e., conformation transitions, in a polymer.