Fracture of Amorphous Polymeric Solids: Reinforcement

Abstract

Although the tensile stress at break (σ b ) and the corresponding ultimate elongation (α b ) of a reinforced elastomer depend markedly on temperature and test rate, characteristic time‐to‐break curves can be obtained utilizing the Leaderman‐Tobolsky‐Ferry superpositioning techniques. In addition, a distinctive failure envelope is obtained when the log σ b T 0/T is plotted against log (α b −1), where T and T 0 (°K) are the test temperature and an arbitrary reference temperature. Delayed ruptured experiments yield qualitatively the same results as forced rupture experiments. Furthermore, an analysis of the Leaderman‐Tobolsky‐Ferry shift parameters indicate a concomitant increase in the apparent activation energy with increasing reinforcement concentration. These observations are explicable by utilizing the failure theory of Bueche and Halpin. It is now apparent that failure is the result of the propagation of tears or cracks within the viscoelastic body and that the time and temperature dependence of the ultimate properties is directly related to the time‐temperature dependence of the modulus. A preliminary picture of the salient molecular events is presented.