Fracture processes in polymeric materials. IV. Dependence of the fracture surface energy on temperature and molecular structure

The study of the influence of flaw size on the tensile strength of poly(methyl methacrylate) samples has been extended over the temperature range −190°C. to 50°C. The fracture surface energy increases with decreasing temperature, while the inherent flaw size of uncracked samples passes through a minimum at about −20°C. The fracture surface energy and inherent flaw size of a copolymer of methyl methacrylate and 10 mole‐% of ethylene glycol dimethacrylate have been obtained at room temperature, by a similar method. These results are examined in the light of the hypothesis already put forward concerning the factors which govern the strength and fracture properties of glassy polymers.