Influence of the molecular weight of poly(methyl methacrylate) on fracture morphology in notched tension

Abstract

Specimens of poly(methyl methacrylate) (PMMA) were prepared by radiolysis of a polymer from an initial viscosity-average molecular weight ( M ̄ v ) of 1.2 × 10 6 down to 2.6 × 10 3. At a molecular weight of 1 × 10 5, abrupt changes in fracture morphology were observed correlating with a similarly abrupt decrease in fracture surface energy (γ). As the molecular weight was decreased further, the fracture morphology resembled more that of very brittle materials such as silicate glasses. Evidence was obtained that Wallner lines can influence the disposition of ribs but not their spacing. An empirical relationship was established between functions of rib spacing ( r) and fracture surface energy.