INFLUENCE OF CROSSLINKING ON THE TENSILE-STRENGTH AND FRACTOGRAPHY OF POLY(METHYL METHACRYLATE)

Glassy crosslinked networks were prepared by copolymerization of methyl methacrylate with up to 4.7 mole‐percent ethylene dimethacrylate. These networks were degraded by exposure to γ‐rays and the solubilized fraction estimated by benzene extraction using the analysis of A. R. Schultz. The efficiency of the Crosslinking agent was found to be 0.5 and this value was used to calculate the molecular weight between crosslinks. The molecular weight of the primary molecules in the network, M, was estimatfrom the radiation dose using the known fact that one fracture requires an energy deposition of 59 ev. Crosslinking was found to have little influence on the tensile strength of networks of primary molecular weight > 105. In contrast. crosslinking raised, the strength of polymers of M < 105 to, a value approaching that of a high molecular weight linear polymer (ca. 70MN/m2). Crosslinking was found to have only a small influence on the gross morphology of fracture surfaces. Copyright © 1979 Society of Plastics Engineers, Inc.