Effect of Stress-Solvent Crazing on Tensile Strength of Polymethyl Methacrylate

摘要

The loss of strength of tensile specimens of polymethyl methacrylate as a result of stress-solvent crazing at 230 C and 5O-percent relative humidity was investigated. The materials tested were commercial cast polymethyl methacrylate sheets of both heat-resistant and ordinary grades from each of two manufacturers. Most of the tests were made on samples O.l5 inch thick and covered with masking paper on one side only. The tensile specimens were artificially crazed by applying benzene to the central portion of the reduced section while under stress and were subsequently broken. Specimens for controls were treated identically except no benzene was applied. Photographs were taken of the crazed specimens before they were tested. Among the factors studied were the sheet-to-sheet variability of crazed and control specimens, the effect of the masking paper on the crazing, and the relative effect of a few large crazing cracks compared with more numerous finer cracks.