Fracture mechanisms of poly(methyl methacrylate) under static torsion in alcohol environments
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Static torsion tests of poly(methyl methacrylate) were conducted in several alcohol environments at room temperature. The critical torsional stress for crazing and/or cracking increased with increasing molar volume of alcohol, and was not correlated with the solubility parameter, nor with equilibrium solubility as reported in previous results on n-alkanes. Crazing stresses in alcohols were generally lower than those in alkanes. According to Fourier transform-infrared microscopy of the surface scratch made in several environments, both in ethanol and in 1 -butanol, some absorptions were detected at 3450–3650 cm−1, probably due to the hydroxyl group of these alcohols caught by hydrogen bonding to oxygen of the carbonyl group in the side chain, whereas in other environments (1 -octanol, n-hexane, and air) there were no absorptions in this region of wave number. These results suggest that at a flaw tip strained under stress, penetrating alcohol molecules are chemically adsorbed in a cluster, which breaks a weak bond (e.g. dipole interaction) between the polymer chains and, as a result, facilitates craze formation and breakdown leading to brittle fracture.
KeywordsCarbonyl Alkane Butanol Molar Volume Brittle Fracture
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