WEATHERING OF GLASS-FIBER-REINFORCED POLYSTYRENE AND POLY(ETHERSULFONE)

Glass‐fiber‐reinforced polystyrene (GFPS1) and polyethersulfone (GFPES) injection‐moldings containing 20 wt% glass have been weathered in Jeddah, Saudi Arabia, for up to one year. The retained strength and ductility were, generally, better than in the corresponding unreinforced polymers. The tensile strength fell to ca 73% of the initial, unexposed value, (GFPS1) and ca 77% (GFPES), whereas the extension to break values fell to ca 50% and 76%, respectively, after one year of weathering. The inclusion of carbon black in reinforced polystyrene (GFPS(B)) resulted in a barely perceptible drop in strength (to ca 98%) and a greatly improved reduction in extension to break, dropping only to ca 81% after one year. Residual stress levels were measured and were found to be insufficient to have a significant influence on fracture behavior. In GFPES they were generally less than 2MN/m2 except at a location ≃0.3 mm from the surface, where compressive stresses of up to 4 MN/m2 were present. No significant change in residual stress occurred with exposure in GFPES. With GFPS1 the stress levels were insignificant ( <1 MN/m2) through most of the bar both before and after exposure. With unexposed GFPS(B) the stresses were <1 MN/m2 except within 0.2 mm of the surface, where they rose steeply, though probably not above 5 MN/m2. After weathering the stresses were everywhere <1 MN/m2, but the sense of the residual stresses had reversed near to the exposed surface. This is attributed to radiant heating, and is undesirable because it may lead to distortion. Copyright © 1990 Society of Plastics Engineers