Effects of two aqueous acidic solutions on glass reinforced vinyl ester resins tubes

Glassfibre reinforced pipe sections [bisphenol A epoxy vinyl ester pipe (H150) and bisphenol A epoxy novolac vinyl ester pipe (P150)] were exposed to different acidic solutions (1M H2SO4 and Co spent electrolyte) at different temperatures (25 and 75 degrees C) and exposure durations (1 and 4 weeks). New mechanical tests were designed and performed to study test sensitive and resin susceptibility to exposure conditions. The various tests performed included a tensile test on laterally loaded pipe sections, a compression test on axially loaded pipe sections, a three point bending test and microstructure analysis (optical microscopy and scanning electron microscopy-energy dispersive spectroscopy). The tensile test and the bending tests were found to be the most sensitive tests to exposure conditions. In general, the tensile test exposure to H2SO4 decreased the slope of force per unit length versus deflection curve, and force for first failure on samples H150 and P150 after 1 and 4 weeks durations. However, the opposite effect of exposure to Co spent electrolyte on P150 occurred mid-test when the slope and force for first failure increased between 1 and 4 weeks durations. Bending test exposure to both solutions on P150 resulted in modulus and stress at 5% strain decreasing with duration of exposure. H150 was little changed by the bending test and sometimes increased in value. Scanning electron microscopy-energy dispersive spectroscopy revealed small cracks on the inner surface of the exposed H150 fibreglass reinforced plastic pipe which had higher sulphur content on the exposed surface up to a depth of similar to 0.3 mm when compared to unexposed surface.