A Study on Chemical Durability of Fiberglass-Reinforced Plastic in NaOH Environment

Abstract

Here we investigate the durability of glass fiber-reinforced polymer bars that were held for a long time (up to 360 days) at temperatures of 20 ºС, 60 ºС and 80 ºС in a NaOH solution (pH=13). A total of 22 specimen groups, including a control group of initial specimens, were tested. The fracture strength tests were performed by the longitudinal bend technique. The durability of the bars when held in alkali at 60 ºС and 80 ºС for up to 55 days was found to decline gradually and constituted 0.86 and 0.84 of the initial strength (86% and 84 %). After 55 days, the point of inflection occurred, and the durability began to decrease sharply, reaching the values of 0.49 (at 60 ºС) and 0.24 (at 80 ºС) at a residence time of 360 days. The durability diminished gradually at a room temperature of 20−23 ºС to attain the value of 0.91 at a holding time of 360 days. A mathematical model is suggested that approximates test results with reasonable accuracy, R2=0.9967, and the time when the conditions change (inflection of strength-to-time curve) was experimentally found to be 60 days.