Effect of Strong Acids on Mechanical Properties of Glass/Polyester GRP Pipe at Normal and High Temperatures

The effects of hydrochloric acids (HCl), sulfuric acids (H2SO4), nitric acids (HNO3), and phosphoric acids (H3PO4) on the physical and mechanical properties of glass fiber/polyester composite pipes internally lined with C glass were investigated. Specimens cut from the pipes were immersed for various periods—30, 60, and 90 days in 20% acid concentration at room temperature and 100°C. The pipes consisted of 27% chopped glass fiber, 16% continuous filaments, 29% polyester resin, and 28% silica sand. Changes in weight, Charpy impact resistance, ultimate flexural strength, and hardness measured over a 3‐month period and the effects of the environment and liquid on these parameters were assessed. The hardness of the outside surface and the inside C glass‐lined surface were compared. Higher values of hardness were obtained on the C glass surface. The effects of acids on composite characteristics were studied using x‐ray diffraction test.