Effects of water or alkali solution immersion on the water uptake and physicochemical properties of a pultruded carbon fiber reinforced polyurethane plate

Carbon fiber reinforced polyurethane (CFRPU) composites exhibit a high potential in infrastructure application due to their easy manufacturing and excellent mechanical properties. In the present article, a pultruded CFRPU plate subjected to water or alkaline solution immersion at various temperatures was investigated, and compared with a commonly used epoxy‐based CFRP plate, in terms of the water uptake and physicochemical properties. As found, CFRPU plates exhibited excellent resistance to both water and alkaline immersion without noticeable degradation in the mechanical properties. No hydrolysis occurred for CFRPU under both immersion conditions for 1 year at 20–60°C. After 1 year of immersion, the tensile properties of CFRPU kept constant or even were enhanced slightly. On the contrary, the epoxy‐based CFRP plate showed a noticeable hydrolysis, and decreased in the tensile properties remarkably, especially in the case of the alkaline immersion. In addition, unlike the bond between carbon fiber and the epoxy, the bond between the carbon fiber and the polyurethane matrix was not affected by the above immersion. Accordingly, CFRPU was considered to be much more durable in the water or alkaline immersion conditions. POLYM. COMPOS., 40:738–748, 2019.