Degradation Characteristics of Glass Fiber Reinforced Plastics Using Unsaturated Polyester as Matrix in Weak Alkaline Aqueous Solution

To verify the applicability of glass-fiber reinforced plastics with an unsaturated polyester matrix in manhole environments, degradation characteristics in a weak alkaline aqueous solution were evaluated by conducting a solution immersion test. We were able to clarify that diffusion of alkaline ions is slower than that of water, effect of accelerated deterioration due to alkali remaining on the sample surface, resin fiber interface preferentially deteriorates due to the diffusion of water, and that the decrease in flexural strength is in good agreement with the logarithmic approximation formula.