Behavior and Mechanisms of Degradation of Thermosetting Plastics in Liquid Environments

Behavior and mechanisms of degradation of thermosetting plastics used as FRP-matrix and GFRP in liquid environments are reviewed based on our experimental fi ndings.The forms of chemical degradation were classifi ed into three types, ʻsurface reaction type,ʼ ʻcorrosion layer forming typeʼ and ʻpenetration type.ʼThe mechanism of each type is dependent on the chemical structures of the resin, the reactivity between resins and liquids, and the diffusivity of liquid in the resins.The corrosion rate was defi ned as change of corrosion thickness with immersion time in the ʻsurface reactionʼ and ʻcorrosion layer forming typeʼ corrosion.By applying the concept of corrosion rate, the residual thickness of the non-corroded region after corrosion could be predicted.For ʻsurface reactionʼ and ʻcorrosion layer forming typeʼ corrosion, a life-prediction method was proposed using the master curve focused on retention of fl exural strength after corrosion.For ʻpenetration type corrosion,ʼ the weight change was important to predict the initiation of decrease in mechanical strength.