Abstract
Corrosion behavior of four kinds of thermosetts as a matrix of corrosion resistant FRP was studied with special attention to their chemical structures. Immersion tests were carried out at various temperatures in 10 wt% NaOH solution up to 3, 000 hr. As a result of testing, corrosion behavior and also mechanism by hydrolysis were found to be affected greatly by the structure of the resin. In iso-phthalic unsaturated polyester resin, degradation of main polymer chain takes place, while crosslinked polymer chain remains unaffected. Thus elastic soft corroded surface layer is formed. In novolack type vinyl ester resin, only at the ester bonds between main and crosslinked chains are attacked from the viewpoint of the structure. However, dense and tight corroded layer in an appearance is formed with longer immersion time which seems to be an incubation period, and severe lowering of strength occured. As for epoxy resins, the one cured by MDA shows no sign of corrosion because of no ester bonding, while the one cured by MTHPA both main and crosslinked chains are dissolved easily as low molecular weight corrosion products, therefore the specimen thickness decreases uniformly.
