Fiber Reinforced Plastics, FRP, are very difficult to be recycled. Styrene-fumaric acid copolymer and glycol were obtained after sub-critical water hydrolysis of FRP. However styrene-fumaric acid copolymer was very difficult to be separated from water due to its hydrophilic groups. Hydrophobic organic solvents were examined to enable the separation of styrene-fumaric acid copolymer from water. Methyl isobutyl ketone and n-propyl acetate showed the best performance. In the presence of phase-transfer catalyst, the carboxyl groups of styrene-fumaric acid copolymer were esterified with benzyl chloride in an almost 100% yield. The modified polymer showed almost equivalent shrinkage control effect to commercial low profile additives for FRP. It means five to ten times upgrade recycling compared with its raw materials.