Unsaturated polyester prepolymer from rosin

Unsaturated polyester prepolymer was synthesized from maleopimaric acid (MPA), diethylene glycol (DEG) and maleic anhydride (MA) in the molar proportions 1:4:3 respectively. MPA was prepared from natural rosin and MA. Kinetic studies of the reaction were performed, and the reactivities of MPA, MA and phthalic anhydride (PA) with respect to diethylene glycol were compared. Copolymerized with styrene, this prepolymer gave samples with higher Vicat distortion temperatures than usual commercial samples prepared from PA, MA and propylene glycol, while mechanical properties such as modulus and strength were similar.