Effect of succinic acid on the shrinkage of unsaturated polyester resin

Abstract

ABSTRACTSuccinic acid was presented as a small molecule low shrinkage additive (LSA) in unsaturated polyester resin (UPR). The effects of succinic acid on the volume shrinkage and the flexural strength of UPR cured at 80 ± 1°C were investigated and compared with those of macromolecule LSAs, including polyvinyl acetate (PVAc), polymethyl methacrylate (PMMA), and polystyrene (PS). The results indicated that the volume shrinkage of succinic acid/UPR specimen was significantly lower than those of specimens with macromolecule LSAs. The flexural strength of succinic acid/UPR specimen was improved. The optimal time of pre‐esterification between succinic acid and the excess dihydric alcohol in UPR was 3.0 h, and the optimal addition of succinic acid was 20 g per 100 g UPR. Compared with 2,2‐dimethyl malonic acid we put forward before, succinic acid was a cheaper and more commercial LSA, which obviously accelerated the pre‐esterification process and presented excellent antishrinkage effect. DSC showed that with the addition of succinic acid, the polymerization of UPR was distinctive. The two‐stage polymerization of UPR glue including the cross‐polymerization of UPR and the homopolymerization of polyester was changed to a one‐stage polymerization with lower exotherm and slower polymerization rate, which was optimal for UPR. FTIR and high resolution magic angle spinning nuclear magnetic resonance (HR/MAS NMR) were applied for the quantitative characterization of pre‐esterification caused by succinic acid. Succinic acid performed better effects on the polymerization of UPR as compared to previous LSAs, and finally the homogeneous micro‐structure of cured succinic acid/UPR formed and was demonstrated by SEM. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41276.