An unsaturated polyester resin is a thermoset precursor in which unsaturated diacids are condensed with a diol and the resulting oligomer is dissolved in a reactive monomer. The double bonds in the backbone and in the monomer copolymerise during curing, so the monomer acts both as a diluent and as a crosslinker [1]. Styrene is the usual monomer, and its fraction controls the viscosity before cure and the crosslink density after it [2]. The cure is initiated by a peroxide and accelerated by a metal soap, and the two have to be matched to the temperature at which the part is processed [3]. Shrinkage during cure is appreciable and causes sink marks unless a low-profile additive is included [4]. The resin absorbs water through the ester linkages, and the hydrolysis of those linkages is what limits the long-term service in a wet environment [5].
- thermoset
- unsaturated diacid
- styrene monomer
- crosslinking
- peroxide initiator
- cure shrinkage
- ester hydrolysis
References
- Nakagawa, Y.; Banno, S.; Matsuyama, K.; Control in curing of unsaturated polyester resin. Advanced Composite Materials 1992, 2, 319-328, 10.1163/156855192x00125.
- Poorabdollah, M.; Beheshty, M.H.; Atai, M.; Investigating curing kinetics and structural relaxation phenomena of unsaturated polyester resin containing silanized silica. Journal of Composite Materials 2016, 50, 2459-2467, 10.1177/0021998315604207.
- Qin, C.; Jin, Q.; Zhao, J.; Wang, Y.; Jiang, C.; Study on the Mechanical Characteristics, Heat Resistance, and Corrosion Resistance of Unsaturated Polyester Resin Composite. Buildings 2023, 13, 1700, 10.3390/buildings13071700.
- Xiao-jing, S.; Ji-lin, P.; Xiao-lin, X.; CURING CHARACTERISTICS OF POLYURETHANE MODIFIED UNSATURATED POLYESTER RESIN/COLOR PASTE MIXTURES. Acta Polymerica Sinica 2013, 013, 1407-1411, 10.3724/sp.j.1105.2013.13075.
- Khoun, L.; Palardy, G.; Hubert, P.; Relation between volumetric changes of unsaturated polyester resin and surface finish quality of fiberglass/unsaturated polyester composite panels. Polymer Composites 2011, 32, 1473-1480, 10.1002/pc.21157.