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Zhong, J. Unsaturated Polyester Resin. Encyclopedia. Available online: https://encyclopedia.pub/entry/61218 (accessed on 09 November 2026).
Zhong J. Unsaturated Polyester Resin. Encyclopedia. Available at: https://encyclopedia.pub/entry/61218. Accessed November 09, 2026.
Zhong, Jack. "Unsaturated Polyester Resin" Encyclopedia, https://encyclopedia.pub/entry/61218 (accessed November 09, 2026).
Zhong, J. (2026, October 21). Unsaturated Polyester Resin. In Encyclopedia. https://encyclopedia.pub/entry/61218
Zhong, Jack. "Unsaturated Polyester Resin." Encyclopedia. Web. 21 October, 2026.

Unsaturated Polyester Resin

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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
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References

  1. Nakagawa, Y.; Banno, S.; Matsuyama, K. Control in curing of unsaturated polyester resin. Advanced Composite Materials 1992, 2, 319-328. [CrossRef]
  2. 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. [CrossRef]
  3. 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. [CrossRef]
  4. 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. [CrossRef]
  5. 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. [CrossRef]
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Subjects: Polymer Science
Contributor MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register : Jack Zhong
View Times: 6
Entry Collection: Polymer Concepts
Revisions: 2 times (View History)
Update Date: 23 Oct 2026
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