Self-cross-linking kinetics of unsaturated polyester poly(fumaric-co-itaconic-co-butanediol)

Abstract

Unsaturated polyester poly(fumaric-co-itaconic-co-butanediol) (poly(FA-co-IA-co-BD)) was prepared with fumaric acid (FA), itaconic acid (IA), and 1,4-butanediol (BD) by melt polycondensation, and its self-cross-linking kinetics was investigated through the percentage of insoluble gel fraction (Q_s) and conversion degree of C=C (DC). The results showed that poly(FA-co-IA-co-BD) had the highest Q_s and DC, when the mole ratio of FA and IA was 1:0.96, which meant that the polyester had the maximum extent of self-cross-linking. And the polyester had the maximum rate constant (k) and the smallest activation energy (E_a). The value of k was temperature dependent, and the higher the temperature, the higher the value of k. Thermodynamics parameters such as ${\mathrm{\Delta }}^{\ne }{G}_{\mathrm{m}}^{ϴ},{\mathrm{\Delta }}^{\ne }{H}_{\mathrm{m}}^{ϴ},\mathrm{a}\mathrm{n}\mathrm{d}{\mathrm{\Delta }}^{\ne }{S}_{\mathrm{m}}^{ϴ}$ were also discussed. The results showed that, ${\mathrm{\Delta }}^{\ne }{G}_{\mathrm{m}}^{ϴ}>0$ , the self-cross-linking reaction of the poly(FA-co-IA-co-BD) occurred at high temperature. The self-cross-linking reaction was an exothermic reaction, ${\mathrm{\Delta }}^{\ne }{H}_{\mathrm{m}}^{ϴ}$ was equivalent to E_a. ${\mathrm{\Delta }}^{\ne }{S}_{\mathrm{m}}^{ϴ}<0$ , the product in the transition state was more ordered. When the mole ratio of FA to IA was 1:0.96, poly(FA-co- IA-co-BD) was the most ordered in the transition state and had the smallest ${\mathrm{\Delta }}^{\ne }{S}_{\mathrm{m}}^{ϴ}$ , and the C=C in the polyester self-cross-linked easily.