Non-isothermal crystallization kinetics of biodegradable regenerated poly(butylene carbonate-co-terephthalate) copolyesters based on post-consumer polyester fabrics

The regenerated poly(butylene carbonate-co-terephthalate) (r-PBCT) copolyesters based on post-consumer polyester fabrics with similar intrinsic viscosity were synthesized via a two-step melt polycondensation method. The characteristic absorption peaks of the Fourier transform infrared (FTIR) spectroscopy and the chemical shift of the proton nuclear magnetic resonance (¹HNMR) spectroscopy both confirmed the successful synthesize of r-PBCT copolyesters. Moreover, r-PBCT copolyesters exhibited five characteristic diffraction peaks where the diffraction intensities gradually increased with the increase of bis(2-hydroxybutyl) terephthalate (BT) unit content. The effect of the BT unit content on non-isothermal crystallization kinetics of r-PBCT copolyesters was investigated by differential scanning calorimetry (DSC). Analysis of the melt crystallization data by Avrami equation modified by Jeziorny and Mo equation revealed the dependence of the crystallization rate on the BT unit content. The Avrami exponent (n) was in the range of 2.69–3.81 and the crystallization rate constant increased with the increase of BT unit content at a given relative crystallinity. It was revealed that the crystallization process of the r-PBCT copolyesters developed as a three-dimensional growth pattern of spherulites and BT units accelerated the crystallization rate significantly. And the r-PBCT copolyester sample with higher bis(2-methyl) butylene carbonate (BC) unit content had a higher F(T) value and required a relatively high cooling rate to obtain sufficient crystallinity. Finally, the crystallization activation energy (∆E) was estimated by Kissinger and Friedman equations, separately. The results further supported that the r-PBCT copolyester with more BT unit content was easier to arrange neatly through accelerated crystallization.

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