Nonisothermal crystallization kinetics of novel biodegradable poly(butylene succinate-co-2-methyl-1,3-propylene succinate)s

Two novel poly(butylene succinate-co-2-methyl-1,3-propylene succinate)s, PBMPSu 95/5 and PBMPSu 90/10, were characterized as having 6.5 and 10.8 mol% 2-methyl-1,3-propylene succinate (MS) units, respectively, by ¹H NMR. A differential scanning calorimeter (DSC) and a polarized light microscope (PLM) employed to investigate the nonisothermal crystallization of these copolyesters and poly(butylene succinate) (PBSu). Morphology and the isothermal growth rates of spherulites under PLM experiments at three cooling rates of 1, 2.5 and 5 °C/min were monitored and obtained by curve-fitting. These continuous rate data were analyzed with the Lauritzen-Hoffman equation. A transition of regime II→III was found at 96.2, 83.5, and 77.9 °C for PBSu, PBMPSu 95/05, and PBMPSu 90/10, respectively. DSC exothermic curves at five cooling rates of 1, 2.5, 5, 10 and 20 °C/min show that almost all of the nonisothermal crystallization occurred in regime III. DSC data were analyzed using modified Avrami, Ozawa, Mo, Friedman and Vyazovkin equations. All the results of PLM and DSC measurements reveal that incorporation of minor MS units into PBSu markedly inhibits the crystallization of the resulting polymer.