Crystallization kinetics and crystalline structure of biodegradable Poly(ethylene adipate)

The crystallization kinetics, morphology and crystalline structure of biodegradable poly(ethylene adipate) (PEA) with high and low molecular weights (HMW, LMW) were systematically investigated. The crystallization kinetics obtained from differential scanning calorimetry analysis indicated that both the primary and secondary crystallizations occur during the isothermal and non-isothermal crystallization processes for HMW and LMW PEA samples. Under the same crystallization condition, LMW PEA was found to crystallize faster than HMW PEA. The PEA sample forming the ring-band spherulite presents a higher Avrami exponent value (n) than that without the ring-band spherulite, due in part to the different crystal growth mechanism. From the results of wide angle X-ray diffraction and Fourier transform infrared spectroscopy, it was confirmed that the crystalline structure of PEA is not dependent on the crystallization temperature (Tc) and MW. From the in-situ FTIR investigation of the crystallization kinetics, it is concluded that, during the isothermal crystallization process at 42 °C, the structural rearrangement of the ester group precedes that of the CC backbone.