Morphological changes during heating in poly(L-lactic acid)/poly(butylene succinate) blend systems as studied by synchrotron X-ray scattering

Blends of poly(L-lactic acid) (PLA) and poly(butylene succinate) (PBS) were prepared in various compositions via melt mixing, and the morphological changes were investigated with differential scanning calorimetry and synchrotron wide-angle and small-angle X-ray scattering techniques at a heating rate of 10 degreesC/min. Differential scanning calorimetry thermograms of PLA/PBS blends showed two distinct melting peaks over the entire composition range. The exothermal peak for PLA shifted significantly to a lower temperature and overlapped with that of PBS around 100 degreesC. A depression of the melting point of the PLA component via blending was observed. The synchrotron wide-angle X-ray scattering during heating revealed that there was no cocrystallization or crystal modification via blending. The synchrotron small-angle X-ray scattering data showed that well-defined double-scattering peaks (or peaks with a clear scattering shoulder) appeared during crystallization, indicating that this system possessed dual lamellar stacks. These peaks were deconvoluted into two components with a peak separation computer program, and then the morphological parameters of each component were obtained by means of the correlation function. The long period and average lamellar thickness of the two components before melting decreased with an increasing content of the other polymer component. (C) 2002 Wiley Periodicals, Inc.