CONICET | Buscador de Institutos y Recursos Humanos

Real-time experiments using small-angle X-ray scattering (SAXS) on biodegradable polyester poly(3-hydroxybutyrate) (PHB) crystallized at 60°C, 80°C and 100°C were performed at different temperatures between 30°C and 140°C. A peak was observed which is associated to the structure of crystalline lamellae. At temperatures higher than 110°C the peak is deformed and there is evidence of an incipient second peak located at q values lower than the first peak. The spectra were analyzed calculating the 1-dimension correlation function and the dimensions of crystalline (lc) and amorphous (la) phase were obtained [1]. For the sample crystallized at 60°C, la is approximately constant as a function of temperature until 70°C and then increments, but for the sample crystallized at 80°C or 100°C, la increases in the whole range of temperature. On the other hand, for the sample crystallized at 60°C, lc is constant as a function of temperature until 110°C where it increases markedly. For the samples crystallized at 80°C and 100°C, lc decreases slightly before a sharp growth at 110°C. The results show the co-existence of lamellae with different dimensions at high temperatures. The variation of lc and la is discussed on the basis of re-crystallization process. The inclusion of a rigid amorphous interphase between crystals and amorphous phase is analyzed and the role of devitrification of this interphase is considered with the aim to explain the changes in la observed at 70°C in the sample crystallized at 60°C. Some authors have observed the devitrification of PHB rigid amorphous fraction at approximately 70°C. Devitrification allows the reorganization and/or re-crystallization forming crystals with different dimensions [2]. In this work the development of an interphase is taken into account to analyse SAXS results.