Structural Studies of Biodegradable Polymer and Fractal. (Part 3). Fractal and Degradation Process of Biodegradable Polyester Blends.

The characteristics of the alkaline degradation process and the mechanical properties of polyester blends of poly (L-lactic acid) (PLLA) and poly (butylene succinate) (PBSU) were studied. The blends were immiscible in the amorphous states from the DSC measurement results. The elongation of PLLA/PBSU blends were large (several hundred percent), however the elongation of PLLA was small (several percent). In regard to the weight decrease of alkaline hydrolysis tests, PLLA had the fastest rate of decrease and PBSU had the slowest rate of decrease. The degradation rate of PLLA/PBSU 75/25 blends and 50/50 blends were close to PLLA. A weight decrease was observed in the PLLA/PBSU 25/75 blends. The degradation rate can be adjusted by blending the PLLA in the PBSU. The results from the measurements of DSC and WAXD showed that the increase of degree of crystallinity was very limited. The characteristic globular cracks of the child (fractal) forms were observed in degraded pure PLLA by means of a scanning electron micrograph. The surfaces with the general unevenness were seen in degraded pure PBSU. The special structures (which were mixed hierarchically) were seen in the blends. Although PLLA/PBSU blends were immiscible, the blends had the structures which were hierarchical. It may contribute to the mechanical properties.