Different samples of poly (L-lactic acid), which were prepared from the melt via quenching (at -50°C) followed by annealing and via slow cooling, were analyzed by WAXS and DSC measurement. The results suggested that the amorphous regions of quenched film are different from the amorphous regions of the quenched film annealed at 60°C, while other quenched samples annealed at 80-120°C seemed to have disordered crystallites. Hydrolysis degradation tests, which were carried out on those samples in 1N NaOH solution at room temperature, revealed that the samples treated at 100°C were degraded more rapidly than the quenched samples. This suggests that annealed samples contain easily hydrolyzable sites, such as voids and crystal defects. It was also observed that the hydrolyzed samples have three different patterns of degradations: 1) decrease of thickness with a regular wearing, 2) the edge of film shows complicated surface boundary and 3) a cracked film surface of small pieces. The photographs of sample surfaces were also taken and analyzed by an image analysis technique. From these observations, degradation process can be analyzed by means of Fractal dimensions and the Fractal model (modified random von Koch curve).
