Influence of crystal and amorphous phase morphology on hydrolytic degradation of PLLA subjected to different processing conditions

Isothermal and non-isothermal crystallization kinetics of poly-L-lactide (PLLA) were studied in order to analyse the effect of crystalline and amorphous morphology on hydrolytic degradation. A modification of the nucleation/growing mechanism was observed in both isothermal and non-isothermal analysis. Samples isothermally crystallized at T-c < 110C showed a higher fraction of amorphous phase which does not relax at T-g. Lower and decreasing values of this 'rigid-amorphous phase' fraction were detected at higher crystallization temperatures (T-c > 110 degreesC). The effect of hydrolytic degradation on the amorphous and crystalline phases depends upon the initial morphology developed during the isothermal crystallization. The larger crystals developed at T-c = 130 degreesC are more resistant to erosion compared to the less perfect and smaller crystals developed at higher levels of undercooling (T-c = 90 degreesC). (C) 2001 Elsevier Science Ltd. All rights reserved.