Accelerated Crystallization of Poly(L-lactide) by Physical Aging

The low-temperature physical aging of amorphous poly(L-lactide) (PLLA) at 25-50 degrees C below glass transition temperature (T(g)) was carried out for 90 days. The physical aging significantly increased the T. and glass transition enthalpy, but did not cause crystallization, regardless of aging temperature. The nonisothermal crystallization of PLLA during heating was accelerated only by physical aging at 50 degrees C. These results indicate that the structure formed by physical aging only at 50 degrees C induced the accelerated crystallization of PLLA during heating, whereas the structure formed by physical aging at 25 and 37 degrees C had a negligible effect on the crystallization of PLLA during heating, except when the physical aging at 37 degrees C was continued for the period as long as 90 days. The mechanism for the accelerated crystallization of PLLA by physical aging is discussed. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116:1190-1196,2010