Accelerated crystallization of poly( L ‐lactide) by physical aging

The low‐temperature physical aging of amorphous poly( L ‐lactide) (PLLA) at 25–50°C below glass transition temperature ( T g ) was carried out for 90 days. The physical aging significantly increased the T g 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°C. These results indicate that the structure formed by physical aging only at 50°C induced the accelerated crystallization of PLLA during heating, whereas the structure formed by physical aging at 25 and 37°C had a negligible effect on the crystallization of PLLA during heating, except when the physical aging at 37°C was continued for the period as long as 90 days. The mechanism for the accelerated crystallization of PLLA by physical aging is discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010