Dual glassy relaxations in physically aged semi-crystalline poly(L-lactic acid)

作者：Shieh Yeong Tarng^*; Jho Jia Cing; Wang Tzong Liu; Yang Chien Hsin; Su Chean Cheng

来源：Polymer International, 2011, 60(7): 1078-1088.

DOI：10.1002/pi.3045

• poly(lactic acid)
• physical aging
• relaxation
• differential scanning calorimetry

Semi-crystalline poly(L-lactic acid) (PLLA) was physically aged below the glass transition temperature for various times to investigate its amorphous phase behavior. During a differential scanning calorimetry heating scan, dual enthalpy recovery endotherms were found to appear in the glass transition region of PLLA, aged at 52 degrees C, of a particular degree of crystallinity (X(c)) within a definite range. Below the lower X(c) limit, only the low endotherm corresponding to the free amorphous phase was observed; above the upper X(c) limit, only the high endotherm corresponding to the constrained amorphous phase was observed. Dual tan delta peaks in dynamic mechanical analysis confirmed the coexistence of the dual amorphous phases. Both lower and upper limits of the X(c) range increased with an increase in isothermal crystallization temperature from the melt. Long-term physical aging at 52 degrees C, which did not affect X(c) allowed the evolution of the free amorphous phase to the constrained amorphous ph

• 出版日期2011-7