A detailed analysis of the three-phase structure of poly(L-lactic acid) was performed by temperature-modulated differential scanning calorimetry upon quasi-isothermal and non-isothermal crystallizations. The TMDSC analyses revealed that the relative amounts of the three fractions of poly(L-lactic acid) depend on the temperature at which crystallization occurs. It was found that rigid amorphous fraction grows in parallel with crystalline phase during quasi-isothermal crystallization at 90 °C, whereas at Tc=130 °C it starts to appear approximately in correspondence with secondary crystallization. At Tc=135 °C RAF practically does not develop. The results prove that RAF development during crystallization depends on the mobility of the chains. The temperature of complete devitrification at 10 °C min-1 seems to be 130 °C: this temperature could be the limit for the formation and the disappearance of rigid amorphous fraction in the PLLA sample analyzed in the present study.
Crystalline, mobile amorphous and rigid amorphous fractions in poly(L-lactic acid) by TMDSC
Righetti MC;Tombari E
2011
Abstract
A detailed analysis of the three-phase structure of poly(L-lactic acid) was performed by temperature-modulated differential scanning calorimetry upon quasi-isothermal and non-isothermal crystallizations. The TMDSC analyses revealed that the relative amounts of the three fractions of poly(L-lactic acid) depend on the temperature at which crystallization occurs. It was found that rigid amorphous fraction grows in parallel with crystalline phase during quasi-isothermal crystallization at 90 °C, whereas at Tc=130 °C it starts to appear approximately in correspondence with secondary crystallization. At Tc=135 °C RAF practically does not develop. The results prove that RAF development during crystallization depends on the mobility of the chains. The temperature of complete devitrification at 10 °C min-1 seems to be 130 °C: this temperature could be the limit for the formation and the disappearance of rigid amorphous fraction in the PLLA sample analyzed in the present study.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
