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Physical aging in PLA through standard DSC and fast scanning calorimetry investigations

Monnier, Xavier, Saiter, Allisson, Dargent, Eric
Thermochimica acta 2017 v.648 pp. 13-22
differential scanning calorimetry, enthalpy, geometry, glass, glass transition, polylactic acid
Physical aging on wholly amorphous polylactide (PLA) has been performed by means of standard differential scanning calorimetry (DSC) and fast scanning calorimetry (FSC) just below its glass transition. Compared to the in-situ aging study through the standard DSC, an increase of 80–90% has been observed in the enthalpy recovery by FSC investigations. Such increase has been related to the high cooling rates used by FSC. Besides, an influence of the sample geometry has been measured when glasses are vitrified by high cooling rates. This implies that the critical thickness involved in the physical aging acceleration is cooling rate dependent. High cooling rates allow to reach the thermodynamic equilibrium, as observed from physical aging investigations by FSC. In addition, few ng of material analyzed by FSC are representative of the bulk one analyzed by standard DSC, when the glass is formed in the same conditions.