Thermal Analysis of Polylactide-Monomethoxy Polyethylene Glycol Blends by Modulated Differential Scanning Calorimetry

The thermal properties of polylactide-monomethoxy polyethylene glycol(PLA-MPEG) blends were studied using temperature Modulated Differential Scanning Calorimetry(MDSC).Results showed that the overlap transitions of recrystallization and melting of the PLA-MPEG blends were discriminated effectually by MDSC.The transition from disordered α' form crystal to ordered α form crystal and the melting of α form were almost at the same time.In the case of 15% MPEG mass fraction,with the increase of heating rate and modulation period,the recrystallization enthalpy on nonreversible curves increased up to about 28 J/g gradually and the melting enthalpy decreased gradually to about 3.3 J/g.The peak shape of melting in the reversible curves transformed from wide multiple peaks to a separating single peak.And the melting enthalpy was raised up to 66.1 J/g.The fraction of melting on reversible curves reached 95.2%.However,the increase of the heating rate and modulation period resulted in the decrease of modulation cycle numbers in phase inversion and thus brought a low resolution.Therefore,in the optimization of the test parameters,the heating rate and the modulation period/amplitude etc.should be considered comprehensively to obtain high resolution and high sensibility of test results.