Study on the Crystallization Process of Polylactic Acid via Modulation Differential Scanning Calorimetry
The crystallization process of polylactic acid(PLA)was studied by conventional differential scanning calorimetry(DSC)and modulation differential scanning calorimetry(MDSC),exploring the influences of testing parameters on the results.The results show that MDSC can effectively separate the overlapping thermal effects of PLA during the heating process,dividing them into reversible and non-reversible curves.In the MDSC mode,both of resolution and sensitivity of curves improve with the heating rate increasing,and the cold crystallization temperature of PLA also increases.It is observed that around the cold crystallization peak of PLA,there is a transition from α″ crystal form to α′ crystal form.The melting temperature of PLA cannot change with heating rate.The transformation of α′crystal form towards α crystal form and the melting of α crystal form occur simultaneously.A longer modulation period also improves the curve resolution and sensitivity but does not affect the transition temperature of PLA.
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