调制差示扫描量热法研究聚乳酸的结晶过程

Study on the Crystallization Process of Polylactic Acid via Modulation Differential Scanning Calorimetry

本文分别采用了传统和调制差示扫描量热法(MDSC)研究了聚乳酸(PLA)的结晶过程,探索了MDSC中调制条件对结果的影响。结果表明,MDSC可以有效地分离PLA在受热过程中重叠的热效应,并将其分割为可逆曲线和不可逆曲线。MDSC模式下,随着升温速率的提高,曲线的分辨率和灵敏度同时得到提高,PLA的冷结晶温度逐渐升高,并观察到在PLA的冷结晶峰伴随有α″晶型向α′晶型转变;而PLA熔融温度不随升温速率的变化而变化,较高的升温速率下观察到PLA α′向α的晶型转变和α晶型的熔融是同时进行的。较长的调制周期也会同时提高曲线的分辨率和灵敏度,但是不会对PLA的相变温度造成影响。

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 fromα″crystal form toα′crystal form.The melting temperature of PLA cannot change with heating rate.The transformation ofα′crystal form towardsαcrystal form and the melting ofαcrystal form occur simultaneously.A longer modulation period also improves the curve resolution and sensitivity but does not affect the transition temperature of PLA.