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利用光学流变显微镜(ORM)在线研究剪切场下左旋聚乳酸(PLLA)非等温结晶过程,采用差示扫描量热法(DSC)和广角X射线衍射(WAXD)研究了剪切后样品的热行为和结晶性能。实验结果表明,施加剪切作用不改变PLLA的晶型,但大大加快了结晶过程,提高了起始温度。PLLA在剪切场下的结晶形态主要受剪切速率的影响,当剪切速率高于临界剪切速率(10s-1)时,PLLA由球晶向串晶转变。随着剪切速率增大,串晶的数量变多变窄,结晶更完善,结晶度增大。与剪切速率相比,剪切时间对PLLA的非等温结晶影响影响较小。
The non-isothermal crystallization process of PLLA was studied by using optical rheological microscope (OMM). The effects of shear stress on the shear strength of PLLA were investigated by differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) Thermal Behavior and Crystallization Properties. The experimental results show that the application of shear does not change the crystal form of PLLA, but greatly accelerates the crystallization process and increases the initial temperature. The crystal morphology of PLLA in the shear field is mainly affected by the shear rate. When the shear rate is higher than the critical shear rate (10s-1), PLLA transitions from spherulites to string crystals. As the shear rate increases, the number of string crystals becomes narrower, the crystal is more perfect, and the degree of crystallinity increases. Compared with the shear rate, shear time has little effect on the non-isothermal crystallization of PLLA.