聚乳酸复合体系结晶行为的研究

Study on the Crystallization Behaviors of PLA and its Composites

采用差示扫描量热仪(DSC)、偏光显微镜(POM)和X射线衍射仪(XRD)对聚乳酸/成核剂体系的结晶行为进行了研究。结果表明:四种不同的成核剂——无机粒子Talc和LAK、聚合物右旋聚乳酸PDLA(3.4)和PDLA(6),都能在一定程度上改善PLA的结晶行为。其中LAK的效果最好,能显著提高PLA的结晶速率和结晶度,添加5%(wt)的LAK,PLA的半结晶时间可控制在2min,结晶度提高到33%;Avrami方程理论结果表明,无机粒子的添加对其成核机理和生长方式无明显影响;PDLA的添加可在体系中形成高熔点的立构复合体SC,从而起到异相成核剂的作用;XRD结果表明,成核剂填充体系对于聚乳酸的基本晶型没有影响,但POM结果显示,PDLA的添加会影响PLA的晶体形貌。

In this study,the crystallization behaviors of polylactide（PLA）and its composites with different nucleating agents were investigated by differentical scanning calorimtery（DSC）,polarizing optical microscope（POM）and X-ray diffraction（XRD）.Four different types of nucleating agents,including inorganic fillers（LAK and talc）and poly（Dlactide）（PDLA3.4and PDLA6）,can effectively enhance the crystallization behavior of PLA.Furthermore,LAK was confirmed to be the most effective one,which significantly accelerated crystallization rate and increased the crystallinity.With the addition of 5wt% LAK into PLA,the half crystallization time（t1/2）can be decreased into two minutes and the crystallinity was increased to be 33%.Based on the Avrami＇s equation,the inorganic fillers have no influence on the nucleation mechanism and geometry of crystal growth of PLA.However,with the addition of PDLA into the PLA matrix,the enhanced crystallization can be explained by the formation of PLA stereocomplex（PLA-SC）,which was found to have a much higher melting temperature and then acted as heterogeneous nucleating agents.XRD results indicated that the addition of nucleating agents had no influence on the crystalline structure,while the addition of PDLA significantly changed the crystal morphology according to the POM investigation.