乳酸低聚物改性的纳米碳酸钙对聚乳酸性能的影响

采用直接缩聚法制备了乳酸低聚物，用该物质对纳米碳酸钙(CaCO₃)进行改性，得到改性纳米碳酸钙(g-CaCO₃)。将g-CaCO₃与聚乳酸(PLA)通过溶液共混制备了g-CaCO₃/PLA复合材料。通过FTIR、吸油值等对g-CaCO₃进行了表征，并采用SEM、DSC、万能试验机、流变测试仪、透湿仪、紫外-可见-近红外(UV-Vis-AIR)分光光度计研究了g-CaCO₃对PLA结构和性能的影响。结果表明，乳酸低聚物的改性降低了CaCO₃的吸油值，改善了CaCO₃与PLA的界面相容性，促进了CaCO₃在PLA基体中的分散；同时，g-CaCO₃在PLA基体中起到成核剂的作用，改善了PLA材料的结晶能力；随着g-CaCO₃添加量的增加，g-CaCO₃/PLA复合材料的拉伸强度和断裂延伸率呈先上升后下降的趋势，当添加5wt%的g-CaCO₃时，拉伸强度比5%CaCO₃/PLA复合材料高50%，比纯PLA高20%，当添加量达到10wt%时，拉伸强度仍比纯PLA高出13%；加入g-CaCO₃能够提高复合材料的储能模量和复数黏度；此外，g-CaCO₃的加入，提高了PLA材料对紫外可见光和水蒸气的阻隔性能。 

Effect of nano-calcium carbonate modified by lactic acid oligomers on the properties of polylactic acid

Lactic acid oligomer was prepared by direct condensation method and used as modifier of nano-calcium carbonate (CaCO₃) to developed modified nano-calcium carbonate (g-CaCO₃). g-CaCO₃ was blended with polylactic acid (PLA) by solution blending to prepare g-CaCO₃/PLA composites. The g-CaCO₃ was characterized by FTIR and oil absorption value etc. SEM, DSC, universal testing machine, rheometer, water vapor transmission tester and UV-Vis-AIR spectrophotometer were used to study the g-CaCO₃ on the structure and performances of the PLA. The results show that the modification of lactic acid oligomer reduces the absorption value of CaCO₃, promotes compatibility between CaCO₃ and PLA and improves the dispersion of CaCO₃ in PLA matrix. At the same time, the g-CaCO₃ acts as nucleating agent in PLA matrix, improving the crystallization ability of the PLA. The tensile strength and strain at break of the g-CaCO₃/PLA composites first rise and then fall as the g-CaCO₃ content increasing. When the g-CaCO₃ content is 5wt%, the tensile strength is 50% higher than that of 5%CaCO₃/PLA composite. When the addition amount of g-CaCO₃ reaches 10wt%, the tensile strength is still 13% higher than that of pure PLA. The storage modulus and complex viscosity of the composites are improved by adding g-CaCO_3. In addition, the addition of g-CaCO₃ enhances the barrier property of PLA to ultraviolet visible light and water vapor.