熔融共混立构复合聚乳酸的制备及其性能研究

Preparation and Properties of Melt Blend Stereo Composite Polylactic Acid

采用微型双螺杆挤出机制备了立构复合聚乳酸(scPLA),并添加聚己二酸/对苯二甲酸丁二酯(PBAT)对其进行增韧改性。采用X射线衍射(XRD)、差示扫描量热法(DSC)、维卡软化点分析(VST)、拉伸和冲击试验等对其进行了测试。结果表明当左旋聚乳酸和右旋聚乳酸比例为1∶1时,能够形成完全的立构复合(SC)晶体结构,不含有同质结晶(HC)晶体结构,且结晶度最高;熔点高达230℃,比聚乳酸均聚物提高了50℃;维卡软化温度高达174. 2℃,比聚乳酸均聚物提高了115℃;力学性能也有了一定提升,但是仍然发生脆性断裂。加入PBAT进行增韧后,样品的韧性得到较大改善,发生塑性变形,屈服强度为68. 6 MPa,断裂伸长率达到9. 8%,冲击强度提高到36. 5 k J/m^2,且断裂强度(77. 7 MPa)没有损失。

Stereocomplex poly( lactic-acid)( sc PLA) was prepared by micro twin-screwextruder,and poly( butyleneadipate-coterephthalate)( PBAT) as toughening modifier. The sample was tested by the method of X-ray diffraction( XRD),differential scanning calorimetry( DSC),vicat softening point( VST),tensile and impact tests. The results showwhen the ratio of poly( L-lactic acid) and poly( D-lactic acid) is 1 ∶ 1,it can form a complete stereocomplex crystal structure without HC crystal structure,and has the highest crystallinity. The melting point is 230 ℃,which is 50 ℃ higher than poly( lactic acid) homopolymer. The Vicat softening temperature is 174. 2 ℃,which is 115 ℃ higher than poly( lactic acid) homopolymer. The mechanical properties are also improved,but brittle fracture still occurs. After adding PBAT toughening agent,the toughness of the sample has been greatly improved and plastic deformation occurs. The yield strength is 68. 6 MPa,the elongation at break is 9. 8%,the impact strength could increase to 36. 5 k J/m2,and the breaking strength is still 77. 7 MPa.