异氰酸酯对聚乳酸/热塑性聚氨酯共混物性能的影响

以4,4^′-二苯基甲烷二异氰酸酯（MDI）为反应增容剂,采用熔融共混法制备了不同MDI含量的聚乳酸/热塑性聚氨酯（PLA/TPU）共混物,采用傅里叶变换红外光谱仪（FTIR）、万能试验机、冲击试验机、扫描电子显微镜（SEM）、差示扫描量热仪（DSC）和旋转流变仪对共混物力学性能、微观形态、热性能和流变性能进行了研究。结果表明：MDI可以有效改善共混物的力学性能,当MDI质量分数为1%时,共混物力学性能最佳,缺口冲击强度为40.0kJ/m²,断裂伸长率为214.1%,与未加MDI的共混物相比,分别增加了4.3倍和5.8倍,拉伸强度稍有下降（47.6MPa）;SEM表明,MDI的加入提高了共混物的相容性,加入MDI后,共混物的断面由海-岛结构变为核-壳包覆结构,相界面作用力增强;DSC测试表明,共混物的玻璃化转变温度、冷结晶温度和熔融温度随着MDI含量的增加而升高;流变测试表明,MDI质量分数的增加,共混物呈现更显著的剪切变稀行为,推测共混反应机理为：MDI质量分数的增加,体系内依次发生PLA的扩链、支化和TPU的交联。

Effect of diisocyanate on properties of polylactic acid/thermoplastic polyurethane blends

Polylactic acid/thermoplastic polyurethane（PLA/TPU） blends with different contents of MDI were prepared by melt-mixing with using 4,4'-diphenyl methane diisocyanate（MDI） as reactive compatibilizer. The reaction mechanism,mechanical properties,morphology,thermal properties and rheological properties of PLA/TPU blends were studied by FTIR,universal testing machine,impact tester,SEM,DSC and rotational rheometer. The results showed that the mechanical properties of the blends can be improved obviously. The comprehensive mechanical properties of the blend was the best when MDI content was 1% with increased notch impact strength and elongation at break to 40 kJ/m² and 214.1%, respectively,about 4.3 times and 5.8 times greater than the corresponding values of blend without MDI,while the tensile strength decreased a little. Fracture surface morphology of blends changed from sea-island structure to core-shell encapsulation structure and the compatibility of blend was improved. The glass transition temperature,cold crystallization temperature and melting temperature of the blends increased with the increase of MDI content through DSC test. The rheological test showed that the blend indicated a more significant shear thinning behavior with the increase of MDI content. Reaction mechanism of blending was that the chain extension of PLA,branching of PLA and crosslinking of TPU occured sequentially in the blends with the increase of MDI content.