含聚乳酸软段聚氨酯材料的结构与性能研究

以左旋丙交酯（L-LA）为原料，首先合成左旋聚乳酸二元醇（PLLA），然后以PLLA、聚四氢呋喃二元醇（PTMG）为软段，4，4'-二环己基甲烷二异氰酸酯（HMDI）、1，4-丁二醇（BDO）为硬段，采用二步法合成一系列含PLLA软段的聚氨酯化合物。通过核磁氢谱、红外分析、差示扫描量热仪、力学性能测试等手段确认并分析了含PLLA软段的聚氨酯弹性体结构与性能的关系。结果表明，软段的性质如玻璃化转变温度、熔点等会明显影响聚氨酯材料的玻璃化转变温度和熔点；虽然刚性软段PLLA可以显著提升聚氨酯材料的力学性能，但是也会导致材料在大应变下的首次回复性能大幅下降。

Structure and properties of polyurethane materials containing a polylactide soft segment

Polylactic acid and its oligomers are well-known biodegradable materials, and copolymerization can make the resulting polyurethane both strong and degradable due to their rigidity and degradability. In this investigation, polydiol of poly (L-lactic acid) (PLLA) has been synthesized from L-lactide (L-LA). Then, the PLLA and commercial polytetrahydrofurandiol (PTMG) have been used as the soft segment, while 4, 4'-dicyclohexylmethane diisocyanate (HMDI) and butadiol (BDO) have been used as the hard segment for the synthesis of polyurethane via a two-step process. The relationship between structures and properties of PLLA-based polyurethanes was investigated by nuclear magnetic resonance spectroscopy (¹H NMR), infrared analysis (FT-IR), differential scanning calorimetry (DSC), and mechanical properties tests. It is found that soft segments can significantly affect the glass transition temperature and melting point of polyurethanes. In addition, the rigid PLLA can significantly improve the mechanical properties of the polyurethanes, but it will also lead to a substantial decrease in the initial recovery performance under large strain. As a result, the effect of the PLLA and PTMG segments on the properties of the polyurethane has been revealed.