聚乳酸在微型双螺杆中的挤出过程

以L-乳酸熔融缩聚法产物为预聚物,以亚磷酸三苯酯(TPPi)为扩链剂,在微型双螺杆挤出机(Haake MiniLab)中通过反应挤出法制备了高分子量聚L-乳酸,挤出产物在微型注塑机中直接成型.研究了挤出温度,螺杆转速,停留时间及TPPi添加量对产物挤出过程中混合扭矩的影响,在最佳条件下所得产物(M-)w达126,000 g/mol,拉伸强度达64.6 MPa,断裂伸长率为4.5%.由1H-NMR证实反应挤出后其分子结构基本不变, DSC结果显示反应挤出后产物熔点为148.9 ℃,结晶度为33.9%.

Preparation of High Molecular Weight Poly(L-Lactic Acid) in Micro Compounder

The process of poly(L-lactic acid)(PLLA) reactive extrusion was studied in MicroCompounder.Triphenyl phosphite(TPPi) was used as chain extender to increase the molecular weight of the PLLA prepared by melt-polycondensation from L-lactic acid.The influences of the temperature,screw speed,resident time and the amount of TPPi were studied on the mixing torque of PLLA.With addition of 2% TPPi,the molecular weight of the PLLA increases from 62,100 g/mol to 126,000 g/mol.The structure of PLLA was kept after the reactive extrusion.The final PLLA products had low Tg ?and Tm? due to existence of the impurities.The mechanical properties of the products are approximate to that of commercial PLLA.