聚碳酸酯熔融挤出后的物性变化

利用配有BM分离型螺杆的单螺杆挤出机研究了聚碳酸酯(PC)颗粒在不同条件下经熔融挤出后的特性黏数(η])和熔体流动速率(MFR)的变化.结果发现:在300℃以下的挤出温度、不同螺杆转速下对烘干的PC树脂挤出加工时,基本不会改变PC的η]和MFR,因而难以用测定η]或相对分子质量的方法判别PC是新料还是回收料;在120℃,-0.1 MPa干燥1.0 h可保证把料彻底烘干,延长干燥时间可促进PC料的固相缩聚,提高η],有利于PC的加工；经多次热加工的PC树脂或PC含有少量水分时,挤出产物的η]明显下降,MFR显著变大,不利于加工.

Variation in physical properties of polycarbonate after melt extrusion

The variation in intrinsic viscosity(η]) and melt flow rate(MFR) of polycarbonate(PC) particles after melt extrusion under different conditions was studied by means of a single-screw extruder equipped with a BM separable type screw.The experimental results show that the η] and MFR have little change when the dried PC is extruded at different speeds of the extruder screw below 300 ℃.Therefore,it is rather difficult to judge whether the PC particles are fresh or recycled material merely according to the test of η] or relative molecular mass.The PC material can be dried completely after being treated in a vacuum oven for an hour at 120 ℃ under-0.1 MPa.Lengthening drying time can not only facilitate the PC′s solid phase polycondensation,but also raise its η] and further benefit its processability.The PC extrudate′s η] decreases obviously while its MFR increases noticeably in case the PC resin undergoes multiple thermal treatments or contains a small amount of water,which militates against the processing of the PC material.