低熔指PE粉拉伸流变加工特性与制品性能分析

Analysis of the Elongational Rheology Processing Characteristics and Performances of PE Powders with Low Melt Flow Index

利用拉伸流变挤出机研究了低熔指PE粉挤出造粒和直接挤出吹膜的特性。采用凝胶渗透色谱(GPC)、核磁共振、动态流变等方法,分析了低熔指PE粉经拉伸流变挤出造粒前后结构与性能的变化,并与双螺杆挤出机进行对比,了解了拉伸流变挤出技术在挤出能力、加工性能、制备原料性能等方面的优势。结果表明,转子直径为40 mm的拉伸流变挤出机最大挤出能力为67 kg/h,与直径相同的双螺杆相比,提高了190%;造粒后树脂的重均分子量均有下降,采用拉伸流变挤出造粒、螺杆造粒得到的树脂的重均分子量分别下降了7.8%、23.8%。利用拉伸流变挤出机对低熔指PE粉直接吹膜,成功制备2种不同型号的低熔指PE薄膜,其落镖冲击强度分别能达到240和137 g,综合性能较好。

The characteristics of extrusion granulation and extrusion blown film of polyethylene(PE) with low melt index by using an elongation rheological extruder were studied.Gel permeation chromatography(GPC), nuclear magnetic resonance,dynamic rheology and other methods were used to study the structural and performance changes of PE powder with low melt index before and after extrusion granulation by elongation rheological extruder.The advantages of elongation rheological extruder in extrusion capacity,processing performance and properties of raw materials were also investigated compared to the twin-screw extruder.The results showed that the maximum extrusion capacity of the elongation rheological extruder with the diameter equal to 40 mm was 67 kg/h,which was 190% higher than that of the twin-screw extruder with the same diameter.After extrusion granulation,the weight average molecular weight of the resin decreased by 7.8% through the elongation rheological extruder and by 23.8% through the twin-screw extruder.Two different types of PE films with low melt index were successfully prepared by directly blowing PE powder by elongation rheological extruder,and their dart impact strength reached 240 and 137 g,respectively,with excellent comprehensive properties.