波浪螺杆注塑长玻纤增强聚丙烯的探究

Study of Wave Screw for Injection Molding Long Glass Fiber Reinforced Polypropylene

针对长玻纤增强热塑性塑料(LFT)注塑过程中需要抑制玻纤折损和促进玻纤分散,以保证玻纤增强效果和制品力学性能的需要,首先比较螺杆构型对长玻纤增强聚丙烯复合材料(LGF–PP)力学性能的影响,然后使用波浪螺杆注塑样条,探索注塑工艺参数对LGF–PP力学性能的影响并观察样条中玻纤的保留长度、分散情况以及玻纤–树脂界面。基于上述结果,进一步分析论证波浪螺杆对于LFT材料注塑的适用性。结果表明,"双波浪计量+销钉混炼"螺杆构型可改善LGF–PP的力学性能稳定性;提高熔胶温度、降低螺杆转速和背压,有利于抑制玻纤在塑化过程中发生的折损,提高复合材料力学性能;波浪螺杆成型的LGF–PP中玻纤平均保留长度在4~6 mm并且均匀分散,玻纤–树脂界面结合牢固。波浪螺杆构型降低了熔体剪切作用和沿程压力,缩短了熔体停留时间,有效平衡了LFT制品内玻纤的保留长度和分散状态。

For ensuring glass fiber reinforcement effectiveness and mechanical properties of molded parts,it should suppress fiber breakage and improve fiber dispersion simultaneously during injection molding of long glass fiber reinforced thermoplastics(LFT).Focusing on requirements above,influences of screw geometry upon mechanical properties of long glass fiber reinforced polypropylene(LGF–PP)were studied firstly and then the wave screw was used for exploring influences of injection molding parameters on mechanical properties of LGF–PP and observing residual fiber length,fiber dispersion and interface between glass fiber and plastic matrix of LGF-PP.Based on these consequences,effectiveness of wave screw for injection molding LFT was analyzed and conformed.The results show that"double wave metering+pin mixing"screw configuration can improve the stability of mechanical properties of LGF–PP.Mechanical properties are improved and fiber breakage is suppressed in the plasticizing process when increasing melt temperature and decreasing screw rotation speed and back pressure.In LGF–PP molded by the wave screw,glass fiber with average residual length of 4–6 mm disperses evenly and bonds resin matrix strongly around interface area.The wave screw geometry reduces melt shearing and melt pressure along screw channel and shortens melt resident time.Therefore,wave screw makes good balance between residual fiber length and fiber dispersion of molded LFT parts.