Modification Of Glass Fiber Reinforced PA66 By Nucleating Agents And Extrusion Molding Process

Glass fiber reinforced PA66 composites because of itshigh strength,high modulus,high temperature resistance and other characteristics,which is one of the important composites instead of metal,are applied extensively in the field ofautomobile and electric appliance industry.Glass fiber reinforced PA66 molded profiles,bars,pipes,plates,sheets,film is widely used in sealing and heat insulation of automobile and civil industry.However,the conventional extrusion process,whichobtain extrusion profiles with high precision through first extrusion and then sizing in standardized dies,are unable to realize the extrusion of GF/PA66,because the range of processing temperature is narrow and extrusion molding performance is poor.In fact,improving the melt crystallization behavior of polymer melt can solve this problem by nucleating agent.The polymer melt can rapid coolin the extrusion die and obtain precision profile with section shape and dimension precision by using a one-step extrusion method without cooling devices.The law on crystallization behavior and flow property of GF/PA66 composites modified by nucleating agent is studyed deeply.The relationships between flow properties and crystallization behaviors and extrusion shaping isinvestigated.The establishment of one-step extrusiontheoryis of great significance to improve the extrusion molding technology and improve the quality of products.The effect of melt crystallization behavior and the process parameter to extrusion flow property and the flow balance is investigated deeply,by using the method of rheological theory,finite element numerical simulation combined with experimental research.Firstly,GF/PA66 is modified byinorganic nucleating agent of MMT and organic nucleating agent of PET.MMT/GF/PA66 and PET/GF/PA66 are prapared by melt blending.The effect of melt crystallization behavior of GF/PA66 to types and content of nucleating agents is investigated by DSC.The results showed that MMT and PET play a significant role of heterogeneous nucleation.The crystallization rate of PA66 is significantly increased at the same time,the crystallization temperature of PA66 is increased.Kinetics of crystallization of GF/PA66 is studyedunder non-isothermal environment by the modified Avrami equations of Jeziorny.The nucleating mechanism and growth style of nylon 66's crystallization process are changed by using MMT and PET.Secondly,rheological behavior and physical property parameters of MMT/GF/PA66 and PET/GF/PA66 composites are investigated by rheological experiment.Flow behavior and flow balance performance of MMT/GF/PA66 and PET/GF/PA66 melt are investigated by finite element numerical simulation technology.The influence law of flow behavior and flow balance performance on extrusion process parameters are obtained.Simulation results show that,melt flowproperty is more stable,and flow balance is more excellent by decreasing melt temperature or decreasing volume flow rate.On the basis of the above research results,the influence law of flow behavior and crystallization behavior on extrusion propertyfurther investigated by extrusion experiment.One-Step extrusion method is firstproposed and applied extrusion of polymer which its apparent viscosity changed remarkably with temperature.The experimentalresults show that,shaping ability of melt processed by one-step extrusion method is improved by increasing the starting temperature of crystallization and accelerating the crystallization rate.In conclusion,one-step extrusion method which realizes rapid forming of polymer melt modified by nucleating agent effectively improve the formability of polymer melt and improve the quality of extrusion profiles.