Study On Long Glass Fiber Reinforced PA66Composite

Polyamide66(PA66) is the commonest thermoplastic engineering plastic. It exhibitsgood mechanical performance, low friction coefficient, medium flame retardancy andmany other advantages. However, PA66possesses high moisture abortion and theproducts of neat PA66exhibit poor dimension stability. Also, the strength of neat PA66is not high enough for structure applications. For advanced applications PA66has to bemodified and reinforced. In convention reinforcing technology glass fiber strands aremixed with PA66directly on extruders. The glass filaments are ground into short chipsand some of them are shorter than the critical length for reinforcing. The reinforcingefficiency is limited.In order to enhance the reinforcing efficiency, continuous glass fiber strands wereimpregnated with PA66melt in an impregnation device and pellets with long glassfibers (LGFR PA66) were produced. The effect of resin features, fiber strand types,compatilizers, coupling agents and wetting agents on the impregnation of the fiberstrands and the mechanical properties of the injection molded PA66composites wereinvestigated. The filament surfaces in impregnated strands were examined under SEMand the length of the filaments in injection molded samples are analyzed statisticallyunder optical microscope. The relationship amount pellet length, injection moldingcondition, mechanical property and filament length of molded samples were studied.Excellent impregnation was achieved under optimum conditions and the resultantLGFR PA66pellets with formulas composed of PA66EPR27, glass strand ER4301,compatilizer493D and coupling agent KH561could exhibit tensile strength230MPa,flexural strength320MPa and notched impact strength35kJ/cm2. As the pellet lengthincreased, the average length of the glass filaments in molded samples and mechanicalstrength increased. Increasing screw speed would reduce the average length and thereinforcement efficiency descended. Increasing the temperature of extruder inlet wouldbe helpful to keep the average length of filaments at higher level and achieve highreinforcement efficiency. The injection molding parameters should be around attemperature290-280℃, screw speed100r/min，injection pressure40MPa, back pressure10MPa and mold temperature80℃. New screw configuration of injection moldingmachine for LGFR plastics has been proposed.