Studies On Rheological Behaviors Of Glass Fiber-polypropylene Melt Suspensions

Owing to the advantages of low weight, high strength, convenient forming, shortmanufacturing cycle, etc. Fiber reinforced thermoplastic composite is gradually becoming asubstitute for the engineering plastics and metal materials. It is already the first selection forlightweight of automobile. The rheological behaviors of polymer melts have importantinfluence on processing process and products’ final mechanical properties. An exhaustivestudying on the rheological properties of fiber-thermoplastic melts can effectively optimizematerial processing and forming process, provide reliable base for the design of processingequipments and reliable date for processing simulation.However, the detailed rheological research on fiber-thermoplastic melts is not enough.Therefore, with the typical fiber-thermoplastic system-glass fiber filled polypropylene melt asthe object, using capillary rheometer, this paper studied the influence of the fiberconcentration, fiber aspect ratio on the rheological behaviors, discussed the flowing regulationin conical channel of different conical angles, and on the basis of previous people’s studies,gave mathematic expression of the rheological behaviors.The results show that: with fibers orienting in the flowing direction, glass fiber-PP meltsobey power law in shear flow over the shear strain rate range of101to104s-1, and inelongation flow over elongational strain rate range of101to103s-1. Melts show obvious shearthinning and tension thinning.While the glass fiber-PP melts flow in the conical channel with different conical angles,the pressure drops on the channel decline first with the increase of conical angle, followed byrising after an critical angle, which becomes smaller with the increase of the fiberconcentration. And the fiber breaking becomes lighter at small conical angle.In this paper, cited and modified Pipes model. Using the modified Pipes model, can buildmathematical relationship between medium parameters, fiber concentration, fiber aspect ratioand the macro flowing regulations of fiber–thermoplastic melts. The results prove the modelprediction results have a good agreement with experiments.