Study On Morphology And Properties Of Glass Fiber And PET Fiber Reinforced Polypropylene Composites

At present, polymer/fiber composites are one of the hottest research topics in polymer science and engineering. Most efforts have been focused on improving polymer-fiber adhesion by compatibility enhancement. The most used techniques include modifications in fiber surface, polymer matrix and/or both. However, few papers have reported about the phenomenon of fiber agglomeration and new types of hybrid composite materials developed in which the combination of two or more kinds of fiber.On this situation, this work takes polypropylene(PP), glass fiber(GF), PET fiber as study objects. It contains two parts as follows: first, the preparation of GF reinforced PP composites in melting extrusion is always going with fiber agglomeration, causing poor fiber dispersion. So the focus of this research is to fabricate a non-agglomerated long glass fiber(NGF) where the glass fibers dispersed individually and evenly before blending, aiming to investigate the influences of fiber agglomeration on morphology, thermal and mechanical performance of long glass fiber reinforced polypropylene(PP) composites. For comparison, the conventional long glass fiber(LGF) reinforced PP composites were also prepared. Second, the PP/PET fiber/GF composites were prepared by co-rotating twin screw extruder granulation. The extrudates were injection molded into standard specimens respectively at temperatures of 230?C and 265?C. The effects of the hybrid of glass fiber and PET fiber and the injection temperature on the properties of composites were studied. The mechanical properties,micromorphology and thermal properties of composites were studied by SEM, DSC,WAXD, TG and universal tensile tests.The results showed,(1) Scanning electron microscopy(SEM) showed that NGF dispersed individually and evenly in the matrix. However, fiber agglomeration was clearly observed to take place for LGF reinforced composites. It indicated that NGF was successfully prepared.(2) Differential scanning calorimeter(DSC) and X-ray diffraction(XRD)indicated that NGF had a better nucleating property towards PP than LGF.Mechanical testing revealed that within certain low fiber content, fiberagglomeration was more effective in bearing the load when interface adhesion was weak. But with Polypropylene grafted with maleic anhydride(PP-MA) as adhesion promoter, the tensile, flexural, and impact strength of PP/PP-MA/NGF composites were apparently increased, comparing with those of PP/PP-MA/LGF composites,which illustrated that fiber agglomeration was a negative factor when an improved interface adhesion was achieved.(3) The morphology of PET fiber was directly affects by Injection molding temperature. At molding temperature of 230?C, it was observed that the injection-molded hybrid composites contained PET fibers. But at 230?C, the melting of PET fiber happened, and then the PET component was in the form of particles.(4) PP can be reinforced by the the hybrid of glass fiber and PET fiber. But no characteristic band of PP β-form was found, and all these PP samples were formed the α-form crystal modification. The PET component that in the form of particles was conducive to improve interfacial adhesion with the PP. By contrast the specimens that injection molded respectively at 230 and 265?C, the former exhibited higher thermal stability, but the tensile strength of the latter was found to be higher than that of the former.