Preparation Of The Long Glass Fiber Reinforced Polypropylene Composites And Study On The Mechanical Properties

Because of better reinforced effect, continuous long fiber reinforced thermoplastic composites (LFRT) have replaced short fiber reinforced materials with the progress of technology and the improvement of performance requirements. It is significant to study the preparation of LFRT and its properties. The key to improving LFRT product performance is how to make the fibers impregnated better, which means that how to improve the interfacial bonding between resin matrix and fibers. A series of matters are carried out around the key in this paper. Continuous long glass fiber reinforced polypropylene composites (LFRT-PP) are studied as the object through the theory combined with experiments. The effects of factors on the interfacial bonding and the mechanical properties after injection are analyzed comprehensively from the theoretical model, the equipment and the technological process.1. A theoretical model of the melt thermoplastic resin impregnating fibers is set up in the paper. This model can effectively reveal the regularity of the complete impregnation time affected by the technological conditions, the viscosity of resins and fiber structure. The methods to improve the interfacial bonding between resin matrix and fiber consist of increasing the residence time of fibers in the device, reducing the melt viscosity, increasing the melt pressure, increasing the breadth of fiber bundle and decreasing the fiber volume content in the bundle.2. Based on the model, the technological conditions of LFRT-PP prepregs’ preparation are analyzed to verify the methods to improve the properties. At the same time, the porosity and the water absorption of prepregs laminated sheet are measured. Finally the effects of the preparation technologies of prepregs on the mechanical properties are analyzed by DOE method. The results show that the interfacial bonding, as well as the mechanical properties after injection, is better with the increasing of the residence time of fibers in the device and the temperature of the impregnation mold, the higher MFI of PP and the proper addition of compatilizer.3. Effects of four injection molding parameters of LFRT-PP (the effects of the pellet length, the temperature of barrel, the screw speed and the injection pressure) on the residual fiber length and the mechanical properties of LFRT-PP are investigated by orthogonal experimental design method in the paper. The residual glass fiber length in the final products is increasing with the increase of pellets lengths. While lower the screw speed, weaken the shearing strength, then larger the residual glass fiber length can be obtained, as well as the optimal parameter levels.