Study On Preparation And Properties Of Short Fiber Reinforce Polypropylene Composites

In recent years, the application of polypropylene (PP) material is used more and more widely, and its performance requirements are also getting higher and higher. The fiber reinforce polypropylene composite has excellent properties such as high strength, high modulus and so on, so that it has attracted people’s attention and becomes one of the hot spots in this research field.In this paper, firstly, the surface modification of the short glass fibers (SGF) and short carbon fibers (SCF) were carried out by the different coupling agents, and the surface was characterized by the Fourier transform infrared spectroscopy (FT-IR). The surfaces of SGF and SCF were modified by different coupling agents, then a series of SGF/PP and SCF/PP composites with different fibers content were prepared by the melt-blending and hot press molding, and their mechanical properties, thermal properties, and fracture morphology were investigated by the electronic universal material testing machine, thermogravimetric analysis(TGA), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and dynamic thermomechanical analysis (DMA).The study on performance of the SGF/PP and SCF/PP composites with different fibers content showed that with adding the short fibers compared with PP, the tensile strength and modulus, flexural strength and modulus, thermal stability and crastallization temperature increased, while the elongation at break and crystallinity decreased and the melting temperature had no obvious change. The mechanical properties indicated that the tensile strength of the SGF/PP and SCF/PP composites was maximum when the content of fiber was 25%, it was increased by 75.9% and 182.8%, respectively; meanwile, the flexural strength was increased by 46.5% and 55.8%, respectively. The TGA demonstrated that the thermal stability of the SGF/PP and SCF/PP composites was maximum when the fiber content was 25%, the T5 was increased by 54.8 ℃ and 65.4 ℃, respectively. The DSC declared that when the SGF/PP composite includes 25% fiber, the crystallization temperature was maximum, Tpc was increased by 5.2 ℃ and the crystallinity was 23.2%; at present, the Tpc of SCF/PP composite was increased by 9.3 ℃, and the crystallinity was 23.7%. The DMA indicated that with adding the short fibers, the storage modulus of the SGF/PP and SCF/PP composites was increased, and the rigidity enhanced.The performance of the SGF/PP and SCF/PP composites which treated by different coupling agents was investigated. The mechanical properties showed that KH550 was the best coupling agent to improve the tensile properties and the flexural properties of the SGF/PP and SCF/PP composites. Their tensile strengths were increased by 18.5% and 19.2%, and flexural strength were increased by 15.3% and 7.04%, respectively. The TGA declared that the thermal stability of the NDZ201 modified SGF/PP and SCF/PP composite was the best, T5 was increased by 12.9 ℃ and 11.1 ℃, respectively. The DSC indicated that KH570 was the best coupling agent to promote the crystallization temperature of SGF/PP and SCF/PP composites,and Tpc was increased by 3.0 ℃ and 1.4 ℃, respectively. But the best coupling agent to improve the crystallinity of SGF/PP and SCF/PP composites was NDZ201 and KH570,respectively, and their values were 26.9% and 26%, respectively. The DMA showed that the storage modulus of the KH550 modified SGF/PP and SCF/PP composites was larger.The SEM analysis demonstated that KH550 was the best coupling agent to improve the interfacial adhesion between short fibers and polypropylene, because KH550 containing amino groups with larger polarity.