Reparation And Property Investigation Of Natural Fiber Reinforced Composite

Natural fiber reinforced thermoplastic composite belongs to environment-friendly materials. In recent years, it has been attracted people’s attentions for its advantage of low cost, partly biodegradable and recycling easily. But compared with synthetic fiber, natural fiber existing characteristics such as short in length, uneven distribution of length and natural curly. Because of it, it was difficult to ensure the fiber’longitudinal straighten in unidirectional natural fiber reinforced composite system. And some special property that natural fiber owned make the fiber entangled easily and has poor dispersivity in matrix resin, which lead to the poor interfacial compatibility of composite. In view of the above questions, this paper take ramie fiber as reinforcement to prepare ramie/PP (polypropylene) unidirectional composite. The effect of processing conditions on properties of composite was analysised, and the interfacial modification were also investigated in this paper. The main research contents were as follows:1. This paper take ramie roving as reinforcing material to prepare ramie/PP unidirectional composite by using moulding process. With the high orientation in ramie roving, ramie fibre palys a good enhancement in the direction of the fibre length. Ramie fibers are loosely arranged in ramie roving for the weak twist of it, in the preparation of composite, the ramie roving can loosed into single fiber state in the case of without affecting fiber’s longitudinal straightness and natural length, which is benefit to improve infiltration properties of the PP matrix to ramie fibers. At the same time, by selecting a proper molding process parameters can ensuring a good formability of ramie/pp composite.2. The effect of molding temperature, pressure, packing time and cooling methods on the properties of ramie fiber reinforced polypropylene composites was investigated in this paper. With the DSC, the effect of cooling conditions on the crystallization of composites were also discussed, and the tensile fracture of composites were analysised by using the finite element analysis software ANSYS. The results shows that processing conditions have great impact on the performance of composites. The samples gained the best mechanical properties when the process conditions such as molding temperature, pressure, packing time, cooling methods are selected as165℃,8MPa,10min, cooled together with the heating plate, the tensile strength reached to44.6MPa. When the composites cooled together with the heating plate, the PP would stay at a higher temperature for a long time, which is benefit to the PP’s crystal nucleation, its melting enthalpy is the highest and the crystallization properties is better than other cooling methods, its melting enthalpy reached to5.55J/g. Through the ANSYS finite element analysis we find the simulation results is the same as the actual situation. That is to say, taking the best technology(165℃,8MPa,10min, cooled together with the heating plate) to prepare ramie/PP composite is reliable.3.With the ramie fiber treated by coupling agent, the mechanical properties of composite improved. When the concentration of coupling agent selected as1%, the ramie/pp composite has the best tensile strength of52.6MPa. Taking the ramie fiber which was untreated and treated by1%concentration of coupling agent as the reinforcement separately, and prepareing the ramie/pp composite with different fiber content. The results shows that the tensile strength and flexural strength improved with the increase of fiber content, and the composite got the best mechanical properties when the fiber content reached to25%. Meanwhile, under the same fiber content, the mechanical strength of the composite that treated by coupling agent are always higher than the untreated one.4. Using different concentration of alkali treating ramie fiber. The properties of the composite that separately treated by alkali, coupling agent, combined treatment of alkali and coupling agent were comparison analysised. The result of SEM analysis shows that the surface of the fiber treated by alkali is rough, having cracks. All of these contributed to the improvement of interface compatibility. The composite got the best tensile strength of55.4MPa when the alkali concentration selected as8%. The combined treatment of alkali and coupling agent not only reached to the purpose of eliminating the extra impurity composition, but also improved the interfacial compatibility of ramie/PP composite. As a result, compared with the alkali treatment and coupling agent treatment, the best modification result were gained by this way, and its tensile strength reached to57.9MPa.