Development And Mechanical Property Research Of Thermo-Plastic Resin Composites Reinforced With Flax Fibers

With the problem of energy sources and environment, it becomes important to develop green composites and study on it. People are getting to pay more attention to the application of cellulosic fiber in composites, especially to the fibers like flax, ramie, jute, sisal. Theses fibers have many excellences. First of all they have good abrasion resistance and high tenacity which make them to substitute the glass fibers in composites. Secondly they belong to regenerative source, and they are also abundance. Lastly they can degrade in nature condition after being abandoned. Recently, thermoplastic resin composites reinforced with fibers like flax, ramie, jute, sisal got development quickly and products have been applied to auto, architecture, traffic, especially in inner decoration of auto.Although there have been many studies on fibers like flax, ramie, jute, sisal reinforced thermoplastic composites in home and out, development of continuous fibers and research of its producing techniques are so little. In this paper, the flax yarn will be used as the continuous reinforcement and the Polypropylene multifilament will be used as thermoplastic resin matrix. The two things will be made into a pp/flax covered yarn, which are ready to be woven into a plain fabric. The flax/pp composite board is accomplished by hot-pressing molding. Some other composite boards are also made, whose flax yarn haven been pretreated. Techniques of covered yarn spinning and plain weaving and hot-pressing are studied. The effect that flax quantity and fabric density and pretreatment have on composites' tensile property is also researched and many problems in producing process are solved.During the spinning of covered yarn the relation between the flax quantity, covered tightness and the hollow twist, hollow-spindle rotate speed is found, which provides convenience in later manufacture.In weaving the actual weft density can not accord with the designed weft density because of covered yarn's slippery surface, low flexibility, and this problem has been solved.In hot-pressing single experiment and orthogonal experiment of temperature, time and pressure are designed to look for a best hot-pressing condition.The composite made by the means of covered yarn is better than composites made by other methods. Tensile properties of composites with different flax quantity and fabric density have been tested and compared.The flax yarn is treated by alkali and coupling agent, after which the properties of flax yarn are changed, especially the alkaline treated yarn. The tensile properties of composites were tested. The results showed that the tensile strength is increased while the tensile modulus is decreased, especially the composites by alkaline treatment.In this paper the continuous flax fiber reinforced Polypropylene composite is accomplished and many problems have been solved to improve composite's properties, which is significant for the development of green composites.