Study On The Preparation And Properties Of PP Composites Filled With Lignocellulose

Lignocellulose can be converted into a new kind of environmental composites by mixed with plastics in a proper way after processing.This new kind of environmental composites feel like natural wood,and have better physical properties than wood.It can be drilled,cut,planed,milled and napped by tools.It is widely used in architecture molding board,railway crosstie,guardrail,hypaethral furniture and so on.Preparation of wood plastic composites is one of the important methods to replace natural wood and recycle waste plastics.In this paper,wood-fiber,bamboo fiber and rice husks were used as fillings to fill PP. Many kinds of composites were made through injection molding.Some experiments about the composites were did,and the compatibility and the microcosmic shape were observed by SEM.The main work and conclusions were as follows:(1) Molding techniques of PP/lignocellulose compositesinjection molding were studied,and the injection process parameters were optimized.The results showed that the appropriate molding temperature was set at 215℃when 20%rice husks were used to fill with PP,the appearance and capability of the sample were better.The molding temperature should be lower,and moreover,the maintain pressure and the time of cooling should be longer when the contents of the fiber were higher.Back pressure made the die full of material.(2) The effects of contents of rice husks on mechanical properties and physical and chemical properties of PP/rice husks composites were studied.The results showed that when the contents of rice husks were 30%,the modulus of rupture and modulus of bending of composites were best,and tensile strength was good.Increase of rice husks contents results in the decrease of composites tenacity but increase of dimensional shrinkage under heat and expansion ratio after water sorption.The contents of 45%were four times more than the contents of 20%at the rate of expansion ratio after water sorption,and the rate of dilating on crosswise was higher than the one on lengthways.SEM photos showed that the phenomenon of twist and drawbench between rice husks and PP when the contents of rice husks were low,and the wrapping capability was very good.(3) The effects of different lignocellulose on mechanical properties and physical and chemical properties of PP/lignocellulose composites were studied.The results showed that when the oaten fiber which had long fiber was used to fill rice husks which had short fiber, the tensile strength increased 13%and modulus of bending was much higher,except that the modulus of rupture was lower than the materials which were made of rice husks.It showed that the mixture of different kinds of fibers had effects about increasing strength. The physical properties of PP/bamboo fiber composites were lower than other composites, and the chemical structure of bamboo fiber meant it had high water absorption,and the percentage of moisture of PP/bamboo fiber composites reached 0.6%.(4) The effects of mechanical properties and physical and chemical properties of composites of three different rice husks sizes were studied.The results showed that the filling had uneven dispersion in PP when it was smaller,and the mechanical properties would decrease;if the filling was too big,there would be more inanition cavern and also could influence the mechanical properties.When the rice husks whose granularity was 60 mesh was used to fill PP,its integrative capability would be the best.