【作者】 薛盘芳；

【导师】 何春霞；

【作者基本信息】 南京农业大学 ， 机械设计及理论， 2008， 硕士

【摘要】 木质纤维经处理后,以适当的方法与塑料复合可以加工成一种新型环保复合材料。其具有天然木材的质感,物理机械性能优于木材,在使用时可以进行钻孔、切割、刨铣和修整。广泛应用于建筑材料、铁路枕木、花栏、露天桌椅等。木塑复合材料的制备对寻求木材的替代材料具有重要意义,也是回收塑料再生利用的有效途径之一。本论文以聚丙烯(PP)树脂为基体,木粉、竹粉、稻壳粉为填料,通过注塑工艺制备了多种PP木塑复合材料。对材料进行了理化性能及力学性能的实验,通过扫描电镜(SEM)观察了纤维间界面相容情况和微观形貌。取得的主要成果如下:(1)研究了制备PP/木质纤维复合材料成型工艺—注塑成型方法,优化了注塑工艺参数。结果表明,稻壳纤维填充含量为20%时,复合材料较为合理的成型温度为215℃,所得的试样外观和材料的性能较好,木质纤维含量越高,其成型温度需适当降低,保压和冷却时间要适当加长,且需加一定背压,以保证物料充模完全。(2)研究了稻壳粉的用量对PP/稻壳粉复合材料力学性生能和理化性能的影响。结果表明,稻壳粉含量为30%时,复合材料静曲强度和弯曲弹性模量均为最佳,拉伸性能也较好。随着稻壳纤维含量的增加,复合材料韧性下降,复合材料受热后尺寸变化率及吸水厚度膨胀率增大,稻壳粉含量为45%的复合材料的吸水厚度膨胀率是20%的4倍,且稻壳粉横向的吸水厚度膨胀率大于纵向吸水厚度膨胀率。通过扫描电镜(SEM)照片可知,低组份的稻壳粉和PP有缠绕、拉丝现象,且包裹性良好。(3)研究了不同木质纤维对PP复合材料的力学性能和理化性能的影响。研究发现,采用纤维较长的麦秆粉与短纤维的稻壳粉混合填充PP时,除静曲强度略低于稻壳粉填充的复合材料外,其抗拉强度提高了13%,弯曲弹性模量也高于单独组分填充的PP复合材料,说明不同长度的纤维混合能起到增强效果。PP/竹粉复合材料的力学性能低于其它木质纤维制得的复合材料,竹粉的化学组成决定了其具有较强的吸水性,复合材料含水率达到0.6%。(4)考察了三种不同粒径的稻壳粉对复合材料力学性能和理化性能的影响。结果表明,填充物颗粒粒径越小,其在PP中分散越不均匀,复合材料的力学性能相应也较差,颗粒粒径过大,粗糙度高的稻壳粉容易在界面处形成空洞缺陷,使其拉伸强度等力学性能下降,当颗粒度为60目的稻壳粉填充PP时,复合材料综合性能最好。更多还原

【Abstract】 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.更多还原