长纤维增强聚合物注塑成型过程中三维网络结构的调控

Control Three Dimensional Network Structure of Long Fiber Reinforced Polymer Injection Molded

以长玻纤增强聚丙烯(PP)注塑制品为研究对象,通过引入微、纳尺度第二增强相调控长纤维在注塑制品中的取向度,从而获得取向度较低的皮层结构,以诱导长纤维在注塑件空间内形成连续、均匀的三维网络结构,从而明显提高制品的力学性能。对不同尺度混杂填充长纤维注塑微观结构的比较分析结果表明:加入纳米尺度第二相碳纳米管(CNTs),在基体黏度提高和CNTs、长纤维交互作用的双重影响下,增加了纤维沿着基体流动方向的阻力,改变了纤维的取向,降低了注塑制品皮层的纤维取向度。但是,由于树脂黏度提高,对纤维的剪切作用增强,纤维折损率加大,其强化效应有所减弱。比较而言,长碳纤维与长玻纤混杂填充,由于纤维间的相互搭接形成的三维骨架结构,既降低了制品微观结构取向度,又提高了制品的力学性能。以自制的长纤维增强PP材料注塑成型了汽车座椅骨架,验证了该微观结构调控的有效性。

Taking long glass fiber reinforced polypropylene(PP)injection molded products as the research object,the orientation degree of long fiber in the injection molded products was regulated by introducing the micro and nano scale second reinforcement phase,so as to obtain the cortex structure with low orientation degree to induce the long fiber to form a continuous and uniform three-dimensional network structure in the injection molded parts,so as to significantly improve the mechanical properties of the products.The comparison results of injection microstructure of hybrid filled long fiber with different sizes show that under the dual influence of the increase of matrix viscosity and the interaction between carbon nanotubes(CNTs)and long fibers,the addition of nano-sized second phase CNTs increases the resistance of the fiber along the flow direction of the matrix,changes the orientation of the fiber and reduces the degree of orientation of the fiber in the injection molded part.However,due to the increase of resin viscosity,the shear effect on the fiber is enhanced,the fiber breakage rate is increased and the strengthening effect is weakened.By comparison,for the hybrid composites with long carbon and glass fibers,since the three dimensional framework structure formed by lapping fibers,the orientation degree of microstructure and the mechanical properties are both improved significantly.Furthermore,the vehicle seat is taken as an example to verify the effectiveness of control of the microstructure.