中文摘要：

采用挤出熔融浸渍工艺制备了长度为12mm的长玻璃纤维（LGF）增强聚丙烯（PP）粒料（LGF质量分数30％），然后经注塑制备了PP／LGF复合材料试样。首先对现有注塑机的喷嘴和止逆装置进行了优化，发现优化后LGF在试样中的三维骨架结构保持性更好，试样的力学性能得到大幅提高。针对注塑机结构优化后剪切分散能力减弱的问题，且为提高LGF在PP中的分散性，在挤出过程中使用张紧轮对LGF施加预张力，发现施加适当的预张力提高了LGF在PP中的分散性，进一步提高了试样的力学性能，但提高的幅度较小。在此基础上，研究了注塑时不同螺杆转速对LGF在试样中的长度分布、平均长度、分散性、三维骨架结构和试样力学性能的影响。结果表明，虽然在较低的螺杆转速下，LGF长度分布相对均匀，保持了较高的平均长度和较好的三维骨架结构，但分散性较差，试样力学性能较低；适当提高螺杆转速可提高LGF的分散性，并能保持一定的三维骨架结构，从而提高试样的力学性能。

英文摘要：

The long glass fiber （LGF） reinforced polypropylene（PP） granules with 12 mm length and 30% LGF were made by the extrusion melt impregnation process, then the PP/LGF composite samples were prepared through injection molding. First of all, the nozzle and non-return valve of the existing injection molding machine were optimized, and it is found that LGF has a better three-dimensional framework structure in the samples and the mechanical properties of the samples are improved significantly after optimization. According to the problem that the shear dispersing ability is weakened after optimizing the structure of the injection molding machine, and to improve the dispersion of LGF in PP matrix, tension wheel was used to exert the tension on LGF during the extrusion process, it is found that the dispersion is improved after exerting the proper tension and the mechanical properties of the samples are further improved but the improvement is slight. On this basis, the influences of different screw rotation speed in the process of injection molding on the length distribution, average length, dispersion, three-dimensional framework structure of LGF in the samples and mechanical properties of the samples were studied. The results show that although LGF has relatively uniform length distribution, keep higher average length and better three-dimensional framework structure under the lower screw rotation speed, but its dispersion performance in the sample is poor, so the mechanical properties of the samples are low. Through increasing the screw rotation speed appropriately, the dispersion performance of LGF can be improved, and the three-dimensional framework structure can be retained to some extent, then the mechanical properties of the samples are also improved.