微型注塑PA6/石墨烯复合材料的结晶与力学性能

为制备综合性能优良的尼龙6(PA6)/石墨烯(Gr)复合材料微型齿轮等微型传动制件,采用固相剪切碾磨(S~3M)技术制备了尼龙6 (PA6)/石墨烯(Gr)复合材料并进行微型注塑,通过偏光显微镜(PLM)、扫描电镜(SEM)、透射电镜(TEM)、差示扫描量热仪(DSC)、万能材料试验机等表征手段,研究了微型注塑条件对PA6/Gr微型样品的微观形貌、结晶行为和力学性能的影响.结果表明:纯PA6和PA6/Gr微型制品均呈典型的"皮-芯"结构,且后者随模具温度和注射速率的增加,皮层厚度减少,剪切层厚度增加;相对于纯PA6,PA6/Gr微型样品的剪切层厚度更小;采用固相剪切碾磨实现了Gr的片层剥离及其在PA6基体中的良好分散,增加注射速率有利于Gr的片层剥层;Gr的加入和微型注塑有利于PA6晶的形成,微型注塑条件下,降低模具温度和增加注射速率均对PA6晶的形成有促进作用;加入Gr、增加模具温度和提高注射速率均会明显提高PA6/Gr微型样品的屈服强度,但会导致相应断裂伸长率的降低.

Crystallization behaviors and mechanical property of PA6/graphene composites prepared by microinjection molding

In order to prepare polyamide 6/graphene (PA6/Gr) composite micropart such as microgear with good comprehensive performance, solid-state shear milling (S³M) technology was used to prepare PA6/Gr composite and the corresponding microinjection molding was conducted. The influence of the microinjection molding condition on the microscopic morphology, crystallization behavior, and mechanical property of the prepared PA6/Gr composite was accordingly investigated by characterizations including polarized optical microscope (PLM), scanning electronic microscope (SEM), transmission electron microscope (TEM), differential scanning calorimeter (DSC), and universal material testing machine. Results show that the typical skin-core morphology was proved perpendicular to the flow direction in both pure PA6 and PA6/Gr microparts. For the latter, with increasing mold temperature and microinjection speed, the thickness of skin layer decreased while that of shear layer increased. Compared with pure PA6, the shear layers of PA6/Gr microparts were thinner. The very strong shear force field during pan-milling proved to be beneficial to the exfoliation of Gr layers and the improvement of their dispersion in PA6 matrix. The increase in the microinjection speed was also advantageous to the exfoliation of Gr layers. It was also found that the incorporation of Gr and the microinjection molding are equally beneficial to the formation of PA6 crystal. Under microinjection molding conditions, decreasing molding temperature and increasing microinjection speed could both promote the formation of PA6 crystal. In addition, the incorporation of Gr, the increase in molding temperature and microinjection speed could equally significantly improve the yield strength of PA6/Gr composite, but would lead to the reduction in the corresponding elongation at break.