超声辅助双螺杆机制备高密度聚乙烯/超高分子量聚乙烯复合材料及性能研究

利用超声辅助双螺杆挤出机制备高密度聚乙烯（PE-HD）/超高分子量聚乙烯（PE-UHMW）复合材料，并考察PE-UHMW含量对复合材料流变性能、结晶行为及力学性能的影响。结果表明，当PE-UHMW的含量不超过2.0 %（质量分数，下同）时，PE-UHMW在PE-HD基体内均匀分散，不存在相分离；由于PE-UHMW的相对分子质量非常大，分子链非常长，缠结程度大，其分子链松驰时间较长，有利于形成结晶前驱体，直至成核，随着PE-UHMW含量的增加，有利于成核，晶核数目明显增加，同时，PE-UHMW与PE-HD的缠结程度变大，约束了PE-HD分子链的运动，使其吸附于晶核心表面，分子链折叠排列形成结晶，最终复合材料体系的结晶度逐渐增大，片晶增厚；加入PE-UHMW后，复合材料的屈服强度、拉伸强度和断裂伸长率均明显提高。

Preparation and Performance of PE?HD/PE?UHMW Blends by Ultrasonic?assisted Twin?screw Extrusion

Ultra high molecular weight polyethylene (PE-UHMW) and high density polyethylene (PE-HD) have a similar molecular composition and structure, and therefore they have relatively good compatibility. In this paper, the PE-HD/PE-UHMW blends were prepared by ultrasonic-assisted twin-screw extrusion, and the effect of PE-UHMW content on the crystallization behavior, compatibility and final mechanical properties of the blends was investigated. The results indicated that the PE-UHMW phase achieved a uniform dispersion without phase separation in the PE-HD matrix at the content lower than 2.0 wt%. As the content of PE-UHMW increases, there is a significant increase in nucleation number for the PE-UHMW domain, which is beneficial to crystallization. Moreover, the degree of entanglement also increases gradually with an increase of PE-HD content. This makes more PE-HD molecules involved in the chain?folding crystallization with the nucleus formed by PE-UHMW, leading to a gradual increase of crystallinity. As a result, the yield strength, breaking strength and elongation at break of the blends were improved significantly with an increase of PE-UHMW content.