UHMWPE初生态微观结构及不同成型条件下制品力学性能研究

Research on the microstructure of UHMWPE primary particles and mechanical performances of products under different processing conditions

超高分子量聚乙烯(UHMWPE)极高的分子量及线性分子链特性使其具备很多的优异性能,在军工、医药卫生等领域的应用越来越广泛的同时,对UHMWPE树脂的性能不断提出更高的要求。故利用高分辨扫描电镜(SEM)、高温凝胶色谱-红外联用(GPC-IR)、拉曼光谱(Raman)及差式扫描量热仪(DSC)对树脂初生态粒子的结晶结构、分子特性及热力学性能进行了研究,并通过控制模压过程中的冷却速率来研究UHMWPE样品的结晶行为,进而分析UHMWPE微观特性与宏观性能之间的关系。研究发现由次级颗粒和微纤组成的UHMWPE初生态粒子中具有大量的片晶和伸直链,分子链排列规整,结晶度高;但在熔融再结晶加工成制品的过程中,分子链的规整性遭到破坏,与初生态粒子相比,结晶度下降、缠结密度变大。另外,不同降温速率的样品中淬冷样品的分子链缠结密度最低,而低缠结、小的晶粒能够提升制品的耐冲击性能及断裂时的真应力。

Ultra-High Molecular Weight Polyethylene(UHMWPE)possesses extremely high molecular weight and linear molecular chain with excellent performances,and the molded products are widely used as structural materials in military,medical&health and other fields.In this paper,high-resolution scanning electron microscopy(SEM),high temperature gel chromatography-infrared(GPC-IR),Raman spectroscopy(Raman)and differential scanning calorimetry(DSC)were used to study the crystal structure,molecular properties and thermodynamic properties of the primary powders.The crystallization behavior of UHMWPE samples was also investigated at different cooling rate during molding to determine the relationship between the microscopic morphology and the macroscopic properties.Results show that the primary particles are composed of sub-particles and fibrils,and exhibit high crystallinity with the neat arrangement of the macromolecule chains.However,this regularity would be destroyed during melting and recrystallizing.As compared with the primary powder,the crystallinity of the molded sheets decreased;while its entanglement density increased.In addition,the quenched sheets reveal the lower entanglement density and smaller crystalline size,thus resulting in strong impact resistance and great true fracture stress.