精细化聚氨酯薄膜鱼眼的形成机理及抑制

以热塑性聚氨酯(TPU)薄膜为样本,研究TPU薄膜表面存在的颗粒状凸起(聚合物鱼眼)的形成机理。文中通过红外光谱、凝胶渗透色谱和扫描电镜等测试手段,充分研究了鱼眼和非鱼眼区域的化学结构和表面形态的差异。凭借差示扫描量热法和热重分析评估其热性能。结果表明,鱼眼区域相对分子质量略高于非鱼眼区域,且两者化学结构不存在显著差异。此外,由于聚氨酯粒料硬段区域氢键聚集,结晶度偏高,制得的TPU薄膜的熔融温度范围为160～200℃,高于工业生产实际加工温度,导致结晶部分不能完全熔融,未熔融颗粒冷却形成鱼眼。研究反驳了工业上将聚合物鱼眼视为物理杂质或超高相对分子质量聚合物的理论,为降低TPU等一类低结晶度聚合物薄膜鱼眼含量提供了理论依据。

Formation Mechanism and Inhibition Method of Thermoplastic Polyurethane Film Fisheyes

The process improvements for the preparation of high performance polymer films are in urgent demand due to the defect of film products,especially granular bulges(fisheyes)existing on the film surface.In this work,thermoplastic polyurethane films were used as samples to find out the formation mechanism of polymer fisheyes.The differences in chemical structure and surface morphology of the fisheye and non-fisheye portions were fully studied by FT-IR,GPC and SEM.The thermal properties were evaluated by DSC and TG.The results reveal that the fisheye portion has a slightly higher molecular weight than the non-fisheye portion,and there is no significant difference in chemical structure between the two parts.More importantly,it is observed that the fisheye portion gets the higher hydrogen bond contents and crystallinity,while the melting temperature of TPU film ranges from 160℃to 200℃,which is higher than the current processing temperature.Thus,the crystalline part cannot melt completely,and the unmelted particles cool down to form fisheyes.The research not only refute the previous theory of regarding fisheyes as physical impurities or ultra-high molecular weight polymers,but also help us to propose theoretical ideas of reducing the fisheye content of polymer films.