Yilmaz Galip, Ellingham Thomas, Turng Lih-Sheng
Polymer Engineering Center, Department of Mechanical Engineering, University of Wisconsin⁻Madison, Madison, WI 53706, USA.
Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI 53715, USA.
Polymers (Basel). 2017 Dec 30;10(1):36. doi: 10.3390/polym10010036.
The processability of injection molding ultra-high molecular weight polyethylene (UHMWPE) was improved by introducing supercritical nitrogen (scN₂) or supercritical carbon dioxide (scCO₂) into the polymer melt, which decreased its viscosity and injection pressure while reducing the risk of degradation. When using the special full-shot option of microcellular injection molding (MIM), it was found that the required injection pressure decreased by up to 30% and 35% when scCO₂ and scN₂ were used, respectively. The mechanical properties in terms of tensile strength, Young's modulus, and elongation-at-break of the supercritical fluid (SCF)-loaded samples were examined. The thermal and rheological properties of regular and SCF-loaded samples were analyzed using differential scanning calorimetry (DSC) and parallel-plate rheometry, respectively. The results showed that the temperature dependence of UHMWPE was very low, suggesting that increasing the processing temperature is not a viable method for reducing injection pressure or improving processability. Moreover, the use of scN₂ and scCO₂ with UHMWPE and MIM retained the high molecular weight, and thus the mechanical properties, of the polymer, while regular injection molding led to signs of degradation.
通过将超临界氮（scN₂）或超临界二氧化碳（scCO₂）引入聚合物熔体中，注射成型超高分子量聚乙烯（UHMWPE）的加工性能得到改善，这降低了其粘度和注射压力，同时降低了降解风险。当使用微孔注射成型（MIM）的特殊满射选项时，发现分别使用scCO₂和scN₂时，所需的注射压力分别降低了30%和35%。对加载超临界流体（SCF）的样品的拉伸强度、杨氏模量和断裂伸长率方面的力学性能进行了研究。分别使用差示扫描量热法（DSC）和平行板流变仪分析了常规样品和加载SCF的样品的热性能和流变性能。结果表明，UHMWPE的温度依赖性非常低，这表明提高加工温度不是降低注射压力或改善加工性能的可行方法。此外，将scN₂和scCO₂与UHMWPE和MIM一起使用时，聚合物保留了高分子量，从而保留了其力学性能，而常规注射成型则导致了降解迹象。
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