【作者】 杜小刚；

【导师】 刘亚青；

【作者基本信息】 中北大学 ， 材料学， 2008， 硕士

【摘要】 超临界二氧化碳被广泛地应用于材料制备及改性领域。本文通过采用超临界二氧化碳辅助挤出和与聚丙烯(Polypropylene,PP)共混相结合的手段,对聚四氟乙烯(polytetrafluoroethylene,PTFE)进行挤出成型及改性研究,实现了PTFE在双螺杆挤出机上的连续挤出成型,并系统地研究了挤出过程中超临界二氧化碳对复合材料体系加工流变性能和力学性能的影响。研究结果表明:采用超临界二氧化碳和与PP共混相结合的手段,可以实现PTFE的连续挤出成型;一定量PP的加入,可有效改善PTFE在挤出机中的输送和熔融塑化;超临界二氧化碳的加入可有效降低聚合物体系粘度和挤出压力,显著提高挤出效率。超临界二氧化碳的引入可显著改善聚合物体系的流动性,增大其加工范围,有利于聚合物的高性能挤出。共混物中PTFE的含量越高,超临界二氧化碳的降粘作用就越明显,表明超临界二氧化碳对具有高链缠结密度的高分子熔体的降粘作用更加显著。力学性能测试结果表明:有超临界二氧化碳作用的PTFE/PP体系的拉伸强度、断裂伸长率普遍低于无超临界辅助成型的样品的值,但韧性及抗冲击性能则大大高于无超临界辅助成型的样品的值。更多还原

【Abstract】 Supercritical carbon dioxide has been widely used in preparing and modifying macromolecular materials.In this paper, extruding and modifying PTFE were studied by use of supercritical CO₂ and mix with PP and the continuous extrusion of PTFE through a twin-screw extruder was realized. Influence of supercritical CO₂ on rheological properties and mechanical properties of macromolecular materials system in extrusion process was researched. Results show that the continuous extruding PTFE is realized by use of supercritical CO₂ and PP. Addition of PP improves feeding and melting of PTFE during extrusion. Addition of supercritical CO₂ can reduce melt viscosity, depress extrusion pressure effectively and advance extrusion efficiency obviously. Supercritical CO₂ can make polymer high yield extrusion under low pressure.The addition of supercritical CO₂ can improve fluidity of polymer melt obviously, extend the process range and be useful of macromolecule extrusion. With the increase of PTFE content in the PTFE/PP blend, the effectiveness of melt viscosity reduction is obvious. So the effectiveness of macromolecular melt viscosity reduction effected by supercritical CO₂ is obvious.Mechanical properties results show that the tensile strength and elongation at break of PTFE/PP blend effected by supercritical CO₂ is lower than what isn’t effected by supercritical CO₂, but the toughness of PTFE/PP blend enhance obviously.更多还原