Expanded polytetrafluoroethylene(ePTFE)is promising in biomedical fields such as covered stents and plastic surgery owing to its excellent biocompatibility and mechanical properties.However,ePTFE material prepared by ...Expanded polytetrafluoroethylene(ePTFE)is promising in biomedical fields such as covered stents and plastic surgery owing to its excellent biocompatibility and mechanical properties.However,ePTFE material prepared by the traditional biaxial stretching process is with thicker middle and thinner sides due to the bowing effect,which poses a major problem in industrial-scale fabrication.To solve this problem,we design an olive-shaped winding roller to provide the middle part of the ePTFE tape with a greater longitudinal stretching amplitude than the two sides,so as to make up for the excessive longitudinal retraction tendency of the middle part when it is transversely stretched.The as-fabricated ePTFE membrane has,as designed,uniform thickness and node-fibril microstructure.In addition,we examine the effects of mass ratio of lubricant to PTFE powder,biaxial stretching ratio and sintering temperature on the performance of the resultant ePTFE membranes.Particularly,the relation between the internal microstructure of the ePTFE membrane and its mechanical properties is revealed.Besides stable mechanical properties,the sintered ePTFE membrane exhibits satisfactory biological properties.We make a series of biological assessments including in vitro hemolysis,coagulation,bacterial reverse mutation and in vivo thrombosis,intracutaneous reactivity test,pyrogen test and subchronic systemic toxicity test;all of the results meet the relevant international standards.The muscle implantation of the sintered ePTFE membrane into rabbits indicates acceptable inflammatory reactions of our sintered ePTFE membrane fabricated on industrial scale.Such a medical-grade raw material with the unique physical form and condensed-state microstructure is expected to afford an inert biomaterial potentially for stent-graft membrane.展开更多
文中以医用级高分子聚氨酯(TPU)为原材料,通过热压成型制备厚1.2 mm TPU片材,并制取75×4哑铃型拉伸试样。在电子万能试验机上以较高的恒定拉伸速率进行拉伸,预先设定应力到某一设定值后停止拉伸,然后应力以一定速度进行减载。实验...文中以医用级高分子聚氨酯(TPU)为原材料,通过热压成型制备厚1.2 mm TPU片材,并制取75×4哑铃型拉伸试样。在电子万能试验机上以较高的恒定拉伸速率进行拉伸,预先设定应力到某一设定值后停止拉伸,然后应力以一定速度进行减载。实验探索了整个拉伸-回复循环中应力与应变的关系,研究了拉伸速度对医用级TPU拉伸强度及断裂伸长率的影响,并对拉伸过程中出现应力发白现象进行探究。结果表明,TPU是一种强而韧的硬弹性高分子材料,在高应力大形变下由弹性提供的可逆形变约80%,粘性提供的不可逆形变约20%。在高应力下材料内部孔洞尺寸变大,由此引起材料由透明转而发白,此光学现象可反复发生。展开更多
基金supports from National Natural Science Foundation of China(grant no.52130302)National Key R&D Program of China(grant no.2016YFC1100300)。
文摘Expanded polytetrafluoroethylene(ePTFE)is promising in biomedical fields such as covered stents and plastic surgery owing to its excellent biocompatibility and mechanical properties.However,ePTFE material prepared by the traditional biaxial stretching process is with thicker middle and thinner sides due to the bowing effect,which poses a major problem in industrial-scale fabrication.To solve this problem,we design an olive-shaped winding roller to provide the middle part of the ePTFE tape with a greater longitudinal stretching amplitude than the two sides,so as to make up for the excessive longitudinal retraction tendency of the middle part when it is transversely stretched.The as-fabricated ePTFE membrane has,as designed,uniform thickness and node-fibril microstructure.In addition,we examine the effects of mass ratio of lubricant to PTFE powder,biaxial stretching ratio and sintering temperature on the performance of the resultant ePTFE membranes.Particularly,the relation between the internal microstructure of the ePTFE membrane and its mechanical properties is revealed.Besides stable mechanical properties,the sintered ePTFE membrane exhibits satisfactory biological properties.We make a series of biological assessments including in vitro hemolysis,coagulation,bacterial reverse mutation and in vivo thrombosis,intracutaneous reactivity test,pyrogen test and subchronic systemic toxicity test;all of the results meet the relevant international standards.The muscle implantation of the sintered ePTFE membrane into rabbits indicates acceptable inflammatory reactions of our sintered ePTFE membrane fabricated on industrial scale.Such a medical-grade raw material with the unique physical form and condensed-state microstructure is expected to afford an inert biomaterial potentially for stent-graft membrane.
文摘文中以医用级高分子聚氨酯(TPU)为原材料,通过热压成型制备厚1.2 mm TPU片材,并制取75×4哑铃型拉伸试样。在电子万能试验机上以较高的恒定拉伸速率进行拉伸,预先设定应力到某一设定值后停止拉伸,然后应力以一定速度进行减载。实验探索了整个拉伸-回复循环中应力与应变的关系,研究了拉伸速度对医用级TPU拉伸强度及断裂伸长率的影响,并对拉伸过程中出现应力发白现象进行探究。结果表明,TPU是一种强而韧的硬弹性高分子材料,在高应力大形变下由弹性提供的可逆形变约80%,粘性提供的不可逆形变约20%。在高应力下材料内部孔洞尺寸变大,由此引起材料由透明转而发白,此光学现象可反复发生。
