淬火工艺对聚四氟乙烯结晶度、拉伸性能和硬度的影响

Influence of Quenching Methods on Crystallinity,Tensile Properties and Hardness of Polytetrafluoroethylene(PTFE)

采用冷压-烧结工艺制备了聚四氟乙烯(PTFE)材料,考察了随炉冷却以及4种淬火冷却工艺对PTFE材料结晶度、拉伸性能和硬度的影响,这些淬火工艺包括:(1)25℃空气淬火,(2)10℃水淬火,(3)0℃冰水混合液淬火,(4)-25℃酒精干冰混合液淬火。结果表明,与随炉冷却工艺相比,4种淬火工艺都降低了PTFE的结晶度、拉伸屈服应力、拉伸强度和硬度,都提高了PTFE的断裂伸长率。除了酒精干冰混合液以外,PTFE的结晶度、拉伸屈服应力、拉伸强度和硬度都随着冷却介质温度的降低而降低。伸长率的提高和硬度的降低意味着材料柔韧性的提高,可见淬火工艺提高了PTFE的柔韧性。酒精干冰混合液对结晶度的影响与空气的相近,但是会引起材料表面不平整。相比之下,常温下的水是一种高效而实惠的提高PTFE柔韧性的淬火介质。

Polytetrafluoroethylene（PTFE） sheets were prepared by molding-sintering method.Influences of natural cooling in the furnace and 4 kinds of quenching methods on crystallinity,tensile properties and hardness of PTFE were investigated.These quenching methods include（1） quenching using air at 25℃,（2） quenching using water at 10℃,（3） quenching using mixture of water and ice at 0℃,（4） quenching using mixture of carbon dioxide ice and alcohol at-25℃.The results show that,compared with natural cooling in the furnace,quenching methods in this experiment lowered crystallinity,tensile strength and hardness of PTFE,but increased its elongation.Except quenching using mixture of carbon dioxide ice and alcohol at-25℃,crystallinity,tensile strength and hardness of PTFE would decrease with decreasing the temperature of cooling medium.All quenching methods in this experiment improved flexibility of PTFE.It was found that water is effective quenching medium to increase flexibility of PTFE.