中文无码第一页,99国产精品偷窥熟女精品视,伊人久久99,无码一起操-巨骚综合网-巨乳色网址-巨乳女上司-巨乳美女脱内衣露巨乳与乳沟-正在播放julia女教师

The tetrafluoroethylene material can be used for a long time at -180～260oC. This material is resistant to acid, alkali and various organic solvents, and it is almost insoluble in all solvents. At the same time, polytetrafluoroethylene has the characteristics of high temperature resistance, its friction coefficient is extremely low, and it does not stick to the reaction medium. Therefore, it is widely used in reaction materials that cannot be tolerated by metal materials.