天天操天天射综合网-91国产高清在线观看-又黄又摸又爽的视频-国内揄拍国内精品少妇av-性v天堂,香蕉久久夜色精品国产更新时间,67194在线观看国产,亚洲国产视频一区色哟哟

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.