... Extremely wide range of chemical adaptability. Cover edge with hot-melt seam welding and ultrasonic welding process, firmly and without ... both inside and outside tube are polypropylene.Welding: a unique hot-melt method, no adhesive,no foreign material off. Main ... , manganese, etc.) as raw material, be screened, after cold isostatic pressing, it is sintered by high temperature, high vacuum porous ,then ...