Why PTFE Processing Method Is Difficult

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. But the processing method of PTFE is difficult and expensive. Why?

Because the high melting temperature 327 °C (621 °F) is above the initial decomposition temperature 200 °C (392 °F). Even when melted, PTFE does not flow, but instead behaves as a gel due to the absence of crystalline phase and high melt viscosity. So, some PTFE parts are made by cold-moulding, a form of compression molding. Here, fine powdered PTFE is forced into a mould under high pressure (10 ~ 100 MPa). After a settling period, lasting from minutes to days, the mould is heated at 360 to 380 °C (680 to 716  °F), allowing the fine particles to fuse into a single mass. 

By this kind of method, PTFE can be made into semi-finished products, like PTFE sheet, tube and rod. Then, it can be further made into thin film and precious machined parts after second processing. PTFE sheets, tubes and rods are widely used in aerospace, chemical industry, electronic, medical fields.