PTFE is a really specific thermoplastics, as it shows ultra high viscosity above melting point. Thus PTFE can’t be directly melted.
PTFE requires then specific processes. It is first shaped with presintered forms : PTFE powder is first compressed to the desired shape, in the corresponding mold, then left to dwelling. Only after these steps, the presintered form is sintered in oven above PTFE melting point. Strong knowledge of PTFE grades or compounds, and calculation of presintered form during this step are essential to produce state of the art parts, at a competitive price. Molds and sintering processes are designed to diminish or even delete machining for fine tolerances.
For enhanced performance, different molding technologies are available. The most common molding process of PTFE is based on axial molding, where molding pressure is applied on ends of the mould. For more complex parts and better properties, one solution is isostatic molding, where the mold is fitted in a chamber fitted with fluid. When pressure is applied to the chamber, it is equally applied on all the surface of the mold, thus allowing uniform properties.
Such know-how in the particular transformation steps, developed at 3P for more than 50 years of PTFE transformation, is also a strong asset in molding solutions for the other high performance plastics, including the 3P’s Xytrex® range.