Polytetrafluoroethylene (PTFE) is a widely used chemical in many applications. Its properties are excellent at sonic frequencies, high temperatures, and protection from chemicals. PTFE is highly flexible and can be used for a variety of applications.
PTFE pastes are used in wire coating processes. They are similar to polymer melts in rheology. However, PTFE preforms exhibit a significant density decrease as a result of stretching. This results in increased elongational strain.
A study of the effects of lubricant properties on PTFE pastes was conducted. The effect of die geometry on PTFE paste extrusion was also investigated. In particular, the influence of the reduction ratio on the extrudate tensile strength was assessed.
Lubricant viscosity is one of the most important factors affecting the PTFE paste extrusion process. PTFE pastes are usually mixed with a lubricant. Ideally, lubricant should have a surface tension that is lower than that of PTFE. This would minimize migration effects.
An Instron capillary rheometer was employed to perform the extrusion experiments. Four zones were used for temperature control. Flow curves were obtained as a function of the geometric characteristics of various dies. These included the length-to-diameter ratio, the entrance angle, and the reduction ratio.
PTFE pastes were conditioned for 24 hours to allow for uniform distribution of lubricant. These were then aged for an additional 24 hours to ensure that they were not affected by liquid migration.
After aging, the PTFE pastes were preformed at a pressure of 2 MPa for 30 s. The resulting PTFE preforms showed an average of 35 degC. Compared to the unaged pastes, PTFE pastes with lubricant were much easier to handle.