Thermoset or Phenolic (Bakelite) caps are known for providing the widest range of chemical compatibility and for being the most temperature tolerant of plastic closures. They also provide the most consistent adherence to close dimensional tolerances. Ideal for pharmaceutical applications. Thermoset closures cannot be remelted after they are formed. Common resins include urea, phenolic, and melamine.
Foam backed PTFE liners resist attack from virtually all chemicals at room temperature and provides resilience for a tight seal with a low moisture transmission rate. F217 has a low density foam core between two solid layers of LDPE. Uses include: Analytical lab samples, high purity chemicals, strong acids, solvents, environmental samples, pharmaceuticals, and diagnostic reagents