The two main parts of a rotary shaft seal are a rigid outer case and the flexible sealing lip (typically made of an elastomeric material). The outer case provides the stiffness and structure needed to keep the seal stable, and protects the lip during installation.
A popular choice for the sealing lip is PTFE, better known as Teflon. Its chemical compatibility, low friction, and outstanding performance at high speeds have made it a favorite among engineers. However, what is the best case material to combine with a PTFE lip for rotary shaft seals?