The performance of Sanitary Diaphragm Valve diaphragm is as follows:

PTFE diaphragm: has good chemical stability and a relatively long service life; this diaphragm is supported by a soft backing material and is available in two forms: double-piece and bonded seal.
Double-piece PTFE: Usually used in valves that are frequently opened and closed, it has a longer service life than bonded diaphragms. When the valve is in the closed position, the spherical contours of the two PTFE pieces can greatly reduce the deformation force on the diaphragm.