EPR (referred to by some companies as EPM) is shorthand for Ethylene Propylene rubber, and is very closely related to EPDM, or Ethylene Propylene Diene Monomer. They are functionally the same thing, and we will refer to them all from here on as EPR.

EPR is most often recommended for steam, water, and automotive brake fluids, but is also excellent with phosphate ester base hydraulic fluids, silicone oils and greases, dilute acids, dilute alkalies, ketones, and alcohols. It also is resistant to Skydrol, sunlight, ozone, aging and weather.  EPR has won broad acceptance in the sealing world because of its excellent resistance to Skydrol and other phosphate ester type hydraulic fluids and in brake systems that use fluids having a glycol base.

EPR has a temperature range of -65-degrees to +300-degrees, with special compounds to +400-degrees.

EPR is not compatible with mineral oil products such as oils, greases and fluids.

Standard durometer, or hardness, is 70 with special compounds also available in 50 durometer.  They are available in standard and metric sizes and come in black.

EPR offers good wear resistance, good compressions set resistance, moderate short-term resilience and good permeation resistance.

Nov. 10, 2015

Next: We’re going to take a little sidetrack away from o-rings and investigate piston cups.