EPDM (ethylene propylene diene monomer) is an M-Class synthetic rubber. EPDM is one of the most popular and versatile rubber compounds available. The main properties of EPDM are its outstanding heat, ozone and weather resistance. EPDM rubber has excellent electrical insulating properties and it has good resistance to steam, ketones, ordinary diluted acids and alkalies.

During the manufacture of EPDM sheet rubber, the compound can be cured with either sulphur or peroxide. The choice of curing method is determined by the end-uses and applications which the compound will service. Depending upon which curing method is chosen, there will be differences in the final properties and characteristics of the cured compound. Knowing these differences can be an important factor in selecting the right EPDM gasket material for servicing a specific application.

EPDM Sheet and Gaskets: Peroxide and Sulphur Curing

EPDM compounds cured with peroxide possess a superior chemical and thermal resistance compared to compounds cured with sulphur. Peroxide cured EPDM can withstand temperatures up to 150°C (300°F) whereas sulphur cured EPDM can only resist temperatures up to 120°C (250°F). The extended temperature service range of peroxide-cured EPDM makes it a preferred choice for producing gaskets to service higher temperature applications.

In addition to extending the serviceable temperature range of EPDM compound, a peroxide cure also improves the heat stability, modulus, compression set and aging resistance of the compound. Peroxide-cured EPDM also has less tendency to bloom and better preserves its colour during the curing process. Finally, peroxide curing of EPDM promotes co-polymerization of the compound with polymerizable plasticizers or agents designed to give controlled hardness and stiffness to the final product.

Sulphur-cured EPDM generally exhibits higher tear and tensile strength. These properties may be important in applications where higher strength and resistance to tearing are desired. The following table summarizes the essential differences between peroxide-cured and sulphur-cured EPDM sheet:

Peroxide-Cured EPDM Sulphur-Cured EPDM
· Higher temperature resistance · Higher tensile strength
· Good resistance to ageing · Higher tear strength
· Lower compression set · Permits use of a wider range of fillers
· Improved resistance to chemicals and oils
· Unlikely to bloom or discolour
· Will not stain metals or PVC

At CRG, we stock a wide selection of EPDM compounds, including commercial, FDA, and peroxide- and sulphur-cured grades. Other grades are available upon request.  Our in-house capabilities for producing gaskets from EPDM compound include waterjet cutting (for high tolerances and precision), flash cutting (for exceptionally smooth edges), die cutting (for small to medium production runs), and hand cutting.  To find out more about the EPDM sheet and gaskets we can supply, please contact our sales department at crg@canadarubbergroup.com.

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