Organic peroxides can be used to crosslink elastomers and are especially useful to maximize resistance to heat aging and compression set. Peroxides work by decomposing to form free radicals when heated. These radicals then couple to create carbon-carbon bonds across polymer chains. The carbon-carbon bonds are stronger than the sulfide crosslinks and therefore provide better retention of properties after heat aging.

All peroxides have a peroxy group (-O-O-). What makes certain peroxides more reactive than others? The answer is simply the chemical composition of the rest of the molecule. The general formula for organic peroxide is R1-O-O-R2, where R1 and R2 represent other chemical groups that are bonded to the -O-O- group. Depending on the chemical structure of R1 and R2, the organic peroxides typically used for crosslinking elastomers can be classified as either Diacyl, Dialkyl, Peroxyester and Peroxyketal.

The Dialkyl peroxides are the most commonly used in rubber crosslinking. Peroxyketals are faster curing due to their shorter reaction times but they also are less efficient in saturated polymers. The Diacyl peroxides are commonly used in silicone crosslinking and Peroxyesters are in used polymerization reactions as well as in elastomer crosslinking.

      Diacyl (dibenzoyl)

      Dialkyl ("bis", dicumyl, DBPH)

      Peroxyester (TBPB)

      Peroxyketal (230, 231)