P-124 is a heat-reactive, brominated octylphenol-formaldehyde resin that conatains methylol groups. P-124 may be used with butyl rubber or other unsaturated elastomers with or without functionality. The presence of functionality allows for a faster cure. P-124 is unique in that it does not require a halogen donor. The use of brominated resins in compounding is especially effective when the rubber may be exposed to heat or repeated use. The rubber will not deteriorate as quickly as rubber crosslinked with other curing agents. P-124 exhibits good processing properties and offers an adequate scorch safety margin in a wide processing range. Rubbers compounded with P-124 exhibit exceptional scorch safety, high temperature stability and excellent dynamic properties. P-124 has a slower cure than P-125 due to a lower bromine content. P-124 has a faint halogen odor, and normal handling precautions should be followed.