CROSS-LINKING OF POLYBUTADIENE RUBBER WITHOUT ANY VULCANIZATION AGENT

Polybutadiene rubber with 10% vinyl unsaturation has been crosslinked without the addition of any vulcanization chemicals. The crosslinks ha ve been created through treatment at high temperature (240-250 degrees C) and elevated pressure (<293 MPa) in a plunger type mold. The treat ment time needed to achieve a cross-linked material is of the order of a few minutes and the reaction rate is shown to be dependent upon the temperature as well as upon the pressure applied. As a result of the severe treatment, some degradation reactions may be expected but caref ul FTIR analysis shows no increased oxidation. There is some consumpti on of the vinyl unsaturation, to an amount comparable to the number of crosslinks formed. The presence of carbon black increases the measure d crosslink density, as expected, but at higher pressures the amount o f extra network material, because of the carbon black, is much larger than at lower pressures, suggesting that the carbon black plays a crit ical role in the network formation process. The stress relaxation prop erties in compression of the rubber material were investigated and fou nd to be comparable to those of a peroxide vulcanizate.