Abstract
Liquid PB having various structures were cured with dicumyl peroxide.
Curing curve, infrared spectrum, degree of swelling, crosslinking density, crosslinking efficiency, double bond concentration, double bond consumption efficiency and sol-gel fraction were measured. The ratio of network chain formation per radical to double bond consumption per radical was also calculated.
The vulcanizate of 1, 2-PB was very high in crosslinking density and consumption of double bond. The crosslinking is supposed to proceed by a chain reaction propagated with pendant vinyl groups.
The vulcanizate of 1, 4-PB had a small crosslinking density and a large amount of residual unsaturation. The curing is presumed to proceed by an abstraction of allylic hydrogens.
1, 2-PB containing terminal acrylic groups showed the highest curing rate and crosslinking density. The molecular weight between crosslinks approximated to a butadiene unit.
Hydrogenated 1, 2-PB containing acrylic end groups were also cured very rapidly, but the crosslinking density was moderate.
It is supposed that highly active acrylic end groups react by a chain mechanism to yield secondary large molecules, which then crosslink intra- and intermolecularly.
