Resole-cured NR vulcanizates with thermally reactedp-t-octylphenol formaldehyde resole

Abstract

Crosslink dissociation of resole-cured NR vulcanizates was studied using steam aging. Four carbon black-filled NR vulcanizates were prepared to investigate the influence of heated p-t-octylphenol formaldehyde resole (at 160°C for 0.0, 1.5, 3.0, and 6.0 h) on the cure characteristics and stability of the crosslinks. By increasing the heating time of the resole, dimethylene ether linkages of the resole decrease while o-methylene quinone intermediates increase. The cure rate of the NR vulcanizates with the heated resole for 1.5 h is faster but those for 3.0 and 6.0 h are slower than that with the unheated resole. In comparison with the vulcanizates containing the nonheated resole, the delta torque of the NR vulcanizate with the heated resole for 1.5 h increases, while those for 3.0 and 6.0 h decrease. The swelling ratios of the four NR vulcanizates decrease after steam aging at 95°C for 7 days. The differences of the swelling ratios before and after steam aging decrease with increase of the heating time of the resole. The decrease of the swelling ratio after the steaming is due to the dissociation of the dimethylene ether linkage in the vulcanizates. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1811–1819, 1998