Functional Group Analysis of the Surface and Cut Surface NBR after Peroxide Cured

Abstract

Acrylonitrile butadiene rubber (NBR, 35 % acrylonitrile contents) cure processing was carried out at different temperatures by rheometer. Surface and cut-surface functional groups were analyzed by X-ray photoelectron spectroscopy (XPS). Surface and cut-surface O element quantities of NBR cured at 140 °C were almost the same (2.1, 2.0 at.%), but much more than the O element content of uncured NBR (0.16 at.%). It means that there are some other chemistry reactions except the peroxide reacted with NBR rubber to get the cross-linking chain. And the oxide functional groups (>*CHOH and >C=O) were made from the O2 which was left in the rubber. However, there are no -COOH on the surface and cut-surface of NBR cured at 140 °C. When the curing temperature is higher than 160 °C, the concentration of O on the surface of the NBR is increasing with the >*CHOH, >C=O and-COOH total functional oxide group number growing up, while the concentration of N1s has contrary trend with curing temperature increasing. It is considered that when the temperature is higher than 160 °C the cross-linking chain on the surface will be broken and the N was getting fewer. And the broken cross-linking chain can not be formed in the internal of NBR so that the concentration of O and N are almost the same as the cut-surface at the different temperature. Then the contact angle of the NBR surface is decreasing with the temperature increase for the increasing of oxide functional groups, while the ones of the cut-surface are same. Therefore, it is found that the surface and the interface of cured NBR after the cross-linking reaction by peroxide DCP have different chemical properties.