Blooming of stearamide (SA) in NBR vulcanizates was investigated for factors such as a bloom weight, nitrile content (AN%) of NBR, the solubility of SA in NBR, relation between the solubility parameters of NBR and SA, and DSC measurement of SA in NBR. The bloom weight decreased with the AN% from 0% to near 29% and the solubility of SA in NBR also increased. In NBR exceeding 29AN%, bloom weight decreased gradually although the solubility decreased. The similar result was obtained in the relation between bloom weight and difference in the solubility parameters of SA and NBR. This shows that either of the two blooming mechanisms is operating in the blooming of SA in NBR. In NBR with low AN%, supersaturation mechanism will explain the blooming of SA well and in NBR with high AN%, energy slope mechanism may be applied for the blooming of SA.
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