INHIBITION OF DETERIORATION OF RUBBERS BY HYDROAROMATICS

Based on the results obtained from our previous works, which concluded that hydrogen donating hydroaromatics can be available as radical scavengers in inhibiting the deterioration of hydrocarbon products at lower oxygen partial pressure, a hydroaromatic type inhibitor which contains various hydroaromatics as its main components produced from coal tar fraction was examined by adding it to natural rubber (NR) and styrene-butadiene rubber (SBR). It was found that the inhibitor was as effective as the conventional amine-type inhibitor. From practical viewpoint, heavy hydroaromatics from petroleum (HHAP) was produced by the hydrogenation of the highly aromatic oil from the heavy fraction of petroleum to improve the physical properties of the previous inhibitor from coal tar fraction. From the deterioration tests for NR, SBR, and chloroprene (CR), the following results could be obtained: (1) HHAP showed excellent inhibiting abilities toward NR and CR, exceeding the conventional inhibitor; (2) inhibiting effect toward SBR could be recognized, but it was not so high as the conventional one; (3) physical properties such as Mooney viscosity and flex cracking were improved by the addition of HHAP. From these results, the hydrogen donation from hydroaromatics is considered to be effective in inhibiting the deterioration of rubbers.