Figure 9 summarizes the comparison of accelerated aging test
results among various sulfur compounds. This figure shows the
ECT in the test condition “with oxygen, with copper catalyst”
after 100 h of heating when the most outstanding increase of the
ECT was detected. Black bars indicate the ECT with reverse
polarity. Changes of the ECT beyond 1,000 pC/ml were
detected in alkyl benzene with sulfide, thiol, sulfoxide and
sulfonic acid compounds.