An ageing study of blends of dodecylbenzene and mineral oil

The practice of backfilling existing paper/mineral oil insulated cables with dodecylbenzene (DDB) in the UK has produced systems where the fluid phase is, in reality, a mixture of these two oil types. This investigation therefore set out to study the ageing behavior of a range of DDB/mineral oil blend systems. Samples ranging in composition from 100% mineral oil to 100% DDB were aged in air (oxidising) and nitrogen (inert) atmospheres and the resulting systems were analyzed using a range of physical and chemical techniques. All approaches produced a consistent picture, demonstrating that the addition of between 10 and 25 % of mineral oil to DDB significantly improves its resistance to ageing under the various conditions imposed in this study. Such blend systems exhibit a combination of properties that renders them superior to either mineral oil or DDB alone.