Thermal aging of paper and pressboard in mineral and ester oils under air and nitrogen atmospheres

The purpose of this paper is to simulate an accelerated ageing of paper and high density pressboard type B.3.1 in three different liquids (mineral oil MO, natural ester VO and synthetic ester SE) for different periods of ageing at 130°C. The materials were aged in sealed vessels under two different atmospheres: air and nitrogen gaps. The effects of aging on physicochemical properties of oil and cellulose are analyzed and compared. It is shown that ageing rate of pressboard and paper are comparable in each type of oil. Nevertheless, it can be underlined that cellulosic materials are less affected after aging in ester oils evidencing a higher degree of polymerization (DPv). The use of 2-FAL in ester oils remains questionable. The reduction of oxygen content in mineral oil minimizes ageing of oil more than solid insulating materials.