2-FAL is formed primarily by thermal or hydrolytic degradation of glucose, usually by elimination at carbon atom 2 and thus it has been proposed that the furan compounds of Kraft paper degradation would originate via hydrolytic degradation processes of the glucose monomer or via degradation of pentosans, compounds found in electrical insulating Kraft paper in lower concentrations (7-8%).

The formation of furan compounds through the thermal degradation of cellulosic insulation paper, cellulose can be the main source of 5-HMF and the second largest source of 2-FAL in kraft paper. On the other hand, compared to cellulose, pentosans are four times more susceptible to thermal degradation when subjected to the same thermal aging conditions.        HOR05FTHP26

In addition, it has been shown that the deterioration of pentosans does not cause detectable amounts of 5-HMF, upholding the theory that 5-HMF is usually generated from the degradation of six-carbon (hexoses) sugars, such as glucose.

The paper / IMO insulating system was aged in sealed tubes under inert atmosphere with different water contents and a correlation was verified between the concentration of degradation byproducts, the GP and the mechanical strength of the paper samples.