Low temperature thermal degradation of cellulosic insulating paper in air and transformer oil

The thermal degradation of cellulose in the form of Kraft insulating paper has been studied in air for up to 140 h and in transformer oil for up to 35 00 h in the temperature range 60-120 degreesC using measurements of the deg ree of polymerization (DP) and (in oil) analysis of furanic degradation pro ducts. Degradation was faster in air than in oil. The DP decreased from the original value of 1.2 x 10(3) to a limiting value in the range of 300-900 depending on temperature and degradation conditions. The variation of the D P with degradation time was consistent with two mechanisms, one in which th e first-order rate constant decreased exponentially with time, and another in which only a limited number of chain bonds were scissionable. The degrad ation rate was first order in scissionable bonds. The major furanic degrada tion products were 2-furaldehyde, 5-hydroxymethyl-2-furaldehyde and furfury l alcohol. Their concentrations continually increased over the timescale of the experiments. (C) 2001 Society of Chemical Industry.