cellulosic paper
Ingredients
cellulose, wood, cotton, lignin, manilla, mineral insulating oil
Preparation Steps
Original Recipe Text
The paper samples were aged in the laboratory under controlled conditions in air and mineral insulating oil (p. 2894). For spectroscopic analysis, samples were cut into small strips (approximately 5 x 20 mm^2) and placed in standard sample cups for NIR reflectance measurement using an ATR detector over the range 300–2500 nm (p. 2894). To remove the masking effect of free water in the carbonyl region (1600–1700 nm) of the FTIR spectrum, samples were dried and exposed to a controlled D2O atmosphere, which replaces H2O with D2O (p. 2894). Crystallinity indices were determined using specific IR peak ratios (1280/690, 1430/900, 2900/1370) and by rates of derivatisation with trifluoroacetic anhydride (TFAA), followed by XPS measurement of surface fluorine concentrations (p. 2894).
Evidence
"Large electrical transformers are insulated with cellulose-based paper and mineral insulating oil, which also serves to cool the windings. The paper ages under the influence of heat, air and moisture and eventually loses all mechanical integrity, at which point the risk of failure due to damage to the insulation increase dramatically"
Remarks
The study investigates the aging of Kraft papers and other cellulosic materials used as electrical insulation. Aging results in oxidation, producing carbonyl and carboxyl ligands (p. 2893). The rate of development of a carbonyl band at 1710 cm^-1 during aging in air yielded an activation energy of 98 +/- 10 kJ/mol (p. 2896). NIR spectra were analyzed using PCA, identifying water/OH features as dominant, but also noting development of carbonyl/carboxyl overtones in the 1700–1900 nm region (p. 2898). The study demonstrated that NIR could successfully distinguish between paper types from different manufacturers, such as Tullis Russell all-wood paper versus wood/manilla blends, and estimate the age of samples with a standard error of prediction of 95 h (p. 2896, 2899). De-hydroxylation during aging was identified as a more likely cause for decreasing accessible hydroxyl groups than changes in crystallinity (p. 2897, 2899).