Fabrication of pH-sensitive cellulose colorimetric papers for rapid detection of water content in transformer oil

The combination of highly hydrophilic plant fiber and water molecule sensitive material can effectively detect the water content in transformer oil. In this study, two types of rapid response cellulose colorimetric papers (Rp and Bp) were fabricated through a simple impregnation method, with cellulosic fiber serving as the substrate, cresol red/thymol blue as the color developer, boric acid as the pH regulator, and silica aerosol as the filler. Rp and Bp were tested and analyzed using various characterization methods, and their performance in detecting bound water content in transformer oil was investigated. The results indicate that Rp changes from magenta to light yellow and Bp changes from lavender to light yellow with the increase of water content of transformer oil. The water content detection accuracy of both is 92 % and 95 %, respectively. The rapid color change of them is due to boric acid's acidity triggering molecular structure changes in the color developers. After six cycles of use, Rp and Bp still exhibited excellent color-changing properties. Therefore, colorimetric papers have the attributes of rapidity, high efficiency, low cost, and desired accuracy, providing an alternative approach for evaluating transformer oil's water content and showing promising application potential.