Effect of pulp and cellulose nanofiber cyanoethylation on the physical properties of transformer insulating paper

The properties of transformer electrical insulating papers are influenced by chemical modification process conducted on fibers. In this research, cyanoethylation of pulps and addition of cyanoethylated cellulose nanofiber (CNF) on dielectric properties involving capacitance, dielectric loss, insulation resistance, breakdown voltage as well as tensile strength of two grade of handsheets made of unbleached long fibers and its mixture with bagasse soda pulp(with the ratio of 1:1) were evaluated after impregnating with mineral oil. In this regard, cyanoethylation of CNF and pulps was performed by grafting of acrylonitrile under alkaline condition at 40 ̊C and room temperature respectively. Then, the nitrogen content of cyanoethylated samples was determined by Kjeldahl method and degree of substitution (DS) calculated. The results showed that cyanoethylation of pulps and CNF caused to decrease capacitance and tensile strength of insulated papers. It was also observed that the chemical modification had slight effect on dielectric loss, but insulation resistance and dielectric voltage were increased.