Effects of hydrogen sulfide on the mechanical and thermal properties of cellulose insulation paper: A molecular dynamics simulation

Abstract

Insulation faults caused by corrosive sulfur contained in oil-paper insulation systems in transformers are a key factor affecting the safety and stable of operation of this critical equipment. To date, sulfur corrosion phenomena have been studied from an experimental point of view; however, little attention has been paid to the microscale mechanism of sulfur corrosion. On the basis of molecular dynamics simulations, we analyze the effects of hydrogen sulfide content on the mechanical and thermal properties of cellulose insulating paper in terms of hydrogen bonding, diffusion coefficients, mean square displacement, and mechanical parameters. The results of our kinetic simulations show that the mechanical properties of cellulose decrease as the content of hydrogen sulfide increases. At a hydrogen sulfide content of 8%, the elastic modulus of cellulose decreases by 33.1%, the volume modulus decreases by 46.4%, the shear modulus decreases by 37%, and the glass transition temperature decreases by 83 K. An increase of hydrogen sulfide content weakens interactions between cellulose chains, leading to increased chain motion, which thereby reduces the thermal stability of cellulose. The effects of hydrogen sulfide molecules on the mechanical and thermal properties of cellulose are mainly attributed to the formation of many hydrogen bonds between hydrogen sulfide molecules and cellulose, which destroy the original hydrogen bond network of the cellulose. At a high hydrogen sulfide content, van der Waals forces between cellulose molecules are weakened, lowering intermolecular interactions and reducing the thermal stability of the cellulose.