Polarity, thermal stability, and hydrophilicity of three-layer crosslinked PPTA/cellulose composite insulation system: Molecular dynamics simulations

Abstract

Preparing a novel insulating paper with relatively low dielectric constant, enhanced thermal stability, and low hydrophilicity has always been the research hotspot of the transformer insulation industry. This paper constructed a three-layer cross-linked poly-p-phenylene terephthalamide (PPTA)/Cellulose composite structure and explored its polarity, thermal stability, and hydrophilicity by molecular dynamics simulation. Results showed that the introduction of PPTA and constructing crosslinking network between the molecules could reduce the polar group density and molecular polarizability of the cellulose system; The three-layer crosslinked system has a 34.1% lower dielectric constant than the pure cellulose system. And the tensile modulus of the three-layer crosslinked structure is up to 92.1% of that of the pure cellulose system; The three-layer crosslinked system has a higher glass transition temperature (Tg) and a lower molecular chain mean square displacement (MSD), compared to the pure cellulose system. The results of the water diffusing from the outside into the fiber system and moving in the fiber system indicated that the three-layer crosslinked PPTA/Cellulose composite system had lower hydrophilicity than the pure cellulose system. This study provides a design basis for the development of the novel high-performance composite insulating paper.