Enhanced Insulation Strength of Meta-Aramid Paper by Co-Modification of Chopped Fiber With Plasma Discharge and Coupling Agent

The interface of fibers and fibrids is a key factor for the insulation strength of meta-aramid paper. In this article, a co-modification method of plasma discharge and coupling agent treatment for chopped fibers is proposed. By optimizing the plasma treating time, the surface hydroxyl groups are introduced to facilitate the grafting of coupling agents. Among three kinds of coupling agents, including amino-propyl-triethoxy-silane (AP), glycidyletheroxy-propyl-triethoxy-silane (GP), and mercapto-propyl-triethoxy-silane (MP), AP shows the best effect on improving the article breakdown strength, which reaches 28.3 kV/mm, 25% higher than the unmodified one. The modified papers showed compact paper structures, reductions of electrical conductivity, and deepening of carrier trap curve. Through the molecular dynamics (MD) simulation, we found that the coupling agent containing hydrogen bond (H-bond) donors rather than acceptors, namely AP, is easier to form new interface H-bonds with precipitated fibrids and does not consume intrinsic H-bonds with chopped fibers, and thus performs better on the fiber-fibrids interface interaction.