Molecule diffusion behaviours of waterproof sealants into silicone rubber insulation for submarine cable joint based on molecular dynamics simulations

Abstract

Abstract The repair joints of high‐voltage cables play a significant role in the urgent cable maintenance, by recovering cable conductor, insulation, shielding layer and waterproof layer especially for submarine cables. However, the molecule diffusion and permeation processes from waterproof sealant into the cable joint insulation occur, leading to the insulation ageing and deterioration. In this article, the molecule diffusion behaviours of six typical molecules from the asphalt‐based and polyurethane‐based waterproof sealants into silicone rubber insulation are investigated. The results show that the order of diffusion coefficients is as follows, phenanthrene > fluoranthene > pyrene > benzo [k] fluoranthene > indeno [1,2,3‐cd] pyrene > polyurethane (PU). The relative molecular mass and binding energy are pivotal factors affecting the diffusion behaviour, while there is a linear relationship between the logarithm of the diffusion coefficient and the ratio of binding energy to relative molecular mass. Besides, the rising ambient temperature increases the fraction of free volume of silicone rubber and decreases the binding energy, thus resulting in a higher diffusion coefficient and an enhanced permeation process of the asphalt‐based sealant. In summary, the PU‐based waterproof sealant, with a much lower permeability than the asphalt‐based material, has a potential application in the waterproof layer for high‐voltage submarine cable repair joints.

Keywords

• ageing
• binding energy
• cable jointing
• diffusion
• high-voltage engineering
• molecular dynamics method