Molecule Diffusion Behaviors of Waterproof Glue into Silicone Rubber Insulation of Submarine Cable Joints Base on Molecular Dynamic Simulation

The repair joint for submarine cable is a pivotal component in the cross-sea interconnection system, which realizes the submarine cable rush repair and rapid restoration of power supply. Current research showed that the molecules from organic waterproof layer for submarine cable joints penetrated into the silicone rubber (SiR) insulation during prequalification tests, which led to the insulation ageing and deterioration. In this paper, the molecule permeation behavior of waterproof sealant molecules into SiR insulation and effect of temperature on it are studied, based on molecular dynamic simulation. The simulation parameters, including free volume, interaction energy and mean square displacement, are employed to evaluate the permeation behaviors of asphalt- and polyurethane (PU)- based waterproof sealant. The results show that, due to the tremendous binding energy between PU and SiR, it does not deeply penetrate, which is indicated that the permeation process of polyurethane-based waterproof sealant is much weaker than that of asphalt-based waterproof sealant. The diffusion coefficients of small molecules from waterproof sealant are enhanced with the increase of temperature. However, the order of diffusion coefficients keeps invariant at any temperature, which is always as follows, Phe > Flu> Pyr > BkF > IcdP > PU. In summary, the polyurethane-based waterproof sealant has a great potential for waterproof layer of submarine high-voltage cable joints.