Icephobic silicone coatings on epoxy substrate
In winter, when the trains run at high speed, snow that falls on the track is easily drawn onto the bottom of the train, and quickly forms ice. Researchers present a facile solution for the problem.
The icing at the train bottom may cause serious safety issues. For a new study, epoxy resin was used as a primary coat and a hydroxyl-terminated silicone oil (PDMS) was coated on it. Siloxane, with amido or epoxy terminal group, named KH 550 or KH 560, respectively, was used as a co-crosslinking agent of the epoxy and PDMS in order to ensure high adhesive strength between the two layers.
The hydrophobic, icephobic and mechanical properties of the coatings were characterised by contact angle measurements, ice-adhesion tests and tensile tests, respectively. The results show that the contact angle of the PDMS coating crosslinked by the KH 550 reaches 114.1°, and it can still show good hydrophobic properties after being immersed in water for 10 days. The adhesive strength of the ice on the PDMS coating is only 2.5% of that of ice on the epoxy coating. The low surface energy and the low elastic modulus should be responsible for the excellent icephobic properties.
High speed trains in winter
Moreover, the bonding force between the PDMS coating and the epoxy primer is also excellent. When the KH 560 was used as the co-crosslinking agent, the hydrophobic and icephobic properties of the top PDMS coating were improved due to its week polarity compared with KH 550. As the researchers point out, the study will be helpful in resolving the problems associated with the running of high speed trains in winter or the electric power system which requires resistance to freezing rain.
The study has been published in Progress in Organic Coatings, Volume 161, December 2021.
