Researchers are designing a coat with a waterproof polymer layer that can heal itself after scratches and tears.
The work is a collaboration between the Norwegian research institute SINTEF and Helly Hansen, and will aim to produce more robust clothing for fishermen.
‘Clearly they [fishermen] are in one of the most dangerous and challenging work environments, so if you can prolong the life of the waterproof it can make them more comfortable and safer,’ said project collaborator Dr Stephan Kubowicz of SINTEF.
The fishing industry still tends to use traditional oilskin clothing, based on heavy cotton cloth waterproofed with linseed oil or sailcloth with a thin layer of tar.
The SINTEF team has previously worked with polyurethane, which is applied in liquid form to the surface of the underlying textile and then hardens. However, it wanted to go a step further and introduce a self-healing capacity and so looked at some basic research being performed in labs worldwide.
‘We considered some different self-repairing mechanisms where the polymer chains rearrange themselves, but the problem was you need higher temperatures to make this happen — higher than room temperature — so it wasn’t suitable for outdoors,’ Kubowicz told The Engineer.
The SINTEF researchers came up with the idea of introducing polymer micro-capsules containing a glue-like substance, into the polyurethane coating at the liquid solution stage.
After preparation, if the coating tears the capsules burst in the damaged area and sealant content is released, which hardens when it comes in contact with water and air — in essence ’healing’ itself.
‘The challenge is, they [the micro-capsules] have to be stable enough to withstand small stresses in preparation and production of the textile, but on the other hand they should break if the coating is damaged,’ Kubowicz said.
In addition he said that lab tests of textile swatches had shown that, following a tear, the adhesion at the joints is still mechanically weak and so they are experimenting using different types of glue and increasing the number of capsules.
The textile work is actually part of the wider EU Safe@Sea project, which is also investigating the potential of flotation devices and wireless alarm functions in clothing for ‘man-over-board’ incidents.