Special combinations of polymers and dyes activate the self-healing power with the help of solar radiation. They can better protect the surfaces of cars, smartphones and building materials and make scratches disappear.
Car paint is like a protective layer. However, they can withstand mechanical forces or other influences only to a limited extent and there is a risk of scratching. Scientists are currently working on how to better protect the surfaces of vehicles. They rely on self-healing, which is said to be triggered by exposure to sunlight. Certain requirements are made of the material for such an additional protective layer: it must be colorless and transparent. After all, it should not cover the actual color of the car paint. In addition, self-regeneration must be possible, which severely limits the choice of materials. Since free-moving particles are essential for self-healing, then the lifetime is rather low. On the other hand, materials with particular hardness weaken in terms of their self-healing function.
Research team Jin Chul Kim, Young il Park and Ji-Eun Jeong of the Korean Institute of Chemical Technology (KRICT) has succeeded in developing a transparent coating material that meets all the necessary properties. In preliminary tests, engineers were able to repair surface scratches within 30 minutes using solar radiation. They built a car model for this purpose. They applied the coating with a special spraying machine. They then exposed the car model to the midday sun for about 30 minutes. Then the scratch disappeared completely and the surface of the coating material was again intact.
A special polymer coating makes scratches on the surfaces disappear
The principle of self-healing works as follows: the newly developed material absorbs sunlight. As a result, the surface temperature increases. This is based on the conversion of light and heat energy. Increased surface temperature causes the surface scratch to regenerate itself. This is because of the interplay of decomposition and rearrangement of chemical bonds in the polymer structure.
The research team used a commercial coating resin to which a dynamic chemical bond, in particular a special urea structure, was added. This substance helps to break down and reassemble the polymer structure. In addition, they mixed with a transparent photothermal dye that actively enables dynamic chemical bonding when exposed to sunlight.
A special polymer coating can absorb light well, so that scratches disappear
There have already been trials with photothermal dyes, which, however, consisted of inorganic materials. However, they were not so easy to apply in industrial applications, mainly because the coating material was not transparent thereby. Moreover, these inorganic materials require a particularly large amount of light energy to produce the photothermal effect. Therefore, the research team relied on transparent organic photothermal dyes. They absorb light very similar to infrared radiation well. In addition, they can be easily mixed with a variety of paints and are inexpensive to produce.
The newly developed coating material is to be used in the future, for example, in smartphones, computers, building materials or in transport applications. Scientists also see great potential in vehicles – mainly because the material can help reduce CO2 reduce. Because, especially when vehicles need to be repainted, mainly organic solvents are used, which are harmful to people and the environment. Replacing these solvents with a new coating material is getting closer to CO2-Neutrality significantly.
Special polymer coatings can be used in many different ways
“The developed technology is a platform technology that synthesizes self-healing coating materials using both cheap commercial polymer materials and photothermal dyes. We expect that they can be used not only in car clearcoats, but also in many other application areas, ”Jin Chul Kim, KRICT Research Director concludes this research project. The state-funded research institute KRICT has existed since 1976 and is dedicated primarily to research and development technologies for chemistry, industry and related fields. The Ministry of Science also supported the research.
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