The weather is getting colder, people put on cold clothes to keep warm. But what if infrastructure such as airplanes, wind turbines, transmission lines and roads are also afraid of the cold? The reporter learned from Tianjin University on November 17 that the team of Professor Zhang Lei from the School of Chemical Engineering of the school successfully developed a "super coating". This new type of coating can put on "cold-proof clothing" for instruments and equipment in outdoor, high-altitude, and high-cold environments, realizing high efficiency, low energy consumption, and no damage to ice and deicing. Related results have been published in the international authoritative journal "Journal of Chemical Engineering".

Traditional methods have low deicing efficiency and high energy consumption

In the high-altitude and high-cold environment, icing on the surface of equipment such as airplanes and transmission lines often causes major economic losses and even catastrophic accidents. The current mainstream deicing methods include electric deicing, hot air deicing, and mechanical deicing. However, these technical methods are generally inefficient and energy intensive. Other de-icing methods based on chemical reagents (such as spraying salt solution) can lower the freezing point of water and reduce ice accumulation on the surface of the equipment, but they are harmful to the environment and corrosive to the surface of metal equipment.

How to prepare an anti-icing and deicing coating that is efficient, energy-saving, environmentally friendly and suitable for high-altitude and high-cold environments has become an important challenge for scientists.

“Currently the more cutting-edge coating materials are often costly or poorly robust, which means they are not durable enough and are easily damaged.” said Yang Jing, a young teacher on the R&D team. “These equipment may be in outdoor environments. Some are still in more extreme environments and will encounter sandstorms. If the robustness and stability of the coating are not good, it will affect the long-term deicing effect."

New materials provide "three insurances" for anti-icing

Zhang Lei's team took a different approach, using new amphiphilic materials combined with photothermal carbon fibers to develop a "super coating" that uses sunlight to generate heat. This super coating combines the hydrophilic segment PVP that can lower the freezing point, the low surface energy material PDMS, and the photothermal carbon fiber that can absorb solar energy. It provides a "triple insurance" to prevent the surface of the device from freezing.

Zhang Lei explained that when the surface of equipment freezes, water often adheres to the surface of the material and then freezes into ice. "We used a hydrophilic segment, which can bind water molecules and lower the freezing point of water, which is equivalent to delaying this process."

The low surface energy material PDMS has a very low adhesion ability and can reduce the adhesion of ice and snow. Just like the non-stick pan has a coating of low surface energy material, it can achieve a non-stick effect when cooking.

"We fuse hydrophilic segments with low surface energy materials to create a new type of amphiphilic coating." Yang Jing introduced that these two materials are hydrophilic and hydrophobic. We all know that hydrophilic and hydrophobic materials cannot They merge with each other, just as water and oil cannot merge. To this end, we connect both ends of the low surface energy hydrophobic segment with hydrophilic segments to form amphiphilic block polymers, and then "weave" this amphiphilic polymer to the cross-linking of low surface energy materials Network. Since there are low surface energy segments in the new segment, it is easy to merge with the cross-linked network. The hydrophilic segments will migrate to the surface of the coating, so that this new type of coating has both the properties of lowering freezing point and adhesion.

Later, Zhang Lei’s team combined this amphiphilic polymer material with carbon nanofibers. The addition of carbon nanofibers can not only absorb sunlight and produce heat and deicing, but also because of its hydrophobicity, it further reduces the adhesion of the PDMS-based coating surface. Focus on. "The surface temperature of the new coating can reach 46℃ under sunlight. It can heat and melt the ice, but also greatly reduces the adhesion of the ice. Only relying on natural conditions such as wind and gravity can make the ice on the surface of the equipment fall off easily "Yang Jing said.

Simple process, low cost, high stability

Experimental results show that the new coating has good stability. After 30 cycles of anti-icing tests, the ice adhesion strength has not changed significantly. And it can withstand acid rain, falling sand, and even 200 times of sandpaper rubbing. Yang Jing introduced that because this new type of coating uses the inherent physical and chemical properties of the material itself, instead of relying on the preparation of microstructures on the coating surface or coating with lubricating oil, the coating’s ice resistance is more stable. Robustness is more prominent.

"This new type of coating utilizes innovative ideas and designs, and the raw material ratio and production process of the coating have yet to be optimized." Zhang Lei said that the cost of the three materials used in the coating is not high, and the production process is better. It is suitable for industrialization, so the prospect of practical application in the future can be expected. It is expected to become a "cold-proof clothing" for various large-scale equipment and precision instruments in high-altitude, outdoor and other environments. "In the next step, we will devote ourselves to developing coatings that can maintain the anti-icing effect under more extreme and harsh environments, and related work is in the process of research."