IIT Bombay’s New Thermally Insulating Coating Material Shows Record Heat Shielding

With the consequences of climate change looming over, the need for innovative and affordable solutions for thermal insulation and space cooling has escalated. A team on engineers from the Indian Institute of Technology, Bombay (IIT Bombay) has achieved a significant breakthrough in passive cooling technology. Led by Prof. Smrutiranjan Parida from the Metallurgical Engineering and Material Science Department, the team has developed a new type of coating material designed to effectively reflect the sun’s heat and reduce heat absorption, providing thermal insulation.

The material, a hydrophobic (water-repelling) epoxy composite coating with fillers, has the capability to reduce heat conduction and impart high infrared reflectance in a thin coating of just about 65 micrometres. Prof. Parida explains, “Our work mainly focused on preparing ‘active additives’ (called fillers), which can be added to a suitable resin to create a temperature shielding coating.” It also protects against corrosion, making it an ideal solution for cooling our living spaces.

Central to the success of the coating are two types of fillers: micron-sized silica-modified hollow microspheres (sHMS) and surface-modified TiO2 nanoparticles. These fillers, when added to a resin such as epoxy, prevent the transfer of heat through the coatings and significantly reflect sunlight, respectively. Prof. Parida emphasizes, “The hollow microspheres have a very low thermal conductivity due to their hollow air-filled structure. The presence of this component in the coating prevents the transfer of heat through the coatings and the TiO2 component is well-known for its higher solar reflectance (>85%).”

Tests conducted by the researchers wherein the coated surface was irradiated using an infrared (IR) lamp, placed at a location giving 60 °C on the surface of the coated metal panel, demonstrated that the composite coating reduced the temperature under the coated panel by 15 to 21 degrees Celsius.

Additionally, the coating exhibited a high solar reflectance of sunlight in the near-infrared (NIR) region of the spectrum, exceeding 72%. Remarkably, despite its thin thickness of just 0.065 to 0.1 millimetre, the new material outperforms other coatings that are typically three to twenty times thicker, making it both efficient and cost-effective.

Moreover, the composite coating showed exceptional resistance to corrosion, with a remarkable 99% corrosion protection efficiency when exposed to Sodium Chloride (NaCl) solution. This feature ensures demonstrates that the coating can protect metal surfaces from the deteriorating effects of their environment, increasing longevity and decreasing maintenance costs.

The use of low-cost materials such as hollow microspheres and a simple manufacturing process makes the coating economically viable for the market. Prof. Parida highlights, “The coating development procedures, including the surface modifications of the fillers, are easy to adopt, single-step, and do not require complex instrumentation. The hollow microspheres used are inexpensive and can be obtained from the industrial waste of coal plants, providing an effective waste management solution.”

Looking ahead, Prof. Parida and his team seek to enhance the coating material by incorporating fire-retardant properties and exploring the production of a VOC (volatile organic compounds)-free waterborne coating system to make it environmentally friendly.

As the world confronts rising temperatures and energy demands, innovative solutions like these are essential for conserving natural resources, reducing emissions, and promoting sustainable development.