In this project, nanosized capsules containing salt hydrate phase change materials for thermal energy storage were developed for coating applications. These capsules were then added to paints to create a zero-energy thermoregulation system for buildings. The development of a reliable capsule synthesis has required much trial and error to fit them to the current commercial paint formulations. We have tested several shell materials:
• Polyurethane – some results have been obtained using both surfactants and Pickering emulsifiers.
• Polydopamine – initial plans were to make polydopamine capsules, which could then be coated with a silver layer. However this was shelved due to lack of results/more promising results elsewhere.
• Polyethylcyanoacrylate (PECA) – this can be used in conjunction with Pickering emulsifiers or surfactants.
• Silica – the most successful synthesis. Nanocapsules can be fabricated using Pickering emulsifiers, creating silica-silica core-shell nanocapsules. Both acidic and basic catalysts can be used, giving different products.
• Halloysites, the most cheap and robust solution for commercial applications because halloysites are raw nanocontainers which can be mined and used in the thermo-responsive paints.
Major results
• Reliable synthesis has been developed to produce all-silica nanocapsules, with sizes from 500-1000 nm. This has not previously been achieved in conjunction with salt hydrate phase change materials. The method is novel, adapted for water based paint formulations.
• The silica shell can be substituted with halloysite nanocontainers, making this a versatile method for including PCM nanocontainers into coating formulations.
• The capsules, after surface modification, can be easily redispersed into oil-based paints (e.g. toluene, xylene as a solvent matrix).
