Fabrication of Transparent Silica/PEG Smooth Thin Coatings on Polymeric Films for Antifogging Applications

Fog accumulation on surfaces typically has a negative effect by reducing their transparency and efficiency. Applications such as plastic packaging, agricultural films, and particularly many optical devices suffer from these negative effects. One way to prevent fogging is to coat the substrate with an antifogging coating having a smooth surface and hydrophilic surface chemical groups. This causes the fog water droplets that come into contact with the substrate to completely flatten across its surface, thus retaining transparency. These coatings are mostly relegated to laboratory research due to their insufficient stability and costly synthetic processes. We proposed the use of organically modified silica particles consisting of a mixture of tetraethyl orthosilicate and methacryloxypropyltriethoxysilane, which were grown in situ in the presence of a corona-activated polyethylene film, thus providing a thin siloxane coating containing activated double bonds. An additional coating of poly(ethylene glycol) diacrylate was then spread on the coated film and polymerized via UV curing. The in situ process and UV curing anchored the coating to the substrate through covalent bonds, which provided additional stability. This coating exhibited low surface roughness and contact angle, which resulted in excellent antifogging properties when exposed to a hot-fog test. Furthermore, the antifogging coating retained its properties after 10 hot-fog cycles, indicating the high coating stability. Additionally, the coating was found durable to immersion in aqueous pH levels 1-13 and detergent solutions as well as to tape test applications and sand test. This coating was compared to a commercially available antifogging spray, which was used to coat a polyethylene film. This resulted in excellent initial antifogging properties, which decreased after exposure to durability tests. The results of the in situ coating process indicate its potential uses for industrial applications.