Study on surface wetting property regulation of greenhouse film and its antifogging performance

In order to eliminate the effects caused by fog, sodium alginate (SA)/nano-SiO₂ antifogging coating was prepared by solution blending method. The effects of coating components on its wettability and antifogging effects were investigated. Importantly, a method for evaluating the antifogging properties of membrane was developed, namely wet and dry cycles (WDC). It was found that the higher the content of nano-SiO₂, the lower the contact angle of the coating, and the best antifogging effect was achieved. When the ratio of SA and nano-SiO₂ was 4:3, the antifogging duration could be more than 144 h under water mist at 60°C. The antifogging coating retains antifogging effect after 10 cycles of test. However, after 20 cycles of WDC, a small amount of fine droplets started to appear, and XPS energy spectrum analysis found that the SA component in the coating almost completely disappeared, indicating that SA is the main reason for preserving antifogging performance under WDC conditions. Interestingly, after 20 cycles of reciprocal rubbing of the coating with a sponge, the surface contact angle rose by 23.4° and still had antifogging effect, indicating that the coating has excellent mechanical strength.