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Saturday, 21 September 2019
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Raw materials & technologies, Technologies, Functional coatings

Dirt resistance of steel topcoats depends on surface wettability and characteristics of pollutants

Tuesday, 4 June 2013

Surface characteristics of exterior coatings like wettability, roughness and composition play an important role regarding the dirt resistance against pollutants.

The wettability of exterior coatings affects the dirt resistance 

Source: Tego

The wettability of exterior coatings affects the dirt resistance 

Source: Tego

Researchers from the Department of Materials Science (Advanced Coatings Research Center of Ministry of Education of China) at Fudan University in Shanghai, China have investigated the dependence of dirt resistance of steel topcoats on their surface characteristics.

Dirt pick-up tests and outdoor exposure experiments  

Contamination of exterior coatings with dirt is a significant problem in seriously polluted environments. To correlate the dirt resistance of exterior coatings with surface characteristics (wettability, roughness and composition), the researchers evaluated steel topcoats using both dirt pick-up tests according to a national standard testing method of China (GB/T 9757-2001) and outdoor exposure experiments in Shanghai. These topcoats included polyvinylidene fluoride (PVDF) paints with various water contact angles (WCAs), polyurethane (PU) paint, polysiloxane (PSiO) paint and 2K fluorocarbon (FPU) paint. Opposite dirt resistance results were obtained from these two dirt pick-up methods. In the outdoor exposure experiments, superhydrophilic PVDF paints showed excellent self-cleaning performance and thus superior dirt resistance. Superhydrophobic PVDF paint exhibited self-cleaning performance initially, but became dirty finally due to a piling up of PM2.5 pollutants. PVDF paints with WCAs of 85°–125°, PU, PSiO, and FPU paints all exhibited poor dirt resistance in the outdoor environment.

Surface wettability and characteristics of pollutants affect the dirt resistance  

The results indicate that dirt resistance depends on surface wettability and the characteristics of pollutants rather than on the surface roughness and composition.

The study was published in: Journal of Coatings Technology and Research, May 2013, Volume 10, Issue 3, pp 339-346.

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