To evaluate how the polymer-coated aluminum panel is stained under the influence of silicone sealing compounds, an outdoor exposure test was carried out using test pieces consisting of an inclined roof and vertical wall. Patterns and extents of stains were analyzed referring to the hydrophilic/hydrophobic surface properties.
Results are as follows
1) The outdoor exposure test caused dark linear stains on the surface observable on the aluminum exterior of ordinary buildings.
2) A dark linear stain appeared in 1 month, and the difference in shape of stains between coating types was not conspicuous.
3) At the lower part of the sealing compound, the contact angle of water droplets became large, showing the increased surface hydrophobicity. This is caused by a material oozed out from the sealing compound.
4) Once the contact angle became large, the surface maintained its hydrophobic property despite repeated water rinsing, making it soon become dirty again after cleaning.
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