I did an experiment on ABS plastic, the contact angle of smooth ABS plastic is around 70° which means hydrophilic surface, but when I treated the surface of this plastic by grinding process using sandpaper 240um and 400um, the contact angle of the ABS plastic grounded is more than 90° ''around 100°", which mean the surface become hydrophobic. So, how can you explain these results ?!! and thank you so much.
Some scientists believe that wettability increases with roughness when the flat or smooth surface is hydrophilic. and the wettability decreases when roughness increases when the smooth surface was hydrophobic.
But, in my case, ABS plastic is hydrophilic. When the roughness increases with the grinding process, the wettability decreases and the surface becomes hydrophobic.
I hope I 'll have an answer as soon as possible and thank you so much.
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