Hydrophobic Self-Cleaning Coating Based on Siloxane Modified Waterborne Polyester

Considerable efforts have been made over the last few decades for developing self-cleaning surfaces exhibiting high water contact angles. In this respect, a chemical method has been used to develop a hydrophobic self-cleaning coating for metal substrates which involves the use of hydroxyl terminated polydimethyl siloxane (PDMS) to achieve a rough surface with lower surface energy. The coating was prepared using lower molecular weight polyester as resin, dimethylethanolamine (DMEA) as neutralizing agent, hexamethylmethoxymelamine (HMMM) as cross-linker and and para-toluene sulphonic acid (p-TSA) as catalyst. The influence of PDMS on the hydrophobicity and self-cleaning property was studied by static contact angle and dust repellency test respectively. It was observed that the contact angle got increased from 700 to 1040 with no further change even after increasing the coating thickness. The hydrophobicity of the PDMS modified coating was sustained upto a temperature ranging from 250C to 900C and also upto 48 hrs of water exposure. The PDMS modified polyester coatings were characterized by surface roughness measurements (AFM), scanning electron microscopy (SEM), EDAX, Fourier transform infrared (FTIR) spectroscopy, self-cleaning test and water contact angle measurements.