Functional hydrophobic coating for phosphogypsum via stoichiometric silanization, hydrophobic characterization, microstructure analysis, and durability evaluation

Gypsum is a typical healthful, eco-type, and energy-saving material. However, because of poor water resistance, its applications were limited. Therefore, this paper reports on a one-step stoichiometry-controlled reaction method for the preparation of long-chain silicones based on micro/nano-layered siloxane aggregates generated in a low-cost solvent. In this study, self-assembled monolayers of octadecyltrichlorosilane were prepared on the surface of beta-hemihydrate phosphogypsum (beta-HPG) samples using n-hexane and dichloroethane, tested for contact angle, mechanical properties, softening coefficient, analysed for hydrophobicity and durability. The results show that the water droplet surface is stable with a maximum contact angle of 144.70 +/- 1.1 degrees, the softening coefficient is 0.92 and the water absorption rate is reduced to 1.1 %. The surface remained well hydrophobic when rubbed 12 times with 600 grit sandpaper under a pressure of 4.4 KPa. The above results show that this hydrophobic coating has a promising application in the protection of large gypsum products.

Automated summary

This study reports a one-step stoichiometry-controlled reaction method for the preparation of long-chain silicones based on micro/nano-layered siloxane aggregates, through the treatment of phosphogypsum samples. It successfully improves the water resistance and durability of gypsum materials.