The research background

Due to the growing global demand for functional textiles in the automotive, healthcare and construction industries, one of the commonly used substrates for these coatings is textiles or fabrics. Until a few years ago, almost all hydrophobic textile coatings were developed from long-chain perfluoroalkyl substances (PFAS). However, environmental regulations have phased out perfluorocarbons, including C-8 fluorocarbons, in all industries because of their biological persistence and their negative effects on human health. The textile industry is still looking for a durable, fluorine-free coating solution that can be cheaply applied to mass production. In order to improve the abrasion resistance and waterproof performance of copolymer coating, the low surface energy of polydimethylsiloxane and the roughness of the surface of lotus leaf were used respectively from the chemical and physical aspects, which can make the coating at the same time take into account the green and waterproof and wear-resistant properties.

Results summary

By using the high surface area and branched structure of gas phase silica (FS), combined with the hydrophobicity of poly (dimethylsiloxane) (PDMS) and the robustness of PU (PU), the layered structure and enhanced function of PDMS-PU and FS graft coatings were prepared. The structural characteristics of FS increase the superhydrophobicity (160° water contact Angle at 2.5wt%); Its branching nature will provide air permeability; A FS-only layered coating method on top of the PDMS-PU coating results in interlocking and strong wear resistance, and hydrophobics do not change significantly after 1000 wear cycles using standard wear test procedures. This work has shown that water-based, mechanically strong, breathable, and superhydrophobic coatings can be produced without the use of fluoridation. The layered coating method provides a new perspective for fine-tuning the hydrophobicity, air permeability and robustness of coating materials.

1. Synthesis scheme of polymer dispersion

In Figure 1, the reactants (diisocyanates and polyols) are first joined together to form a prepolymer. Then, these prepolymer chains were connected with (a) butanediol (BD)(1) to form polymers. Finally, water was added to prepare PDMS-PU copolymer particle dispersion by antisolvent precipitation in water. (b) PdMS-PU-Si particle dispersion was generated by dispersing with gas phase silica particles (FS)(1) in anhydrous solvent and then antisolvent precipitation in water. The term Si in PDMS-PU-Si is used to distinguish between gaseous silica covalently connected to the polymer and FS particles.