A dual-crosslinking strategy for waterborne polyurethane coatings to achieve outstanding anti-smudge and anti-corrosion properties

Abstract

The inferior anti-smudge properties and compromised anti-corrosion performance of waterborne polyurethanes (WPUs) stem from the presence of abundant hydrophilic groups in their polymer networks. Despite various hydrophobic segments have been introduced in WPU skeleton to lower the impacts of hydrophilic groups, the limited migration capability of hydrophobic segments in waterborne matrix often result in unsatisfactory performance. Herein, we fabricate a multifunctional PDMS-modulated WPU coating employing sorbitan monooleate (SP), a renewable bio-derived polyol, as an internal crosslink agent, and hexamethoxymethylmelamine (HMMM) as a post-crosslink agent to fully eliminate the polar hydrophilic groups in the molecular linkages and further enhance the crosslink density of the coating. It is found that the coating exhibits exceptional anti-graffiti and self-cleaning effects when subjected to tests involving oil-based and water-based pens and inks, as well as common household liquids like milk, coffee, cooking oil, ethanol, n-hexadecane, etc. Such anti-smudge coating could readily remove carbon powder-like dust with water, ensuring a clean surface, and also possess a certain level of resistance to fingerprint smudges. Apart from excellent mechanical robustness and impressed durability after 500 cycles of writing erase tests, the coating also remains intact and has anti-smudge properties when folded or bent. For chemical resistance, the coating can resist at least 18 h of acid, alkali, and salt intrusion without being damaged. Moreover, the sufficient crosslink density imparts the coating with good thermal stability and outstanding anti-corrosion performance in extremely corrosive environments. This research presents a facile and effective approach for developing stain and corrosion-resistant PDMS-modulated waterborne polyurethane materials with high protective reliability and long lifespan through the dual-crosslinking strategy.