Hydrophobic silsesquioxane-modified lignin-incorporated polyurethane film

Abstract

Polyurethane (PU) is widely used in adhesive, foam, and coating applications. Currently, there is an urgent need to enhance PU's hydrophobic, thermal, and flame-retardant properties to improve its performance while minimizing its environmental impact. In this work, we introduce a new recyclable PU-derived composite film with enhanced superhydrophobicity and flame retardancy. The coating formulation consisted of 50 wt% water-based silsesquioxane lignin (WL) as a superhydrophobic constituent, 0.12 wt% sulfoethylated lignin (SL) as a dispersant, and 1 wt% epoxidized oil as a plasticizer. The aqueous-based PU film exhibited superhydrophobic performance (164° ± 2° water contact angle and 4° ± 2° low sliding angle) and enhanced mechanical strength. Flame-retardant analysis indicated a limiting oxygen index improvement from 18.5% in pure PU to 25.5% in the lignin-incorporated PU formulation. The formulation demonstrated superhydrophobic and flame-retardant improvement when coated over wood, metal, and paper surfaces, and these properties were resistant to sandpaper abrasion, UV ozone exposure, and thermal exposure. This aqueous phase polyurethane (PU) formulation is suitable for coating various surfaces with environmentally benign properties.