Phytic acid-based superhydrophobic coating endows bamboo with excellent water and mildew repellent properties

Abstract

To ensure bamboo-based composites can withstand harsh environments, it is important to develop superhydrophobic and mildew-resistant coatings for the surfaces of the product. Achieving these functions on bamboo surfaces remains a challenging research problem. We applied a phytic acid (PA)-based hybrid coating to bamboo surfaces using a layer-by-layer self-assembly technique, and superhydrophobicity was further enhanced through modification with low surface energy substances. Scanning electron microscopy-Energy disperse spectroscopy (SEM-EDS) mapping results initially confirmed the successful creation of a microscale structure with improved hierarchical roughness on the bamboo surface. Following modification with octadecylamine (OA), the polyethyleneimine (PEI)/PA-Fe^3 + /OA/Bamboo demonstrated outstanding superhydrophobic performance, with a water contact angle reaching 151° and remaining above 150° without significant change over 2 min. Despite undergoing abrasion, scratch and tape peel tests, the PEI/PA-Fe³⁺/OA/Bamboo maintained high hydrophobicity, with a water contact angle remaining above 140°. Finally, phytic acid-based hybrid metal coordination complexes created a dense protective coating on the bamboo surface. This coating both prevented Aspergillus niger from accessing internal nutrients and inhibited its adhesion to the bamboo surface. Thus, the successful application of the superhydrophobic coating enhanced the mildew resistance of bamboo.