Characteristics of natural corn starch/waste paper fiber composite foams treated by organic-inorganic hybrid hydrophobic coating technology.

With the growing global awareness of environmental protection, the demand for biodegradable materials to replace traditional plastic foam has become increasingly urgent. Starch-based foam, with its abundant availability, low cost, and biodegradability, has shown great potential as an alternative to plastic foam. However, its inherent high hydrophilicity and relatively low mechanical performance limit its widespread application. The aim of this study is to modify corn starch (NCS) and waste paper fiber (WPF) using citric acid (CA) and stearic acid (SA), and to develop an efficient hydrophobic coating through an organic-inorganic hybrid approach. This successfully resulted in the preparation of hydrophobic corn starch/waste paper fiber composite foam materials. Experimental results showed that the foam materials treated with a palmitic acid (PA)-modified nano-SiO2 coating (MCF@PA) exhibited excellent hydrophobic performance, with a water contact angle reaching as high as 138°, and a significant reduction in moisture absorption to 3.1 %. In water immersion tests, the material maintained buoyancy and shape stability, demonstrating excellent self-cleaning properties. Additionally, the coating significantly enhanced the material's compressive strength, increasing by 90 kPa, while also retaining thermal stability. However, the coating prepared by this method increased the material's hardness and reduced its biodegradability, which poses challenges for environmental sustainability. This study provides a new approach for preparing high-strength foam materials with excellent hydrophobicity and mechanical performance, paving an economical and efficient pathway for industrial production.