Water resistant and biodegradable waste gelatin-based coating as sustainable biomass surface paper sizing

Paper is an important sustainable material widely used in various fields, whereas its strong hydrophilicity limits its broader application. Herein, water resistant and biodegradable waste gelatin-based coating as surface paper sizing that consists of concurrently hydrophilic and hydrophobic components was demonstrated. The hydrophilic gelatin and hydrophobic stearic acid individually fulfilled the loosely packed structure filling and the hydrophobic surface forming. Furthermore, γ-(2,3-epoxypropoxy) propytrimethoxysilane was blended with the two-phase emulsion via a scalable process, enabling the coated paper to attain the desired mechanical strength, water stability, and durability. After the sizing process, the coated corrugated paper exhibited high strength with a tensile index of 68.92 ± 2.98 N·m/g, which was greater than twice enhancement than that of initial one. The coated corrugated paper maintained good wet strength (tensile index ≈ 31.57 N·m/g), which was stronger than that of the dry initial corrugated paper, and retained almost the same surface water repellency after the abrasion resistance test, suggesting its good water stability and durability. Importantly, the coated corrugated paper could completely biodegrade (∼10 weeks) in soil. Thus, our proposed waste gelatin-based coating can be recommended as a sustainable and eco-friendly surface paper sizing, extending the broader application of paper materials in different usage scenarios.