Enhancement of Drying Performance of Biologic Paint Using Cellulose Nanocrystals and Chitosan

Conventional paints pose major environmental and health concerns due to their reliance on heavy-metal pigments and volatile organic compound (VOC)-emitting binders, emphasizing the need for sustainable alternatives. Previous formulations of biologic paints that combined bacteria-derived dsRED pigment protein and casein-based binders, while devoid of toxic components, suffered from prolonged drying times (~16 min), limiting their practical applicability. The present study addresses this key limitation by incorporating cellulose nanocrystals (CNC) and chitosan as biologic additives to enhance drying kinetics. Paint formulations containing 2%, 5%, and 10% of each additive were tested under controlled environmental conditions (20 °C, 60% relative humidity) following the GB/T 1728–2020 standard. Both CNC and chitosan significantly reduced drying time in a concentration-dependent manner (p < 0.001). The 10% CNC and 10% chitosan formulations achieved 61% and 44% reductions in drying time, respectively, relative to the unmodified biologic paint (12.96 ± 1.07 min at baseline). Regression analyses indicated that each 1% increase in CNC or chitosan concentration reduced drying time by 0.77 min and 0.58 min, respectively. The optimized paints exhibited acceptable drying times (5–7 min). These findings demonstrate an advancement in the development of biologically derived coatings, providing a feasible pathway toward safe and sustainable alternatives to conventional synthetic paints.