Ultrathin Biomaterial Coating for Flame-Retardant Medical Paper

Paper has the multiple advantages of being breathable, sustainable, environmentally friendly, and non-toxic for medical care. However, the flammability stemming from the raw materials of paper has limited its use in medical heat therapy. In this paper, a composite flame-retardant coating is assembled layer by layer on a medical paper surface using medically safe natural biomaterials with starch and adenosine triphosphate as internal layers, and starch and phytic acid as external layers. With the layer-by-layer assembly using the ultrathin adsorption method, the microscopic morphology and elemental mapping reveal that all the biomaterials are deposited uniformly and have completely capsulated the paper surface fiber. The flame-retardant coating shows less impact on medical paper appearance morphology and mechanical properties in medical usability. The coated medical paper exhibits significant flame-retardant performance, such that the limiting oxygen index increases from 19.70% to 25.40% where both internal and external layers reached 100 layers (BL), and relevant residual charring in the thermogravimetric test increases 17.00 wt% in a nitrogen atmosphere and 18.00 wt% in an air atmosphere at 800 °C. The peak and total heat release rates of 100 BL medical paper reduced by approximately 91.10% and 53.10%, respectively, and the variations in both CO and CO2 production also suggest that flame-retardant coating could effectively inhibit combustion. Benefiting from the intumescent flame-retardant function of different biomaterial combinations and the multilayer design on different thermal response temperatures, the flame retardancy of medical paper significantly improved, and this advancement will make medical heat therapy safer and healthier for patients.