In this study, in order to improve mechanical properties of cotton fabrics, nano-micro sized calcium carbonate (CaCO 3 ) was deposited in situ on cotton fabrics. The mechanical properties, surface morphology, crystalline index, infrared spectrum, thermal property, and wettability of the deposited fabrics were measured and discussed. The results showed that the breaking strength of cotton fabric increased by about 10% after in situ deposition of nano-micro calcium carbonate. After ultrasonic washing, the strength of cotton fabric deposited CaCO 3 was still increased by about 10%. The crystallinity of the cotton fabric deposited with calcium carbonate increased from 76% to 84%. The hydrogen bond between cellulose molecules and calcium carbonate was confirmed by infrared spectroscopy. The hydrophilicity and thermal properties of cotton fabric were not significantly influenced by calcium carbonate deposition. This provides a new idea for improving the mechanical properties of cotton fabric.breaking strength, cotton fiber, crystalline index, nano-micro calcium carbonate | INTRODUCTIONCotton is a rich natural source of cellulose polysaccharide. Cotton fabric is favored because of its excellent wearing comfort, breathability, and dyeability. 1,2 However, the low strength of cotton fabrics may have certain impact on their wearability. The main methods used to improve the strength of cellulose materials are alkali treatment 3 and nanoparticle coating. 4 Among these, alkali treatment is the most widely used method. The tensile strength of natural fibers, such as hemp fibers, 5 okra fibers, 6 and Juncus effusus fibers, 7 improved after alkali treatment. 8

The use of dopamine to synthesize melanin as a natural dye on fabrics has the disadvantages of complicated processing, long processing time, and high cost. This study simplifies the processing conditions of the oxidative polymerization of dopamine and develops wool fabric melanin coatings with different finishing effects by adjusting the reaction time. The results of computer color matching, ultraviolet (UV) protection properties, and color fastness indicated that the treated wool fibers were effectively dyed, and they achieved UV resistance properties comparable to those realized in other studies in a relatively short time. The degree of lightness (L) and UV protection factor of the treated fabric reached up to 13.3 and 80+, respectively. Samples W/PDA 60 and W/PDA 120 absorbed more than 95% of the UV light. The color fastness was greater than Grade 4. The Fourier infrared spectrum and X‐ray diffraction studies revealed that the chemical and crystalline structures of the wool fiber did not change significantly after the treatment. The breaking strength of samples W/PDA 60 and W/PDA 120 was about 50% higher than that of the original wool fabric. This efficient and simple method provides a feasible and promising solution for the color deepening and UV finishing of high value‐added wool products. It can be a potential choice for upgrading the printing and dyeing industries from the perspective of ecological protection.