Preparation and application of waterborne cellulose acetate/waterborne polyurethane nanocomposite emulsion finishing agent for leather

To address issues with traditional water-based polyurethane (WPU) leather finishing agents like soft, sticky films, poor water resistance, and slow drying speed, a green, environmentally friendly leather finishing agent was developed using cellulose acetate to modify WPU. Through emulsification of water-based cellulose acetate (WCDA) with WPU emulsion, a nanocomposite emulsion (WCDA/WPU) was created, exhibiting a flexible structure, small particle size, high hardness, rapid drying, water resistance, and strong adhesion the substrate. This agent has a high solid content, excellent mechanical properties, fast drying, and strong binding with leather, overcoming previous limitations. Its properties result from the synergistic advantages of its components, providing a superior alternative to traditional WPU leather finishing agents. The WCDA/WPU nanocomposite emulsion consists of small WPU particles in a large WCDA particle space, with an oil-in-water core-shell structure. At a ratio of 1:3 (WPU:WCDA), the emulsion has a solid content of 56.68 % and a particle size of 195.32 nm. The resulting film has excellent mechanical properties with an elongation at break of 618.45%, a tensile strength of 9.77 MPa, and a B hardness. The wear rate is 0.983 %, and the drying time is 1.5 times faster than WPU. The film surface is compact and smooth, with a static water contact angle of 94.6 degrees, enhancing hydrophobicity. When applied to leather finishing, the WCDA/WPU nanocomposite emulsion improves air and water permeability by 205.9 % and 40.1 % respectively. Water absorption rates decrease by 19.81 % at 0.25 h and 14.74 % at 24 h, indicating improved resistance to dry and wet friction. In conclusion, leather treated with WCDA/WPU nanocomposite emulsion outperforms traditional methods.