Flame Retardancy and Hydrophobicity of Cotton Fibers via the Treatment of the Phosphorus‐Silicon Modified Cottonseed Meal

ABSTRACT Cotton fibers are widely used in the textile industry due to their natural hydrophilicity, breathability, and comfort, but their highly flammable nature severely limits their use in protective clothing, home furnishings, and other applications. In order to meet the multi‐functional requirements of cotton fibers, such as hydrophobicity and flame retardancy, combined with the research trend of eco‐friendly bio‐based flame retardant research, this study uses cottonseed meal as the core raw material. Phosphoric acid and polymethylhydrosiloxane were selected as modification agents, with H 2 O 2 serving simultaneously as both solvent and degrading agent. A bifunctional reagent CPSi with flame‐retardant and hydrophobic properties was successfully prepared by a one‐pot method. Through the dipping‐baking‐curing finishing process, cotton fiber DC‐CPSi with hydrophobic and durable flame‐retardant properties was prepared. To characterize the coating on the cotton fibers, we employed techniques such as Fourier Transform Infrared Spectroscopy (FTIR), X‐ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM) to examine the morphology and bonding modes of the dual‐function reagent. After 50 washing cycles, the durable hydrophobic flame‐retardant cotton fiber (abbreviated as DC‐CPSi‐50) showed a damage length of 65 mm in the vertical combustion test (VFT) and a limit oxygen index value (LOI) of 35.6%, indicating excellent durable flame retardancy. The PHRR and THR of DC‐CPSi‐50 were reduced by 82.69% and 41.41%, respectively, compared with untreated cotton fibers, demonstrating excellent flame‐retardant performance. Additionally, the flame‐retardant cotton DC‐CPSi‐50 exhibited good hydrophobic performance, achieving a contact angle of 128.23° at 30 s, significantly higher than the 84.63° contact angle observed in the control cotton. This study uses bio‐based cottonseed meal combined with a simple and environmentally friendly synthesis process, providing a new approach for developing safer, more functional, and environmentally friendly textile finishing technologies. This method has significant application potential in protective clothing, household textiles, and other areas that require high performance and sustainability.