Phosphorylation of Milkweed Fibers With a Phosphate Ester: Effect on Fiber Properties and Optimization of Reaction Conditions

ABSTRACT

This study explores the phosphorylation of milkweed fibers using phosphate ester (PE) in the presence of urea, aiming to optimize reaction conditions and determine their effect on fiber properties. The impact of reaction temperature, duration, and phosphate ester ratio on the efficiency of phosphorylation was investigated using the Box–Behnken Response Surface Methodology (RSM). The optimal parameters obtained were 129°C, 3 h, and 1 eq of PE, respectively. Under these conditions, the estimated results yielded a total charge of 4844 mmol/kg, a phosphorus content of 4.7%, and a fiber length of 0.94 mm. Analytical techniques, including SEM/EDX, FTIR, and solid‐state NMR, were used to characterize the fibers, providing insight into their chemical and morphological modifications. Thermal stability and flame retardancy were evaluated using thermogravimetric analysis and flammability tests. The phosphorylation process enhances the thermal stability and flame‐retardant properties of fibers while affecting their hydrophobicity and increasing their surface energy from 11.07 mN/m for untreated fibers to 31.79 mN/m for highly phosphorylated fibers. This work demonstrates the potential of chemically modified milkweed fibers as sustainable materials for various applications where high electrostatic charge and flame resistance are required.