Synthesis and characterization of guar gum-based polyurethane dispersions by varying diisocyanates for textile applications

The synthesis of guar gum (GG)-based waterborne polyurethane dispersions (GWPUDs) via step-growth polymerization for textile finishing was carried out to evaluate the effect of diisocyanate structure on dispersion properties and end-use performance. In the first step, a hydrophilic NCO-terminated polyurethane prepolymer was synthesized using GG as the bio-based polyol, selected diisocyanates, and dimethylolpropionic acid (DMPA) as an internal emulsifier. In the next stage, five formulations were prepared by adding the calculated amounts of 1,4-butanediol (BDO) as a chain extender to the NCO-terminated prepolymer. Finally, neutralization was performed with triethylamine (TEA), and then distilled water was added slowly to obtain stable GWPUDs. The existence of GG and BDO in the polyurethane network was confirmed by Fourier-transform infrared spectroscopy (FTIR). FTIR showed the disappearance of the characteristic –NCO absorption peak at 2158.1 cm ⁻¹ and the appearance of the –NH stretching band at 3324.8 cm ⁻¹ . The dispersion particle size distribution was measured by dynamic light scattering. The X-ray diffraction method was used to investigate crystallinity, and the findings indicated that GWPUDs are semi-crystalline with a greater value of percentage crystallinity (61.55%) for GWPUD _TDI . Thermogravimetric analysis revealed that the GWPUDs based on cycloaliphatic diisocyanates exhibited higher thermal stability (T ₅₀ % 406°C) than the GWPUDs based on aromatic diisocyanates. The prepared GWPUDs were applied to dyed and printed fabrics by using the pad–dry–cure technique and the main textile performance parameters such as colorfastness to washing, colorfastness to perspiration, pilling resistance, and tear strength. The treated fabrics demonstrated notable improvements, with colorfastness to washing increasing from 2 to 4–5, colorfastness to perspiration from 2–3 to 4–5, and pilling resistance from 3 to 4–5. An enhancement in tear strength was also observed, with cycloaliphatic diisocyanate–based formulations delivering superior performance for both dyed and printed textile substrates.