Four polyurethane/polyamide copolymer dispersions (PUCON-co-APAS) were prepared from castor oil-based polyol (CON). Castor oil (CO) was firstly transesterified with triethanolamine at 210 A degrees C for different time intervals: 30, 60, 90 and 120 min, to produce CON30, CON60, CON90 and CON120 polyols, respectively. The hydroxyl and acid values, density, viscosity, chemical structure analysis of the CON polyols were determined. The polyols were used to prepare PUCON30-co-APAS, PUCON60-co-APAS, PUCON90-co-APAS, and PUCON120-co-APAS copolymer dispersions in five steps using prepolymer self-emulsification solvent process. The first step is the prepolymer preparation step, in which CON was reacted with dimethylolpropionic acid and excess toluene diisocyanate to produce PUCON (NCO) . The second step is the copolymerization step, in which PUCON (NCO) was reacted with amino-terminated aromatic polyamide sulfone. The following processes are neutralization, chain extension and dispersion steps. The prepared copolymer dispersions were characterized using FTIR, DLS, TGA, DSC and GPC. Additionally, the physical, chemical and mechanical properties of the prepared copolymers were studied. The results showed an increase in the hydroxyl number of CON with increasing transesterification time. Stronger H-bonds and smaller particle sizes are produced using CON with higher transesterification time in the preparation of the copolymer dispersions.