Surface Morphology of Chlorine and Castor Oil-Based Polyurethane–urea Coatings

The present work deals with surface properties of chlorine containing polyurethane–urea (PU–urea)-coating films. First, isocyanate-terminated pre-polymers were synthesized using castor oil as renewable resource, isophorone diisocyanate, and different weight percentages of 2-chloroethanol and 2,2,2-trichloroethanol. The resultant isocyanate-terminated pre-polymers were cured under atmospheric moisture to obtain chlorine containing PU–urea coatings. The surface properties of the coating films were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and X-ray diffraction. All characterization techniques suggest that the presence of chlorine species on the surface results in different surface properties when compared to control PU–urea (without the chlorine group)-coating film surface. The viscoelastic, swelling, and contact angle (CA) properties were studied for the prepared coating films. The glass-transition temperatures (Tg) were obtained in the region 29.2–35 °C for the coating films. Tg increased by increasing the chlorine content in polyurethane-coating formulations. The CA for the coating films was found to be in the range of 76°–64° and these properties were found to be decreased with increase in the weight percent content of the chlorine moiety in the final coating formulation. Similarly, the higher chlorine content-coating films have shown more water uptake properties. The overall comparative results indicate that the chlorine containing PU–urea-coating films have different surface-coating properties and these depend upon the chlorine content in the final coating formulation as compared with PU–urea surfaces.