Synthesis and characterization of new eco-friendly water reducible polyester coating for application in automotive paint systems

Environmental issues are a major concern, especially in automotive industries. Recently, water-born coatings have high attraction due to strict health regulations related to emission of hazardous organic solvents from solventbased coatings. Polyester resins have been used for automotive coatings in all layers like primer, basecoat andclearcoat as well as interior or exterior parts, such as air cleaner, oil filters, wheels , bumpers and etc. In this research, a water reducible polyester resin was synthesized by polycondensation polymerization process. Fourier Transform Infrared Spectroscopy (FT-IR) was used to characterize the chemical structure of synthesized polyester resin. CARDURA E10 was added into the reaction vessel at 210˚C during 3h until the epoxy group peak was disappear at 908 cm-1 according to Figure 1. Also, the ring opening of the epoxy groups of CARDURA observed OH groups (3444 cm-1). The results confirmed the disappearance of the anhydride peak (1768 cm-1) and appearance of carbonyl group (1728 cm-1) in the produced resin. Figure 2 shows the visual appearance of synthesized polyester resin which is clear, transparent and yellowish viscous liquid. Acid and hydroxyl values of resulted polyester resin were determined by titration method equal to 61.7 and 60.2 respectively. Also, another polyester resin with different glass transition temperature (Tg) was synthesized and optimized regarding to extent of netrulizing groups to reach stable dispersion.