Effects of different dicarboxylic acid on the UV-curable urethane resins made from palm fatty acid distillate Kim Teck Teo, Aziz Hassan, Seng Neon Gan Ó American Coatings Association 2020 Abstract A series of four polyol macromers with similar hydroxyl number was prepared by reacting palm fatty acid distillate with neopentaglycol, pen- taerythritol, and separate equimolar amounts of isoph- thalic acid (IPA), terephthalic acid (TPA), phthalic anhydride (PA), and adipic acid (AA). Each macromer was then copolymerized with 2-hydroxylethyl acrylate (2-HEA) and toluene diisocyanate to produce the UV curable resins labeled as UA–IPA, UA–TPA, UA–PA, and UA–AA, respectively. The glass transition tem- perature (T g ), pendulum hardness, and adhesion prop- erties of the cured films were studied. In general, all the resins produced coatings with high gloss and good adhesion. When accelerated weathering tests were carried out, films of UA–TPA could withstand UVA exposure up to 1500 h. When subjected to methyl ethyl ketone double rub test, cured films of UA–IPA and UA–TPA could withstand the highest double rubs at 90 times, followed by UA–PA and UA–AA at 45 and 15 times, respectively. Under salt spray corrosion test for 720 h, cured films showed good corrosion resistance with no observable blistering, except for UA–AA that showed slight blistering. Excellent water resistance was achieved by all cured films with good adhesion and minimal gloss reduction. Keywords PFAD, Urethane acrylate, UV curable, Coatings, T g , Accelerated weathering test, Water resistant, Gloss Introduction Development of new polymers with enhanced proper- ties for various substrates has been constantly explored by surface coating scientists. 1–3 The requirements for metallic substrates have led to the developments of UV curable coatings 4,5 to meet specific requirements such as decorative panels of different colors, sizes, and shapes. In addition, the coatings for certain applica- tions may require specific properties such as high gloss, good adhesion, and flexibility. UV curing has become a well-accepted technology successfully introduced into many modern organic coating sectors. It offers major advantages of energy saving, no volatile solvent, and fast curing cycle. It has become a rapidly growing technology within the coating, adhesive and related industries. It has found a large variety of industrial applications due to its distinctive advantages, high efficiency, and environ- mental friendliness. 6–8 The main raw materials in a typical UV curable formulation are an oligomer, reactive diluent (usually a monomer), and photoiniti- tator. Most of the commercial formulations are based on acrylic functional oligomers and monomers 9,10 such as epoxy acrylate, 11,12 urethane acrylate, polyester acrylate, and polyether acrylates. 13 Urethane acrylate as a resin for UV curable coatings has the best mechanical and chemical properties among all classes of acrylic oligomers. Schwalm et al. 14 have developed a series of UV-curable waterborne hyperbranched poly- urethane acrylate resins whose mechanical properties of coatings, either hard or flexible, were dependent on molecular weight, functionality and chemical structure. Dai et al. 15 have reported the synthesis of unsaturated polyesters by melt polycondensation of itaconic acid with 1,4-butanediol and glycerol. UV curable coatings were formulated from these polyesters and acrylated epoxidized soybean oil to produce coatings with excellent adhesion and flexibility. K. T. Teo, A. Hassan, S. N. Gan (&) Chemistry Department, University of Malaya, 50603 Kuala Lumpur, Malaysia e-mail: sngan@um.edu.my K. T. Teo e-mail: ktteo@siswa.um.edu.my A. Hassan e-mail: ahassan@um.edu.my J. Coat. Technol. Res. https://doi.org/10.1007/s11998-020-00379-4