Paint & Coatings Industry - February 2009 - (Page 28) Hydroxy Ethyl Fatty Amide Effect on the Perfomance Properties of Polyesteramide Resins Based on Acrylic Copolymers ne of the major pollutants emitted by a surface coating is organic solvent used during processing and application. Hence, efforts have been made to develop alternative technologies that minimize the use of organic solvents in surface coatings. These include the use of coating curing agents derived from vegetable oils, which have been directly used to obtain coating films. Since these oils, by themselves, cannot directly meet the desired film properties, a number of oil modifications have been proposed such as alkyd, epoxy, polyesteramide, polyurethanes, polyurethaneamide, etc.1-10 The polyesteramide resins hold considerable application scope in the coatings field.11 A number of polyesteramides have been developed from FIGURE 1 | IR spectrum of acrylic copolymer. 100 Transmittance [%] 80 60 40 20 0 2925.73 2854.58 1738.45 1463.92 1379.01 1303.72 1244.32 1174.66 1092.57 1067.23 1023.01 980.12 840.44 723.09 O different oils e.g., dehydrated castor oil,12 pilu fat,12 argemone,13 linseed14, etc. The presence of repeating units of ester (-COOR) and amide (-NCOR) in the polymeric chain of polyesteramide (PEA) improves the ease of application, thermal stability, chemical and water resistance, and causes faster drying and enhanced hardness over normal alkyds.15 These polyesteramides have shorter curing times at elevated temperature, while considerably longer times at room temperature. In the present study, an acid-functional acrylic copolymer has been synthesized using butyl methacrylate and maleic anhydride. In addition, the hydroxyl ethyl fatty amide of castor oil has also been synthesized and used as a curing agent for the acid-functional acrylic copolymer to form polyesteramide resins. The effect of crosslinking agent on the acrylic copolymers was examined. A series of coating compositions with varying amounts of acrylic copolymer and hydroxyl ethyl fatty amide were prepared, and their mechanical, optical and chemical resistance properties studied. Experimental Reagents Castor oil was procured from a commercial manufacturer. Maleic anhydride, butyl methacrylate (BMA), diethanolamine, zinc oxide, methanol, xylene, acetone, and potassium hydroxide were of LR grade. Synthesis of Acrylic Copolymer The copolymer was synthesized by dissolving maleic anhydride (1 mol) in 100 ml of xylene in a 3-neck flask with inlet for N2 gas, reflux condenser and mechanical stirrer. BMA (exactly 1 mol) containing 1.4 gm of benzoyl peroxide was added drop wise at a constant rate into the flask over the period of 2 hours keeping the temperature constant at 95 °C. The reaction mass was stirred for another 2 hours to complete the reaction. The resulting copolymer was diluted with acetone and precipitated with methanol with constant stirring. Table 1 shows the characteristics of the acrylic copolymer. 4000 3500 3000 2500 2000 1500 1000 500 TABLE 1 | Acrylic copolymer characteristics. Copolymer Code A Monomers (mol) BMA 1 MA 1 Number Average Molecular Wt. (Mn) 8297 Poly Weight Average Dispersity Acid Molecular Index Value Weight (Mw) (PDI) 19210 2.325 345 By Sukhen Mistry and Devendra Agarwal, Department of Oil & Paint Technology | Harcourt Butler Technological Institute, Nawabganji, Kanpur, India 28 FE BRUARY 2009 | W W W . P C I M A G . C O M http://WWW.PCIMAG.COM
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