Studies on Poly(Styrene-co-Maleic Anhydride)-Modified Polyesteramide-Based Anticorrosive Coatings Synthesized from a Sustainable Resource Fahmina Zafar, Eram Sharmin, S. M. Ashraf, Sharif Ahmad Materials Research Laboratory, Department of Chemistry, Jamia Millia Islamia, New Delhi 110025, India Received 27 May 2003; accepted 4 November 2003 ABSTRACT: Polyesteramide (PEA) coating resin, synthe- sized from linseed oil, a sustainable resource, was found to show improved physicomechanical and acid-resistance properties. To further improve these properties in terms of alkali resistance, scratch hardness, and thermal stability and to reduce the baking temperature, we have attempted to incorporate styrene into the polymer backbone through its copolymer with maleic anhydride. The structural elucida- tion of modified PEA resin (SCPEA) was carried out by FTIR, 1 H-NMR, and 13 C-NMR spectroscopes. The physico- mechanical and chemical-resistance properties were investi- gated by standard methods and thermal stability was inves- tigated by thermogravimetric analysis method. A compara- tive study of these properties of PEA and SCPEA was carried out. It was observed that the SCPEA showed better properties than the reported one. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2538 –2544, 2004 Key words: coatings; curing of polymers; adhesion; gloss INTRODUCTION Alkyds comprise an important class of polymeric binders in the field of coatings and paints. However, under stringent environment, their applicability is limited owing to their relatively inferior water, alkali, and chemical resistance. This is attributed to the ester linkages present in the resin backbone, which is prone to hydrolysis. 1 Vegetable oil based polyesteramide (PEA) resins containing sufficient amide linkages are known to impart satisfactory water, chemical, and thermal resistance to their films. 2 Several PEA resins have shown their superiority to alkyd resins. 3 PEA resins were developed from linseed oil, dehy- drated castor oil, pilu fat, annona squamosa, arge- mone seed oil, pongamia glabra, and other oils. 3–7 The high melting point, low solubility, lower intractability, high drying time, and temperature cause difficulties in their application as coating materials. 8 To overcome these drawbacks, in our earlier publications, we re- ported the development of alumina-filled PEA and urethane-modified alumina-filled PEA anticorrosive coating materials. 2,3 Other modifications include the incorporation of isocyanates, amino resins, acrylic monomer, vinyl, and chlorinated rubber in PEA and alkyds, which have also been reported. 2,9 –12 Literature survey reveals that polystyrene has been a subject of popular interest for coating technolo- gists. 13 It gives fairly hard, colorless, and water alkali as well as thermal-resistant coatings. 14,15 Over the years, several attempts were made for the incorpora- tion of styrene in the backbone of polymeric resins by various methods. Usually, such an incorporation of polystyrene is carried out through double bonds where homopolymerization cannot be ruled out. Con- trary to the above, polystyrene can expectedly be in- corporated in the backbone of polymer through suit- able functional groups. 16 –19 Because this approach does not involve fatty acid unsaturation, it would provide a wider perspective for selection of oils. It was also observed that other factors being the same, the higher the styrene content in the resin backbone, the lower the resistance to aromatic solvents with a lower gloss. 20 Poly(styrene-co-maleic anhydride), a bifunc- tional acrylic copolymer, is capable of reacting with alcohols, amines, and other groups to produce many derivatives because of the anhydride groups in its backbone. 21 It possesses a combination of chemical and mechanical properties that may help in the devel- opment of high-performance anticorrosive coatings. It was reportedly used as a modifier of latex paints to increase adhesion and gloss in the resin of low-baking temperature and time. 22 It is reported that replace- ment of phthalic anhydride by maleic anhydride in the case of alkyds has led to shorter stoving time and alkyds of better color and drying properties. 23 Surpris- ingly, in the case of fatty acid PEA formed from veg- etable oil where high baking temperature is often a Correspondence to: S. Ahmad (sharifahmad jmi@yahoo. co.in). Journal of Applied Polymer Science, Vol. 92, 2538 –2544 (2004) © 2004 Wiley Periodicals, Inc.