Synthesis and characterizations of high oil length alkyd resin with dehydrated castor oil and acrylic pimaric acid

[Display omitted] •High oil length alkyd resin was synthesized.•Structures of the alkyd resin were investigated by FTIR and 1H NMR.•Dehydrate castor oil and acrylic pimaric acid were used. Alkyd resin (AR) has been widely used for paint applications due to its good adhesion, flexibility and durability. They were polymerized from three different kinds of monomers: polyols, aromatic diacids and vegetable oils or fatty acids. In this work, acrylic pimaric acid (APA) was evaluated as an bio-based substitute for the aromatic diacid monomer including phthalic anhydride (PA) in the synthesis of high oil length (65 % oil by weight) alkyd resins (HOARs). APA was synthesized from the Diels-Alder reaction between rosin acid (RA) and acrylic acid (AA). The resins were characterized in terms of gloss, pencil hardness, impact strength, alkali resistance and thermal stability. APA can be incorporated when the polyesterification reaction is performed in two-stages, that is, it is only added with ethylene glycol (EG) in the first stage polyesterification reaction, because the reactivity of APA is weaker than that of PA. The structure of the prepared HOARs was investigated by FTIR and 1H NMR spectroscopy. The results show that HOAR having 9 % APA has good gloss, pencil hardness and impact strength and excellent alkaline resistance. The price is decreased by about 20 % compared to conventional AR and it can be widely used as a binder in the field of the protective paint.