Karanja (Millettia pinnata (L.) Panigrahi) seed oil as a renewable raw material for the synthesis of alkyd resin

• The oil content of karanja seed is found to be ∼27%.
• Alkyd resins are synthesized by the two-stage alcoholysis–polyesterification method.
• Drying of the alkyd resins is carried out by blending with epoxy resin.
• Synthesized resins show suitable characteristics for application as coating material.

Non-edible vegetable oils are an important class of bio-resource for producing polymeric materials due to their large abundance, low cost and renewability. Karanja (Millettia pinnata) tree is an evergreen, drought resistant, nitrogen fixing tree belonging to Leguminaceae family. Karanja seed oil (∼27 wt%) mainly consisting of triglycerides is a good source of non-edible vegetable oil for synthesizing alkyd resin. Triglyceride was first converted to monoglyceride by glycerolysis process. The monoglyceride was then reacted with phthalic and/or maleic anhydride to produce alkyd resins. The synthesized resins were characterized by FT-IR and 1H NMR spectroscopy. The surface characteristic of the cured resins was studied by SE microscopy. The physico-chemical properties of the resins such as colour, acid value, free fatty acid content and iodine value were evaluated. The coating performance of the cured resins was tested by measuring chemical resistance, thermal stability, pencil hardness, gloss and adhesion.