Cardanol is a renewable resource based on cashew nut shell liquid, which consists of a phenol ring with a C15 long aliphatic side chain in the meta position with varying degrees of unsaturation. This structure makes the molecule highly reactive for many routes of chemical modifications. Due to its unique C15 hydrophobic alkyd chain and rigid and chemically resistant phenolic moiety, this molecule can be a candidate or replacement for corrosion-resistant coating applications. To synthesize a cardanol-based monomer with improved properties, cardanol glycidyl ether (LITE 2513HP, Cardolite®) was chemically modified from the unsaturation sites of the side chain by means of epoxidation in the presence of hydrogen peroxide and formic acid. The structure of the modified cardanol resin (side-chain epoxidized cardanol glycidyl ether (SCECGE)) was confirmed via proton nuclear magnetic resonance, Fourier transform IR spectroscopy, and epoxy equivalent weight titrations. This modified resin was cured with petroleum-based epoxy hardeners, 4-4’-methylene biscyclohexanamine. Also for comparison, another cardanol-based diphenol diepoxy resin, NC514 (Cardolite®), and a petroleum-based epoxy resin, diglycidyl ether of bisphenol-A (DGEBA), were thermally cured with the listed epoxy hardener at stoichiometric ratios. The extent of the curing reaction and curing mechanism of different epoxy/amine systems were explored using mid-IR techniques and differential scanning calorimetry and we determined that secondary epoxides are not as reactive as primary glycidyl epoxides. The glass transition, modulus, and strength of the cured SCECGE resins were lower than that of NC514 and DGEBA due to the lower extent of reaction of the secondary epoxides.<br/>

Synthesis and characterization of cardanol-based epoxy/amine systems and analysis of secondary epoxies

255th National Meeting (2018)

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