Phenalkamine curing agents for epoxy resin: characterization and structure property relationship

Purpose The purpose of this study is to synthesize structurally different phenalkamines based on cardanol, a renewable material obtained from cashew nut shell liquid, and to evaluate their effect on performance properties of the coatings. Design/methodology/approach For this purpose, the Mannich reaction between cardanol, formaldehyde and various diamines such as diaminodiphenyl methane (DDM), hexamethylene diamine, Jeffamine D400 and Jeffamine T403 were carried out to produce novel phenalkamines. Resultant phenalkamines were used as curing agents for commercial DGEBPA epoxy resin and were evaluated for performance properties. Findings The mechanical, optical, chemical, thermal and anticorrosive properties were evaluated and compared with those of commercial phenalkamine AG141. It was observed that anticorrosive properties evaluated using a salt spray test and electrochemical impedance spectroscopy revealed significant improvement in anticorrosive performance of coatings cured with synthesized phenalkamines based on DDM and T403 as compared to the coatings based on commercial phenalkamine AG141. Research limitations/implications To obtain optimum performance properties of the coatings, a combination of phenalkamines can be used. Practical implications Curing time and gel times of all the phenalkamines can be further studied under wet and humid conditions. In addition, the variation in coating properties under humid conditions can be investigated. Originality/value In this study, newer phenalkamines were synthesized and used as curing agents for epoxy coatings. So far, there have been no reports indicating the synthesis and application of phenalkamines based on polyetheramines, namely, Jeffamine D400 and Jeffamine T403, in coating applications.