Phenalkamines as Epoxy Hardeners

Recent years have seen increased work on the synthesis and use of bio-compatible, environmentally friendly, solvent-free and plant-based products due to declining petroleum products and the environmental damage caused by petroleum derivatives. Phenalkylamines, a hardener obtained through the modification of Cardanol chemical, one of the plant-based products, are establishing their place in the market and their use is steadily increasing. Cashew nut contains liquid at a 25% ratio, and this liquid contains Cardanol, Cardol, anacardic acid and 6-methyl cardol. (Figure 1.) Among these, Cardanol exhibits superior properties due to its chemical structure. The phenol groups on it act as a catalyst in epoxy curing while also facilitating adhesion to the surfaces to which it is applied. The long aliphatic chain, with its nonpolar structure, exhibits water-repellent properties and provides anti-corrosive properties, thus protecting metal or concrete surfaces.1

Figure 2. Phenalkamine synthesis from Cardanol

Epoxy coatings are widely used to protect metal and concrete substrates. However, certain problems need to be solved due to the slow curing rates of epoxies with amines, the toxic properties of the amines used, and the need to use phenol chemicals that are harmful to health when used with Mannich bases. 3 In this context, phenalkylamines are synthesized from Cardanol via Mannich reaction. Phenalkylamines emerge as alternative products to epoxy-amines as they do not contain phenol, carry the superior properties of Cardanol's chemical structure, and contain highly reactive amine groups. They stand out in many respects, particularly due to their vigorous reaction with epoxies even at -5ºC, their ability to work even in high humidity due to their nonpolar structure, and their resistance to chemicals.4 While the industrial application areas using Cardanol have recently increased, their use is particularly widespread in surface coatings, paints, varnishes, lacquers, adhesives and laminates. 5 Within the scope of modifying Cardanol and obtaining different phenalkamine structures, our company conducts work in various fields, and it has been determined that the coating properties obtained provide faster curing compared to conventional epoxy-amine systems and have durable mechanical properties.   Dr. Cemil Dizman Research and Development Director İzel Kimya       Merve Boy Research and Development Manager İzel Kimya    

References 1) https://www.european-coatings.com/Editorial-archive/Highperformance -in-a-nutshell 2) Coline Voirin, Sylvain Caillol, Nilakshi V. Sadavarte, Bhausaheb V. Tawade, Bernard Boutevinab and Prakash P. Wadgaonkar. Functionalization of cardanol: towards biobased polymers and additives. Polym. Chem., 2014, 5, 3142. 3) Mary C. Lubi & Eby Thomas Thachil (2000) Cashew nut shell liquid (CNSL)- a versatile monomer for polymer synthesis, Designed Monomers and Polymers, 3:2, 123-153. 4) Balachandran VS, Jadhav SR, Vemula PK, John G. Recent advances in cardanol chemistry in a nutshell: from a nut to nanomaterials.Chem Soc Rev. 2013 Jan 21;42(2):427-38. 5) Laura Puchot. Cardanol : a bio-based building block for new sustainable and functional materials. Polymers. Université de Cergy Pontoise, 2016.