Synthesis and characterisation of low-cost cardanol polyurethanes

Purpose - The purpose of this paper is to develop a flexible, as well as a rigid, polyurethane (PU) product using polyols derived from renewable resource for suitable application. Design/methodology/approach - Cardanol is converted into corresponding glycidyl ether by reacting it with epichlorohydrin. The resulting glycidyl ether is hydrolysed to the corresponding diol in the presence of a heteropolyacid, which acted as a catalyst. The diol obtained is used for synthesising PU's by reacting it with various mole ratios of toluene diisocyanate (TDI) and isophorone diisocyanate (IPDI) and their physicomechanical, chemical and morphological properties are studied. Findings - The polyol selected for the present paper has unique structural characteristics such as C15 chain length, which contributes to flexibility, and an aromatic ring, which imparts rigidity in the final application of resulting PU. By choosing optimum ratio of NCO/OH, it is possible to obtain a system, which can be used for the development of a flexible as well as a rigid polymer for suitable application. Research limitations/implications - The cardanol and dodecatungstosilic acid used are of a particular grade and of a particular manufacturer. Furthermore, it could be obtained from different sources and of different grades. The spectral studies done are purely qualitative. Gloss is tested for the samples at 600, whereas other angles can also be used. Practical implications - The method developed provided a simple and practical solution to improve performance characteristics of PU resins, which also proves to be cost effective. Originality/value - The PU product developed due to its enhanced coating properties can be used in various surface-coating applications.