Epoxidation of CNSL Mixture, Cardanol, and Cardol: A Sustainable Solution for PVC Plasticization

ABSTRACT Epoxidation is an effective method for enhancing the plasticizing properties of biobased oils for the plasticization of poly(vinyl chloride) (PVC), among other applications. Epoxy groups not only increase the affinity with PVC but also enhance its thermal and mechanical properties. Cashew nut shell liquid (CNSL), an inedible oil derived from agricultural waste, comprises cardanol, cardol, and anacardic acid. These compounds, phenols with long alkyl chains, contain unsaturation that can be epoxidized. This project aims to evaluate the feasibility of utilizing technical CNSL (80% cardanol and 20% cardol) as a PVC plasticizer. Various plasticizers were synthesized from pure cardanol or technical CNSL through esterification and epoxidation to enhance compatibility with PVC and plasticizing properties. Notably, as far as we know, mixtures of cardanol and cardol derivatives have been epoxidized for the first time. The chemical structures of these plasticizers were fully characterized using 1 H nuclear magnetic resonance (NMR) spectroscopy. Furthermore, the mechanical properties, thermal stability, and chemical resistance of PVC films plasticized with these additives were investigated. Practical Applications : Cardanol, once esterified and epoxidized, has demonstrated good plasticizing capabilities for certain polymers including PVC. This naturally occurring product is obtained after distillation of a crude oil from the shell of cashew nuts, the cashew nutshell liquid (CNSL). Other components present in this oil, such as cardol, have also demonstrated significant pertinence in the plasticization of PVC. Using the crude oil or a mixture of components as precursors for plasticizers for PVC would reduce the cost of the plasticizing agent and avoid possible loss or waste linked to the separation of the raw compounds, currently carried out.