Bio-based novolac resins from cashew nut processing waste: Alternative resource for the development of high-value sustainable products

Abstract

In the last decades, there is an increasing trend for replacing petro-based adhesives with sustainable and eco-friendly alternatives, especially in the wood industry. In this work it was developed and characterized novolac-type phenolic resins from the full use of the cashew nut shell liquid (CNSL), an agro-industrial residue and a rich source of phenolic compounds, sustainable alternative to petroleum-derived chemicals, to develop bio-based polymers. CNSL and paraformaldehyde were reacted, using oxalic acid as a catalyst, under a solvent-free methodology. A dark and viscous resin of high molar mass and thermally stable was obtained. The development of highly bio-based adhesives was proposed by combining CNSL-based novolac resin (CNSL-nov) with commercial epoxy resin (DGEBA), as an alternative to conventional hardeners. The use of the epoxy-novolac system proved to be efficient and promising in obtaining new highly cross-linked polymers with excellent thermal performance and with potential for wood industry, improving the bio-based content of high-performance adhesive.