(16b) Synthesis & Characterization of Molecularly Hybrid Bisphenols Derived from Lignin & Cashew Nutshell Liquid: Resin and Polymer Properties

Vinyl Ester (VE) resins can be used to create polymers with favorable properties for high performance applications. Standard industrial VE resins are comprised of monomers with a bisphenolic structure, which result in polymers with high strengths, moduli, thermal stabilities, and chemical resistances. Most of the commercially available VE resins are derived from bisphenol A (BPA). Unfortunately, BPA is considered unsustainable because it is synthesized from petrochemical feedstocks. It has also been scrutinized for its toxicity to the human endocrine system. Bio-based alternatives are being investigated to mitigate the negative aspects of BPA.

Lignin, a bio-based resource, is a favorable feedstock for the synthesis of VE resins due to its extensive aromaticity. Lignin is the second most abundant natural resource and a major byproduct of the pulp and paper industry. Vanillin can be derived from lignin and further reduced to vanillyl alcohol, a viable platform chemical for the production of bisphenols. Cashew nutshell liquid (CNSL) is an aromatic, renewable resource produced from the inedible shells of cashew plants. CNSL contains many phenolic lipids, the primary of which is cardanol. Cardanol’s C15 alkyl chain, which can be naturally saturated or unsaturated, may impart water and thermal resistant properties to the resultant polymer network.

This study shows the synthesis and properties of lignin-derived vanillyl alcohol coupled with CNSL-derived cardanol (VAC). The VAC is an asymmetric bisphenol that is then functionalized to produce a dimethacrylate (VACDM). All dimethacrylates used in this work were blended with a reactive diluent, analyzed for their rheological properties, and cured. The resulting polymers were characterized via FT-IR, TGA, DMA, and fracture toughness to quantify the thermomechanical, thermogravimetric, and mechanical properties. The bio-based dimethacrylates were compared to BPA-derived industrial standard Vinyl Ester 828 (VE828) and the structurally similar bisphenol A dimethacrylate (BPADM).