Renewable Epoxy Thermosets from Fully Lignin-Derived Triphenols

Abstract

A series of fully renewable triphenols (TPs) with various number of methoxy group substituents (n = 0–6) were synthesized using lignin-derived phenols (guaiacol and 2,6-dimethoxyphenol) and aldehydes (4-hydroxybenzaldehyde, vanillin, and syringaldehyde). The structural evolution from TPs to epoxy thermosets was followed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. Thermomechanical properties of the resulting epoxy thermosets were investigated by dynamic mechanical analysis (DMA), tensile analysis (TA), and thermogravimetric analysis (TGA). Increasing the content of methoxy groups decreased the glass transition temperature (132–118 °C) and glassy modulus (2.7–2.2 GPa). Thermal stability of high-methoxy-content thermosets was reduced due to electron-donating effects and higher oxygen content. Conversions and isolated yields of TPs significantly decreased as the number of methoxy substituents increased, which markedly determined the feasibility of TPs as precursors for polymers. This work widens the synthesis route of fully lignin-derived polyphenols, yielding polymers with thermomechanical properties comparable to bisphenol A (BPA) based materials. Evaluation of methoxy substitution provides insight for the selection of lignin-derived monomers.

Choosing the Right Lignin to Fully Replace Bisphenol A in Epoxy Resin Formulation

“…These attributes cause lignin to have lower reactivity toward ECH than BPA and possibly result in resin with lower homogeneity. Lignin can be incorporated into epoxy resin via three different methods: 1) blending with petroleum‐based epoxy resin, [24,25] 2) modification of lignin followed by epoxidation, [23,26–30] and 3) epoxidation of unmodified lignin [16,31,32] . Although many studies have focused on utilizing lignin in epoxy resin, [23,27,33,34] they mostly used modified lignin (fractionated or lignin monomers) [23,27,29] .…”

Preparation of Renewable Epoxy-Amine Resins With Tunable Thermo-Mechanical Properties, Wettability and Degradation Abilities From Lignocellulose- and Plant Oils-Derived Components

“…Indeed, the aromatic moieties present in these bio-based chemicals confer rigidity to the resulting polymers (Wang et al, 2017; Feghali et al, 2018). For example, there have been many reports on epoxy resins from eugenol (Wan et al, 2016), vanillin (Fache et al, 2015a,b; Hernandez et al, 2016; Mauck et al, 2017; Nicastro et al, 2018; Savonnet et al, 2018; Zhao et al, 2018), ferulic and sinapic acids (Maiorana et al, 2016; Janvier et al, 2017; Ménard et al, 2017), guaiacols (Maiorana et al, 2015), and creosol (Meylemans et al, 2011) with promising performances capable of competing with current DGEBA-based materials. However, few researchers have considered the potential toxicity of these BPA substitutes, especially endocrine disruption, which remains a crucial health issue for both plastic sector workers and consumers (Jiang et al, 2018).…”

Biobased phenol and furan derivative coupling for the synthesis of functional monomers

“…The group of Zhao has prepared fully bio-based polyphenols from guaiacol or pyrogallol, and 4hydroxybenzaldehyde, vanillin, or syringaldehyde ( Figure 10). 59,60 It is a formaldehyde-free synthesis and the only drawback is the use in excess of the guaiacol or the pyrogallol which can be evaporated.…”