Bio‐based epoxy‐anhydride thermosets from multi‐armed cardanol‐derived epoxy oligomers

Abstract

Three bio-based multi-armed epoxy oligomers were synthesized via a ring-opening reaction of cardanyl glycidyl ether with lignin-derived polyphenols, followed by the epoxidation of the double bonds in the side chains of the cardanol segments. These oligomers were then used to prepare epoxy-anhydride thermosets with 4-methyl hexahydrophthalic anhydride (MHHPA) and 1,8-diazabicyclo[5.4.0]undec-7-ene as the hardener and catalyst, respectively. The combination of differential scanning calorimetry and gel content results showed that the extent of cure was >90% when the formulations were heated at 110 C for 48 h. The cardanol-derived thermosets exhibited markedly higher alpha transition temperatures (T α ), tensile strength, and modulus relative to thermosets based on epoxidized soybean oil. The improved thermal and mechanical properties of these thermosets were attributed to the increased chain rigidity imparted by the aromatic moieties in the cardanol and creosol residues, as well as the hydrogen bonding interactions between the hydroxyl groups. Furthermore, the T α values of these thermosets increased with the anhydride equivalents and the functionality of the epoxides, which led to higher crosslinking densities and more rigid MHHPA contents.

Oil‐based epoxy and their composites: A sustainable alternative to traditional epoxy

“…The addition of hydroxyl and aromatic groups from cardanol-derived oligomers showed improved mechanical and thermal properties. 44 Similarly, Moreira et al synthesized cardanol methacrylate from epoxidized cardanol using methacrylic acid and esterification under solventfree conditions. Methacrylate cardanol was used as an adhesive for dental application with collagen crosslinker.…”

Robustly Curing Epoxy Novolacs by Linear and Cyclic Siloxane-Functionalized Eugenol: Impact of Topologies of Cross-Linkers on Properties of Thermosets

“…To make epoxy resins and derived materials more sustainable, biobased curing agents from renewable resources have received great attention. For example, various biobased feedstocks such as vegetable oils, − sugars, amino acids, − cashew nut shell liquid, − guaiacol, , tannic acid, − vanillin, − eugenol, , and itaconic anhydride , have been used to synthesize biobased curing agents. They usually bear more than two reactive hydrogens, at least one cyclic anhydride group, or certain catalytic moieties that can lead to cross-linking of epoxy resins as bisphenol A diglycidylether (DGEBA).…”

Synergistic Dual-Cure Reactions for the Fabrication of Thermosets by Chemical Heating

“…The candidate thermoset system we chose for this study is epoxy/anhydride, which has gained recent popularity due to its sustainability evaluation compared to more conventional epoxy systems. − As an example, Wang et al recently published on a bioderivable epoxy/anhydride resin, named P oly- E ster C ovalent A daptable N etwork (PECAN), which was designed in analogy to a conventional epoxy/amine formulation used for wind blades which demonstrated up to 40% lower GHG emissions and recyclability while maintaining all requisite performance metrics . Despite the benefits of this system, sluggish initiation at temperatures below 80 °C coupled with long cure times (>5 h) may be prohibitive to its widespread adoption by industry.…”