Multifunctional Biobased Benzoxazines Blended with an Epoxy Resin for Tunable High-Performance Properties

Abstract

Biobased polybenzoxazines incorporate natural phenolic structures to produce polymers with near-zero shrinkage, high char yields, and high chemical and thermal resistances, garnering great interest as sustainable high-performance polymers. Herein, difunctional and trifunctional benzoxazine monomers, bisguaiacol-furfurylamine (BG-f) and triguaiacol-furfurylamine (TG-f), respectively, were synthesized from renewable guaiacol, vanillin, and furfurylamine using solventless procedures. Benzoxazines were blended with varying weights of epoxy resin and thermally cured to produce benzoxazine-epoxy (BG-f-E and TG-f-E) polymers. These polymers displayed glass transition temperatures ranging from 130 to 157 °C (peak of the loss modulus), thermal stabilities from 299 to 329 °C in both N2 and air, and char yields ranging from 35% to 58%. BG-f-E and TG-f-E with greater benzoxazine content produced stiffer materials exhibiting glassy storage moduli values upward of 3.48 and 3.69 GPa, respectively. BG-f-E polymers displayed higher molecular weight between cross-link values (646 g mol–1 to 981 g mol–1) compared to TG-f-E polymers (316 g mol–1 to 465 g mol–1) and exhibited fracture energies upward of 404 J m–2. These investigations demonstrate the utility of incorporating biobased benzoxazines into benzoxazine-epoxy resin formulations to design sustainable polybenzoxazines with tunable thermal and mechanical properties for high-performance polymer applications.

Chrysin-Based Bio-Benzoxazine: A Copolymerizable Green Additive for Lowering Curing Temperatures and Improving Thermal Properties of Various Thermosetting Resins

“…Clearly, the thermally activated phenolic hydroxyl group in CHR-ac can not only react with the epoxy group, but also catalyze the ring-opening polymerization of benzoxazine. Therefore, the copolymerization between benzoxazine and epoxy in CHR-ac/DGEBA can take place in a relatively lower temperature rather than that after ring-opening polymerization of oxazine ring as previously reported benzoxazine/epoxy blending systems . As shown in Figure S8, characteristic bands in CHR-ac/DDM-BMI are observed to be located at 832 and 690 cm –1 belonging to imide CH wagging of the vinylene and CH–H out-of-plane bending mode in maleimide, respectively .…”

Novel Combination of Vinyl Benzoxazine and Its Copolymerizable Diluent with Outstanding Processability for Preparing a Bio-Based Thermoset

“…As a new type of thermosetting resin, polybenzoxazine has attracted worldwide attention in the past 30 years owing to its prominent performances in terms of not only thermal and mechanical properties − but also flexibility of molecular design, − low dielectric constant, − very low surface free energy without using fluorine atoms, and excellent flame retardancy. − Unfortunately, applications of benzoxazine have encountered processing problems because most benzoxazine monomers are solid at room temperature and their melting temperatures are generally higher than 90 °C. − Until now, poor processability of benzoxazine monomers is still the key barrier that limits the development of polybenzoxazine resin.…”

A novel benzoxazine derived from diphenol amide for toughing commercial benzoxazine via copolymerization

“…[23][24][25] These shortcomings have been universally admitted as serious problems in practical applications. 15 To solve these connatural weaknesses, scholars have tried a considerable number of strategies, ranging from blending with elastomers, 26,27 thermoplastic resins 28 and thermosetting resins 29 to synthesis of new benzoxazine. 52,53 However, these attempts encountered various new problems.…”