Zizhao Qian,Yuanxiang Xiao,Xujun Zhang,Qing Li,Lujie Wang,Feiya Fu,Hongyan Diao,Xiangdong Liu
Bisphenol A (BPA) is the main precursor in the synthesis of epoxy resins. However, because of its toxic and nonrenewable nature, BPA is unsuitable in the sustainable preparation of epoxy resins. In contrast, Diphenolic acid (DPA) is renewable but its carboxyl group limits its applications in bio-based thermosets. In this study, we report a novel amidation route to tailor DPA to produce epoxide monomers that present epoxy resins with a high performance. The diphenolic amides exhibited very low toxicities when compared with that of BPA, and also provided an unexpected autocatalytic effect on the curing reactions when succinic anhydride (SA) was used as the hardener. Dynamic mechanical analyses (DMA) and tensile test results confirmed the remarkable thermomechanical properties of the cured epoxy resins, which may be attributed to the increased cross-linking density and enhanced hydrogen bonding by the amide groups. Among the SA-cured epoxy resins, diglycidyl ether of diphenolic ethylamide exhibited the best performance, which included a high T g of 114 °C, char yield (CY) of 20%, tensile strength of 60.2 MPa, and toughness value of 185 MPa. In addition, the DPA-derived epoxy resins have great potential in the preparation of bio-based composites because they act as excellent interfaces between the resin and cotton fibers (CoFs). Our study presents a new strategy to prepare bio-based epoxy resins with a high performance, emphasizing the greater potential of amidated DPA derivatives to replace BPA in the epoxy resin market.
Zizhao Qian,Qing Li,Lujie Wang,Feiya Fu,Xiangdong Liu
As a renewable chemical, diphenolic acid (DPA) has attracted immense interest in bio-based polymer science. However, its application for polybenzoxazines is limited due to decarboxylation, that is, the release of CO 2 during the curing reaction of benzoxazine. In this study, the amidation strategy of converting DPA to diphenolic amides (DPAM) was demonstrated to solve this problem while simultaneously improving the thermal properties of polybenzoxazine. DPA was amidated by separately using four amines (hexamine, cyclohexylamine, furfurylamine, and aniline), then reacted with furfurylamine and paraformaldehyde to synthesize their benzoxazine monomers. By using TGA and DMA, all amide-containing polybenzoxazines were found to exhibit excellent thermal stabilities. Among all of the benzoxazine resins, poly(DFA-fa), which was obtained from amidation with furfurylamine, exhibited the highest glass transition temperature ( T g ) of 310°C and a decomposition temperature ( T d10 ) of 406°C. Furthermore, a possible post-curing reaction mechanism was proposed to explain the outstanding thermal performance of poly(DFA-fa) resin. This study proposes an innovative strategy to solve the decarboxylation of DPA-based polymers, which is of significance for high-performance bio-based polymers. Graphical
Zhiyuan Chi,Zongwei Guo,Zice Xu,Mengjie Zhang,Ming Li,Lei Shang,Yuhui Ao
Searching a renewable and flame-retardant alternative to bisphenol A epoxy resins is a necessary development trend. Diphenolic acid , a plant derivative, has been proven to be one of the sustainable alternatives to bisphenol A. However, how to impart the flame-retardant property to diphenolic acid thermosets is still a challenge to synthesize high performance intrinsic flame-retardant bio-based epoxy resins. A flame-retardant bio-based epoxy resin (TEBA) was designed and synthesized via a three-step synthetic pathway from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)、diethanolamine and diphenolic acid (DPA). The chemical structures of the intermediate and final products were confirmed by 1 HNMR and FTIR spectroscopy. TEBA cured with 4,4′-diaminodiphenylmethane (DDM) curing agent was compared with a standard bisphenol A epoxy resin (DGEBA). Due to the combination of phosphorus and nitrogen in the main chain, the TEBA-DDM shows superior flame retardancy. Compared with DGEBA-DDM, LOI of TEBA-DDM increased from 25.8% to 42.3%, UL-94 test rating from no rating to V-0 rating, self-extinguishing within 3s. The peak heat release rate (PHRR) in the cone calorimetry test decreased by 67%. total heat release (THR) and total smoke generation (TSP) decreased by 27% and 35%, respectively. In addition, the flame retardant mechanism of TEBA epoxy thermosets was researched by FTIR, residual char photograph, SEM, TG-IR analysis and Raman spectroscopy . Meanwhile, TEBA-DDM and DGEBA-DDM have comparable mechanical properties .
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