A resveratrol-based epoxy resin with ultrahigh Tg and good processability

Recent Development of Functional Bio-Based Epoxy Resins

The development of epoxy resins is mainly dependent on non-renewable petroleum resources, commonly diglycidyl ether bisphenol A (DGEBA)-type epoxy monomers. Most raw materials of these thermoset resins are toxic to the health of human beings. To alleviate concerns about the environment and health, the design and synthesis of bio-based epoxy resins using biomass as raw materials have been widely studied in recent decades to replace petroleum-based epoxy resins. With the improvement in the requirements for the performance of bio-based epoxy resins, the design of bio-based epoxy resins with unique functions has attracted a lot of attention, and bio-based epoxy resins with flame-retardant, recyclable/degradable/reprocessable, antibacterial, and other functional bio-based epoxy resins have been developed to expand the applications of epoxy resins and improve their competitiveness. This review summarizes the research progress of functional bio-based epoxy resins in recent years. First, bio-based epoxy resins were classified according to their unique function, and synthesis strategies of functional bio-based epoxy resins were discussed, then the relationship between structure and performance was revealed to guide the synthesis of functional bio-based epoxy resins and stimulate the development of more types of functional bio-based epoxy resins. Finally, the challenges and opportunities in the development of functional bio-based epoxy resins are presented.

Bio-Based Thermosetting Resins: From Molecular Engineering to Intrinsically Multifunctional Customization

Recent years have witnessed a growing interest in bio-based thermosetting resins in terms of environmental concerns and the desire for sustainable industrial practices. Beyond sustainability, utilizing the structural diversity of renewable feedstock to craft bio-based thermosets with customized functionalities is very worthy of expectation. There exist many bio-based compounds with inherently unique chemical structures and functions, some of which are even difficult to synthesize artificially. Over the past decade, great efforts are devoted to discovering/designing functional properties of bio-based thermosets, and notable progress have been made in antibacterial, antifouling, flame retardancy, serving as carbon precursors, and stimuli responsiveness, among others, largely expanding their application potential and future prospects. In this review, recent advances in the field of functional bio-based thermosets are presented, with a particular focus on molecular structures and design strategies for discovering functional properties. Examples are highlighted wherein functionalities are facilitated by the inherent structures of bio-based feedstock. Perspectives on issues regarding further advances in this field are proposed at the end.

Synthesis of a Novel P/N-Triazine-Containing Ring Flame Retardant and Its Application in Epoxy Resin

To meet the environmental protection and flame retardancy requirements for epoxy resins (EPs) in certain fields, in this study, a novel triazine-ring-containing DOPO-derived compound (VDPD), derived from vanillin, 2,4-Diamino-6-phenyl-1,3,5-triazine, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), was synthesized using a one-pot method. Flame-retardant epoxy resin (FREP) was prepared by adding various ratios of VDPD to EP and curing with 4,4-diaminodiphenylmethane (DDM). The curing behavior, thermal stability, mechanical properties, and flame-retardant properties of the FREP were examined in various tests. According to the results, when the amount of VDPD added to the EP increased, the glass transition temperature of the FREP decreased linearly, and the flame-retardant properties gradually improved. With a 0.4 wt.% P content, the vertical burning rating of EP/DDM/VDPD-0.4 (according to the theoretical content of VDPD) reached the V-0 level, and the LOI value reached 33.1%. In addition, the results of a CCT showed that the peak heat release rate (PHRR) of EP/DDM/VDPD-0.4 decreased by 32% in comparison with that of the EP. Furthermore, compared with those of the EP, the tensile strength of EP/DDM/VDPD-0.4 decreased from 80.2 MPa to 74.3 MPa, only decreasing by 6 MPa, and the tensile modulus increased. Overall, VDPD can maintain the mechanical properties of EP and effectively improve its flame-retardant properties.

The Flame Retardant and Mechanical Properties of the Epoxy Modified by an Efficient DOPO-Based Flame Retardant

Currently, the mechanical performance reduction caused by excessive phosphorus content in the halogen-free flame-retardant EP has been an obstacle to its extensive application. This study presents the effective synthesis of a novel flame-retardant BDD with great efficiency, achieving an optimum phosphorus level of merely 0.25 wt %. The structure of BDD was verified by FTIR, 1H NMR, 31P NMR and XPS spectra. To investigate the flame-retardant properties of BDD, several EPs with various phosphorus levels were synthesized. The addition of phosphorus to the EP significantly increases its LOI value from 25.8% to 33.4% at a phosphorus level of 0.25 wt%. Additionally, the resin achieves a V-0 grade in the UL 94 test. The P-HRR and THR of the modified resin measured by the cone calorimeter are also significantly reduced. At the same time, the addition of a modest quantity of BDD has a minimal impact on the mechanical properties of epoxy resin. This study shows that the removal of hydroxyl groups significantly enhances the fire resistance of phosphate-based flame retardants, thereby providing a novel approach to synthesizing efficient flame retardants.