Phosphorus-containing flame retardant epoxy thermosets: Recent advances and future perspectives

Lignin derivative vanillin when coupled with diamines and diethyl phosphite followed by reaction with echichlorohydrin yields high-performance flame retardant epoxy resins. Biorenewable and environment-friendly flame retardant alternatives to bisphenol A epoxy resins (having plenty of applications such as coatings, adhesives, composites, etc.) have captured great attention due to their ecological and economic necessity. Vanillin, an industrial scale monoaromatic compound from lignin, is a promising sustainable candidate for high-performance polymers, while synthesis of diepoxies is challenging. Meanwhile, bio-based epoxy resins combining high performance and excellent fire resistance are more difficult to be achieved. In this paper, two novel bio-based epoxy monomers EP1 and EP2 were synthesized by one-pot reaction containing Schiff base formation and phosphorus–hydrogen addition between vanillin, diamines, and diethyl phosphite, followed by reacting with epichlorohydrin. Their reactivities are similar to...

Vanillin-Derived High-Performance Flame Retardant Epoxy Resins: Facile Synthesis and Properties

The versatile characteristic of epoxy and its diversity made it suitable for different industrial applications such as laminated circuit board, electronic component encapsulations, surface coatings, potting, fiber reinforcement, and adhesives. However, the pervasive applications in many high-performance field limited the epoxy use because of their delamination, low impact resistance, inherent brittleness, and fracture toughness behavior. The limitations of epoxy can be overcome by incorporation and modification before their industrial applications. Currently, modified epoxy resins are extensively used in fabrication of natural fiber-reinforced composites and in making its different industrial products because of their superior mechanical, thermal, and electrical properties. Present review article designed to be a comprehensive source of recent literature on epoxy structure, synthesis, modified epoxy, bio-epoxy resin, and its applications. This review article also aims to cover the recent advances in natur...

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Recent advances in epoxy resin, natural fiber-reinforced epoxy composites and their applications

Conventional thermosets are built by nonrenewable fossil resources and are arduous to be reprocessed, recycled, and reshaped due to their permanent covalent cross-linking, and their flammability makes them unsafe during use. Here, for the first time, we synthesized a novel Schiff base precursor from abundant and renewable lignin derivative vanillin and produced malleable thermosets (Schiff base covalent adaptable networks (CANs)) combining high performance, super-rapid reprocessability, excellent monomer recovery, and arbitrary permanent shape changeability as well as outstanding fire resistance. The Schiff base CANs exhibited high glass transition temperatures of ∼178 °C, tensile strength of ∼69 MPa, tensile modulus of ∼1925 MPa, excellent flame retardancy with UL-94 V0 rating and V1 rating, and high LOI of ∼30%. Meanwhile, three Schiff base CANs showed high malleability with the activation energy of the bond exchange of 49–81 kJ mol–1 and could be reprocessed in 2–10 min at 180 °C. These Schiff base CAN...

Robust, Fire-Safe, Monomer-Recovery, Highly Malleable Thermosets from Renewable Bioresources

The combination of DOPO and 2-aminobenzothiazole (ABZ) was designed to develop P/N/S-containing flame retardant DOPO-ABZ, and its chemical structure was confirmed by HRMS, FTIR, and 1H and 31P NMR. The reduced thermal stability of EP/DOPO-ABZ formulations was found through DSC and TGA, as compared to that of EP. Fire properties were evaluated by LOI, UL-94, and cone calorimeter tests, respectively. The results indicated that DOPO-ABZ imparted flame retardance to EP, and that EP/7.5 wt % DOPO-ABZ passed the V-0 rating, and acquired a LOI value of 33.5%; moreover, when the loading of DOPO-ABZ increased to 10 wt %, it could further suppress the heat release and smoke release of the curved epoxy resin. Finally, the flame-retardant mechanism was studied by TG-FTIR and py-GC/MS, disclosing that DOPO-ABZ exerted predominant gaseous-phase activity of fire inhibition via generating phosphorus-containing free radicals and nitrogen/sulfur-containing volatiles.

Synthesis of a Novel P/N/S-Containing Flame Retardant and Its Application in Epoxy Resin: Thermal Property, Flame Retardance, and Pyrolysis Behavior

Pyrolysis route of a novel, flame retardant constructed by phosphaphenanthrene and triazine-trione groups and its flame-retardant effect on epoxy resin

Epoxy thermoset with enhanced flame retardancy and physical-mechanical properties based on reactive phosphaphenanthrene compound

Flame retardant and toughening behaviors of bio‐based DOPO‐containing curing agent in epoxy thermoset

Three types of melamine cyanurate (MCA) with micrometer-size sphere-like, micrometer-scale rod-like, and nanometer-scale flake-like morphologies were synthesized by changing the chemical circumstances of the reactions. The microcosmic morphologies of MCA were characterized via scanning electron microscopy and X-ray diffraction. After the MCAs with different morphologies were incorporated into polyamide 6 (PA6), the flame-retardant properties of the MCA/PA6 composites were investigated using the limited oxygen index (LOI), UL94, and cone calorimeter tests. The MCA/PA6 composites with nanometer-scale flake-like MCA obtained an LOI value of 29.5% and a UL94 V-0 rating, which were higher than those with micrometer-size sphere-like and rod-like MCAs. However, the different morphologies did not affect the heat release rate, total smoke release, average carbon monoxide yield, and average carbon dioxide yield based on the cone calorimeter. The flame-retardant mechanism of MCAs with different morphologies was investigated via thermal gravimetric analysis (TGA) and TGA-Fourier transform infrared spectra. The results show that the different morphologies of MCA resulted in different dispersed evenness of MCA. Further, the nanometer-scale flake-like morphology of MCA brought more interactions of hydrogen bond between MCA and PA6, which resulted in the delay of MCA decomposition and the enhancement of MCA flame-retardant effect. The nanometer-scale flake-like MCA had a better performance compared with the other samples because of the delaying and even release of flame-retardant effect by the decomposition of evenly dispersed MCA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40558.

The effect of morphology on the flame-retardant behaviors of melamine cyanurate in PA6 composites

High-performance flexible polyurethane foam based on hierarchical BN@MOF-LDH@APTES structure: Enhanced adsorption, mechanical and fire safety properties.

Yong Qiu

Papers

Pyrolysis route of a novel, flame retardant constructed by phosphaphenanthrene and triazine-trione groups and its flame-retardant effect on epoxy resin

Epoxy thermoset with enhanced flame retardancy and physical-mechanical properties based on reactive phosphaphenanthrene compound

Flame retardant and toughening behaviors of bio‐based DOPO‐containing curing agent in epoxy thermoset

The effect of morphology on the flame-retardant behaviors of melamine cyanurate in PA6 composites

High-performance flexible polyurethane foam based on hierarchical BN@MOF-LDH@APTES structure: Enhanced adsorption, mechanical and fire safety properties.