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To prepare flame-retardant epoxy resin, phosphorus compound containing di-hydroxyl group (10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phospha phenanthrene-10-oxide, DOPO-HQ) was reacted with uncured epoxy resin (diglycidyl ether of bisphenol A, YD-128) and then cured using a curing agent (dicyandiamide, DICY). This study focused on the effect of...
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A phosphine oxide-containing bio-based curing agent was synthesized by addition reaction between furan derivatives and diphenylphosphine oxide. The molecular structure of the as-prepared bio-based curing agent was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. Dynamic mechanical analysis results in...
Citations
... The presence of phosphorus atoms in the structure of the cured epoxy resins, even in low concentration, can improve their flame resistance [9][10][11]. Phosphorus compounds are environmentally friendly and exhibit low toxicity. ...
... Phosphorus compounds are environmentally friendly and exhibit low toxicity. They can reduce the flammability of polymeric materials by acting both in vapor phase through a radical mechanism to interrupt the combustion process and in condensed phase by facilitating the formation of a layer of carbonaceous residue that acts as a barrier against heat transfer and the diffusion of combustible gases and smoke [9,12,13]. 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and its derivatives have been shown to be very effective in reducing the flammability of epoxy resins. DOPO exhibits superior thermal and thermo-oxidative stability, acting in the gas and condensed phases to increase flame resistance. ...
The design and manufacture of innovative multifunctional materials possessing superior characteristics, quality and standards, rigorously required for future development of existing or emerging advanced technologies, is of great importance. These materials should have a very low degree of influence (or none) on the environmental and human health. Adjusting the properties of epoxy resins with organophosphorus compounds and silver-containing additives is key to the simultaneous improvement of the flame-resistant and antimicrobial properties of advanced epoxy-based materials. These environmentally friendly epoxy resin nanocomposites were manufactured using two additives, a reactive phosphorus-containing bisphenol derived from vanillin, namely, (4-(((4-hidroxyphenyl)amino)(6-oxido-6H-dibenzo[c,e][1,2]oxaphosphinin-6-yl)methyl)-2-methoxyphenyl) phenylphosphonate (BPH), designed as both cross-linking agent and a flame-retardant additive for epoxy resin; and additional silver-loaded zeolite L nanoparticles (Ze–Ag NPs) used as a doping additive to impart antimicrobial activity. The effect of BPH and Ze–Ag NPs content on the structural, morphological, thermal, flame resistance and antimicrobial characteristics of thermosetting epoxy nanocomposites was investigated. The structure and morphology of epoxy nanocomposites were investigated via FTIR spectroscopy and scanning electron microscopy (SEM). In general, the nanocomposites had a glassy and homogeneous morphology. The samples showed a single glass transition temperature in the range of 166–194 °C and an initiation decomposition temperature in the range of 332–399 °C. The introduction of Ze–Ag NPs in a concentration of 7–15 wt% provided antimicrobial activity to epoxy thermosets.
... An idealized structure of epoxy DGEBA resin is presented in Figure 14. Since the first commercial interest arose in the 1940s, EPs have proved to be superior among all thermosetting resins because of their high tensile strength/modulus, low shrinkage on cure, dimensional stability, and chemical inertness even though they have never been the cheapest [73,74]. Currentky, EP is frequently used as a polymeric matrix in the development of high-performance materials in applications where thorough, durable coating and adhesives are needed in the electrical industry and commercial and military aircraft industries [71]. ...
Thermosetting resins are used in many applications due to their great mechanical properties, chemical resistance, and dimensional stability. However, the flammability of thermosets needs to be improved to minimize fire risk and meet fire safety regulations. Some commercially available flame retardants have an adverse effect on people’s health and the environment. Thus, the development of novel, more sustainable flame retardants obtained or derived from biomass has become an objective of contemporary research. The objective of this study is to summarize recent progress on bio-based flame retardants for thermosetting resins so as to promote their prompt development. Groups of biomass compounds with a potential for flame retardant industrial applications were introduced, and their thermal degradation was investigated. The authors focused mostly on the thermal degradation of composites containing bio-based flame retardants determined by thermogravimetric analysis, their tendency to sustain a flame determined by a limiting oxygen index, and fire behavior determined by a cone calorimeter test. The results showed that the mode of action is mostly based on the forming of the char layer. However, in many cases, there is still a necessity to input a high amount of additive to achieve significant flame retardancy effects, which may adversely impact mechanical properties.
The utilization of epoxy resin (EP) is widespread across various industries. Nevertheless, its combustibility restricts its broader utilization. Additive flame retardants have proven effective in enhancing EP flame retardancy in recent decades. However, poor weather and aging resistance have always been the defects of added flame retardants. A reactive flame retardant (VPD) was synthesized from 3, 5‐diamino‐1, 2, 4‐triazole and phenylphosphonic dichloride, and was used to prepare VPD/EP flame retardant epoxy thermosets. The mechanical properties of the VPD/EP flame retardant epoxy thermosets are lower than those of pure epoxy, because the distance between molecules of VPD is increased compared with that of DDM, the cross‐linking density of the polymer after curing is decreased, and the intermolecular force is reduced. The VPD/EP flame retardant epoxy thermosets have a 40% reduction in total heat release compared to pure EP, an increase in limiting oxygen index value from 24.7% (pure EP) to 29.4%, and a V‐1 rating in UL‐94 testing. The obtained EP has not only good flame retardancy but also better weather resistance and aging resistance than additive flame retardants.
Highlights
An intrinsic flame‐retardant P and N coacting EP was designed and synthesized.
The intrinsic flame‐retardant EP has excellent weather and aging resistance.
The presence of the P, the residual char generated by combustion is denser.
Two types of isomeric bi‐DOPO flame retardants named DHK and DMG were successfully prepared and their flame retardant properties were investigated. Although they had the same phosphorus content, the corresponding thermoset DHK/EP and DMG/EP show different flame retardancy. The flame retardant mechanism was compared by thermal analysis coupled with Fourier transform infrared (TG‐FTIR), residue FTIR, elemental analysis, Raman spectra, SEM and cone calorimetry. More phosphorus was remained in the residue of DHK/EP which suggests better condensed phase flame retardancy than that of DMG/EP. However, DMG showed better flame inhibition effect than that of DHK. The results of mean square displacement, free volume fraction and cohesive energy density in molecular dynamics simulations showed that the weakening of the movement ability of the DMG/EP molecular segments should be the reason for the increased in toughness. This showed that although flame retardants possessed the same composition, their structure will also affect their flame retardant mechanism and properties, which provided a guide for the design and preparation of high‐efficiency flame retardants. This article is protected by copyright. All rights reserved
Epoxy resins are widely used in many fields because of their excellent physical and chemical properties. Unfortunately, epoxy resins are inherently combustible materials and have great fire hazard. Three methods are employed to endow epoxy resins with good flame-retardant properties, and they are intrinsic flame-retardant, additive flame-retardant and reactive flame-retardant. Reactive flame-retardant epoxy resins become a research trend due to their good flame-retardant, thermal stability and mechanical properties. In this review, the combustion process, flame-retardant mechanism and classification of flame-retardant epoxy resins are briefly analyzed. Several important characterization methods of flame-retardant epoxy resins are introduced. Importantly, the latest research progresses of reactive flame-retardant epoxy resins are summarized and discussed, including halogen-, phosphorus-, nitrogen-, silicon-, multi-elements containing, and bio-based flame-retardant epoxy resins. Furthermore, the future perspectives of reactive flame-retardant epoxy resins are put forward. This work may provide some new insights for the design of reactive flame-retardant epoxy resins.
With the increasing demand of industry, the fabrication of single-component epoxy (EP) systems with satisfactory flame retardancy and thermal stability is of great significance. Herein, a novel phosphorus/nitrogen-containing single-component EP (EP/DOPO/BDM/BICP) system was synthesized via incorporating N,N′-bismaleimide-4,4′-diphenylmethane (BDM), benzimidazolyl-substituted cyclotriphosphazene (BICP) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) into EP. In our previous work, we found that DOPO could promote the decomposition of BICP to produce dissociative benzimidazoles under heating, which endowed the as-fabricated epoxy thermoset with rapid curing speed. However, the addition of DOPO reduced the glass transition temperature (Tg) of epoxy thermosets. To deal with this problem, bismaleimide with superior heat resistance was added. The results indicated that the addition of BDM improved the thermal stability, flame retardancy and smoke suppression of EP/DOPO/BDM/BICP. The obtained thermoset exhibited UL94 V-0 rating, limiting oxygen index (LOI) of 40.5% and low total smoke production (TSP) of 10.4 m² due to the synergetic flame-retardant effect of phosphaphenanthrene, polybismaleimide and cyclotriphosphazene. This research offers a viable approach to develop single-component EPs with improved flame retardancy, thermal stability and rapid-curing ability.
