Effect of phosphorus‐containing flame retardants on flame retardancy and thermal stability of tetrafunctional epoxy resin

A novel phosphorus‐containing, nitrogen‐containing, and sulfur‐containing reactive flame retardant (BPD) was successfully synthesized by 1‐pot reaction. The intrinsic flame‐retardant epoxy resins were prepared by blending different content of BPD with diglycidyl ether of bisphenol‐A (DGEBA). Thermal stability, flame‐retardant properties, and combustion behaviors of EP/BPD thermosets were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limited oxygen index (LOI) measurement, UL94 vertical burning test, and cone calorimeter test. The flame‐retardant mechanism of BPD was studied by TGA/infrared spectrometry (TGA‐FTIR), pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), morphology, and chemical component analysis of the char residues. The results demonstrated that EP/BPD thermosets not only exhibited outstanding flame retardancy but also kept high glass transition temperature. EP/BPD‐1.0 thermoset achieved LOI value of 39.1% and UL94 V‐0 rating. In comparison to pure epoxy thermoset, the average of heat release rate (av‐HRR), total heat release (THR), and total smoke release (TSR) of EP/BPD‐1.0 thermoset were decreased by 35.8%, 36.5% and 16.5%, respectively. Although the phosphorus content of EP/BPD‐0.75 thermoset was lower than that of EP/DOPO thermoset, EP/BPD‐0.75 thermoset exhibited better flame retardancy than EP/DOPO thermoset. The significant improvement of flame retardancy of EP/BPD thermosets was ascribed to the blocking effect of phosphorus‐rich intumescent char in condensed phase, and the quenching and diluting effects of abundant phosphorus‐containing free radicals and nitrogen/sulfur‐containing inert gases in gaseous phase. There was flame‐retardant synergism between phosphorus, nitrogen, and sulfur of BPD.

Section: Introductionmentioning

confidence: 99%

Flame‐retardant performance and mechanism of epoxy thermosets modified with a novel reactive flame retardant containing phosphorus, nitrogen, and sulfur

Huo

Wang

Yang

et al. 2017

“…Among these phosphorus‐containing compounds, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and its derivatives are the most commonly used flame retardants for EPs due to their dramatic flame‐retardant efficiency . They mainly exert flame‐retardant quenching effect through releasing free PO radicals and terminating the combustion chain reaction in gaseous phase, as well as interacting with the decomposing polymer and increasing char yields in condensed phase . Various kinds of DOPO derivatives were prepared through the reaction of DOPO and other flame‐retardant functional groups to construct high‐efficiency flame‐retardant system.…”

Section: Introductionmentioning

confidence: 99%

“…[13][14][15] They mainly exert flameretardant quenching effect through releasing free PO radicals and terminating the combustion chain reaction in gaseous phase, 16,17 as well as interacting with the decomposing polymer and increasing char yields in condensed phase. 18,19 Various kinds of DOPO derivatives were prepared through the reaction of DOPO and other flameretardant functional groups to construct high-efficiency flameretardant system. Another approach to high-efficient flame-retardant system is to mix different flame retardants.…”

Section: Introductionmentioning

confidence: 99%

Synergistic flame‐retardant effect and mechanisms of boron/phosphorus compounds on epoxy resins

Tang

Qian

Qiu

et al. 2017

To explore the component synergistic effect of boron/phosphorus compounds in epoxy resin (EP), 3 typical boron compounds, zinc borate (ZB), boron phosphate (BPO 4 ), and boron oxide (B 2 O 3 ), blended with phosphaphenanthrene compound TAD were incorporated into EP, respectively. All 3 boron/phosphorus compound systems inhibited heat release and increased residue yields and exerted smoke suppression effect. Among 3 boron/phosphorus compound systems, B 2 O 3 /TAD system brought best flame-retardant effect to epoxy thermosets in improving the UL94 classification of EP composites and also reducing heat release most efficiently during combustion. Among these phosphorus-containing compounds, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and its derivatives are the most commonly used flame retardants for EPs due to their dramatic flame-retardant efficiency. [13][14][15] They mainly exert flameretardant quenching effect through releasing free PO radicals and terminating the combustion chain reaction in gaseous phase, 16,17 as well as interacting with the decomposing polymer and increasing char yields in condensed phase. 18,19 Various kinds of DOPO derivatives were prepared through the reaction of DOPO and other flameretardant functional groups to construct high-efficiency flameretardant system. Another approach to high-efficient flame-retardant system is to mix different flame retardants. When they were applied into EPs, usually, they endowed epoxy thermosets with remarkable flame retardancy by means of group synergistic effect or component synergistic effect. [20][21][22][23] In reported literatures, inorganic flame retardants have frequently been chosen to mix with other flame retardants for constructing highefficiency flame-retardant system due to their low cost, low toxicity, and high thermal stability. [24][25][26] Among them, boron compounds such as zinc borate (ZB), boric acid, boron oxide (B 2 O 3 ), boron phosphate (BPO 4 ), melamine borate, and so on were often chosen to be utilized in EPs. It has been reported that boron compounds could improve the flame retardancy of EPs by increasing char yield, suppressing smoke, releasing water, and absorbing heat.

“…Epoxy resin (EP) plays an increasingly important role in many fields of application due to its excellent adhesive property, good corrosion resistance, high thermal stability, and outstanding mechanical properties. [1][2][3][4] However, the application of EP is limited because of its inflammability in air, which will release a large amount of toxic and hazardous smoke. Therefore, it is essential to improve the flame retardancy of EP.…”

Section: Introductionmentioning

confidence: 99%

“…As a rule, adding and reacting with flame retardant are 2 main ways to improve the flame retardancy of polymers, while additive flame retardants are applied more widely than reactive flame retardants due to their easy preparation and extensive sources. Some traditional flame retardants like Mg(OH) 2 , Al(OH) 3, Sb 2 O 3 , and phosphorus-containing compounds are widely used, [5][6][7][8] while some new flame retardants such as graphene, lactate dehydrogenase (LDH), carbon nanotubes, α-zirconium phosphate (α-ZrP), and MoS 2 gradually attract greater attention. [9][10][11][12][13][14] Among these, graphene is a new kind of 2-dimensional material consisting of sp2-bonded carbon sheets, and its use extends to various fields owing to its large specific surface area, outstanding mechanical properties, excellent thermal and chemical performance, and so on.…”

Section: Introductionmentioning

confidence: 99%

A novel graphene hybrid for reducing fire hazard of epoxy resin

Wang

et al. 2017

Epoxy resin (EP) is more and more important in many fields, but its application is limited due to the inflammability in air of EP. Therefore, reducing the fire hazard of EP is necessary. In this work, a kind of hybrid flame retardant (α‐ZrP‐RGO) consisting of a 2‐dimensional inorganic reduced graphene oxide (RGO) modified with a planar‐like α‐zirconium phosphate (α‐ZrP) particles was prepared successfully via 1‐step hydrothermal method. The effects of α‐ZrP‐RGO on the thermal performance, flame retardancy, and smoke suppression of EP were investigated by preparing EP composites containing both EP and α‐ZrP‐RGO. Thermogravimetric results revealed that α‐ZrP‐RGO could improve the char yield of EP at 700°C obviously. In addition, compared with pure EP, the peak heat release rate and the total heat release of EP composites were decreased significantly, while the limited oxygen index of EP composites was increased. Meanwhile, the smoke production rate of EP composites was reduced obviously with the addition of α‐ZrP‐RGO. The enhanced flame retardancy and smoke suppression of EP composites were mainly attributed to not only the physical barrier effect of both α‐ZrP and RGO but also the catalytic effect of α‐ZrP during the combustion process of EP composites.