Synergistic Flame Retardant Research Articles

Effects of a Macromolecule Spirocyclic Inflatable Flame Retardant on the Thermal and Flame Retardant Properties of Epoxy Resin.

A new strategy for the preparation of an integrated three-source intumescent flame retardant (IFR) has been developed to improve the flame-retardant and smoke suppression performance of epoxy resin (EP) with a synergistic flame retardant effect. Herein, the synthesis of a macromolecular spirocyclic phosphorus/nitrogen-containing IFR poly sulfonamide spirocyclic pentaerythritol bisphosphonate (SAPC) is reported via a two-step method that uses pentaerythritol, phosphorus oxychloride and sulfonamide (SAA) as raw materials. Subsequently, the SAPC was incorporated into EP to prepare the composite to investigate its thermal stability, flame retardancy, and smoke suppression performance. Herein, a differential scanning calorimetry (DSC) analysis showed that the addition of SAPC increased the glass transition temperature (Tg) of the composite. Cone test results indicated that the incorporation of 8 wt % SAPC significantly improved the flame-retardant performance for the composite, with a 43.45% decrease in peak of heat release rate, a 28.55% reduction in total heat release, and a 30.04% decrease in total smoke release. Additionally, the composite received the V-0 rating in a UL-94 vertical burning test, accompanied by the “blowout” phenomenon. After the addition of SAPC, the amount of flammable gas products from the EP composite decomposition was obviously suppressed, and the amount of non-flammable as was increased. All of this suggests a good dilution role of SAPC. There are enough reasons to believe that the enhanced flame-retardant and toxicity suppression performance for the EP composite can be attributed to the good coordination of carbonization agent, acid source, and blowing agent in the SAPC structure.

A Phosphorous‐Aluminium‐Nitride Synergistic Flame Retardant to Enhance Durability and Flame Retardancy of Cotton

AbstractIn this paper, a Phosphorous ‐ Aluminium ‐ Nitride synergistic flame retardant (PAN) was synthesized by phosphoric acid, glycerol, aluminium sulfate and urea, though a one‐pot process. The PAN was durably grafted onto the surface of cotton fabric by the simple process of soak‐dry‐cure. At the same time, the synergistic effect of the aluminium element and Phosphorous ‐ Nitrogen flame retardants (PN) was investigated. The flame‐retardant effect is the best when the conttent of alumium is 2.5 mol% (percentage of phosphoricacid) in PAN. The analyses of FTIR and XPS results suggested that PAN was grafted onto the cotton by forming a strong P−O‐C covalent bond on the surface of fiber. The SEM and Whiteness test proved that the flame‐retardant finishing cotton fabric do possess good morphology and whiteness. The thermal stability and flame retardancy of the PAN treated cotton fabric were assessed by TG and vertical flammability test. Then, found the aluminium sulfate in PAN had synergistic effect, and the PAN had significant flame retardancy in application.

Preparation of a synergistic reactive flame retardant based on silicon, phosphorus and nitrogen and its application to cotton fabrics

A novel compound containing silicon, phosphorus and nitrogen, named 1-(9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide)-4-(trimethoxysilylmethyl) piperazine (DOPO-PiP-Si), was synthesized as a reactive flame retardant and applied to prepare flame-retardant cotton fabrics. Its structure was characterized by Fourier transform infrared spectra, 1H and 13C nuclear magnetic resonance (1H NMR and 13C NMR), and flame retardancy of treated cotton fabrics was investigated thoroughly using the limited oxygen index (LOI), vertical burning test, thermogravimetric analysis and cone calorimetry test (CONE), respectively. The LOI value of the cotton fabrics treated with DOPO-PiP-Si increased to 27.6% and the char length decreased to 12.2 cm without afterflame and afterglow. From the results of CONE test, the peak heat release rate and total heat release of treated cotton fabrics decreased from 230.8 to 161.1 kW/m2 and from 6.4 to 4.5 MJ/m2, respectively. Besides, the char residue reached 19.1%, which indicated that the treated cotton fabrics had excellent char formation ability and thermal stability. The morphology of char of the treated cotton fabrics was also characterized by scanning electron microscopy, it can be seen from results that the structure of fiber had no shrinkage and a few bubbles were distributed on the surface of fiber, which suggested that the treated cotton fabrics could display gas-phase flame retardant mechanism.

Flame Retardancy, Fire Behavior, and Flame Retardant Mechanism of Intumescent Flame Retardant EPDM Containing Ammonium Polyphosphate/Pentaerythrotol and Expandable Graphite.

The intumescent flame retardant ethylene–propylene–diene rubber (EPDM) was prepared using intumescent flame retardant (IFR), including ammonium polyphosphate (APP) /pentaerythrotol (PER) and expandable graphite (EG), as the flame retardant agent. The effects of IFR and EG on the flame retardancy, fire behavior, and thermal stability of the EPDM were investigated. The results show that IFR and EG have excellent synergistic flame retardant effects. When the mass ratio of IFR to EG is 3:1 and the total addition content is 40 phr, the limiting oxygen index (LOI) value of the EPDM material (EPDM/IFR/EG) can reach 30.4%, and it can pass a V-0 rating in the vertical combustion (UL-94) test. Meanwhile, during the cone calorimetry test, the heat release rate and total heat release of EPDM/IFR/EG are 69.0% and 33.3% lower than that of the pure EPDM, respectively, and the smoke release of the material also decreases significantly, suggesting that the sample shows good fire safety. In addition, the flame retardant mechanism of IFR and EG is systematically investigated by thermogravimetric analysis/infrared spectrometry (TG-IR), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), and the results indicate that IFR and EG have only physical interaction. Moreover, the reason why IFR exhibits a poor flame retardant effect in EPDM materials is explained.

Renewable vitamin B5 reactive N–P flame retardant endows cotton with excellent fire resistance and durability

A bio-based P–N synergistic flame retardant ammonium salt of d-Panthenol-tri (methylphosphonic acid) (ADPTMPA) was synthesized using a formaldehyde-free and solvent-free strategy for the highly efficient preparation of durable flame-retardant cotton. The ADPTMPA structure was verified by 1H NMR, 13C NMR and 31P NMR. FT-IR test revealed successful grafting of the flame retardant onto the cotton through P–O–C covalent bonding. The morphologies and structures of pure cotton and treated cotton were characterized by SEM and XRD, and the elemental compositions of cotton samples were analyzed by EDX. Volatile pyrolysis products of treated cotton were analyzed by TG-IR. Flame retardancy and washability of treated cotton were analyzed by limiting oxygen index (LOI) and vertical flammability tests (VFT). The LOIs of 40 wt% ADPTMPA treated cotton before and after 50 laundering cycles was determined as 46.5% and 35.8%, respectively. VFT showed the treated cotton exhibited no smoldering and continuous burning. All carbon lengths of treated cottons were less than 60 mm. The heat release rate and total heat release of treated cotton were decreased by 91.34% and 58.01% compared with pure cotton, respectively. There was 29.42 wt% carbon residual remaining when the treated cotton was exposed to heat flow of 35 kw/m2. The treated cotton exhibited excellent flame retardancy and washability. Additionally, the mechanical properties and whiteness of the treated cotton were well-maintained.

Preparation of cobalt-based metal organic framework and its application as synergistic flame retardant in thermoplastic polyurethane (TPU)

Firstly cobalt-based metal-organic framework material (Co-MOF) was designed and synthesized; its composition was studied by fourier transform infrared spectroscopy (FTIR) and energy dispersion spectrum (EDS), and the micrographs were observed by scanning electron microscope (SEM). Several burning test results showed that the flame retardant of TPU was obviously improved by the help of combination of 4.5 wt% APP/1.5 wt% Co-MOF. TPU is easily flammable with severe molten drops, so its limited oxygen index (LOI) is only 21.7 and cannot pass any UL-94 grade in vertical burning test. Whereas in TPU/6.0 wt% (4.5APP/1.5Co-MOF) composites, LOI raised to 28.2 and no dripping was produced in vertical burning test, so it passed UL-94 V-0 grade. Similarly, TPU released a large amount of heat and smoke in cone test, peak heat release rate (pHRR) reached 1359 kW m−2 and smoke production rate (SPR) was 0.11 m−2 s−1; however, in TPU/6.0 wt% (4.5APP/1.5Co-MOF) composites, pHRR reduced sharply to 257 kW m−2 and SPR dropped to 0.04 m−2 s−1. Most of all, some mechanical loss caused by the APP were partly recovered by substitutional use of Co-MOF.

The effect of ammonium polyphosphate on the mechanism of phosphorous-containing hydrotalcite synergism of flame retardation of polypropylene

Ammonium polyphosphate (APP) is well known to have a synergistic action with phosphorus-based flame retardants in enhancing the flame retardant performance of matrix polymers, but the effect of APP and phosphorous-containing hydrotalcite on synergistic effect and degradation mechanism of polypropylene (PP) has not been thoroughly studied. In the present work, a synergistic flame retardant containing P3O105− intercalated Mg/Al hydrotalcite modified by rare-earth coupling agent (W-LDH-P) and APP were prepared and used as compounded flame retardant (W-LDH-P/APP) for PP matrix. The W-LDH-P/APP and PP composites(PP/W-LDH-P/APP) possess a limiting oxygen index (LOI) value of 27.8% and achieves the V-0 standard of the flame retardant plastic. Additionally, the heat release rate (HRR), total heat release (THR) and total smoke release (TSR) for the PP/W-LDH-P/APP composites were decreased by 44.0%, 21% and 75% compared with PP/W-LDH-P. These results demonstrate that APP dramatically enhances the flame retardancy of the PP. The synergistic effect and degradation mechanism of APP and W-LDH-P are confirmed by SEM and TGA analysis. These analyses reveal that the APP and W-LDH-P promoted the formation of a more continuous and compact char layer during the burning process for PP matrix.

Occurrence and fate of antimony in plastics

Antimony (Sb) is a technology critical element whose presence is ubiquitous in manufactured products, and in particular in plastics where it is used extensively as a flame retardant synergist for brominated compounds, as a catalyst for polyethylene terephthalate production, and as a pigment for colour. This study reviews the usage, regulations and fate of Sb in plastics by examining primary data on its production, applications, contents in and migration from manufactured objects, and presence in and release from waste, including the disposal and recycling routes for this material (i.e., non-controlled disposal, incineration, landfilling and recycling). Consumption of Sb and the relative apportioning of the metalloid between different uses in plastics change continuously and are largely driven by dynamic economic factors; accordingly, reference to secondary data or sources can be misleading. Since Sb is not recovered from plastics, its fate is entirely linked to the fate of plastics themselves which, as far as disposal and recycling are concerned, might be dictated by the presence of co-associated regulated substances such as brominated flame retardants. Significantly, because of the high leachability of Sb from bottom incineration ashes, the EU considers the metalloid as the most problematic substance regarding the potential reuse of this material.

Synergistic effects of a highly effective intumescent flame retardant based on tannic acid functionalized graphene on the flame retardancy and smoke suppression properties of natural rubber

Tannic acid (TA), natural phenolic compounds abundant in many plants, exhibit low flammability and good absorbility because of multidentate properties. Based on it, a novel intumescent flame retardant (IFR) system (AGT) that consists of ammonium polyphosphate (APP)/TA functionalized graphene (TGE) presents synergistic flame retardant and smoke suppression for natural rubber (NR) due to the dual flame retardant functions of each component. The novel AGT system is of interest to a variety of fields because of its distinct flame retardant and relatively good mechanical properties in comparison to traditional IFR system. Cone calorimeter results reveal that the AGT system could clearly change the decomposition behavior of NR and form a highly graphitized and phosphorous-containing carbonaceous structure char layer on the surface of the composites, consequently resulting in synergistic effects on the flame retardancy and smoke suppression properties. Moreover, TGE endows NR composite excellent mechanical properties within an effective additive mass of AGT system.

Synergistic Flame Retardant Effect of Organic Phosphorus–Nitrogen and Inorganic Boron Flame Retardant on Polyethylene

In this study, to develop an organic/inorganic synergistic flame retardant, organic phosphorus–nitrogen flame retardant 6,6‐(((sulfonylbis(4,1‐phenylene)) bis(azanediyl))bis(thiophen‐2‐ylmethylene))bis(6H‐dibenzo[c,e][1,2]oxaphosphinine 6‐oxide (DOPO‐N) and inorganic boron flame retardant zinc borate (ZB) were selected. The flame retardant properties of polyethylene (PE) containing ZB/DOPO‐N were investigated. PE/20%ZB/10%DOPO‐N had better thermal stability and flame retardant properties. The limiting oxygen index of PE/20%ZB/10%DOPO‐N reached 24.6%, and UL 94 V‐0 rating was attained. The peak heat release rate, total heat release, average effective heat combustion, and fire growth index of PE/20%ZB/10%DOPO‐N were lower than when ZB and DOPO‐N were added separately. In addition, the flame retardant mechanism was investigated using scanning electron microscopy, X‐ray diffraction, energy dispersive X‐ray, and Fourier transform infrared spectroscopy. ZB/DOPO‐N simultaneously exerted condensed phase and gas phase flame retardant effect. POLYM. ENG. SCI., 60: 414–422, 2019. © 2019 Society of Plastics Engineers

Highly efficient adsorption and recycle of phosphate from wastewater using flower-like layered double oxides and their potential as synergistic flame retardants

Here, a novel Mg/Al-layered double oxide (MgAl-LDO) with a flower-like architecture was synthesized through facile green co-precipitation and calcination methods for phosphate separation and recycle from wastewater. The as-prepared MgAl-LDO demonstrated high specific surface area of 200.17 m2/g based on its 3D hierarchical flower-like structure. The phosphate adsorption was well conformed to Pseudo-second-order kinetic model and Langmuir model, suggesting a homogeneous monolayer chemisorption with a maximum adsorption capability of 103.61 mg P/g. The existence of Cl−, NO3− ions did not interfere with phosphate adsorption, while high concentration SO42− and CO32− affected the phosphate adsorption. In addition, adsorption mechanism analysis revealed that high-efficiency phosphate capture by MgAl-LDO was mainly due to the electrostatic adsorption, surface inner-sphere complexation, ligand exchange and precipitation combined process. Remarkably, the phosphate adsorbed MgAl-LDO (P-LDO) can be employed as synergistic flame retardant to improve the flame retardancy of paper.

An efficient synergistic system for simultaneously enhancing the fire retardancy, moisture resistance and electrical insulation performance of unsaturated polyester resins

Unsaturated polyester resins (UPR) are usually used in the field of electronic appliances, but their inherent flammability and hygroscopicity severely limit their wide application. In this research, dimelamine pyrophosphate (DMPY) was synthesized and constituted a synergistic flame retardant system (FRs) with aluminum diethylphosphinate (ADP). The FRs was applied to flame retarded UPR thermosets and the fire retardancy, moisture resistance, mechanical properties and flame retarded mechanisms of UPR/FRs were comprehensively investigated. When as low as 15 wt% FRs was incorporated, UPR/FRs achieved UL-94 V-0 rating during vertical burning tests and the limiting oxygen index value reached 27.9%. FRs stimulated UPR matrix to form uniform, stiff and dense char layer on materials surface during combustion process. Besides, the phosphine and phosphine oxygen radicals and inert gases generated from FRs exerted the inhibition and dilution effect in gas phase. Thus, the heat release and effective heat combustion of UPR/FRs were conspicuously suppressed. Moreover, UPR/FRs retained satisfactory flame retardancy and mechanical performance after water resistance tests. The moisture resistance of UPR/FRs was evidently enhanced compared with UPR and it led to the maintenance of electrical insulation properties of water treated UPR/FRs. Overall, the superior fire safety, moisture resistance and electrical insulation performance promised the flame retardant UPR thermosets crucial application values in the key areas.

Synthesis and application of self-crosslinking and flame retardant waterborne polyurethane as fabric coating agent

A series of self-crosslinking and flame retardant modified waterborne polyurethanes (SFR-WPU) were synthesized and the chemical structure of SFR-WPU was characterized by FT-IR. Particle size, particle size distribution and zeta potential were tested to evaluate the emulsion stability. Afterwards, SFR-WPU as a finishing agent was coated on polyester fabric. The experimental results of limiting oxygen index (LOI) and vertical burning test (VBT) indicated that when the content of FRC-6 was 9.07 wt% in SFR-WPU, the LOI, afterflame time, afterglow time and damaged length values of the coated polyester fabric were 27.5%, 4.7 s, 0.0 s and 10.9 cm, respectively, but the LOI, afterflame time, afterglow time and damaged length values of the pristine polyester fabric were only 20.1%, 62.0 s, 0.0 s and 30.0 cm, respectively. Even after AATCC standard washing process, the LOI, afterflame time, afterglow time and damaged length values of the coated polyester fabric changed slightly to be 26.8%, 5.0 s, 0.0 s and 12.3 cm, respectively. Then, the flame retardant mechanism was explored by testing thermal property and char residue of polyester fabrics with thermogravimetry (TG), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). It was found that SFR-WPU obviously reduced the initial decomposition temperature of the fabric, but significantly improved the residual carbon content, which was contributed by the synergistic flame retardant effect of P and N elements in SFR-WPU from both condensed-phase and gas-phase, respectively.

Synergistic effect of organically modified zinc aluminum layered double hydroxide in intumescent flame‐retarding polypropylene composites containing melamine phytate and dipentaerythritol

In this article, an organically modified zinc aluminum layered double hydroxide (OLDH) was prepared by a facile and effective method. The aim for preparing and decorating LDH is to improve the dispersion of OLDH particles in polypropylene (PP). Fourier transform infrared (FTIR) spectra and X‐ray diffraction (XRD) spectra have verified the feasibility for preparing OLDH. In contrast with LDH, the hydrophobicity of OLDH was obviously changed after introduction of sodium dodecyl benzene sulfonate. Together with melamine phytate/dipentaerythritol (MPA/DPER), OLDH was introduced into PP by melt blending. Surprisingly, the synergistic effect of OLDH and MPA/DPER was obviously found in flame‐retarding PP. When the content of MPA/DPER and OLDH are 27 phr and 3 phr, the limiting oxygen index value of PP composites is 30.5% and samples can pass UL‐94 V‐0 rating. Thermogravimetric analysis demonstrates that the participation of OLDH can further enhance the thermal stability of PP/MPA/DPER. Moreover, the surface morphology and chemical structure of PP composites after combustion were systematically analyzed by optical photos, SEM, FTIR spectra, and X‐ray photoelectron spectroscopy spectra, respectively. The results reveal that the reinforcing effect of OLDH for char layers structure becomes the main reason for improving the flame retardancy of PP composites. Based on abovementioned analysis, a potential synergistic flame retardant mechanism was primarily proposed. POLYM. ENG. SCI., 59:2301–2312, 2019. © 2019 Society of Plastics Engineers

Synthesis of a novel dual layered double hydroxide hybrid nanomaterial and its application in epoxy nanocomposites

Ease of undesirable agglomeration and low efficiency are two problems that highly restrict the application of MgAl-layered double hydroxides (MgAl-LDH) as suitable flame retardants for epoxy resins. Herein, a new strategy that chose MOFs as the precursor to connect two different LDHs into a hybrid nanomaterial is reported. Nanosheets of NiCo-layered double hydroxides (NiCo-LDH) with multidimensional nanostructures were uniformly anchored on the surface of MgAl-LDH slabs. This led to a better dispersion and stronger interaction within the epoxy matrix, resulting in enhanced strength of the char layers, and also enabled synergistic flame retardant effect to the epoxy nanocomposite, when compared to the case of the unmodified epoxy. The sample passed V-0 rating in UL-94 test and its peak of heat release rate was reduced by 66.7% in cone calorimeter test with the addition of only 2.5 wt% of as-prepared flame retardant. Besides, due to the unique structure of the nanofiller, the mechanical properties of the nanocomposite were only slightly impacted. This is the first report on the synthesis of a dual LDH hybrid nanomaterial, which moreover, improved the flame retardancy of epoxy nanocomposite even when added in relatively low amounts.

Synergistic Flame‐Retardant Effect of an Aryl Boronic Acid Compound and Ammonium Polyphosphate on Epoxy Resins

AbstractTo develop new organic/inorganic synergistic flame retardants, organic compound containing boron and nitrogen, 2,4,6‐tris‐(4‐boronphenoxy)‐(1,3,5)‐triazine (TNB) was synthesized. The flame retardant properties of epoxy resins (EP) containing TNB and ammonium polyphosphate (APP) were investigated. When 5% of TNB/APP (w/w was 1:2) was added to EP, the limiting oxygen index (LOI) of EP containing TNB/APP was 29.5%, and UL 94 V‐0 rating was achieved. Its peak heat release rate (PHRR) and total heat release (THR) decreased. In addition, the mechanical properties of EP containing TNB/APP were not affected significantly. Using scanning electron microscopy and energy dispersive spectrometer (SEM‐EDX), Fourier transform infrared spectroscopy (FTIR), and Pyrolysis‐gas chromatography mass spectrometry (PY‐GC‐MS), the flame‐retardant mechanism was investigated. It was indicated that TNB/APP had good synergistic flame‐retardant effects, which was effect in the gas and condensed phases simultaneously.

Multiple synergistic effects of graphene-based hybrid and hexagonal born nitride in enhancing thermal conductivity and flame retardancy of epoxy

The heat shock, thermal aging and fire hazard of induced by delayed heat diffusion in microelectronic devices require a high-efficiency thermal management system with high-performance electronic packaging materials. In this work, the significant thermal conductivity and flame retardancy of polymer-based thermally conductive composites (PTCs) are addressed by multiple synergistic effects of hexagonal born nitride (hBN) and few flame-retardant functionalized graphene. Briefly, a multifunctional hydrophilic graphene-based hybrid containing Ni(OH)2 nanoribbons and reduced graphene oxide (RGO) was synthesized by two-step hydrothermal process. The resulted RGO@Ni(OH)2 hybrid and hBN sheets (lateral size of 4.37 ± 1.68 μm and thickness of 80 ± 21 nm) used as synergistic and main fillers, respectively, was simultaneously added into EP matrix. As expected, the binary fillers showed multiple synergistic effects for improving the thermal conductivity and flame retardancy of composites. Typically, the good dispersion and interfacial interaction of RGO@Ni(OH)2 hybrid in matrix can not only inhibit the stacking aggregation behavior of hBN sheets, but also bridge adjacent hBN sheets, both of which resulted in a high thermal conductivity (2.01 W/mK) of ternary composites with a synergistic increment of 39.4% comparing to EP/hBN. On the other hand, their synergistic flame retarding effect including catalytic carbonization, endothermic action and barrier effect induced by RGO@Ni(OH)2, as well as “tortuous path” effect of hBN sheets, jointly led to the formation of a compact and robust char layer in condensed phase during combustion. As a result, EP/hBN/RGO@Ni(OH)2 exhibited a desired flame ratardancy with considerable reductions being seen in peak heat release rate, total heat release and total smoke production, i.e., 33.5%, 33.8% and 43.0% comparing to neat EP.

Recycled electronic plastic and marine litter

Black consumer plastics are often contaminated with hazardous chemicals because of technological constraints on sorting dark plastic during recycling of municipal waste coupled with the convenience of waste electrical and electronic equipment (WEEE) as a secondary source of black plastic. In this study, samples of beached plastic litter (n = 524) from southwest England were categorised according to origin, appearance and colour (black versus non-black) before being analysed by x-ray fluorescence (XRF) spectrometry for elements that are characteristic of EEE. The small number of items of WEEE retrieved (n = 36) were largely restricted to wiring insulation and constructed of lead-stabilised polyvinyl chloride (PVC). Among the remaining samples, Br, Cd, Cr and Pb were commonly detected in all categories of black plastics (n = 264) with maximum concentrations of 43,400 mg kg−1, 2080 mg kg−1, 662 mg kg−1 and 23,800 mg kg−1, respectively. Moreover, concentrations of Br were significantly correlated with concentrations of the flame retardant synergist, Sb (n = 22), and 35 samples were potentially non-compliant with regard to limits defined by the Restriction of Hazardous Substances Directive. For plastics of other colours (n = 224), Br and Pb were detected in fewer samples and Br was co-associated with Sb in only two cases, with occasional high concentrations Cd, Cr and Pb largely attributed to the historical use of cadmium sulphide and lead chromate pigments. An avian physiologically-based extraction test applied to selected samples cut to mm-dimensions revealed bioaccessibilities ranging from <0.1% for Cr in a green fragment to about 2.4% (or about 580 mg kg−1) for Pb in black PVC. The recycling of WEEE into consumer, industrial and marine (e.g. fishing) plastics that are mainly coloured black appears to be an important vehicle for the introduction of hazardous chemicals into the environment and a source of their exposure to wildlife.

Synthesis of P–N–Si synergistic flame retardant based on a cyclodiphosphazane derivative for use on cotton fabric

A durable and effective flame retardant (FR) was synthesized in this work by taking advantage of the high reactivity of a cyclodiphosphazane derivative, without the use of formaldehyde. The FR is halogen-free and has the synergistic effect of phosphorus, nitrogen and silicon. Fire resistance of the cotton fabrics is significantly enhanced after the FR treatment. The limiting oxygen indices of cotton treated with 30% FR increase from 18.2 to 52.9% and decrease to 27.2% after 50 launder cycles, demonstrating that the proposed material is a durable FR. The thermo-gravimetric analysis results indicate that compared with the control cotton, the degradation process of the treated cotton occurred at a lower temperature range, the degree of degradation was lower, and the residue is improved. The total heat release and the effective heat combustion values are notably lower for the treated cotton than the control cotton. Furthermore, mechanical property tests demonstrate that the tensile strength is largely retained, while the bending length of the treated cotton partly increases. The surface morphology of the treated cotton is investigated with scanning electron microscopy. Fourier transform infrared and elemental analysis show that the FR was successfully grafted onto the surface of the cotton fabric. 1H, 13C, and 31P nuclear magnetic resonance verify the chemical structure of the FR.

Thermal Stability and Flame Retardancy Properties of Epoxy Resin Modified with Functionalized Graphene Oxide Containing Phosphorus and Silicon Elements.

Phosphorus- and silicon-modified graphene oxide was prepared to improve the thermal stability and flame retardancy properties of epoxy resin. 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and vinyltriethoxysilane (VTES) were successfully grafted onto the surface of graphene oxide (GO) through solvothermal synthesis and hydrolysis–condensation reaction, respectively. Subsequently, the functionalized graphene oxide grafted by DOPO and VTES (DOPO–VTES–GO) was incorporated into the epoxy resin by the solution blending method. The effect of DOPO–VTES–GO on the thermal stability and flame-retardant properties of epoxy resin was systematically studied. Thermogravimetric analysis showed that the thermal stability and char residue yield of DOPO–VTES–GO/epoxy were increased obviously compared with those of pure epoxy resin and DOPO–GO/epoxy. Cone calorimeter test results showed that DOPO–VTES–GO/epoxy had better flame retardancy than pure epoxy resin and DOPO–GO/epoxy on reducing the peak of heat release rate, total heat release, and total smoke production. Furthermore, the char residue after the cone calorimeter tests was investigated by scanning electron microscopy–energy-dispersive X-ray spectrometry, Raman spectroscopy, and Fourier transform infrared measurements. These results demonstrated that the DOPO–VTES–GO can enhance the graphitization degree of char residues and promote the formation of the thermally stable char. In addition, the mechanism of flame retardancy was proposed, and DOPO–VTES–GO exerts the synergistic effect mainly by means of catalytic charring in the condensed phase and capturing hydroxyl or hydrogen radicals from thermal decomposition of epoxy resin in the gas phase. This work provides novel insights into the preparation of phosphorus–silicon–graphene oxide ternary synergistic flame retardants for thermosetting polymer materials.