Flame Retardant Agent Research Articles

A facile and durable flame retardant approach for silk fabric through Kabachnik-Fields reaction

This study facilely developed the durable flame retardant (FR) silk fabric by bonding phosphonate groups to silk fiber through Pudovik addition of diethyl phosphite onto Schiff base aldehyde-amine intermediate, namely Kabachnik-Fields reaction. The cross-linking mechanism between FR agent and silk fiber, the thermal resistance, FR ability and durability, and FR mechanism of the modified silk were studied. The modified silk had increased thermal resistance. The modified silk fabric with diethyl phosphite over 13.8 g/L had the self-extinguishing ability and obtained the char length of lower than 11.0 cm and LOI value of higher than 27.4 %, suggesting high FR ability of the modified silk. The modified silk also reached self-extinction after 15 robust launderings, which should be attributed to the covalent cross-linking of phosphonate groups onto silk fiber. The char residue analyses suggested a condensed charring FR mechanism for the modified silk. The Pudovik addition of diethyl phosphite onto silk macromolecular participated Schiff base intermediate shows great possibility to act as effective and durable FR strategy for silk textile.

Preparation and flame retardant properties of cotton fabrics treated with resorcinol bis(diphenyl phosphate)

A flame-retardant agent, resorcinol bis(diphenyl phosphate) (RDP), was synthesized with resorcinol, phenol and phosphorus oxychloride under a catalytic action of magnesium chloride. Synthesized RDP was applied to cotton fabrics with a bridging agent of urea-formalin resin (UFR) to endow them with flame retardancy. The vertical flammability tests were performed, revealing that cotton fabrics treated with 25% RDP and 15% UFR could exhibit the most reasonable flame retardancy. Here, other properties of cotton fabrics, such as mass increment, color change, resistance to washing and hand feeling, were found to be almost unspoiled. The suitable heat-treating condition for temperature and duration was determined to be 160 °C and 2 min. The results of scanning electron micrography, energy dispersive X-ray and Fourier transform infrared spectroscopy showed that RDP was strongly bonded to cotton fiber with a successful bridging action of UFR. Thermogravimetric analysis confirmed that the coated cotton fabrics possessed flame retardant properties.

Progress in Biodegradable Flame Retardant Nano-Biocomposites.

This paper summarizes the results obtained in the course of the development of a specific group of biocomposites with high functionality of flame retardancy, which are environmentally acceptable at the same time. Conventional biocomposites have to be altered through different modifications, to be able to respond to the stringent standards and environmental requests of the circular economy. The most commonly produced types of biocomposites are those composed of a biodegradable PLA matrix and plant bast fibres. Despite of numerous positive properties of natural fibres, flammability of plant fibres is one of the most pronounced drawbacks for their wider usage in biocomposites production. Most recent novelties regarding the flame retardancy of nanocomposites are presented, with the accent on the agents of nanosize (nanofillers), which have been chosen as they have low or non-toxic environmental impact, but still offer enhanced flame retardant (FR) properties. The importance of a nanofiller’s geometry and shape (e.g., nanodispersion of nanoclay) and increase in polymer viscosity, on flame retardancy has been stressed. Although metal oxydes are considered the most commonly used nanofillers there are numerous other possibilities presented within the paper. Combinations of clay based nanofillers with other nanosized or microsized FR agents can significantly improve the thermal stability and FR properties of nanocomposite materials. Further research is still needed on optimizing the parameters of FR compounds to meet numerous requirements, from the improvement of thermal and mechanical properties to the biodegradability of the composite products. Presented research initiatives provide genuine new opportunities for manufacturers, consumers and society as a whole to create a new class of bionanocomposite materials with added benefits of environmental improvement.

High-Safety and High-Voltage Lithium Metal Batteries Enabled by a Nonflammable Ether-Based Electrolyte with Phosphazene as a Cosolvent.

The high reactivity between lithium metal and traditional carbonate electrolytes is a great obstacle to realize the long-term cycling ability of lithium metal batteries. Ether-based electrolytes have good stability toward lithium metal anodes. However, the oxidation stability of ether-based electrolytes is generally lower than 4 V, which limits the application of high-voltage (>4 V) cathodes and restricts the energy density. The high flammability of ether is another key issue that hinders the commercialization of ether-based electrolytes. To address these issues, herein, we report a high-voltage, nonflammable ether-based electrolyte with F-, N-, and P-rich hexafluorocyclotriphosphazene (HFPN) as a cosolvent. HFPN can not only act as a highly efficient flame-retarding agent but also form a dense and homogeneous solid electrolyte interphase (SEI) layer rich in LiF and Li3N on the lithium metal anode, which stabilizes the lithium/electrolyte interface and inhibits the formation of lithium dendrites. Moreover, the HFPN-based electrolyte has a wider potential window than 4 V. As a result, with this electrolyte, high-voltage lithium metal batteries exhibit a capacity retention of ∼95% after 100 cycles. This study may provide a new pathway for developing safe, high-energy, and dendrite-free lithium metal batteries.

Poly(Vinyl Chloride) Spheres Coated with Graphene Oxide Sheets: From Synthesis to Optical Properties and Their Applications as Flame-Retardant Agents.

A new method to obtain poly(vinyl chloride) (PVC) spheres, which consists of an interaction between commercial PVC grains and hexyl ethyl cellulose and lauroyl peroxide at a temperature of 60 °C, is reported. The addition of the graphene oxide (GO) sheets dispersed in dimethylformamide to the reaction mixture leads to the generation of composites made of PVC spheres coated with GO sheets. Scanning electron microscopy studies have demonstrated that this method allows for the transformation of PVC grains with sizes between 75 and 227 μm into spheres with sizes varying from 0.7 to 3.5 μm when the GO concentration in the PVC/GO composite mass increases from 0.5 to 5 wt.%. Our studies of Raman scattering and FTIR spectroscopy highlight a series of changes that indicate the appearance of ClCH=CH–, CH2=CCl–, and/or –CH=CCl– units as a result of PVC partial dehydrogenation. New –COO– and C–OH bonds on the GO sheet surfaces are induced during the preparation of PVC spheres coated with GO sheets. A photoluminescence (PL) band with a maximum at 325 nm is reported to characterize the PVC spheres. A PVC PL quenching process is demonstrated to be induced by the increase in the concentration of the GO sheets in the PVC/GO composite mass. The perspectives regarding the use of this composite as a flame-retardant material are also reported.

Smoke suppressant in flame retarded thermoplastic polyurethane composites: Synergistic effect and mechanism study

Considerable smoke and toxic volatiles generation has compromised the application of thermoplastic polyurethane (TPU) and caused a great threat to human life. Here, nano-MgFe layered double hydroxide (MgFe-LDH) with uniform particle size was synthesized to reduce smoke density and toxic gases of TPU composites using ammonium polyphosphate (APP) as a flame retardant agent. The results show that the combination of 16 wt.% APP and 4 wt.% MgFe-LDH greatly decreased the smoke density (D20min and Ds, max), smoke production rate (SPR) and heat release rate (HRR) of TPU composites. Furthermore, the MgFe-LDH synergist demonstrated high efficiency in decreasing total volatiled products and toxic volatiles evolved, such as the CO, HCN and isocyanates. The reason was mainly attributed to the chemical reaction between MgFe-LDH and APP, which can promote the compactness of char layers with fine microstructure formed in the decomposition process of MgFe-LDH/APP/TPU composites. The protective char layers could act as barriers between combustion zone and matrix to protect the unburned substrate and promote smoke suppression effect.

Synthesis and characterization of PEDSCD and its application as a flame retardant in epoxy resins.

In this study, a flame retardant agent, called PEDSCD, is synthesized through a polycondensation reaction. PEDSCD is a chemically expanded phosphorus-containing flame retardant, which is introduced in epoxy resin (EP) to improve its flame retardancy. The molecular structure and thermal stability of PEDSCD are characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and thermogravimetric analysis, and EP/PEDSCD composites are investigated in detail. EP/PEDSCD exhibits good stability and flame retardancy. These properties are attributed to the triazine structure introduced into the flame retardant system. The triazine structure starts to decompose at a lower temperature and also reacts with the phosphorus element to form P Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N–, which increases the viscosity of the melt. This inhibits the generation of smoke and reduces the peak of heat release. PEDSCD shows good thermal stability and low flammability. Further, the weight loss from 500 to 800 °C is only 16 wt%, and the residual mass at 800 °C is 32 wt%. With the addition of PEDSCD, the flame retardant quality of the EP/PEDSCD composites is gradually enhanced, and the carbon residue becomes denser, which isolates the heat transfer and inhibits the volatilization of flue gas. The limited oxygen index (LOI) value of 27% and a vertical burning V-0 rating are achieved when PEDSCD is used in combination with ammonium polyphosphate (APP). The cone calorimeter test shows that the peak heat release rate is reduced by 29% and low gas content is generated, which verifies that the combination of PEDSCD and other phosphorus-containing flame retardants exhibits significantly enhanced flame-retardant properties. PEDSCD exhibits a charring and barrier effect in the condensation phase. Overall, using basic characterization and flame retardancy testing, it is proved that PEDSCD exhibits good flame retardancy when added to EP.

Synthesis and characterization of PEDMCD as a flame retardant and its application in epoxy resins.

In this study, a highly effective flame retardant agent, called polybicyclopentaerythritol phosphate-O-4-imino-p-phenylmethane-4-imino-2-chloro-1,3,5-s-triazine (PEDMCD), has been prepared through a direct polycondensation reaction. PEDMCD was incorporated into epoxy resin (EP) to improve the flame retardancy of EP. The molecular structure and thermal stability of PEDMCD were analyzed by nuclear magnetic resonance spectroscopy. Further, the structural properties, composition, and thermal stability of the PEDMCD/EP composite were characterized by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). PEDMCD exhibited both high thermal stability and high flame-retardant performance; these properties were attributed to the phosphorus-containing structure on the side groups and a triazine structure as the molecular backbone, which played the role of a foaming carbon source. With the addition of PEDMCD, the flame-retardant behavior of PEDMCD/EP composites was gradually enhanced. Furthermore, the amount of char residue of the PEDMCD/EP composite at 500 °C was increased from 21% to 34%. The peak value of the mass loss rate of PEDMCD/EP decreased from 0.52 to 0.35 g s−1. Further, the TSP of the sample decreased from 44.2 m2 to 24.6 m2, and the total oxygen consumption decreased from 64.2 g to 30.4 g. Accordingly, owing to the incorporation of PEDMCD, EP begins to decompose sooner, and the carbon layer formed by decomposition reduces the decomposition rate of the EP matrix. Based on the results of characterization measurements and flame retardancy testing, it is confirmed that PEDMCD exhibits good flame retardancy when applied in EP.

Pyrolysis mechanism and kinetics of high-performance modified lignin-based epoxy resins

Lignin used was extracted from the bio-ethanol production residue by enzymatic hydrolysis method. In this study, a novel lignin-based flame retardant agent (Lig-F) was synthesized by modification using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and piperazine (PA) as grafting reactants, and characterized by thermogravimetric analysis coupled with Fourier transformation infrared spectroscopy (TG-FTIR). Three degradation stages were observed by TG analysis. FTIR results showed that significant variations in functional groups such as the presence of CN at 3060 cm−1, CaromaticP at 1478 cm−1, PO at 1203 cm−1, PN at 866 cm−1, and Caromatic-O-P at 749 cm−1 had been detected after grafting reaction. Epoxy resin (EP) composites with different amounts of Lig-F (2–10 %) were prepared through a curing agent, 4,4′-diaminodiphenylmethane (DDM). The investigation on thermal stability of EP composites demonstrated that more char residue with high thermal stability was obtained after pyrolysis as compared to EP, which was due to the highly efficient charring performance derived from PA-based DOPO compound. Furthermore, the content of char residue increased with the increase of Lig-F addition. The flame retardancy determined by limiting oxygen index (LOI) presented that EP composite containing 10 % Lig-F exhibited the highest LOI value of 34.8 %. Finally, the activation energy of Lig-F, an important component in the polymeric system of lignin and EP, was investigated, and significant effects of PA-based DOPO were mainly reflected in the early and final stages of decomposition as compared to general lignocellulosic biomass materials.

2,4,6-Tribromophenol Disposition and Kinetics in Pregnant and Nursing Sprague Dawley Rats.

2,4,6-Tribromophenol (TBP, CAS no. 118-79-6) is a brominated chemical used as a precursor, flame retardant, and wood antifungal agent. TBP is detected in environmental matrices and biota, including human breast milk, placenta, and serum. To address reports of TBP accumulation in human placenta and breast milk, studies were conducted to characterize TBP disposition and toxicokinetics in timed-pregnant or nursing Sprague Dawley rats following a single oral dose to the dam. Animals were administered [14C]-TBP (10 μmol/kg, 25 µCi/kg, 4 ml/kg) by gavage on gestation day 12 and 20, or postnatal day 12 and serially euthanized between 15 min and 24 h for collection of blood and tissues from the dam and fetuses/pups. Observed plasma TBP Cmax (3 and 7 nmol/ml) occurred at 15 min in both GD12 and GD20 dams while Cmax (3 nmol/ml) was observed at 30 min for PND12 dams. Concentrations in tissues followed plasma concentrations, with kidneys containing the highest concentrations at 30 min. GD12 litters contained a sustained 0.2%-0.3% of the dose (5-9 nmol/litter) between 15 min and 6 h while GD20 fetuses (2%-3%) and placentas (0.3%-0.5%) had sustained levels between 30 min and 12 h. The stomach contents (approx. 1 nmol-eq/g, 6-12 h), livers (0.04-0.1 nmol-eq/g) and kidneys (0.1-0.2 nmol-eq/g) of PND12 pups increased over time, indicating sustained exposure via milk. Systemic exposure to TBP and its metabolites occurs in both the directly exposed mother and the indirectly exposed offspring and is rapid and persistent after a single dose in pregnant and nursing rats.

Gallic acid-derived phosphorus-based flame-retardant multifunctional crosslinking agent for PU coating

Gallic acid-derived phosphorus-based flame-retardant multifunctional crosslinking agent for PU coating

Synthesis of a Novel Phosphorus-Containing Curing Agent and Its Effects on the Flame Retardancy, and Thermal Stability of Epoxy Resins

A novel curing agent containing phosphorus and carboxyl group compound diphenyl(2,3-dicarboxylpropyl)phosphine oxide (DPDCPPO) was synthesized and used as a curing and flame retarding agent for epoxy resins (EP). Its chemical structure was well characterized by Fourier transform infrared (FTIR) spectroscopy, 1H, 13C and 31P NMR. The DPDCPPO was mixed with phthalic anhydride (PA) by different weight ratios into epoxy resins to prepare flame retardant EP thermosets. The flame retardant properties, combusting performances, and thermal degradation behaviors of the EP thermosets were investigated by limiting oxygen index (LOI), vertical burning tests (UL-94), cone calorimeter measurement, and thermogravimetric analysis (TGA) tests. The surface morphologies and chemical compositions of the char residues for EP thermosets were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The water resistant properties were evaluated by placing the samples into distilled water at 70°C for 168 h. The results revealed that the flame retardant EP thermosets passed V-0 flammability rating and the LOI value reached 33.2% when the weight ratio of DPDCPPO and PA was 20 : 80. The cone test results revealed that the combustion parameters of the flame retardant EP thermosets including heat release rate (HRR) and total heat release (THR) significantly decreased compared with pure EP thermosets. The TGA results indicated that the incorporation of DPDCPPO promoted the decomposition of epoxy resins matrix ahead of time compared with that of pure EP, and led to a higher char yield and thermal stability at high temperature. The morphological structures and analysis of the XPS of the char residues revealed that DPDCPPO benefited the formation of a sufficient, compact and homogeneous char layer, with rich flame retardant elements on the epoxy resin material surface during combustion. After completing the water resistance tests, the EP/20 wt % DPDCPPO/80 wt % PA thermosets retained excellent flame retardancy, and the moisture absorption of the EP thermosets decreased with the increase of DPDCPPO content in the thermosets, due to the existence of the P–C bonds and the rigid aromatic hydrophobic structure.

Halloysite Nanotubes: Interfacial Properties and Applications in Cultural Heritage.

The peculiar surfaces of halloysite nanotubes and their biocompatibility are attracting the interest of researchers based on the wide range of attainable applications. The large aspect ratio of this nanotubular material ensures promising properties as a reinforcing agent in polymeric matrixes, such as cellulose and its derivatives, that entail strengthening due to, for instance, aging-induced degradation. The halloysite cavity has a suitable size for hosting a large variety of active species such as deacidifying (calcium hydroxide) and flame retardant agents (fluorinated surfactants) for a controlled and sustained release relevant to the conservation of cultural heritage. Additionally, anionic surfactants can be selectively adsorbed at the inner surface generating inorganic micelles able to solubilize hydrophobic species in a controlled cleaning protocol. We briefly discuss how the natural halloysite nanotubes can be supportive in various conservation processes of cultural heritage and present an outlook for future perspectives.

Preparation of Zeolitic Imidazolate Frameworks and Their Application as Flame Retardant and Smoke Suppression Agent for Rigid Polyurethane Foams.

In order to reduce the fire risk of rigid polyurethane foams (RPUF), three kinds of zeolitic imidazolate frameworks (ZIFs) were prepared. The results of Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM and X-ray diffraction (XRD) showed that ZIFs were successfully prepared. The combustion test results showed that the heat and smoke production of the composite containing ZIFs was obviously reduced. In particular, the peak heat release rate (PHRR) of ZIF-8/RPUF decreased from 740.85 kW/m2 (Ref. RPUF) to 489.56 kW/m2, while the PHRR of ZIF-7/RPUF and ZIF-11/RPUF is 598.39 and 583.36 kW/m2, respectively. The addition of ZIFs improved the thermostability of the composite. The T50% of ZIF-8/RPUF, ZIF-7/RPUF and ZIF-11/RPUF increased to 364, 382 and 380 °C, respectively. The maximum light absorption of ZIF-7/RPUF and ZIF-11/RPUF was about 88%, which is higher than that of ZIF-8/RPUF (75%). The results of Raman spectroscopy showed that the ID/IG value of Ref. RPUF is 2.96, while the ID/IG value of ZIFs/RPUF reduces to less than 2.80. The main mechanism of ZIFs for reducing the fire risk of RPUF was the catalysis and incarbonization of ZIFs during combustion based on the results of thermogravimetric analysis and Raman spectroscopy of char residue.

Heavy metal free thermal stabilizing-flame retarding modifier for plasticized poly(vinyl chloride)

Our research aimed to find a new material that can be an efficient heavy metal free flame retardant for plasticized poly(vinyl chloride) comparable to the conventional flame retardants. One of these extraordinary materials is Oxydtron using as an admixture for concrete. Oxydtron showed unexpected efficiency as a flame retardant agent and an excellent heat stabilizer as well. Limiting oxygen index (LOI), static heat stability, Congo-red, and differential scanning calorimetry (DSC) were carried out. The thermal tests proved that Oxydtron is suitable to improve plasticized poly(vinyl chloride) performance at high temperatures applications in terms of flame retarding and thermal stability. Therefore, the positive result obtained by the addition of Oxydtron is reducing of plasticized poly(vinyl chloride) flammability by 25.23%, and increasing its thermal stability as well.

Synthesis and characterization of SPDSCD and its flame retardant application on epoxy resins

In this study, a flame retardant agent, 2,4,8,10-tetraoxo-3,9-diphosphospiro[5.5]undecane spirophosphate-4,4-diaminopair benzene disulfone-1,3,5-himetriazine (SPDSCD), is synthesized through a direct polycondensation reaction. SPDSCD is a chemically expanded phosphorus-containing flame retardant in epoxy resins (EP). The molecular structure of SPDSCD and thermal stability are characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and thermogravimetric analysis, and EP/SPDSCD composites were investigated in detail. These properties are associated with the phosphorus-containing spiro structure on the main molecular chain which can promote condensation polymerization into carbon during pyrolysis, the new nitrogen-containing carbon source, and the triazine structure. SPDSCD shows good thermal stability and low flammability, the weight loss from 500 to 800 °C was only 6.1 wt%, and the residual mass at 800 °C was 48.9 wt%. With the addition of SPDSCD, the flame retardant quality of the composites was gradually enhanced, the carbon residue becomes denser, which isolates heat transfer and inhibits the volatilization of flue gas. The addition of 20 wt% SPDSCD in the EP sample was associated with a limited oxygen index (LOI) value of 26% and a vertical burning V-0 rating. Cone calorimeter test shows that the peak heat release rate is reduced by 75%; the heat release rate curve enters the heat release platform area with a value lower than the first peak, TSP is reduced by 24%, the ac-CO2Y value reduced by 25.6%, indicating that SPDSCD/EP produced less CO2, which obviously prevented the combustion of volatile gas. SPDSCD exerted a charring and barrier effect in the condensation phase. Using basic characterization and flame retardancy testing, this work determined that SPDSCD has good flame retardancy when added to EP.

Ultrasonic-Assisted Synthesis of Zinc Borates: Effect of Boron Sources

Sonochemistry meaning ultrasound-assisted chemistry plays an important role in the synthesis of inorganic compounds. Among these inorganic compounds, zinc borates are used for the flame-retarding agent. In this study using zinc chloride (ZnCl2), boric acid (H3BO3), Na2B4O7and#183;10H2O, Na2B4O7and#183;5H2O and NaOH as raw materials, a zinc borate compound in the formulae of Zn3B6O12and#183;3.5H2O was obtained using an ultrasonic probe. Crystal structures of samples were identified using X-ray diffraction (XRD). The symmetric and asymmetric stretching between boron and oxygen atoms were searched by Fourier-transform infrared (FT-IR) and Raman spectroscopies. The effects of boron sources on sample morphology were examined by scanning electron microscopy (SEM). From the results, it was seen that Zn3B6O12and#183;3.5H2O can easily be produced from these raw materials with the synthesis parameters of 80-90and#176;C and 40-55 min. From the SEM results, it was seen that the minimum particle size obtained was 172 nm. Reaction efficiencies were calculated between 79.6 and 94.0 and#177; 0.5%. Thermal feature of the obtained pure phase, investigated with the thermogravimetric analyses. The dehydration of the synthesized Zn3B6O12and#183;3.5H2O was seen between 262 and 413and#176;C with a total mass loss of 13.25%.

Ultrasonic-Assisted Synthesis of Zinc Borates: Effect of Boron Sources

Sonochemistry meaning ultrasound-assisted chemistry plays an important role in the synthesis of inorganic compounds. Among these inorganic compounds, zinc borates are used for the flame-retarding agent. In this study using zinc chloride (ZnCl2), boric acid (H3BO3), Na2B4O7and#183;10H2O, Na2B4O7and#183;5H2O and NaOH as raw materials, a zinc borate compound in the formulae of Zn3B6O12and#183;3.5H2O was obtained using an ultrasonic probe. Crystal structures of samples were identified using X-ray diffraction (XRD). The symmetric and asymmetric stretching between boron and oxygen atoms were searched by Fourier-transform infrared (FT-IR) and Raman spectroscopies. The effects of boron sources on sample morphology were examined by scanning electron microscopy (SEM). From the results, it was seen that Zn3B6O12and#183;3.5H2O can easily be produced from these raw materials with the synthesis parameters of 80-90and#176;C and 40-55 min. From the SEM results, it was seen that the minimum particle size obtained was 172 nm. Reaction efficiencies were calculated between 79.6 and 94.0 and#177; 0.5%. Thermal feature of the obtained pure phase, investigated with the thermogravimetric analyses. The dehydration of the synthesized Zn3B6O12and#183;3.5H2O was seen between 262 and 413and#176;C with a total mass loss of 13.25%.

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.

Application of tannic acid and ferrous ion complex as eco-friendly flame retardant and antibacterial agents for silk

Traditional flame retardants (FRs) for textiles are limited by toxicity, environmental persistence and bioaccumulation. There is an urgent need to develop environmentally benign FRs. For this purpose, the combination of tannic acid (TA, a specific form of hydrolysable tannin) and ferrous ion was applied to simultaneously impart durable FR and antibacterial functions to silk fabric. A ternary TA-ferrous ion-silk complex was fabricated by adsorption of TA on silk followed by mordanting with ferrous salt. After treated with 20% TA (on the weight of fabric) and 2 g/L ferrous sulfate, silk fabric exhibited an obvious increase in limiting oxygen index from 23.6% to 27.5%, a significant decrease in damaged length from 30.0 to 11.2 cm after vertical burning, and a significant increase in antibacterial rate from 22% to 95%. Even after 20 washes, the treated fabric still had the same FR ability as the unwashed one, and an antibacterial rate of above 90%, exhibiting excellent washing durability. The high thermal stability of the treated fabric in nitrogen indicated the formation of a ternary TA-ferrous ion-silk complex which was responsible for excellent washing durability. The observation on the morphological structure of charred products from vertical burning revealed the good charring capability of the treated fabric which contributed to enhanced FR behavior. This research proposes an eco-friendly FR treatment for silk and a novel application of hydrolysable tannins in the FR modification of textiles.