Smoke Suppression Effect Research Articles

Tri-source integrated adenosine triphosphate complexed copper ions anchored to boron nitride surfaces for enhancing flame protection of waterborne epoxy coatings

The abundant C, P, and N elements in the structure of adenosine triphosphate (ATP) can act as carbon, acid, and gas sources, and thus can be used as an efficient intumescent flame retardant. Here, a layer of polydopamine (PDA) with polyhydroxyl groups was firstly loaded on the surface of BN to provide a bridging effect for the surface modification of BN. Then, ATP-Cu was immobilized on the BN surface by complexation of ATP with Cu2+, resulting in an efficient inorganic-organic-metal composite flame retardant (BNP@ATP-Cu). This composite flame retardant effectively combined the high barrier effect of BN, the high swelling property of ATP and the catalytic carbon formation activity of Cu2+. The experimental results revealed that the EP loaded with BNP@ATP-Cu showed the lowest backside temperature (171.2 °C), indicating the highest thermal barrier effect. Moreover, BNP@ATP-Cu/EP exhibited the most significant swelling characteristics (22.7 mm, 17.46) and smoke suppression effect (42.8 %). In contrast, the carbon residue of BNP@ATP-Cu/EP (30.8 %) was significantly higher than that of the other coated samples, which was related to the combined effect of BN and ATP-Cu. The above relevant results fully demonstrated the effectiveness of the composite flame retardants in improving the fire resistance of epoxy coatings.

Rheological and Aging Properties of Nano-Clay/SBS Composite-Modified Asphalt.

Nano-organic montmorillonite (OMMT) not only inhibits the harmful asphalt fume generation during the production and construction processes of asphalt mixtures but also effectively improves the performance of asphalt pavements. In order to prepare asphalt materials with smoke suppression effects and good road performance, this study selects nano-OMMT and SBS-modified asphalt for composite modification of asphalt mixtures and systematically investigates its road performance. Through the temperature sweep test, the frequency sweep test, the multiple stress creep recovery (MSCR) test, the bending beam rheometer (BBR) test, and the atomic force microscope (AFM) test, the high-temperature rheological properties, low-temperature rheological properties, high-temperature properties and aging resistance of the modified asphalt are studied. The research findings indicate that OMMT can effectively reduce the sensitivity of modified asphalt to load stress and improve its high-temperature rheological properties. SBS-modified asphalt shows increased creep stiffness and a decreased creep rate after OMMT modification, resulting in reduced flexibility and decreased low-temperature crack resistance. After short-term and long-term aging, the complex modulus aging index of OMMT/SBS composite-modified asphalt is lower than that of SBS-modified asphalt, and the phase angle aging index is higher than that of SBS-modified asphalt, demonstrating that OMMT enhances the aging resistance of SBS-modified asphalt. OMMT inhibits oxidation reactions in the asphalt matrix, reducing the formation of C=O and S=O bonds, thereby slowing down the aging process of modified asphalt and improving its aging resistance.

Preparation of P/N/Si‐containing covalent organic framework‐based flame retardants and their application in epoxy resins

AbstractBalancing the enhancement of flame retardancy of epoxy resin while maintaining its mechanical capacities intact poses a significant challenge in the realm of flame‐retardant epoxy resins. To reach the above objectives, a COF‐based synergistic flame retardant with phosphorus, nitrogen, and silicon (PA‐COF@MT) was synthesized using phytic acid (PA), montmorillonite (MT), and covalent organic framework (COF). When PA‐COF@MT was added at 4 wt%, EP/PA‐COF@MT exhibited a reduction of 42.1% in peak heat release rate (PHRR), 45.84% in total heat release (THR), and 59.8% in total smoke production (TSP) compared with the pure EP. LOI increased by 30.5% and UL‐94 tested to V‐0 grade. flame‐retardant index (FRI) value of 3.03, achieving a “good” rating. Fire growth indices and mean effective combustion heat were increased while mechanical properties also improved. These findings suggest that the flame retarding mechanism of PA‐COF@MT is mainly through vapor phase and condensed phase actions. The combined effects of phosphorus, nitrogen, and silicon make the surface of carbon residue solid and dense, resulting in excellent heat insulation and smoke suppression effects. In simple terms, this study provides new insights into COF‐based flame retardants. Combining low‐cost and simple preparation methods, PA‐COF@MT has broad application prospects in flame‐retardant epoxy resin systems.

Synthesis of phosphorus fluorine containing polymers for flame-retardant, low surface energy and good dielectric performance epoxy resin electronic packaging materials

In order to satisfy the application of epoxy resin (EP) in high-end electronic packaging, phosphorus fluorine containing polymers were synthesized to simultaneously enhance the flame retardant, dielectric, and hydrophobic properties of EP. Through the reaction of 2-hydroxyethyl methacrylate and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), a monomer named HEMA-P was synthesized. By copolymerizing (2,2,2-trifluoroethyl methacrylate and 1H, 1H, 7H-dodecafluoroheptyl methacrylate) with HEMA-P through the typical reversible addition-fragmentation chain transfer (RAFT) polymerization, two phosphorus fluorine containing polymer modifiers named 3FOP and 12FOP with different lengths of fluorine side chain were obtained. The flame-retardant level of FOP/EP composites reached V-1 level. The limited oxygen index (LOI) values of 3FOP/EP and 12FOP/EP composites (10 wt% additive amount) increased to 33.6 ± 0.5 % and 32.8 ± 0.3 %, respectively, with corresponding peak heat release rates (pHRR) decreased by 37.8 % and 33.2 % compared with neat EP, suggesting the FOP modified EP composites have good flame retardant and smoke suppression effects. The mechanical properties of the FOP/EP composites can also be improved. Notably, with the 10 wt% addition of 12FOPs, the water contact angle of 12FOP/EP composite reached 116.5°, which was 40.7 % higher than that of EP. Moreover, the dielectric constant decreased with the increasing fluorine content. The thermal stability and possible thermal degradation pathways of 3FOP and 12FOP were characterized by TG-IR, Py-GC/MS, and Raman spectroscopy. Based on experimental results, we innovatively revealed a phosphorus fluorine synergistic flame retardancy mechanism.

Fabrication of green montmorillonite modified bio-based rigid polyurethane foam with improved flame retardancy and enhanced mechanical properties

A low-carbon and sustainable green rigid polyurethane foam was prepared by compounding montmorillonite (MMT) with homemade barium phytate (BAPA). The flame retardancy, thermal stability and mechanical properties of the modified RPUFs investigated using the limiting oxygen index (LOI) method, cone calorimetry (CONE) and thermogravimetry. The results showed that the BAPA/MMT2 composite containing 2 wt% MMT had the highest LOI (25.1 %), and its peak heat release rate (PHRR) and total heat release (THR) were reduced by 14.33 % and 34.68 %, respectively, compared with that of the BAPA/MMT0 material without added MMT. In addition, the smoke production rate (SPR) and total smoke release (TSR) were reduced by 20.54 % and 30.77 %, respectively. BAPA/MMT2 had good flame retardancy and smoke suppression effect. The mechanical properties of BAPA/MMT2 with 2 wt% MMT were improved. The flame retardant mechanism confirmed that BAPA and MMT synergistically improved the quality of the carbon layer. At the same time, phosphorus-containing compounds (PO·), CO2 and water vapor were produced, which diluted the combustible gas in the gas phase and inhibit the flames spread. The current results provided a new strategy for the preparation of high-performance RPUFs.

Fabrication of nickel phytate modified bio-based polyol rigid polyurethane foam with enhanced compression-resistant and improved flame-retardant

A bio-based flame retardant nickel phytate (PA-Ni) was synthesized and combined with soybean oil-based polyol (SO) to create a green rigid polyurethane foam (RPUF) with enhanced compressive strength, good thermal stability and flame retardant. The results showed that the RPUF-SO2/Ni3 with 3 wt% PA-Ni had the highest initial and termination temperature, maximum thermal decomposition rate temperature and carbon residue, and better thermal stability. Its limiting oxygen index was increased by 2.6% compared with RPUF-SO2 without PA-Ni added, and the peak heat release rate (PHRR) and total heat release rate (THR) were reduced by 14.92% and 19.92%, respectively. In addition, RPUF-SO2/Ni3 had the lowest Ds under the conditions of flame (18.90) and flameless (22.41), and had the best smoke suppression effect. And the compressive strength of RPUF-SO/Ni3 was significantly enhanced by the addition of PA-Ni. The results show that the improvement of flame retardancy of RPUF is mainly the result of the combined effect of gas-phase and condensed-phase flame retardancy, among which the flame retardancy of RPUF-SO/Ni3 was the best. The current findings offer a practical way to produce green and low-carbon RPUF as well as promising prospects for the material's safe application.

Half etching of ZIF-67 towards open hollow nanostructure with boosted absorption ability for toxic smoke and fume in epoxy composites

Metal-organic frameworks (MOFs) are favored in the field of flame retardancy due to the catalytic effect of metal nodes on char layer formation and the synergistic flame-retardant effect of organic ligands containing elements such as nitrogen and phosphorus. However, the inherent microporosity of MOFs limits their adsorption efficiency for toxic smoke and flammable gases. In this work, an organic phosphorus-modified MOF with a distinctive nanostructure of hierarchically porous (P-Co-MOF/ZIF) was successfully synthesized. In brief, an amino-functionalized zeolitic imidazolate framework (NH2-ZIF) was initially synthesized through a ligand substitution reaction with ZIF-67. Subsequently, organic phosphorus flame retardants were grafted on NH2-ZIF, and the acidic substances generated during this process were used to synchronously half etch ZIF, resulting in a ZIF with a high specific surface area and unique nanostructure. Through this simple synthetic method, the catalytic ability of transition metals in ZIF is preserved, and organic phosphorus flame retardants are incorporated into ZIF, resulting in the synergistic flame-retardant effect of phosphorus and nitrogen. Additionally, its unique hierarchically porous nanostructure can effectively enhance the adsorption of volatile products during the combustion process, thereby offering outstanding flame retardancy and smoke suppression effects for epoxy resin (EP). The results indicate that adding 2 wt% P-Co-MOF/ZIF to EP can increase the limiting oxygen index value to 29.5%. Furthermore, the peak of heat release rate, total heat release, and total smoke production of the composite material can decrease by 43.3%, 37.9%, and 38.1%, respectively, compared to EP. Therefore, this work will provide new inspiration for designing functional nanostructures and synthesizing efficient flame retardants.

Low temperature carbonization, smoke suppression and durable flame retardancy of cotton fabric spray-assisted coated by phosphorus nitrogen silicon composite system

To solve the problems of flammability, smoldering, smoking and flame retardant durability of cotton fabric, flame retardant fininshing was executed using spray assisted self-assembly method, and P/N/Si synergistic flame retardant system was constructed by polyethylene imine (PEI), phytic acid (PA) and 3-aminopropyltriethoxysilane (APTES). Cotton cellulose carbonized at low temperature prompting by PA catalytic effect, and this cooperated with PEI thermal decomposition to endow cotton fabric with flame retardancy and smoking suppression by reducing its pyrolysis rate at high temperature and lessening combustible products. Meanwhile APTES as silane coupling agent further improved its flame retardant durability and smoke suppression effect. The synchronous thermal analysis results indicate that cotton fabrics treated by PA/PEI/APTES composite system present significant low-temperature carbonization trend, and their initial decomposition temperatures advance by 46.5℃-75.9℃. Moreover, they form 4.6 %-44.9 % aromatic structure char through dehydration and carbonization reactions during the low-temperature carbonization process, improving their thermal stability at high temperature, and their after-flame and smoldering phenomena disappear. The damaged length of treated fabric with five layers reduces to 5.0 cm, its limiting oxygen index reaches 33.7 %, and it presents excellent flame retardant durability and smoke suppression effect. This low-temperature carbonization mechanism possesses importantly innovative significance for the flame retardant finishing of cotton fabric, and it not only more actively guides the selection of flame retardants to make them match with the material required, but provides a new thinking method for flame retardant material research in the future.

Enhancing fire performance and thermal stability of flexible PVC with lanthanum phytate montmorillonite

This study presents a breakthrough approach to enhance the thermal stability, mechanical properties, and flame retardancy of flexible PVC (fPVC). It introduces lanthanide phytate montmorillonite (Pa-La-Mt) as an innovative nanofiller. Pa-La-Mt was synthesized by intercalating sodium phytate and lanthanum chloride into the interlayer space of montmorillonite (Mt), effectively increasing the layer spacing. The analysis of this study, using X-ray diffraction (XRD) and Fourier infrared spectrometer (FTIR), confirmed this structural transformation. The influence of Pa-La-Mt on the structural and performance aspects of fPVC composites was thoroughly examined. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), mechanical testing, limit oxygen index (LOI), and cone calorimeter (CONE) revealed compelling outcomes. Pa-La-Mt not only improved the dispersion and compatibility of Mt. within the fPVC matrix but also enhanced the thermal stability and mechanical performance of fPVC composites. Most notably, Pa-La-Mt exhibited remarkable flame retardant and smoke suppression effects on fPVC composites. It led to a substantial increase in LOI value, a reduction in the peak heat release rate and total heat release amount, and a decrease in CO and CO2 emissions. This underlines Pa-La-Mt as a promising nanofiller with profound implications for various fPVC applications.

Effect of magnesium hydroxide fly ash compounded flame retardant on the properties of polyvinyl chloride

Abstract This study investigated the effects of compound flame retardants on polyvinyl chloride (PVC) film. Four F-M/PVC composite film materials (F0.1M0.1/PVC, F0.1M0.2/PVC, F0.1M0.3/PVC, and F0.1M0.4/PVC) were obtained by blending different ratios of fly ash (FA) and magnesium hydroxide (MH(OH)2, MH) compounded flame retardants (F-M) with PVC. The mechanical properties, thermal stability, and smoke density of the composite film materials were examined. The results showed that the loss of mechanical properties of F0.1M0.2/PVC composites was small. TGA analysis showed that the thermal stability of the four F-M/PVC composites was improved. The degradation temperature of pure PVC at T50 was 286.5°C, and that of F0.1M0.2/PVC composites was 335.38°C. Smoke density analysis showed that the maximum smoke density of pure PVC was 6.310, and the maximum smoke density of the composite material (F0.1M0.4/PVC) was reduced to 5.960, which had a better smoke suppression effect. For the comprehensive utilization of Salt Lake magnesium resources, the development of PVC composite film materials to provide the experimental basis has a strong practical value.

Self-assembly Fe-Co MOF@BN and epoxy resin nano composites with highly enhanced flame retardancy and smoke suppression properties

A shuttle-shaped Fe-Co bimetallic metal organic frameworks (MOFs) on sheet-like hexagonal boron nitride (h-BN) was fabricated via an organic-inorganic hybrid strategy, forming a novel Fe-Co MOF@BN flame retardant, and the hybrids together with ammonium polyphosphate (APP) were incorporated into epoxy resins to explore their flame retardancy and smoke suppression effects. When combining 0.5 % Fe-Co MOF@BN with 9.5 % APP, the peak heat release rate, peak smoke release rate, CO production rate, and peak CO2 production rate of the EP composite (EP/APP/Fe-Co MOF@BN) were reduced by 73.7 %, 71.4 %, 70 %, and 80 % respectively, compared to epoxy. The limiting oxygen index increases to 30.2 %, indicating the EP/APP/Fe-Co MOF@BN composites have superior fire safety performance. The excellent fire performance of EP/APP/Fe-Co MOF@BN composites benefiting from the barrier effect of Fe-Co MOF@BN lamellar structure, the catalytic carbonization of Fe and Co, the gas phase dilution of APP and the enhancement of the cross-linking degree of the char layer. Meanwhile, Fe-Co MOF@BN improves the dispersion of APP in the EP composites, which broadens the application range of MOF and h-BN. Herein, the EP/APP/Fe-CoMOF@BN composites with high flame retardancy, low smoke production rate, and excellent mechanical properties provide a feasible solution for the use of EP under high temperatures.

Flame retardancy and smoke suppression effect of zinc borate-graphite intercalation compound/Fe2O3 on silicone rubber foams

To enhance the flame retardancy and smoke suppression of silicone rubber foams (SRFs), a novel flame retardant, zinc borate-graphite intercalation compound (ZB-GIC), was synthesized and used in conjunction with Fe2O3. The results showed that ZB-GIC markedly improved the flame retardancy and smoke suppression of SRFs, and Fe2O3 significantly improved the smoke suppression of SRFs. ZB-GIC and Fe2O3 had an excellent synergistic effect on flame retardant and smoke suppression. 5 wt% ZB-GIC synergistically with 5 wt% Fe2O3 resulted in SRFs passing the UL-94 V-0 rating, whose limiting oxygen index (LOI) value reached up to 43.7%. Its peak heat release rate (PHRR), total heat release (THR), peak smoke production rate (PSPR), and total smoke production (TSP) decreased by 67.42%, 89.55%, 76.86%, and 91.67% compared to pure SRF. The ZB-GIC produced incombustible gas and a large amount of H2O when heated, which reduced the intensity of gas-phase combustion. The ZB filled the interlayer gaps formed after the expansion of GIC to enhance the strength of the char layer, and Fe2O3 further strengthened the char layer. Our work has greatly reduced the fire hazards of SRFs and provided a promising flame retardant for the large-scale production of high-performance SRFs.

Enhancing the UV resistance and flame retardancy of epoxy resin composites with fluorescent carbon dots

AbstractCarbon dots (CDs) are a novel class of carbon material which have gained widespread usages owing to their exceptional optical properties, low toxicity, and high biocompatibility. The nitrogen‐doped carbon dots (N‐CDs) using a normal curing agent of 4,4′‐diaminodiphenylmethane as resource was expected to not only have good compatibility with epoxy resin (EP), but also bring luminescent property to EP composites. It was interesting that the N‐CDs‐EP composites with 12.5 wt% addition exhibited a limiting oxygen index value of 31.4% and reached UL‐94 V‐1 grade, indicating a good flame retardancy. Compared with pure EP, the incorporation of N‐CDs formed more residual char and had extra smoke suppression effect. Besides, the N‐CDs‐EP composites exhibited a low transmittance less than 10% for the light wavelength below 490 nm. The N‐CDs contributed to the light shielding capabilities of the N‐CDs‐EP composites, which could effectively shield purple, blue, and cyan light. Furthermore, the mechanical properties including bending strength and impact strength, the dielectric property, and hydrophobicity of N‐CDs‐EP composites were also improved. The simple but effective modification strategy might be expected to be applied in many polymer systems.

Preparation of bio‐based soybean oil polyol modified 3630 polyol‐based rigid polyurethane foam and its improved thermal stability, flame retardant, and smoke suppression performances

AbstractRigid polyurethane foam (RPUF) with 3630 polyol‐based components was modified using bio‐based soybean oil (SO) polyol. The effects of soybean oil polyol on the thermal stability, flame retardant and smoke suppression performances of the modified RPUFs were investigated by thermogravimetric analysis, integral programmed decomposition temperature (IPDT), pyrolysis kinetic analysis, limiting oxygen index, conical calorimetry and smoke toxicity analysis. The results indicated that the RPUF‐SO2 (10 wt% soybean oil polyol) had the highest thermal decomposition rate temperature, initial thermogravimetric temperature, termination temperature, residual rate, IPDT and activation energy. Under various circumstances, the total heat release (THR) of RPUF‐SO2 was 1.41, 1.61, and 2.51 MJ/m2, respectively, and the peak heat release rate (PHRR) was lowered by 22.40%, 45.68%, and 19.86% in comparison to the original RPUF‐0. In the meantime, RPUF‐SO2 had the best light transmittance (57.20 and 60.60%), the lowest toxic gas emissions (0.31, 0.44, and 0.38 kg/s), and the lowest Ds (32.46 and 29.07). It also had an excellent smoke suppression effect. According to the current study, RPUF‐SO2 performed better in terms of heat stability, flame retardancy and smoke suppression. This made it a good benchmark for further bio‐based soybean oil polyol modified RPUFs.

Chemical, pyrolysis, combustion properties and mechanism analysis of wood treated with biomass-based carrageenan-collagen modified ammonium polyphosphate

Biomass-based flame retardants are characterized by readily available raw materials and are environmentally friendly, making the design of green and efficient biomass-based flame retardants a critical direction in the development of flame-retardant technology. In this study, a novel biomass-based flame retardant (Acc) was developed using ammonium polyphosphate (APP) as a raw material in combination with the biomass materials carrageenan (CAR) and collagen (COL). Flame-retardant wood was prepared via ultrasonic impregnation. Via various analytical and testing methods, such as the Limiting Oxygen Index (LOI), thermogravimetric analysis, scanning electron microscopy, Raman spectroscopy, cone calorimetry, and thermogravimetric–infrared coupling, the combustion performance of biomass-based flame retardants on wood was investigated to elucidate the flame-retardant mechanism. The results indicated that the flame retardant with a CAR:COL:APP ratio of 1:1:3 exhibited the best flame-retardant effect, with an LOI of 31.8 %. The peak heat release rate was reduced to 53.8 % compared with that of untreated wood, and both the peak smoke release rate and total smoke release were reduced by 63.2 % and 49.2 %, respectively, demonstrating a significant smoke-suppression effect. Analysis of the mechanism revealed that APP, COL and CAR generated non-combustible gases such as ammonia and gases containing P and S when exposed to fire. These gases dilute oxygen and eliminate •H and •HO radicals in the gas phase, thereby exerting flame-retardant effects. Acc promotes the formation of a dense crosslinked carbon layer containing N=C, N-C/P-N, N-H, and C-O-P. This carbon layer acts as a physical barrier, isolating oxygen (O2), blocking gas emissions, and slowing heat exchange. This study provides a new avenue for the development of green and sustainable flame retardant wood.

Self‐emulsification synthesis of epoxy phosphate ester and its flame‐retardant mechanism in flexible poly(vinyl chloride)/magnesium hydroxide composites

AbstractA trade‐off dilemma exists for simultaneously improving the mechanical properties and flame resistance of flexible polyvinyl chloride (fPVC)/magnesium hydroxide (MH) composites. In this study, epoxy phosphate ester (EPE), a hydrophobic surface modifier of MH, was synthesized using a self‐emulsification method. After modification, EPE was bonded to the surface of MH (MHEPE) without altering its morphology. The results of limiting oxygen index and cone calorimetry tests indicated that fPVC/MHEPE exhibited better flame retardancy and smoke suppression effects than did fPVC/MH. The peak of the heat release rate, total heat release, peak of the smoke production rate, and total smoke production of the fPVC/MHEPE composite were 206.0 kJ m−2, 45.90 MJ m−2, 0.0729 m2 s−1, and 9.88 m2, which were 8.64%, 14.00%, 27.61%, and 9.02% lower than those of the fPVC/MH composite, respectively. For the fPVC/MHEPE composite, a compact and continuous char residue formed, which could inhibit heat and flammable volatile migration between the matrix and burning zones. In the gas phase, the dilution effect of H2O vapor reduced the concentrations of O2 and flammable volatiles. The free‐radical quenching effect of ·PO and ·PO2 also played a vital role in extinguishing flame and terminating combustion. Further, the introduction of EPE improved the tensile and impact strengths of the fPVC/MH composites because of the excellent interfacial compatibility between MHEPE and the fPVC matrix. This study provides a simple and workable solution for the trade‐off dilemma, and the remarkable flame retardancy and mechanical properties of the fPVC/MHEPE composite render it a promising cable material.

In situ construction of epoxy crosslinked Si-Al zeolite-like catalytic structure in wood to achieve high flame retardancy

As green renewable resources, wood and its composites are widely used in the construction field, which puts forward higher requirements for their flame-retardant performance. In this study, a high-temperature hydrothermal crystallization method for in situ constructing an epoxy crosslinked Si–Al zeolite-like structural wood composite (WZLC) was reported. Under the action of amine guiding agents and epoxy resin, the zeolite-like catalytic structure constructed in poplar wood comprised negative electrocatalytic sites, which can efficiently catalyze the formation of the carbon layer and endow WZLC with excellent flame retardant, smoke-suppression, and self-extinguishing properties. Compared with the untreated wood (WN), the thermal stability of the treated wood (WZLC) was greatly improved, and the amount of volatile organic compounds released during the decomposition process was significantly reduced. The heat release rate, total heat release, smoke production rate, and total smoke production of WZLC1 decreased by 50.23%, 44.14%, 45.21%, and 28.46%, respectively. Particularly, CO and CO2 yields of WZLC significantly decreased by 92.26% and 92.02%, respectively, indicating that the Si–Al zeolite-like catalytic structure displayed excellent catalytic flame retardant properties, which can effectively decrease the thermal decomposition rate and combustion risk of the WZLC. This method uses less flame retardants to achieve a good flame retardant and smoke suppression effect, thereby reducing the risk of environmental pollution caused by too many flame retardants.

The preparation of layered double hydroxide wrapped with triazine-based organic framework to enhance the flame retardancy for polypropylene

Layered double hydroxide (LDH) can be used as a flame retardant (FR) for polypropylene (PP) because of its excellent flame retardancy and smoke-suppression effects. However, the agglomeration of LDH seriously affects its dispersity in the PP matrix, thus limiting its application as a FR polymer. This study aimed to enhance the dispersion of LDH in the PP matrix for improving its flame retardancy performance. Herein, a reactive triazine-based organic framework (TOF) was designed and formed by the in situ polymerisation of cyanuric chloride and melamine, and then the LDH surface was covered with TOF to obtain a novel core–shell FR (LDH@TOF), with TOF as the ‘shell’ and LDH as the ‘core’. Subsequently, LDH@TOF was melted into the PP matrix as nanofillers to prepare PP and LDH@TOF composites (PP/LDH@TOF). As expected, the PP/LDH@TOF composites exhibited superior flame-retarding performance (limiting oxygen index of 29.2% and UL-94 V-0 rating) and favourable smoke-suppression performance at 20 wt% of LDH@TOF loading. Moreover, the peak heat release rate, total heat release and total smoke production of PP/LDH@TOF composites decreased by 29.9%, 12.1% and 12.4%, respectively, compared with those of PP and LDH composites. The outstanding flame retardancy properties of the PP/LDH@TOF composites were attributed to the better dispersibility of LDH@TOF in the PP matrix, the synergy of the physical barrier effect of nanosheets and the dense carbonisation acceleration of LDH@TOF. The findings of this study provide a highly efficient approach for functionalising LDH for expanding its application value of PP composites.

The preparation and fire extinguishing mechanism research of a novel high-efficiency KHCO3 @HM dry powder

Hydromagnesite (HM) is a widely distributed primary natural carbonate mineral. To expand the application range of hydromagnesite and tap its fire-extinguishing potential, a new type of high-efficiency KHCO3 @HM dry powder was prepared by coating potassium bicarbonate on the surface of hydromagnesite with a dip coating method. KHCO3 @HM dry powder obtained a chemical inhibition effect through this method, and the fire extinguishing efficiency has been further improved. A series of tests were carried out to confirm the excellent physical and chemical inhibition effect of KHCO3 @HM dry powder. Specific surface area tests showed that the specific surface area of KHCO3 @HM dry powder (31.405 m2/g) was higher than NH4H2PO4 dry powder (12.766 m2/g). Flowability tests showed that KHCO3 @HM dry powder (0.04 g/s) achieved the same flowability as NH4H2PO4 dry powder (0.04 g/s). Local oil basin fire experiments showed that the average fire extinguishing time of KHCO3 @HM dry powder was shorter with less powder consumption. Under 0.2 MPa driving pressure, the fire extinguishing time of KHCO3 @HM dry powder was 2.2 s faster than NH4H2PO4 dry powder, and the dry powder consumption was 3.71 g less than NH4H2PO4 dry powder. The cooling effect of KHCO3 @HM dry powder (208 ℃) in 10 s was better than NH4H2PO4 dry powder (157 ℃), and KHCO3 @HM dry powder (399 ppm) showed a better smoke suppression effect than NH4H2PO4 dry powder (545 ppm). The pyrolysis of KHCO3 @HM dry powder reduced the fire temperature, diluted the oxygen concentration, and captured free radicals. The final pyrolysis products formed a thick oxide film to provide good heat insulation and asphyxiation effects. The excellent cooling, dilution, asphyxiation, and chemical inhibition mechanisms of KHCO3 @HM dry powder were demonstrated, and finally achieved a comprehensive performance comparable to NH4H2PO4 dry powder.

Preparation and characterization of UiO‐66‐NH2 adsorbed triethyl phosphate: Flame retardancy and smoke suppression for epoxy resins

AbstractThe zirconium‐based metal–organic framework material (UiO‐66‐NH2) was synthesized by solvothermal method, and its excellent adsorption performance was used to combine it with the phosphorus‐based flame retardant triethyl phosphate (TEP) and to improve the flame retardant and smoke suppression properties of epoxy resin (EP). The morphology, chemical composition, and structure of the synthesized flame retardant were analyzed by scanning electron microscope, energy dispersion spectrum, Fourier transform infrared spectroscopy, and x‐ray diffractometer. The cone calorimeter measurement of EP composite materials shows that EP composite materials have good flame retardant and smoke suppression properties. Compared with EP, after the UiO‐66‐NH2 flame retardant which adsorbs TEP is added, the peak heat release rate, total heat release, peak smoke release rate, total smoke production, carbon monoxide release rate, and carbon dioxide release rate of EP composites have been reduced. From the results of thermal analysis and scanning electron microscope, it can be seen that the synthesized flame retardant can act both in the condensed phase and in the gas phase. Thereby, the combustion of the matrix and the diffusion of the toxic gas, smoke and heat generated during the combustion are inhibited, and the flame retardant and smoke suppression effects are achieved.Highlights Make full use of the excellent adsorption performance of MOF. TEP was fully adsorbed in UiO‐66‐NH2 pores. UiO‐66‐NH2 in synergy with TEP improves EP flame retardancy.