Heat Release Rate Values Research Articles

Intrinsically flame-retardant epoxy vitrimers with catalyst-free multi-reprocessability towards sustainable carbon fiber composites

An intrinsically flame-retardant epoxy vitrimer with multi-reprocessability was successfully constructed and applied to carbon fiber-reinforced composites with the aim of promoting more economical and sustainable development in the field of fire-safe applications. In this work, a catalyst-free flame-retardant epoxy vitrimer constructed by synthesizing phosphaphenanthrene-derived anhydride (DPI) and using triethanolamine (TEOA) as a multifunctional transesterification modifier was used to solve the two major problems of flame retardancy and recyclability at once. The epoxy resin and its composites exhibit excellent flame retardancy, mechanical properties, and rapid repairability, yet the ability to pass the UL-94 V-0 rating even after reprocessing the epoxy resin five times; while the value of the peak heat release rate (PHRR) and the total heat release (THR) reduced by 58% and 35%, showing great suppression on heat release. In addition, the resin can be completely degraded under mild conditions, enabling 100% recycling of the carbon fibers.

Uncertainty quantification of unconfined spill fire data by coupling Monte Carlo and artificial neural networks

ABSTRACT Due to the complexity of spill fire, predicting heat release rate (HRR) is a challenging aspect, therefore, identifying key contributors to uncertainty is essential to develop reliable models for fire risk assessment. We propose a framework that couples Artificial-Neural-Network (ANN) and Monte Carlo Uncertainty Quantification (UQ) to quantify the uncertainties of spill fire parameters on peak HRR variance. The ANN spill fire model, trained on experimental spill fire data, shows good agreement with measured HRR values. By coupling with Dakota for Monte Carlo uncertainty propagation, the framework identifies major contributors to peak HRR uncertainty for fixed and continuous unconfined spill fires. This is achieved by investigating two uncertainty sources: data scarcity and input parameters. UQ results indicate that the confidence intervals widen at points where data are scarcer. Sensitivity analysis shows that in the case of fixed quantity spills, the fuel amount and properties parameters contribute to 54.4% and 22.6% of peak HRR variance, respectively. For continuous spills, the discharge rate and fuel properties parameters account for 41.8% and 39.3% of peak HRR variance, respectively. This work can be utilized in developing more advanced predictive ANN models for spill fire scenarios, ultimately enhancing fire probabilistic safety analysis in nuclear power plants.

Ternary intumescent flame retardant composition containing ionic liquid towards efficiently flame‐retardant polystyrene

AbstractIt is of great importance to enhance ability of charring formation for polystyrene (PS) to overcome non‐charring feature during burning. Here, we demonstrate a kind of ternary intumescent flame retardant composition composed by a novel ionic liquid butyltriphenylphosphonium‐chelated orthoborates (IL) with self‐expanded flame retardant, ammonium polyphosphate (APP) and expandable graphite (EG), to improve flame retardancy of PS. This ternary composition promotes limited oxygen index (LOI) value to 26.6 ± 0.5% and UL‐94 V0 level for PS composite with 15 wt% total loading. In addition, the peak value of heat release rate and smoke production rate of PS composite with ternary composition are separately reduced by 79.7% and 70.7% comparing to neat PS as well as 44.4% and 29.2% to its IL‐free binary counterpart in cone calorimeter test. Meanwhile, the ternary composition displays compact charring bulk constructed by large‐expansion‐volume vermiform expanded graphite. The TG‐FTIR technique is used to analyze gaseous profiles. The rheological property discloses that expansion behavior of the ternary composition contributes to robust viscoelasticity of composite and advantageous network construction at high temperature. Given the fire performance of the ternary composition, the combination of IFR and IL provides an opportunity for rational design and fabrication of functional flame‐retardant system.

Enhancement of Radiative Power Using a Divergent Splitter Plate Design in H2–Air Non-Premixed Micro-Combustor

Abstract Micro-combustion based power generation devices can be considered as future alternatives to batteries in miniature electronic devices. Micro-combustors operating in non-premixed mode are free from flashback but face the challenge of properly mixing fuel and air within a small volume. In this work, the effect of a divergent fuel–air splitter design on the mixing performance and combustion characteristics of H2–air fueled diffusion micro-combustor is studied. The laminar reacting flow is simulated using the finite volume method and a detailed hydrogen kinetic mechanism. Three divergent splitter designs are compared with the commonly used rectangular splitter to study the effect on radiation power, an essential parameter for thermophotovoltaic power generation. The best-performing divergent and base rectangular splitter designs are investigated in detail. The study shows that the micro-combustor with divergent splitter design reduces mixing distance (Lmix) by 5–23% depending on inlet velocity and channel height. With the divergent splitter, the peak value of the heat release rate also increases slightly, implying enhanced combustion. The divergent splitter increases the high-temperature surface area of the outer wall as compared to the rectangular splitter. This leads to the micro-combustor with divergent splitter producing significantly higher radiation power (>10%) than the rectangular splitter for larger channel heights and higher inlet velocities.

Thermally managed and fireproof composite aerogels for safer and year-round energy saving

Seasonable and spontaneous replacement approach of daytime radiative cooling to solar thermal conversion is challenging yet imperative for year-round thermal management materials. Meanwhile, the fire safety of thermal management materials is extremely important but often overlooked. Herein, we report a bio-inspired and fireproof aerogel presenting dynamically self-switchable ability of daytime radiative cooling and solar thermal conversion, composed of thermochromic microcapsules (TC), boron nitride nanosheets (BN), and bio-based materials (alginate and phytate). In hot environments, TC/BN composite aerogel shows solar reflectivity of 91.8 % and IR emissivity of 84.3 %, promoting heat radiation to outer space and achieving an average temperature drop of ∼5.62 °C. Attributed to the thermochromic mechanism, TC/BN composite aerogel can harvest visible light of 87 % in the solar spectrum to increase the material temperature by 28.3 °C, under an environment of −8.8 °C. Based on the EnergyPlus simulation, the employment of TC/BN composite aerogel contributes to decreasing the energy consumption of buildings in both hot and cold regions, including Cairo, Singapore, Alaska, Yakutsk, and so on. Besides, the peak values of heat release rate and total heat release during the combustion of TC/BN composite aerogels are significantly decreased by 70.6 % and 58.4 %, compared to those of TC composite aerogel. The produced protective char layer enhanced by BN nanosheets is capable of isolating the fire and suppressing the fire propagation, improving the fire safety of composite aerogels designed. The TC/BN composite aerogels provide a smart thermal regulation mode for radiative cooling and solar heating, overcome the problems from changing weather and environment, and significantly promote the practical application by enhanced fire safety.

Optimizing combustion and emissions in natural gas/diesel dual-fuel engine with pilot injection strategy

For the clean and efficient operation of agricultural power, a non-road common-rail engine was modified to achieve natural gas/diesel dual-fuel (NDDF) combustion mode. Under low load conditions, NDDF combustion deteriorates and fuel economy decreases due to lower pressure and temperature inside the cylinder. Therefore, effects of injection pressure, pilot injection timing (SOIpilot) and pilot injection quantity (Qpilot) on in-cylinder combustion, emission characteristics and fuel economy of NDDF engine with pilot injection strategy were investigated at low load. Results show that with the increment of injection pressure, the diesel fuel beam penetration distance increased, prompting the diesel more quickly and fully mixed with fresh charge. The maximum in-cylinder pressure increased, the combustion center (CA50) moved forward, the ignition delay period was shortened, and soot, HC, C2H4 and C3H6 emissions were reduced, while BTE was improved. When SOIpilot moved forward, the pilot injected diesel and natural gas were more fully mixed, which promoted the generation of activation radicals and combustion intensity of main injected diesel. Pmax first increased and then decreased, the peak value of first heat release rate (HRRP1) gradually decreased, the peak value of second heat release rate (HRRP2) continuously increased, the combustion duration decreased, and the soot, CO and HC emissions decreased. At SOIpilot = −30 °CA ATDC, unregulated emissions reached the lowest level, while BTE was 35.55 %. With the increment of Qpilot, both Pmax and HRRP1 increased, CA05 and CA50 moved forward, combustion duration was extended, COV decreased significantly, and all emissions except NOx decreased, especially aldehyde emissions.

The fabrication of flame-retardant viscose fabrics with phytic acid-based flame retardants: Balancing efficient flame retardancy and tensile strength

Viscose fabrics have been widely used in various applications, but their potential fire hazard has been a concern. To address this issue, improving the flame retardancy of viscose fabrics has become a significant priority. Phytic acid (PA) and xylitol were used to create a novel flame retardant, PAXY. PAXY was finished on viscose fabrics by pad-dry-curing process, and the performance of coated viscose fabrics was investigated. The results showed that the limiting oxygen index value of PAXY13–100 (fabrics finished with a 100 g/L flame-retardant solution and the flame retardant synthesized by a 1: 3 M ratio of PA to xylitol) reached 32.8 % and the heat release rate value was decreased by 77 %. Based on the findings from the analysis of both the gas phase and condensed phase products, PAXY promoted the dehydration of viscose fabrics to produce a denser char layer, which inhibited the production of flammable gases. Surprisingly, the breaking force retention of PAXY13–100 reached 90 % in warp and 114 % in weft. Compared with that of 100 g/L PA-treated fabrics, the breaking force of PAXY13–100 increased by nearly 400 %. This work provides a new strategy for PA-based flame-retardant finishing with the synergy of flame retardancy and breaking force retention.

Multifunctional graphitic carbon nitride/manganese dioxide/epoxy nanocomposite coating on steel for enhanced anticorrosion, flame retardant, mechanical, and hydrophobic properties

Benzidine (Bz) was used to modify the nanofiller, manganese dioxide (MnO2), and the resulting Bz/MnO2 was then encased in pure epoxy resin (EP) with graphitic carbon nitride (GCN). The effectiveness of epoxy-coated mild steel in protecting against varying concentrations of GCN/Bz-MnO2 was assessed through the use of electrochemical techniques in natural seawater. The flame retardancy capabilities of the epoxy coating were significantly improved by the incorporation of GCN/Bz-MnO2. The EP-GCN-Bz/MnO2 nanocomposites display peak heat release rate (PHRR) and total heat release (THR) values which are 79 % and 62 % lesser than that of pure EP, respectively. When compared to a pure epoxy coating, the results of salt spray tests indicated that the addition of GCN/Bz-MnO2 improved corrosion protection and decreased water absorption. Electrochemical impedance spectroscopy (EIS) studies showed that the epoxy-GCN/Bz-MnO2 coating still had an improved resistance of 6.40E10 Ω.cm2 even after 30 days of exposure to seawater. Scanning electrochemical microscopy (SECM) displayed lowest ferrous ion dissipation (1.0 I/nA) in the EP-GCN/Bz-MnO2 nanocomposite coated steel. Potentiodynamic polarization testing showed that EP-GCN-Bz/MnO2 had a lower current density (icorr: 0.03 µA/cm2) in comparison with other coatings. This is mainly because the Bz alteration of the MnO2 nanoparticles and their successful coordination with GCN sheets result in a noticeably more compact nanostructure that lowers aggregation and increases binding capacity. Surface-modified GCN was found to be improved in its breakdown products, leading to the production of a strong, inert nanolayered covering, according to Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) analysis. Water contact angle (WCA) of 160° demonstrates the exceptional water resistance of the recently developed EP-GCN/Bz-MnO2 coating. In terms of hardness and adhesion strength, Bz/MnO2 wrapped in GCN had good mechanical characteristics on the epoxy substrate. The improved adhesive strength (18.3 MPa) for mild steel coated with EP-GCN/Bz-MnO2 was attained prior to being immersed in seawater. The EP-GCN/Bz-MnO2 crystallizes form a robust, inert coating that prevents ions from accessing the specimen. The coating has increased adhesive strength as a result, and it can withstand deep immersions without losing its integrity. Hence, the EP-GCN/Bz-MnO2 nanocomposite might work as a useful coating component in the automotive industry.

Intercalated kaolinite with ammonium dihydrogen phosphate as an effective flame retardant to enhance the flame retardance and smoke suppression of epoxy resins

AbstractTo improve the compatibility and flame retardance of kaolinite (Kaol) in polymeric materials, ammonium dihydrogen phosphate (ADP) was intercalated into kaolinite to obtain a novel intercalated kaolinite (K‐ADP) for enhancing thermal stability, flame retardance, smoke suppression, and mechanical performance of epoxy resins (EPs). The results show that the presence of K‐ADP exerts a more positive effect on reducing the heat release and smoke generation of EPs than the same addition of Kaol. Condensed phase analysis shows that EP/K‐ADP composite generates more aromatic cross‐links in the condensed phase to reinforce the compactness and intumescence of char compared to EP/Kaol composite. Especially, 5 wt% K‐ADP confers a 43.7% reduction in peak heat release rate value and a 36.3% reduction in peak smoke production rate value to EP. Toxic gases analysis shows that K‐ADP conduces to inhibiting the release of combustible gases including isocyanates and aromatic volatiles, and generating incombustible gases including ammonia and carbon dioxide to reduce the intensity of EP combustion. The mechanical test shows that K‐ADP imparts less adverse impact on mechanical behavior to EP composites than Kaol due to the good dispersion and compatibility between K‐ADP with EP matrix.

Fabrication of sustainable flame retardant cotton fabrics via foam finishing with sodium polyborate

The conventional process of imparting flame retardancy to cotton fabrics requires the consumption of large amounts of water, chemicals, and energy, which usually involves halogen-containing and phosphorus-containing chemicals. In this work, an eco-friendly sodium polyborate (SPB) foam was creatively introduced onto the cotton fabric surface by a bladed coater to improve the fire resistant performance. For the cotton sample with only 6.7% weight gain (WG) of SPB coating, the LOI value of cotton fabric (SPB treated cotton-1) was enhanced to 32.6% from 18.5%, the damaged length was decreased to 5.7 cm, and the sample self-extinguished in the vertical burning test. The peak of heat release rate value, total heat release value, and total smoke production (TSP) value decreased by 87.0%, 72.7%, and 22.2% respectively compared with those of the control sample. The TSP was further decreased by 80.6% when the WG of SPB was 16.7%. Besides, the SPB treated cotton showed enhanced antibacterial activities against S.aureus and E.coli. Particularly worth mentioning is in the SPB foam finishing procedure, no organic solvent and P or Cl-containing chemicals were involved, and the processing time was only around 3 min with obviously reduced water consumption, compared with dip-padding finishing. More importantly, SPB treated cotton kept good softness, whiteness, water vapor permeability, and air permeability. The SPB foam finishing in this work shows considerable potential in realize good flame retardancy on cotton fabrics by eco-friendly and high-efficient strategy.

Synergistic Effects of 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-Based Derivative and Modified Sepiolite on Flame-Retarded Poly (Ethylene Oxide)-Poly (Butylene Adipate-Co-Terephthalate) Composites.

A 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based derivative (PN-DOPO) combined with aluminium phosphates-coated sepiolite (Sep@AlPO4) was used to improve the flame retardance, thermal stability and mechanical performances of poly (ethylene oxide) (PEO)/poly (butylene adipate-co-terephthalate) (PBAT) blends. The synergistic effects of PN-DOPO and Sep@AlPO4 on flame-retarded PEO/PBAT composites were systematically discussed. Results indicated that introducing 5 wt% Sep@AlPO4 with 10 wt% PN-DOPO into PEO/PBAT achieved a V-1 rating for the UL-94 test and increased the limiting oxygen index value to 23.7%. Moreover, the peak heat release rate (p-HRR), average HRR and total heat release values of PEO/PBAT/PN10%/Sep5% composites decreased by 35.6%, 11.0% and 23.0% compared with those of PEO/PBAT, respectively. Thermogravimetric analysis (TGA) results confirmed that PN-DOPO/Sep@AlPO4 enhanced the initial thermal stability and char yield of PEO/PBAT matrix, and TGA/Fourier transform infrared spectrometry results revealed that the composites exhibited the characteristic absorption peaks of phosphorous-containing groups and an increase in gas-phase volatiles during thermal degradation. The morphological structures of the residues indicated that PN-DOPO and Sep@AlPO4 mixtures produced a more dense and continuous char layer on the composite surface during burning. Rheological behaviour revealed that higher complex viscosity and modulus values of PEO/PBAT/PN-DOPO/Sep@AlPO4 sample could also promote the crosslinking network structure of condensed phases during combustion. Furthermore, the PEO/PBAT/PN-DOPO/Sep@AlPO4 composites exhibited superior elongation at break and flexural performance than the PEO/PBAT system. All results demonstrated that the PEO/PBAT system modified with PN-DOPO/Sep@AlPO4 showed remarkable flame retardance, and improved thermal stability and mechanical properties, indicating its potential application in areas requiring fire safety.

Flame retardancy, thermal behavior and mechanical properties of an epoxy resin and cyanate ester resin copolymer containing a bio phytate-based flame retardant

In this research, a bio-based flame retardant (DNPA), was fabricated via a reaction involving a DOPO derivative (DOPO-NH2) and phytic acid, and was conducted by 1H NMR and FTIR. Then DNPA was incorporated into epoxy resin and cyanate ester resin copolymer (EPCE) to fabricate EPCE/DNPA composites. A comprehensive investigation was conducted to evaluate both the fire behavior, thermal performance and mechanical properties of the composites. Notably, the EPCE composite with 10 wt% DNPA (EPCE/10DNPA) achieved a V-0 rating and exhibited a 28.3 vol% LOI value. The EPCE/10DNPA demonstrated a 16.2 % decrease in the peak heat release rate value and a 13.9 % reduction in the total heat release value, respectively, compared to EPCE.

Hierarchical rigid porous composites towards impact resistance and fire safety

Impact injuries and fire risks generally coexist simultaneously in extreme environments. In this context, it is of great necessity to design impact resistant materials with both flame retardant performance and thermal stability. Here, a multi-functional flame retardant coating was prepared from the combination of silica sol (Si-sol), phytic acid (PA) and expandable graphite (EG) by graft modification with γ-propyl-trimethoxysilane (KH550). Subsequently, hierarchical composites were fabricated using one-pot foaming and brush coating method, where the carbon fiber cloth and coating served as the surface layer, while rigid polyurethane foams (RPUF) acted as the interlayer. The hierarchical structure endowed the RPUF composites with high compression resistance and impact resistance properties. Furthermore, the flame retardant coating could effectively reduce the values of peak heat release rate and peak smoke production rate of RPUF composites by 77.5% and 81.8%, respectively. Therefore, these RPUF composites can effectively prevent impact damage and achieve excellent flame retardancy, making them promising candidates as safety protective materials.

Flammability and combustion behavior of the polyester/cotton blended fabric via an independent flame-retardation for two components strategy

Polyester/cotton (Terylene/cotton, T/C) blended fabrics are universally applied in clothing and household textiles due to the combination of excellent moisture absorption properties from cotton and dimensional stability from polyester, but high flammability and combustion resulting from the “scaffolding effect” become a major obstacle. Herein, we developed a novel flame-retarding T/C blended fabric to inhibit the “scaffolding effect” via independent flame-retardation for two components strategy, in which the copolymerized flame retardant of the polyester fibers and the cotton fibers were blended, and then halogen-free ammonium vinyl phosphonate (AMVP) was grafted onto the cotton component. The flammability and combustion behavior of the flame-retarding T/C blended fabric were assessed, and the mechanism of the flame retardant was analyzed. The results indicated that the limiting oxygen index (LOI) of the treated blended fabric could be increased to 37.2 %, which had excellent self-extinguishing property. The peak heat release rate (PHRR) and total heat release (THR) values of treated blended fabrics were severally reduced by 54.3 % and 66.5 % in comparison with the blended fabrics without grafted of AMVP. Furthermore, the combustible products of blended fabric generated during the thermal degradation process were effectively decreased in the gas phase due to the independent flame retardant char-formation of two components inhibited the “scaffolding effect”. This study offers a new flame retardant strategy for the fabrication of blended fabrics.

A novel phosphorus-nitrogen-based hyperbranched polysiloxane for improving the fire safety of PA6 with suppressed melt droplets and good mechanical properties

The combustible defects of polyamide 6 (PA6), especially the flammable melt-dripping behavior, have greatly limited its application in some particular fields. In this work, a halogen-free hyperbranched polysiloxane (PBDSi) containing DOPO and Schiff base was designed via Michael's addition reaction and dehydration-condensation reaction. Results showed that the char yield (Yc) of PBDSi attained 37.9 wt%, confirming the satisfactory charring behavior of PBDSi for preparing flame-retardant PA6. Just by adding 3 wt% of PBDSi, the serious melt droplets of PA6 were suppressed effectively. The prepared PA6/PBDSi-3 with 5 wt% of PBDSi could achieve the highest value of limited oxygen index (LOI) of 27.2 %, while that of PA6 is 21.0 %. Meanwhile, PA6/PBDSi-3 obtained an apparent reduction in the peak heat release rate (PHRR) value of 31.1 % compared with pure PA6. The cooperated effect of DOPO, Schiff base, and polysiloxane that contributed to generating a silicon-phosphorous-rich char layer and releasing incombustible volatiles that were determined to be the essential factor for the improved fire safety of PA6/PBDSi were explored intensively. Inspiringly, PA6/PBDSi composites exhibited a slight mechanical loss concerning PA6, overcoming the great challenge of developing additive flame-retardant materials to balance mechanical properties and fire safety.

EXPERIMENTAL INVESTIGATION OF THE EFFECTS OF WATER ADDITION INTO THE INTAKE AIR ON COMBUSTION PARAMETERS, ENERGY BALANCE AND DEVELOPING AN EMPIRICAL COMBUSTION DURATION RELATION IN AUTOMOBILE DIESEL ENGINE

The effect of the water addition into the intake air (WAIA) on cylinder pressure, temperature, heat release rate (HRR), combustion duration (CD), and energy balance in an automotive diesel engine have been investigated experimentally. Also, an empirical correlation has been developed for estimating CD using the HRR. This relation has been developed by applying the multiple curve fitting method, taking into account experimental results for different water ratios such as (2, 4, 6, 8, and 10) %, different engine loads, and different engine speeds such as (2000, 2500, 3000, 3500, and 4000) rpms. The test results showed that cylinder pressure values generally increased at (2000, 2500, and 3500) rpm, but they decreased at (3000 and 4000) rpm for all of the selected water ratios. Also, maximum cylinder temperature values have occurred at crank angles farther from TDC for WAIA. Cylinder temperature values mostly decreased at (2000, 2500, and 3000) rpms, but they generally increased at (3500 and 4000) rpms for WAIA. Also, maximum cylinder temperature values were occurred at crank angles farther from TDC for WAIA. HRR values generally decreased at (2000, 2500, 3500, and 4000) rpms, but they generally increased at 3000 rpm. It has been determined that the CDs were generally shortened at all of the engine speeds under full loads with water addition. CD values for NDF and (2.42, 4.22, 5.95, 8.32, 9.46) % water ratios have been determined as (13.10, 12.96, 12.93, 12.68, 12.95, and 13.576) °CA, respectively, at 2000 rpm. The effective power values according to the chemical energy of the fuel generally decrease with WAIA at 2000 rpm. However, the effective power values according to the chemical energy of the fuel increase for high WRs at 4000 rpm.

Enhancing thermal stability, mechanical properties, and flammability of polyvinyl alcohol using amide‐functionalized hydrogel and zinc oxide nanoparticles

AbstractNew polyvinyl alcohol (PVA) nanocomposites containing zinc oxide (ZnO) nanoparticles and a hydrogel were prepared by the solution casting method. ZnO nanoparticles grafted co‐polymer (Zn‐g‐CP) was synthesized through the reaction of ZnO nanoparticles with vinyltriethoxysilane and then the radical co‐polymerization with 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS). The amide functionalized hydrogel was prepared via an in situ polymerization of acrylamide and N,N′‐methylene bisacrylamide (MBA) as a crosslinker in a solution of PVA. The corresponding results indicated that the simultaneous presence of both Zn‐g‐CP and hydrogel could significantly increase flammability, thermal stability, and the tensile strength of PVA. The results of the X‐ray diffraction (XRD) and field‐emission scanning electron microscopy (FE‐SEM) indicated a uniform dispersion of ZnO nanoparticles and an enhanced compatibility with the PVA matrix. Thermogravimetric analysis (TGA) in both N2 and air atmospheres, indicated that the temperature at 50% mass loss and the char residue values of PVA nanocomposite containing 6 wt% of Zn‐g‐CP in the presence of hydrogel (PZH12 sample) were enhanced, which was evident by the increased thermal decomposition temperature. The peak of heat release rate (pHRR) value of the PZH12 sample was obtained 56.9% lower than that of the neat PVA demonstrating a significant improvement in flammability behavior. Also, the flame‐retardant performance of PZH12 improved, as compared to the pure PVA, with UL‐94 V1 rating and LOI of 27.2%. The tensile strength (Ts) and elongation at break (EB) values for the mentioned sample enhanced by 62.5% and 7.2% compared to those of the neat PVA, respectively.Highlights Preparation of vinyl functionalized ZnO nanoparticles (VZnO). ZnO grafted co‐polymer (Zn‐g‐CP) from a radical polymerization on the VZnO surface. Preparation of an amide‐sulfonated hydrogel in the PVA solution. The effect investigation of hydrogel and Zn‐g‐CP on the PVA properties. The results exhibited the enhanced flame retardancy and mechanical properties of PVA.

Combination of bio-based tannic acid, sophora flower extract and metal salts: A facile route towards improving durable flame retardancy and UV resistance of silk fabrics

Environmental engineering placed green demands on the functional modification of textiles. Here, the combination of bio-based tannic acid, sophora flower extract and metal salts was used to manufacture silk fabrics with flame retardancy and UV resistance via a facile impregnation strategy. With different metal salts treated, the modified silk fabrics named silk/TA/SFE-TE, silk/TA/SFE-Fe and silk/TA/SFE-Cu achieved self-extinguishing in the vertical burning test, with limiting oxygen index values of 31.7 ± 0.4 %, 30.2 ± 0.2 % and 30.9 ± 0.3 %, respectively. In the cone calorimetry test, the peak heat release rate values of the three silk fabrics modified with metal salts were all significantly suppressed, and the total smoke production values of silk/TA/SFE-TE and silk/TA/SFE-Fe were reduced from the original 0.178 m2 to 0.126 m2 and 0.138 m2, respectively. Furthermore, silk/TA/SFE-TE, silk/TA/SFE-Fe and silk/TA/SFE-Cu displayed high ultraviolet protection factor values and thus had good UV resistance, owing to the presence of tannic acid and sophora flower extract. Most importantly, the flame retardancy and UV resistance of the three silk fabrics modified with metal salts were still superior to those of the original silk fabrics after 30 washing cycles. In short, this facile route for the preparation of functionalized silk fabrics provides a novel idea for the development of advanced textiles.

Flame-retardant and antibacterial flexible polyurethane foams with high resilience based on a P/N/Si-containing system

In this work, the coatings used phosphorylated chitosan (PCS) and GP-108 via the dip-coating method presented exceptional flame retardancy and antibacterial properties for flexible polyurethane foams (FPUF). PCS/GP@FPUF with 35% weight gain of PCS/GP can receive the UL-94 V-0 rating and obtain a 32% reduction of peak heat release rate value compared with that of FPUF, and it remains relatively dense char residues. The effective heat of combustion of PCS/GP@FPUF is 21.6 kJ/g, presenting a 22% decrease compared with that of FPUF. Meanwhile, the PCS/GP coatings mainly have the condensed-phase flame-retardant mechanism associated with the analysis of char residues and the volatile products released through the thermal degradation process. X-ray photoelectron spectroscopy results confirm that the char residues of PCS/GP@FPUF consist of highly-graphitized carbon and it formed P-N-Si synergistic char layers. In addition, the antibacterial rates of PCS/GP@FPUF against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are 99.99%, and the incorporation of GP-108 does not influence the antibacterial properties of PCS. Importantly, the resiliency of FPUFs has been slightly influenced. Briefly, the flame-retardant and antibacterial FPUFs with wonderful resiliency are hopeful to be applied as filler materials for vehicle seats and obtain longer service lives.

Investigation of nanocomposite system with long-chain phosphorus-containing intercalator-modified montmorillonite nanosheets

The biodegradable polyester polybutylene adipate-co-terephthalate (PBAT) is a synthetic material that can melt and ignite easily when exposed to fire. Herein, we synthesized a long-chain phosphorus-containing intercalator by grafting 9,10-dihydro-9-oxa-10-phos-phaphenanthrene10-oxide (DOPO) onto long-chain quaternary ammonium salts (BHMDAC). Then inserted it into the sodium-based montmorillonite (MMT) nanosheets at the ratio of 25.9 wt% to obtain organic modified nanosheets. Subsequently, they were mixed into the PBAT matrix, and a series of performance such as microscopic dispersion, thermal stability, flame retardancy, mechanism and mechanical properties of nanocomposite were investigated. Compared with PBAT (1138.42 kW/m2), PBAT/MMT-(DOPO-BHMDAC) 5 wt% exhibited the lowest peak heat release rate value (508.04 kW/m2), which was reduced by 55.37 %. After adding 1 wt% MMT/DOPO-BHMDAC, the tensile strength of the sample increased from 25.1 MPa to 32.0 MPa, and the elongation at break increased to 826 %. This work provides a new perspective for future research on high-performance degradable polyester materials.