Total Heat Release Rate Research Articles

Facile construction of organic–inorganic hybrid flame-retardant system based on fully biomass: Improving the fire safety and mechanical property of epoxy resin

As the contradiction intensifies both the increasing consumption of petroleum resources and environmental protection, the exploitation and utilization of biological resources have reached an unprecedented height. Hence, an organic–inorganic hybrid system, called ammonia phytate modified oyster waste nanosheets (TOSP@PAA), was constructed via mechanochemical strategies and used for flame-retardant EP. The characterization revealed that TOSP@PAA showed a specific layer crosslinking structure by the NH3+OP bond. The calcination experiment revealed that TOSP@PAA possessed excellent self-charring performance and formed a highly intumescent char residue layer at high temperatures. In addition, the combustion tests indicated that EP with TOSP@PAA showed noticeable fire safety (e.g., ∼74.0 % and 60.2 % decline in peak heat release rate (pHRR) and total heat release rate (THR) at only 8 wt% content) and excellent heat insulation properties. Remarkably, EP with TOSP@PAA exhibited good mechanical properties with remarkable improvement in flexural properties. The work provides new sights on the facile preparation of environmentally friendly flame retardants and explores a new way to strengthen the fire safety and mechanical property of EP.

Multifunctional waterborne polyurethane nanocoatings based on large-scale exfoliated mono-layered montmorillonite nanosheets

Ultrathin two-dimensional (2D) nanosheets have driven the development of multifunctional materials. However, persistent challenges with complex processes, low production rates, and high costs have prevented ultrathin 2D nanosheets from realizing their full potential in nanocomposite. Herein, large-scale exfoliated montmorillonite (MTM) mono-layered nanosheets in polyethyl-phosphate glycol ester were assembled into environment-friendly waterborne polyurethane to obtain multifunctional nanocoatings with superior matte performance, favorable flame retardancy, and high adhesion. Specifically, a significant 98.2 % decrease of 60° gloss from 65.0 GU to 1.2 GU was observed, which almost wholly diffuses incident light due to the rougher surface. Besides, total heat release and total smoke rate were decreased by a maximum of 27.1 % and 34.4 %, respectively. Surprisingly, the nanocoating with excellent anti-blocking properties has outstanding adhesion to PU leather. These nanocoatings on leather and fabric showed potential for engineering applications. This study may provide new insight for application of ultrathin 2D nanosheets in multifunctional materials.

The designation of highly efficient intrinsic fame-retarding epoxy materials via the regulation of the phosphorus and nitrogen content for the curing agents

Epoxy resin (EP) is one kind of widely applicated thermosetting resin with excellent manufacturability, mechanical performance and chemical resistance, but its flammability seriously limited its widely application. In this work, the flame-retarding curing agent (BIPD) with was prepared by a simple one-step substitution reaction between benzimidazole (BI) and phenylphosphonyl dichloride (PD). When the mass fraction of BIPD is 10 %, the flexural strength and impact strength are 174.7 MPa and 14.9 KJ/m2, respectively, which are 15.5 % and 69 % higher than those of EP/BI10. The EP/BIPD10 passed the UL-94 V-0 rating with a limiting oxygen index (LOI) reaching to 33 %. Meanwhile, the peak of heat release rate (PHRR) and total heat release rate (THR) of EP/BIPD10 decreased by 50.2 % and 37.8 %, the total smoke production (TSP) and the mass percentage of residues increased by 10.4% and 204.1 % than that of EP/BI10 in the cone calorimeter (CC) measurement, showing a jointly flame-retarding process in the condensed and gas phase. Furthermore, the results of Raman spectrum, the thermogravimetric infrared spectroscopy (TG-FTIR) and pyrolysis-gas chromatography/mass spectrometry (PY-GC/MS) confirmed the conclusion.

Synthesis of DOPO-Based Phosphorus-Nitrogen Containing Hyperbranched Flame Retardant and Its Effective Application for Poly(ethylene terephthalate) via Synergistic Effect.

To obtain industrialized poly(ethylene terephthalate) (PET) composites with highly efficient flame retardancy, a phosphorus-nitrogen (P-N) containing hyperbranched flame retardant additive was synthesized by 9,10-dihydro-9-oxa-10-phospho-phenanthrene-butyric acid (DDP) and tris(2-hydroxyethyl) isocyanurate (THEIC) through high temperature esterification known as hyperbranched DDP-THEIC (hbDT). The chemical structure of the synthesized hbDT was determined by FTIR, 1H NMR, 13C NMR, and GPC, etc. Subsequently, hbDT/PET composites were prepared by co-blending, and the effects of hbDT on the thermal stability, flame retardancy, combustion performance, and thermal degradation behavior of PET were explored to deeply analyze its flame retardant mechanism. The test results showed that hbDT was successfully synthesized, and that hbDT maintained thermal stability well with the required processing conditions of PET as retardant additives. The flame retardant efficiency of PET was clearly improved by the addition of hbDT via the synergistic flame-retardant effect of P and N elements. When the mass fraction of flame retardant was 5%, the LOI of the hbDT/PET composite increased to 30.2%, and the vertical combustion grade reached UL-94 V-0. Compared with pure PET, great decreased total heat release (decreased by 16.3%) and peak heat release rate (decreased by 54.9%) were exhibited. Finally, the flame retardant mechanism of hbDT/PET was supposed, and it was confirmed that retardant effect happened in both the gas phase and condensed phase. This study is expected to provide a new idea for the development of low toxic, environment-friendly and highly efficient flame retardant additive for polyesters in an industry scale.

Simplified modelling of transient upward flame spread on combustible element

This paper presents the development and validation of a simplified model to simulate upward fire growth and flame spread on vertical surface with combustible materials. The model consists of the following main sub-models: a one-dimensional combined heat and mass transfer model perpendicular to the vertical surface to compute gaseous fuel production due to decomposition and combustion of the combustible material, a simplified model to calculate surface heat flux, and a transient flame growth model based on an existing steady state flame model that takes into account transient heat feedback due to combustion. Validation of the model is checked by comparison of the predictions of this model against FDS (Fire Dynamic Simulator) simulation results and experimental results wherever available, including the following: flame growth with variable heat release rates of solid materials under various levels of external irradiation, temperature distribution through thickness of the wall, and propagation of the pyrolysis front. To demonstrate capability of the new model, vertical burning and upward flame spread on 2.4 m high panels of wood and 5.0 m high panels of PMMA are carried out and compared with FDS simulations. The new model calculation results, including propagation of the pyrolysis front, total heat flux and heat release rate are in good agreement with FDS simulation results. However, the new model requires a fraction (a few minutes of CPU time) of that for carrying out the corresponding FDS simulation (CPU time of 2 days).

Preparation of a copper porphyrin derivative and its surface modification for simultaneously endowing PET fibers with dyeing, flame retardant and anti-dripping performance

Polyethylene terephthalate (PET) fibers are the most numerous synthetic fibers in the world, but their flammability and high-temperature melt dripping limit their further applications. To address these issues, a copper porphyrin derivative, i.e., copper 2‑methoxy-4-(10,15,20-tris(4-((diphenylphosphoryl)oxy)-3-methoxyphenyl) porphyrin-5-yl) phenyl diphenylphosphinate (MTPD-Cu) was firstly synthesized from biomass vanillin in this paper. Then, MTPD-Cu was used for the surface modification of PET fibers via the dyeing process to prepare multifunctional PET fibers (FR-PET) with dyeing, flame retardant and anti-dripping properties. The flame retardancy, thermal stability, anti-dripping and color fastness of FR-PET were evaluated by limiting oxygen index (LOI), burning test, micro combustion calorimetry (MCC), thermogravimetric analyzer (TGA), and water washing color fastness test. The results revealed that the LOI value increased from 21% for pure PET fibers to 29.8% for FR-PET fibers. Meanwhile, compared to pure PET fibers, the total heat release (THR) and peak heat release rate (PHRR) of FR-PET decreased by 79.8% and 57.8%, respectively. The residual char of FR-PET was significantly improved whether in nitrogen or in air atmosphere at 800 °C, showing good char forming ability. In addition, FR-PET exhibited no melt dripping phenomenon and was pink with excellent color fastness to washing. Furthermore, the possible flame retardant and anti-dripping mechanisms were also proposed. This work provides a simple and easy modification method to simultaneously endow PET fibers with dyeing, flame retardancy and antibacterial properties, which is easy to be prepared on a large scale.

Fire spread among multiple vehicles in tunnels using longitudinal ventilation

The characteristics of fire spread among multiple vehicles in tunnels using longitudinal ventilation were investigated by analyzing the experimental data from a series of fire tests in a 1:15 scale tunnel. Further, a simple theoretical model for gas temperature in a tunnel with multiple fire sources was proposed and used in analysis of the experimental data. The results showed that, for objects (wood piles) placed at a same separating distance downstream of the fire, the fire spread occurred faster and faster along the tunnel. Validation of the simplified temperature model for multiple fire sources was made against both model and full-scale tunnel fire tests. The model was further used to predict the critical conditions for fire spread to the second and third objects. Comparisons with the test data showed that average excess temperature of 465 K (or an equivalent incident heat flux of 18.7 kW/m2) could be used as the criterion for fire spread, and this was verified further by other model-scale tests and full-scale tests. The results showed that the critical fire spread distance monotonously increases with the heat release rate, and decreases with the tunnel perimeter. For multiple fire sources with equivalent heat release rates, as the separation distance between the first two fire sources increases, the critical fire spread distance from the second fire source to the third fire source decreases, but the total fire spread distance from the first fire source to the third one increases. If the total heat release rate at the site of a downstream fire source is greater than that at the former fire source, the critical fire spread distance becomes longer.

Effects of Bio-Based Polyelectrolyte Complex on Thermal Stability, Flammability, and Mechanical Properties Performance Utilization in PLA/PBS Composites

In this study, the two eco-friendly flame retardants of the polymeric type (PA-PEI) and monomeric type (PA-Arg) phytate amine complexes were prepared via the ionic reaction of polyethylenimine (PEI) or arginine (Arg), respectively, with phytic acid in an aqueous solution. The chemical structure and thermal stability of PA-PEI and PA-Arg were characterized by Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). In order to improve the flame retardancy of the polylactic acid (PLA)/polybutylene succinate (PBS) biocomposites (P/15B-based biocomposites), the flame retardants PA-PEI and PA-Arg were embedded into P/15B by thermal blending procedures, respectively, to obtain P/15B/PA-PEI series and P/15B/PA-Arg series biocomposites. The TGA analyses demonstrated that incorporating PA-PEI or PA-Arg into the P/15B polymer enhances the char residues in these P/15B biocomposites. The XRD and SEM analyses of the P/15B/PA-PEI series and P/15B/PA-Arg series suggested the PA-PEI and PA-Arg were embedded into the P/15B polymer matrixes, respectively. The mechanical results showed that P/15B/PA-Arg series exhibited higher values than the P/15B/PA-PEI series biocomposite, which were associated with less roughness of P/15B/PA-Arg than that of the P/15B/PA-PEI series. The flammability results of the P/15B/PA-PEI series and P/15B/PA-Arg series biocomposites exhibited a V-2 level in UL94 vertical test. Further, the fire resistance performance of P/15B-based biocomposites was enhanced by incorporating PA-PEI or PA-Arg into the P/15B matrix through the analyses of the Cone calorimeter test (CCT), as a comparison with neat P/15B. The peak heat release rate (pHRR), the total heat release rate (THR), and char residues of P/15B/15PA-Arg biocomposite were significantly improved to 280.26 kW/m2, 107.89 MJ/m2, and 10.4%, respectively. The enhancement of the P/15B-based composites’ fire resistance is attributed to the interplay effect on the catalytic and condensed effect on the thermal decomposition of PA-PEI or PA-Arg in P/15B biocomposites. The resultant eco-friendly flame-retardant P/15B biocomposites reported in this study can be widely applied in various fields, including construction, electronic appliances, and other fields.

Reactive P/S/N-containing synergistic flame retardant towards eco-friendly durable flame-retardant cotton fabric: Flame-retardant property, durability and mechanism

Developing eco-friendly durable flame-retardant cotton fabric not only expands its application area, but also caters to the healthy and environmentally friendly concept of consumers. Herein, a reactive P/S/N-containing synergistic flame retardant (PSN) was synthesized to prepare eco-friendly durable flame-retardant cotton fabric through chemical modifying method. Flame-retardant finishing deteriorated the softness, whiteness, tensile strength and air permeability of cotton fabric. PSN conferred outstanding flame retardancy, fire safety and durability to cotton fabric. For treated fabric with the add-on of 14.2%, it achieved an LOI value of 36.5% and extinguished spontaneously even after 50 laundering cycles. Its peak heat release rate, total heat release and fire growth rate index values decreased sharply than those of the control fabric. PSN exhibited high-efficiency flame-retardant behavior, and the synergy between P, S and N elements facilitated the formation of intumescent barrier on the fiber surface during combustion. The hydrolysis of covalent bond and formation of phosphate/sulphonate during laundering both accounted for the decrease in flame retardancy of treated fabric.

Experimental studies of the effect of burner location on the development of building fires

Building-related safety design and assessment requires precise and quantifiable fire laws. However, the effect of fire source location on flame behavior and combustion products has not been fully elaborated leading to a lack of precision in the corresponding risk assessment. The experiments were carried out in a 1/2-scale compartment to investigate the effect of burner location on the self-extinguishing behavior. Six burner positions were used and combustion conditions were varied by adjusting the opening factor and total heat release rate (HRR). Flame behavior, temperature, critical HRR, oxygen and carbon monoxide concentrations were recorded and analyzed. Results showed that the burner location could change the flame behavior and its critical conditions. The effect of burner position on the roof temperature could be quantified by the newly proposed position factor. The oxygen and carbon monoxide concentrations in the smoke layer were significantly higher when the burner was near a wall or corner than in other positions. The critical HRR for flame extinction varied with burner position because the process by which the flame entraining air and air into the opening was changed. Experimental results in this study provide accurate data support and physical mechanisms for predicting building fire development.

Modeling of spark ignition in gaseous mixtures using adaptive mesh refinement coupled to the thickened flame model

In standard LES of spark ignition using the thickened flame model (TFM) and a static mesh, in other words without the use of adaptive mesh refinement (AMR), a progressive increase of the thickening factor F from unity to the nominal value is a consequence of the progressive increase of the cell size away from the spark plug. If the refined mesh is limited to a small region around the spark plug, the computational cost is limited but F will increase very rapidly as soon as the flame leaves the spark region, leading to an erroneous prediction of the total heat release rate as shown in this study. Conversely, using a large refined mesh region will allow such a progressive increase of F but at the cost of a strongly increased computational cost. To solve this issue, two new spark ignition models called TFM-AMR-I and TFM-AMR-I-Ftrans are proposed for TFM. These models are based on TFM-AMR Mehl et al.(2021) which employs AMR to ensure the desired thickening level and a constant number of grid points across the flame. It also uses a realistic spark plug energy model as in Colin et al.(2019). To avoid the aforementioned issue, a physical criterion is proposed to start the increase of F only when the flame kernel can be considered self-sustained. As this criterion is given by a model transport equation, the possible convection of the kernel outside the spark region doesn’t prevent the model to work properly. Secondly, in both models the increase of F is no more dictated by the cell size of the static mesh but it is given by an additional transport equation that controls the growth rate of F in time.These models are applied to the laminar propane/air ignition experiment presented in Colin et al.(2019). It is first shown that the experimental MIE is correctly recovered when using a DNS type resolution, that is, F=1 at any time. Then both proposed LES ignition models are applied to the same case: they recover correctly the MIE of the DNS provided the stretch correction of Quillatre (2014) is applied, which confirms the need to correct the effect of stretch with TFM. At the same time, TFM-AMR-I under-predicts the total heat release rate, which is attributed to the jump of the thickening factor at each AMR level removal. On the contrary, TFM-AMR-I-Ftrans compares better with the DNS, which is attributed to the continuous evolution of F with this model. Finally, it is shown that both models lead to a computational time reduction of a factor between 2 and 6 compared to static mesh TFM simulations.

High enthalpy efficiency lignin-polyimide porous hybrid aerogel composite phase change material with flame retardancy for superior solar-to-thermal energy conversion and storage

Liquid-solid organic phase change materials (PCMs) exist shortcomings of leakage, poor solar-to-thermal conversion efficiency, and flammability, which restrict the application scope of solar-thermal energy storage. To meet these problems, PCMs (ZrP-PI@PEG) with excellent thermal energy storage, solar-to-thermal conversion, and flame retardancy were fabricated in this study. The polyimide (PI)/sodium lignosulfonate-zirconium phosphate (SL-ZrP) hybrid-aerogels (ZrP-PI) were prepared by freeze-drying and thermal imidization. ZrP-PI aerogels composited with polyethylene glycol (PEG) via vacuum impregnation to fabricate the composite PCMs (CPCMs, ZrP-PI@PEG). The in-situ biochar generated from SL-ZrP increases both solar-to-thermal conversion and flame retardant of CPCMs. The final result demonstrates that ZrP-PI@PEG exhibits a superior adsorption ratio (95.5%) and outstanding latent heat (157.67 J/g), as well as about 13% flame retardant index decrease in heat release rate (HRR) and total heat release rate (THR). Furthermore, ZrP-PI@PEG shows great thermal stability and reliability after conducting a leakage experiment and thermal cycling test. These superior resultants indicate that ZrP-PI@PEG has a good potential for widespread and long-term use in solar thermal energy storage. • A novel biomass/polyimide aerogel composite phase change material was successfully prepared by a simple method. • The as-prepared composite exhibited excellent thermal energy storage, solar-to-thermal conversion and flame retardancy. • The relative enthalpy efficiency of the composite reaches up to ∼95.5%.

Synthesis and Characterization of a New Copolymer Consisting of Polyamide 1210 and Reactive Phosphorus-Nitrogen Flame-Retardant.

The thermal stability and reactivity of organophosphorus flame-retardants play a critical role in synthesizing copolymerized flame-retardant polyamides. Herein, this work successfully synthesizes a flame-retardant CEPPA-DDA salt (CDS) with both good thermal stability and high reactivity by reacting 2-carboxyethyl phenyl phosphonic acid (CEPPA) with 1,12-dodecanediamine (DDA). Flame-retardant polyamide 1210 (FRPA) is further prepared by copolymerizing the CDS, DDA, and sebacic acid (SEA). The test results show that the introduction of CDS can significantly improve the flame-retardant properties of FRPA. Specifically, the flame-retardant polyamide 1210 (FRPA-7) with 7 wt% CDS addition can reach V-0 grade according to UL-94 standard, accompanying limiting oxygen index value of 30.2% and tensile strength of 38.62MPa. Compared with pure polyamide 1210, the peak heat release rate and total heat release rate of FRPA-7 reduce by 24.11% and 9.40%, respectively. This study provides a simple strategy to prepare flame-retardant polyamides with high flame retardancy and good mechanical properties, which are expected to show great potentials in future industrial applications.

Hierarchical hybrid glass fibers modified by hyperbranched polyphosphoramide and graphene oxide sheets to improve flame retardancy and suppress candlewick effect of poly(lactic acid)/glass fibers composites

AbstractGlass fibers (GFs) reinforced polymer composites display high mechanical performance but deteriorated flame retardancy due to the “candlewick effect” caused by fibers. To solve this problem, novel hierarchal hybrid glass fibers (GF@HBPPA@GO) were prepared by multistep coating of 3‐aminopropyltriethoxysilane (APTES), hyperbranched polyphosphoramide (HBPPA) and graphene oxide (GO) in sequence. Several GFs reinforced poly(lactic acid) (PLA) composites were fabricated with the same GFs loading. PLA/GF@HBPPA@GO composite showed the highest limited oxygen index (LOI) value of 25.2% and much decreased peak heat release rate, total heat release and mass loss rate, corresponding to a drop of 23.2%, 16.6%, and 53.8% respectively compared with PLA/GF‐APTES composite. Meanwhile, it maintained similar tensile and impact strength values. The improved flame retardancy was mainly attributed to the good synergistic effect of HBPPA and GO on generating high‐yield char residues encapsulating GFs perfectly in the condensed phase, which effectively reduced the interface energy and increased the surface roughness of GFs to suppress the wetting and spreading of PLA melt toward the flame zone, and consequently weakened the candlewick effect of GFs and achieved better flame retardancy. This provides new ideas for preparing fiber reinforced polymer composites with encouraging mechanical properties and outstanding fire safety simultaneously.

Superior intrinsic flame-retardant phosphorylated chitosan aerogel as fully sustainable thermal insulation bio-based material

Owing to the arising environmental pollution and energy-related challenges, the utilization of renewable polysaccharides such as chitosan (CS) in the preparation of biodegradable aerogel heat-insulation materials represents a growing interest. In this study, a simple and low-cost route was proposed to synthesize a phosphorylated chitosan (PCS) with a high substitution degree of phosphate groups in a homogeneous H3PO4/acetic acid solution, and its chemical structure was confirmed using FT–IR spectroscopy, nuclear magnetic resonance, and X–ray photoelectron spectroscopy. An outstanding intrinsic flame-retardant PCS aerogel was directly fabricated via freeze-thawing and freeze-drying process. Remarkably, limited oxygen index values of the PCS aerogels increased to above 80%, and their UL–94 test results achieved V–0 rating. The peak heat release rate and total heat release rate values of PCS-4 aerogel significantly decreased by 91.2% and 73.0% compared with those of chitosan aerogel, respectively. The bio-based PCS aerogel with superior intrinsic flame retardancy, low thermal conductivity, and excellent hydrophobicity shows promise as new sustainable flame-retardant heat-insulation material.

Making polycarbonate flame retardant: Flame retardant selection and calorimetric analyses

Polycarbonate (PC) has been widely applied in aerospace and railway industries, and it is imperative to improve its fire safety related properties, especially heat release properties. Particularly, the MARHE value (maximum average rate of heat emission) directly obtained from the cone calorimeter (CONE) test is a comprehensive property that is presented in the EN45545-2 standard developed by the EU. In order to study the effect of flame retardants on the MARHE of polycarbonate, four flame retardants with different flame retardant mechanisms were used to prepare low heat release PC. CONE was used to characterize the heat release performance of PC, focusing on exploring the factors affecting MARHE and the method of preparing low heat release materials. The flame-retardant mechanism of PC was studied by SEM and TG/DTG. Meanwhile, the flame retardant index (FRI) is calculated as a reference for the flame retardant performance of PC. Results show the MARHE of HPCTP/PC is reduced by 31.12%, and it is confirmed that MARHE is influenced by time to ignition (TTI), peak heat release rate (PHRR), total heat release rate (THR), and the shape of the peak. Mica-RDP/PC materials were prepared based on the conclusions of MARHE derivation. RDP and Mica play a typical synergistic flame-retardant mechanism, with MARHE reductions from 20.31% to 20.00% of the single-component systems to 31.39%. All FRI values of PC materials are in the range of Good flame retardancy. This study provides a feasible way for the deep understanding and wide application of MARHE and the improvement of the fire safety performance of PC.

An iron phenylphosphinate@graphene oxide nanohybrid enabled flame-retardant, mechanically reinforced, and thermally conductive epoxy nanocomposites

The epoxy (EP) resin is being intensively applied in electronics packaging, the 5th generation communication technology (5G) and composite tanks for pressurized hydrogen fuel storage. For these applications, to date it has remained a grand challenge for EP to achieve a demanding property portfolio, e.g., the combination of satisfactory fire retardancy, high thermal conductivity (λ) and excellent mechanical properties. Herein, we report an iron phenylphosphinate-functionalized graphene oxide (FeHP@GO) nanohybrid by a facile yet scalable in-situ self-assembly method. Compared to the virgin EP, the EP nanocomposite with 2.0 wt% of FeHP@GO shows 42.5 % improvement in the limiting oxygen index (LOI), 46.2 % and 23.5 % reductions in the peak heat release rate (PHRR) and total heat release rate (THR), respectively, and a desired UL-94 V-0 rating. In addition, the resultant EP nanocomposite also exhibits improved tensile strength and λ (increased by 32.6 % and 96.0 %, respectively) relative to virgin EP. Such desirable integrated performances outperform those of the previously-reported EP counterparts, because of the multiple synergistic effects between FeHP and GO. This work provides an innovative strategy for the design of multifunctional EP nanocomposites, which holds the great promise for many industrial applications.

A green, effective, and synergistic flame retardant for poly(ethylene-co-vinyl acetate) resin

It is a challenge to prepare flame-retardant composites via addition of low content of fire retardant all the time. In this contribution, a compounding method based on combining long-chain phosphaphenanthrene (DPP) flame retardant and two dimensional (2D) black phosphorene (BP) is used to achieve molecule-scale dispersion of a Si-P flame retardant in poly(ethylene-co-vinyl acetate) (EVA) matrix (donated as EVA/DBP) by the interaction of intermolecular hydrogen bonds. By this way of doing, EVA/DBP composites with various flame retardant contents were investigated. Cone calorimeter, vertical combustion, thermo-gravimetric analysis, scanning electron microscope, Raman Spectrum, and Fourier transform infrared spectroscopy are used to evaluate the flame retardance and analyze the corresponding mechanisms. The results show that the DBP can effectively improve the flame retardant properties and thermal stability of EVA with slight influence on its mechanical performance. Compared with pure EVA resin, EVA/DBP composite with 5 wt% dosage of DBP achieves UL94-V0 rating, 9.6% increased in limiting oxygen index (LOI), 16.1% and 47.5% reduction in total heat release (THR) and peak heat release rate (PHRR), respectively. Moreover, the tensile yield stress and elongation at break are only reduced by 8.1% and 6.2%, respectively. It shows that the interaction between DBP and EVA effectively promote gas phase fire resistance.

Crystallization of sodium metaborate on the surface of layered double hydroxide imparts high flame retardancy properties to epoxy coatings

To address the phenomenon of rapid fire spread in high-rise steel buildings, this paper used the in situ growth method to crystallize sodium metaborate (SMB) on the surface of layered double hydroxide (LDH) and grafted Ti-O onto LDH@SMB hybrid material by hydroxyl action. The synthesized LDH@SMB@Ti (LST) hybrid material was then doped into epoxy resin (EP) to prepare a composite coating. The fire test showed that the LST/EP coating makes the steel plate reach a stable temperature in a shorter time, so that the plate temperature did not continue to rise, and the temperature on the back side of the plate was stabilized at 172.9 °C, which was 87.4 °C lower compared to pure EP. This proves that the LST material gives the coating stronger fire retardant properties upfront and strengthens the continuous insulation ability of the char layer. Cone calorimeter tests showed that the total heat release rate (THR) of LST/EP was reduced by 47.3% and the total smoke release rate (TSR) was reduced by 45.4%, proving the excellent fire and smoke suppression performance of LST/EP. In the expansion performance test, the expansion height and expansion rate of LST/EP reached 29.90 mm and 23.36 respectively, and the expansion of char layer was more uniform. This indicates that the addition of LST hybrid material can improve the mechanical strength of char layer and attenuate the heat transfer rate in the vertical direction. The residual char of LST/EP was 33.2% by thermogravimetric analysis, indicating that the addition of LST could reduce the volatilization of volatile components and improve the thermal stability of EP.

Understanding the Flame Retardant Mechanism of Intumescent Flame Retardant on Improving the Fire Safety of Rigid Polyurethane Foam.

Combinations of multiple inorganic fillers have emerged as viable synergistic agents for boosting the flame retardancy of intumescent flame retardant (IFR) polymer materials. However, few studies on the effect of multiple inorganic fillers on the flame retardant behavior of rigid polyurethane (RPU) foam have been carried out. In this paper, a flame retardant combination of aluminum hydroxide (ATH) and traditional flame retardants ammonium polyphosphate (APP), pentaerythritol (PER), melamine cyanurate (MC), calcium carbonate (CC), and expandable graphite (EG) was incorporated into RPU foam to investigate the synergistic effects of the combination of multiple IFR materials on the thermal stability and fire resistance of RPU foam. Scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) revealed that 8 parts per hundred polyols by weight (php) filler concentrations were compatible with RPU foam and yielded an increased amount of char residue compared to the rest of the RPU samples. The flame retardancy of multiple fillers on intumescent flame retardant RPU foam was also investigated using cone calorimeter (CCTs) and limiting oxygen index (LOI) tests, which showed that RPU/IFR1 (APP/PER/MC/EG/CC/ATH) had the best flame retardant performance, with a low peak heat release rate (PHRR) of 82.12 kW/m2, total heat release rate (THR) of 15.15 MJ/m2, and high LOI value of 36%. Furthermore, char residue analysis revealed that the use of multiple fillers contributed to the generation of more intact and homogeneous char after combustion, which led to reduced decomposition of the RPU foam and hindered heat transfer between the gas and condensed phases.