Cone Calorimetry Research Articles

Green vanillin coupled with P/N/Si flame retardant for poly (L-lactic acid)

To better solve the flammability of poly (l-lactic acid) (PLLA) and meet environmental concerns, developing bio-derived flame retardants for PLLA is an alternative method. A green flame retardant (VKD) was synthesized in the work. Vanillin was modified using 3-amino-propyl-triethoxysilane (KH550) prior to coupling with 9, 10-dihydro-9-oxa-10-phosphafi-10-oxide (DOPO). As the blend ratio of VKD to PLLA was 20 wt%, the limiting oxygen index (LOI) and UL-94 were 25.5% and V-0 rating, respectively; and the residual carbon rate reached 9.14% at 600 °C, which was 3.3 times higher than that of PLLA. In the cone calorimetry test, the peak heat release rate (pHRR) and total heat released (THR) reduced by 9.9% and 20.5%, respectively, and total smoke production (TSP) decreased by 26.8%, indicating that VKD/PLLA had good flame retardancy and smoke suppression properties. It was mainly attributed to initial condensation phase obstacle and following combination of gaseous phase quenching and carbon/silicon composite barrier. The VKD/PLLA maintained balanceable mechanical properties and good degradation. Then green VKD would broaden PLLA in the application of engineering such as electronic products and automotive interior materials.

Processing Method and Performance Evaluation of Flame-Retardant Corrugated Sandwich Panel.

In this study, in order to expand the engineering application range of thermoplastic corrugated sheets, flame-retardant thermoplastic corrugated sheets were prepared by the thermoplastic molding method. Based on our previous research results, we prepared flame-retardant prepreg tapes with the flame retardant addition accounting for 15%, 20%, and 25% of the resin matrix. Then, we prepared flame-retardant thermoplastic corrugated sandwich panels with corresponding flame retardant addition amounts. The limiting oxygen index test, vertical combustion test, cone calorimetry test, and mechanical property test were carried out on each group of samples and control group samples. The results showed that when the flame retardant was added at 25%, the flame retardant level could reach the V0 level. Compared with the control group, the flexural strength and flexural modulus decreased by 2.6%, 14.1%, and 19.9% and 7.3%, 16.1%, and 21.9%, respectively. When the amount of flame retardant was 15%, 20%, and 25%, respectively, the total heat release decreased by 16.3%, 23.5%, and 34.1%, and the maximum heat release rate decreased by 12.5%, 32.4%, and 37.4%, respectively.

A honeycomb-inspired carboxymethyl chitosan-covalently link NH2-black phosphorene biobased cellulose green nanocomposites with tremendously enhancement fire safety and thermal conductivity

Biobased carboxymethyl chitosan-modified black phosphorene (BP-CMC) was prepared through an amidation reaction between amino group functionalized black phosphorene (NH2-BP) and CMC. Density functional theory (DTF) express that the adsorption energy between urea and phosphene is −6.28 eV, indicating a strong interaction. The resulting BP-CMC was further applied to reinforce the mechanical, flame-retardant and thermal conductivity performance of honeycomb cellulose nanofiber (CNF) film via vacuum filtration. Cone calorimetry test (CCT) result exhibits that the introduction of 30 wt% BP-CMC significantly promoted the fire safety of CNF. For instance, a 98.41% reduction in smoke production rate (SPR), 92.00 % decline in CO release and a 61.31% decrease in heat release rate (HRR) were observed compared to neat CNF. Furthermore, Thermogravimetric infrared (TG-IR) indicates a significant decrease in the release of flammable gases. Raman spectra verify that the incorporation of 30 wt% BP-CMC improves the graphitization degree of residual chars, thus limiting the transfer of heat and oxygen. The improvement in fire safety is attributed to the formation of an intumescent flame-retardant system, which is rich in carbon source (CMC), acid source (BP) and gas source (amino). Simultaneously, the introduction of 30 wt% BP-CMC into CNF leads to considerable enhancement in thermal conductivity (up to 17.49 %), thermal diffusion (utmost to 43.45 %) and heat capacity (increased by 19.23 %). Moreover, the 30 wt % addition of BP-CMC into CNF possesses excellent mechanical properties with the improvement of toughness (increased by 143.50 %) and tensile strength (increased by 140.90 %). This strategy not only provides a new strategy for functionalizing BP but also upgrades the application potential of BP nanosheets in the fire safety of polymer composite films.

Experimental investigation of conductive heat transfer and fire protection in a polymer-based plate heat exchanger

Polymer-based heat exchangers offer several attractive features for thermal management applications such as low-cost, lightweight, antifouling, and anti-corrosion characteristics. However, their thermal performance is compromised primarily by the low thermal conductivity and high-flammability. This work consists of developing new polymer-based plate heat exchangers, which are made from epoxy resin reinforced by banana fibres and manufactured using the vacuum bag resin transfer moulding technique. The aim of this research is to improve both the heat transfer efficiency and thermal protection. The proposed approach involves incorporating silicon carbide powder as charge into samples to increase their thermal conductivity, and applying an intumescent fire-retardant coating to improve their capacity to withstand heat and flames. To determine the efficacy of this approach, a cone calorimetry test was performed to examine the thermal distribution within the plate heat exchanger samples and to assess fire reaction parameters during a fire scenario. The results revealed a notable increase in thermal conductivity, due to the addition of silicon carbide powder. Furthermore, the intumescent fire-retardant coating substantially improved the samples’ thermal resistance. This result has been verified by thermogravimetric analysis conducted during this work. These findings suggest that using banana fibres-reinforced epoxy resin, combined with silicon carbide powder and intumescent fire-retardant coating, has the potential to enhance the overall thermal performances of plate heat exchangers. The addition of silicon carbide powder increases the thermal conductivity by 36%. This demonstrates the feasibility of utilizing sustainable and biodegradable materials to manufacture heat exchangers that are more efficient and eco-friendly.

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.

Comparison of multi‐component and mono‐component intumescent flame retardants for thermoplastic polyurethane composites

AbstractConventional intumescent flame retardant (IFR) is comprised of multiple components (acid, carbon, and gas source). In comparison, “all‐in‐one” design of mono‐component IFR is effective to impart the homogeneity to functional sources in polymer matrix, which is significant to improve the synergy against combustion. In this work, a core‐shell structured mono‐component IFR (MAPP@FDS) are prepared with ammonium polyphosphate (APP) and furfural‐derived Schiff base (FDS) and applied to modification of thermoplastic polyurethane (TPU). TPU composite with the as‐prepared mono‐component IFR (TPU/MAPP@FDS) exhibits V‐0 rating in UL‐94 test and a limiting oxygen index (LOI) value of 32.0%, with prominent bulkiness of carbonaceous layer. Cone calorimetry tests (CCTs) showed a significant reduction in total heat release (THR) and peak heat release rate (pHRR) for TPU/MAPP@FDS compared with the TPU composites with multi‐component IFR. By analyzing the morphology and composition of residual char, the flame‐retardant mechanism of TPU/MAPP@FDS is reasonably proposed. This work illustrates the superiority of the integration to prepare mono‐component IFR and provides a potential method in developing TPU composites with remarkable flame retardancy.Highlights TPU/MAPP@FDS achieves a LOI value of 32.0% and UL‐94 V‐0 rating. TPU/MAPP@FDS exhibits significantly enhanced flame retardancy compared with TPU composites incorporated multi‐component IFR. The synergy in multi‐component IFR is prominently strengthened.

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.

Peacock flaunting tail inspired-multiple interactions between black phosphorene and glass powder with safety shield fire of epoxy resin

Black phosphorene (BP) has caused widespread attention for excellent dimension effects and thermal stability. Herein, glass powder (GP), a waste from ceramic production, is blended with black phosphorene (GBP) for reducing the fire hazard of epoxy resin (EP) matrix. Density functional theory (DFT) reveals that the adsorption energy between BP and SiO2 and Al2O3 are −3.55 and −4.27 eV, respectively, indicating a strong interaction between BP and GP. The results of cone calorimetry test (CCT) indicate that the flame retardant performance of EP can tremendously promote through adding 1.5 wt% GBP nanosheets, for instance, the peak heat release rate (pHRR) and the total heat release (THR) are decreased by 27.76 % and 31.42 %, respectively. Epoxy composites with only 1.5 wt% GBP nanosheets can reach UL-94 V-0 rating level with a limit oxygen index (LOI) of 29.7. These positive results are attributed to the collaborative function of physical obstacle, free radicals capturing and catalytic char formation between BP and GP components. In addition, the thermal conductivity decreased by 8.91 %, and the tensile strength increased by 39.99 % with the 1.5 wt% addition amount of GBP nanosheets. This work has a promising foreground for exploiting the resue of waste to satisfy the requirement of sustainable practical applications.

Thermal Stability and Flame Retardancy of Rigid Polyurethane Foam Composites Filled with Phase-Change Microcapsule.

The flammability of rigid polyurethane foam (RPUF) limits its application. A new type of chitosan phase-change microcapsule (CS/PCM) was successfully prepared by the condensation method with chitosan and gum acacia as the wall material and paraffin as the core material. CS/PCM was introduced into RPUF composite material as filler to improve the thermal and flame-retardant properties of polyurethane. The morphology, structure, thermal properties and flame retardancy of the materials were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), thermogravimetric (TG) analysis, differential scanning calorimetry (DSC) and cone calorimetry. It is found that when the CS/PCM content is 30 wt%, the latent heat of phase transition of RPUF-30 is 12.308 J/g, the limiting oxygen index (LOI) is 26.1% and the fire risk is reduced. The flame-retardant mechanism shows that the barrier effect provided by chitosan plays an important role in effectively blocking the transfer of heat and combustible gas, and improving the flame-retardant property of the composite. This paper provides a new idea for the application of CS/PCM in RPUF.

Multifunctional fire-resistant and flame-triggered shape memory epoxy nanocomposites containing carbon dots

Carbon quantum dots (CDs) are widely used as semiconductor systems, due to their facile synthesis and optical characteristics. CDs have been employed to enhance the light emission, UV resistance, and anticorrosive performances of epoxy nanocomposites (ENCs). Herein, we investigated the use of CDs to prepare multifunctional cycloaliphatic ENCs showing shape recovery capability. Following a waste-to-wealth approach, CDs were obtained from humic acid by a hydrothermal route. ENCs containing CDs exhibited photoluminescence, while the simultaneous addition of CDs and hexadecyltrimethoxysilane accounted for heat/flame-triggered shape recovery capability and hydrophobicity (contact angles as high as 137°). The polar character of silane-functionalized CDs allowed for their segregation at the surface of ENCs, making them very fire resistant. In particular, the CDs exerted an outstanding thermal shielding effect on the surface of ENCs, lowering the heat transfer at the boundary layer and increasing the time to flaming combustion up to ∼ 76 %. Besides, the graphitic nature of CDs and their charring behavior led to a huge increase in the back temperature at the ignition point (up to ∼ 30 %) during burn-through tests. Notwithstanding the low loadings (not exceeding 0.3 wt%) of CDs, ENCs lost their structural integrity only after almost 1 min of blowpipe flame application to their surface, whereas the resin counterpart degraded in less than 20 s. Besides, cone calorimetry tests carried out on ENCs highlighted a significant reduction of total smoke release (up to ∼ 40 %) compared to unfilled epoxy. Finally, we demonstrated the possibility of using multifunctional ENCs containing CDs as unique identification technology for polypropylene packaging, opening new perspectives on the effective protection of genuine products from counterfeiting.

Unraveling the surface heat flux heterogeneity in cone calorimetry of cylindrical charring material: Insights from experiments and 2D modeling

Although originally designed for planar samples, cone calorimeter is frequently used for the flammability assessment and pyrolysis modeling of non-planar objects, like electrical cables. Prescribing the boundary conditions for the numerical models of such objects requires knowledge about the radiative and convective heat fluxes along the sample circumference. In this work, we performed gasification and flaming experiments and 2D numerical simulations on birch cylinders. During the gasification of a single-rod, the char front propagated faster vertically than horizontally, while similar rates were observed in the flaming condition. With five rods, ∪- and ∩-shaped char fronts were observed in gasification and flaming conditions, respectively. From the simulations, we extracted detailed heat flux distributions, with main deviation from flat samples being the steep reduction in incident radiation between the top and sides of the cylinders. Moreover, in five-rod configurations, radiative flux to the sides of the central rod increases up to 10 (gasification) and 20 kW m−2 (flaming). On the outermost rod, the descending flame induces downward-moving waves of heat fluxes with amplitudes 20 kW m−2 for convection and 15 kW m−2 for radiation. Simplified expressions for the heat transfer boundary conditions were tabulated for practical engineering applications.

Balanced Thermal Insulation, Flame-Retardant and Mechanical Properties of PU Foam Constructed via Cost-Effective EG/APP/SA Ternary Synergistic Modification.

To address the challenge of balancing the mechanical, thermal insulation, and flame-retardant properties of building insulation materials, this study presented a facile approach to modify the rigid polyurethane foam composites (RPUFs) via commercial expandable graphite (EG), ammonium polyphosphate (APP), and silica aerogel (SA). The resulting EG/APP/SA/RPUFs exhibited low thermal conductivity close to neat RPUF. However, the compressive strength of the 6EG/2APP/SA/RPUF increased by 49% along with achieving a V-0 flame retardant rating. The residual weight at 700 °C increased from 19.2 wt.% to 30.9 wt.%. Results from cone calorimetry test (CCT) revealed a 9.2% reduction in total heat release (THR) and a 17.5% decrease in total smoke production (TSP). The synergistic flame-retardant mechanism of APP/EG made significant contribution to the excellent flame retardant properties of EG/APP/SA/RPUFs. The addition of SA played a vital role in reducing thermal conductivity and enhancing mechanical performance, effectively compensating for the shortcomings of APP/EG. The cost-effective EG/APP/SA system demonstrates a positive ternary synergistic effect in achieving a balance in RPUFs properties. This study provides a novel strategy aimed at developing affordable building wall insulation material with enhanced safety features.

Tannic acid's role as both char former and blowing agent in epoxy‐based intumescent fire retardants

AbstractA novel intumescent fire‐retardant coating formulation has been developed by taking advantage of the inherent stability of large cyclic polyphenols (e.g., tannic acid) to remove the need for a dedicated blowing agent, specifically melamine. Cone calorimetry data indicate a lower fire growth rate (FIGRA) (5.0 ± 1.3 vs. 2.4 ± 0.7 kW m−2 s−1) upon removal of melamine. Total smoke release (TSR) increases following this removal (178 ± 21.4 vs. 305 ± 13.2 m2 m−2), which indicates the role of tannic acid in gas generation. Thermogravimetric analysis resulted in similar residue yield from the examined systems (36 ± 1.3% vs. 34 ± 1.7%) despite removal of a dedicated blowing agent. These results indicate that tannic acids multistep degradation allows it to behave as both a char forming and blowing agent in intumescent systems. The observed reduction of acid loading between the melamine‐tannin system and the melamine‐free composition (15.6% vs. 10.6% wt. ammonium polyphosphate, respectively) is also significant. Tannic acid occurs in agricultural waste products, which is encouraging for the pursuit of sustainable chemistry and addressing potential adverse health effects in humans combined with reducing the overall phosphorous loading.Highlights Melamine was removed from the intumescent without compromising stability. The resulting intumescent char was stronger despite less expansion. Tannic acid is attributed as both the charring and blowing agent. The tannin‐based coating requires a lower acid loading for similar performance.

Sustainable production and evaluation of bio-based flame-retardant PU foam via liquefaction of industrial biomass residues

The utilization of low-cost renewable feedstock, such as furfural residue and crude glycerol, presents great potential for advancing the bio-based polymer industry. Firstly, this study explored the feasibility of using furfural residue liquefaction in the presence of crude glycerol to synthesize biopolyols. The optimal conditions for liquefaction were determined to be 220 ℃, 3 h, with a 7% sodium hydroxide loading and 9% biomass loading. The hydroxyl and acid numbers of prepared biopolyols were found to be comparable to those of commercial polyols, which were 460 mg KOH/g and 2.25 mg KOH/g, respectively. Subsequently, newly bio-based flame-retardant polyurethane (PU) foam was produced using obtained biopolyols, isocyanate, and flame retardants. The foam demonstrated a compressive strength of 286 kPa and a density of 0.050 g·cm−3, with its thermal conductivity measured at 0.032 W·m−1·K−1. To enhance the flame retardant and insulation properties of the PU foam, 2% of modified hollow silica (Kh-SiO2) was incorporated. PU foams produced under optimal conditions exhibited a limiting oxygen index of 27.25%, demonstrating exceptional fire-retardant characteristics. Cone calorimetry tests revealed that the PU composites had a 45.7% lower peak heat release rate and a 35.7% lower smoke release rate than neat PU foam. Additionally, the synchronous thermal analyzer (STA) revealed that the PU foam exhibited potential thermal insulation performance. This study provides a technically feasible and sustainable approach to valorize furfural residue and crude glycerol for producing biopolyols and flame-retardant insulation PU foam.

Preparation of Crust Type Dust Suppression Gel Based on Plant Extraction Technology for Ginkgo biloba Leaves: Characterization, Properties, and Function Mechanism

The coal industry plays an essential role in China’s economic development, and issues such as occupational health and environmental pollution caused by coal dust have attracted a great deal of attention. In accordance with the principles of environmental protection and waste management, this study used carboxymethyl ginkgo cellulose (CL) extracted and modified from Ginkgo biloba leaves as a matrix, and a graft copolymerized with sodium 3-allyloxy-1-hydroxy-1-propanesulfonate (AHPS) and N-isopropylacrylamide (NIPAM) monomers to prepare low-cost, environmentally friendly, and high-performance coal dust suppression (C-A-N). By optimizing fitting experimental data through three factors and two response surface analyses, the optimal dust suppression efficiency ratio was determined to be 4:8:5, and its swelling and water retention properties were analyzed. The microstructure, chemical reaction process, combustion performance and crusting property of the dust suppression gel were analyzed using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (SEM), cone calorimetry, and consolidation layer strength tests. Relevant experiments show that the dust suppression gel prepared in this study has the characteristics of a strong wettability and minor impacts on the calorific value of coal, as well as green and environmental protection. When the wind speed is 10 m/s, the dust suppression effect reaches 93%, and the hardness of the solidified layer reaches 39.6 KPa. This study analyzed the migration and combination of functional groups in the interaction system using molecular dynamics simulation software. The microscopic effect and mechanism between dust suppression gel and coal are revealed from a molecular point of view. The feasibility and accuracy of the molecular dynamics simulation were verified by the consistency between simulation results and experimental data. Therefore, combining the utilization of waste resources with dust suppression can have important economic and social benefits.

A cationic, durable, P/N-containing starch-based flame retardant for cotton fabrics

A cationic, durable flame retardant for cotton fabrics, 6-(2-(dimethoxy phosphoryl)-2-(trimethyl ammonium)) methoxy-2-methoxy-polysaccharide ammonium phosphate (DTPAP), was synthesized. Its structure was verified by NMR and FTIR spectroscopy. According to the FTIR spectra and X-ray photoelectron spectroscopy (XPS), DTPAP formed P(=O)-O-C bonds with cellulose molecules and firmly grafted to cotton fabrics, giving the fabric a high durability. DTPAP-25-treated fabrics passed the vertical flame test (VFT), and the limiting oxygen index (LOI) was 43.9 %. After 50 laundering cycles (LCs), the DTPAP-25-treated fabrics had an LOI of 29.9 %, passed the VFT, and retained their flame retardancy. EDS data showed that, compared with engrafted cationic ammonium phosphate flame retardants, the DTPAP-treated fabrics contained fewer metal ions. Cone calorimetry data showed that DTPAP-25-treated fabrics did not display concentrated heat release. The results suggested that DTPAP exhibited a condensed-phase flame retardant mechanism, and the introduction of cations into the ammonium phosphate flame retardant reduced ion exchange, which improved the durability.

Preparation and thermostability of a Si/P/N synergistic flame retardant containing triazine ring structure for cotton fabrics

A new synergistic flame retardant named Bisiminopropyl trimethoxysilane-1,3,5-triazine-O-bicyclic pentaerythritol phosphate (BTPODE) was synthesized, which is a type of Si/P/N flame retardant. This was accomplished by grafting aminopropyl trimethoxysilane and bicyclic pentaerythritol phosphate onto a triazine ring structure, serving as an intermediate. The structure of BTPODE was determined using nuclear magnetic resonance (1H NMR, 13C NMR, and 31P NMR) and Fourier transform infrared spectroscopy (FT-IR). SEM was used to detect the surface morphology of cotton fabrics, which suggested that BTPODE had been resoundingly stick to cotton fabrics. The flame retardant properties of cotton fabrics were evaluated by measuring the limiting oxygen index (LOI) and conducting vertical flammability experiments. Cotton fabrics with a weight gain of 20.73 % achieved an LOI value of 32.5 %. Thermogravimetric (TG) experiments demonstrated the samples' good thermostability. Furthermore, under nitrogen conditions, the char residue of cotton fabric with a weight gain of 20.73 % was 36.85 %. The cone calorimetry test (CONE) showed a significant reduction in the TSP value, indicating a certain level of smoke suppression performance. Finally, based on the obtained experimental results, the fire-retardant mechanism principle of the flame retardant was deduced.

Synthesis of a novel dimethylglyoxime-bridged phosphinate and its application in flame-retardant epoxy resins

Considering the need for flame retardancy in epoxy resin (EP), a novel dimethylglyoxime-bridged phosphinate (DMG-DC) has been suggested and applied for the purpose of flame-retardant modification of epoxy resin. As a result of the substitution reaction between dimethylglyoxime (DMG) and diphenylphosphoryl chloride (DPPC), DMG-DC was successfully characterized chemically. The research has demonstrated a notable enhancement in the flame-retardant characteristics of EP/DMG-DC. Especially, with the addition of 15 wt.% DMG-DC, the EP composite passed the UL-94 test with a V-0 rating and achieved a limiting oxygen index (LOI) value of 28.4 %. In addition, cone calorimetry test (CCT) results showed that the peak heat release rate (PHRR), total heat release rate (THR), and carbon dioxide production (CO2P) of EP/DMG-DC-15 were reduced by 54.1 %, 35.2 %, and 64.4 %, respectively, compared to EP. Not merely, the activities of DMG-DC in the gas and condensed phases also enhanced the flame retardancy of EP. That was the decomposition of DMG-DC not only released phosphorus-containing radicals to trap reactive radicals and nitrogen-containing inert gases to dilute flammable materials but also promoted the epoxy matrix to form more char residues. Generally, this work develops a novel dimethylglyoxime-bridged phosphinate with the potential in the application of flame-retardant polymers.

Synthesis of MXene-Based functional coatings on rigid polyurethane foam surfaces: A comparative study of layer-by-layer self-assembly and hydrothermal methods

A flame retardant for rigid polyurethane (RPUF) was designed and synthesized to expand the application field of RPUF. The flame retardants, namely MXene/PEI/PA-L and MXene/PEI/PA-H, were synthesized using phytic acid (PA), polyethyleneimine (PEI), and MXene through layer-by-layer (LBL) self-assembly method and hydrothermal method, respectively. In terms of mechanical performance, MXene/PEI/PA-L imparted brittleness to RPUF while MXene/PEI/PA-H enhanced its toughness, enabling RPUF to adapt to diverse application scenarios. The flame retardant properties were evaluated via vertical combustion test, cone calorimetry test, and thermogravimetric test, and the gas phase flame retardant mechanism was analyzed by TG-FTIR. MXene/PEI/PA constituted a N-P-Ti synergistic flame retardant system. During combustion, MXene/PEI/PA formed a layered dense carbon layer to cut off the external oxygen transport channel and absorbed many oxygen-containing free radicals. MXene/PEI/PA-L demonstrated efficient smoke suppression capability, while MXene/PEI/PA-H showed superior thermal insulation performance. The ignition time (TTI) of the composite foam reached 47 s, the total smoke release (TSR) value decreased by 92 %, and the flame retardant grade reached 5VA. Coated RPUF had excellent flame retardant ability.

Heat release rate of oriented strand board through cone calorimetry test: a numerical analysis

Heat release rate of oriented strand board through cone calorimetry test: a numerical analysis