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

Kapok fiber (KF) with a naturally hollow structure has found an increasing application in filling and composite materials, most of which have a demand of flame retardancy. To realize this high-value utilization, KF was phosphorylated by a reactive phosphorus- and nitrogen-containing flame retardant for enhanced fire safety. The flame retardant was first synthesized by the reaction of urea and diethylene triamine pentakis (methyl phosphonic acid) (a commercially available scale inhibitor) with low cost, and then, applied in the phosphorylation of KF in the presence of dicyandiamide. In thermogravimetric analysis, phosphorylated KF showed 38.1% residue weight in nitrogen and 10.2% residue weight in air at 700°C, whereas the residue weight of KF was 8.4% in nitrogen and 1.5% in air. In microcalorimetric analysis, the heat release capacity and total heat release of phosphorylated KF displayed a reduction of 81% and 55%, respectively. In vertical combustion test, phosphorylated KF was difficult to ignite and had no afterburning or smoldering. The tests indicated that phosphorylated KF had excellent charring properties, low heat release, and good flame retardancy. This work suggests a promising strategy of enhancing the flame retardancy of KF and increasing its applicability in filling and composite materials. [ABSTRACT FROM AUTHOR]

The soft nap and deep pile that impart comfort and warmth to cotton fleece also amplify its flammability. Using ambient aqueous processing, an environmentally benign polyelectrolyte complex (PEC), consisting of poly(allylamine hydrochloride) and sodium hexametaphosphate, was deposited on cotton fleece. This treatment adds only 12.5% weight, reduces peak heat release by 68% and total heat release by 74%, and protects from fire via intumescence. Without treatment, fleece burns aggressively with long afterburn and afterglow times, leaving no residue. With the applied PEC, the fabric self-extinguishes within a few seconds and exhibits no afterglow. In addition, it withstands at least five simulated laundering cycles in alkaline detergent, maintaining a 57% reduction in fire growth capacity afterward. The original soft surface can be restored to the fleece by manual brushing. This simple and environmentally benign treatment provides an opportunity to effectively protect highly flammable textured cellulosic textiles in a safe way. [ABSTRACT FROM AUTHOR]

The present work proposes to investigate the effect of an ultrahigh molecular weight silicone rubber (UHMW-SR) and two ethylene methyl acrylate copolymers (EMA) with different methyl acrylate (MA) content on the mechanical and fire performance of a fireproof acrylonitrile butadiene styrene copolymer (ABS) composite, with an optimum amount of ammonium polyphosphate (APP) and aluminum diethyl phosphinate (AlPi). ABS formulations with a global flame retardant weight content of 20 wt.% (ABS P) were melt-compounded, with and without EMA and UHMW-SR, in a Brabender mixer. During this batch process, ABS P formulations with UHMW-SR and/or EMA registered lower torque values than those of ABS P. By means of scanning electron microscopy (SEM), it was possible to observe that all ABS composites exhibited a homogenous structure without phase separation or particle agglomeration. Slightly improved interfacial interaction between the well-dispersed flame-retardant particles in the presence of EMA and/or UHMW-SR was also noticed. Furthermore, synergies in mechanical properties by adding both EMA and UHMW-SR into ABS P were ascertained. An enhancement of molecular mobility that contributed to the softening of ABS P was observed under dynamic mechanical thermal analysis (DMTA). An improvement of its flexibility, ductility and toughness were also registered under three-point-bending trials, and even more remarkable synergies were noticed in Charpy notched impact strength. Particularly, a 212% increase was achieved when 5 wt.% of EMA with 29 wt.% of MA and 2 wt.% of UHMW-SR in ABS P (ABS E29 S P) were added. Thermogravimetric analysis (TGA) showed that the presence of EMA copolymers in ABS P formulations did not interfere with its thermal decomposition, whereas UHMW-SR presence decreased its thermal stability at the beginning of the decomposition. Although the addition of EMA or UHMW-SR, as well as the combination of both in ABS P increased the pHRR in cone calorimetry, UL 94 V-0 classification was maintained for all flame-retarded ABS composites. In addition, through SEM analysis of cone calorimetry sample residue, a more cohesive surface char layer, with Si-O-C network formation confirmed by Fourier transform infrared (FTIR), was shown in ABS P formulations with UHMW-SR. [ABSTRACT FROM AUTHOR]

In this manuscript, the UiO-66-NH2(Zr) (MOFs) was adopted to modify ammonium polyphosphate (APP), and the novel synergistic integrated flame retardant system (APP@MOFs) was formed. The flame retardants were incorporated to the thermoplastic polyurethanes (TPU) matrix, and the effects of APP@MOFs on reducing flammability of thermoplastic polyurethanes were compared and investigated. The results show that the flame retardant and smoke suppression performances of TPU/APP@MOFs composites are improved significantly. The pHRR, THR, SPR, TSP, YCO, and YCO2 of TPU/APP@MOFs composites decreased by 75.76%, 86.19%, 69.74%, 86.34%, 57.14%, and 76.37% in comparison with pure TPU. Furthermore, the char residues increased from 0.11 (pure TPU) to 32.3% (TPU/APP@MOFs composites). Generally, the APP@MOFs have great effect on improving the flame retardant and smoke suppression performances of TPU due to the catalytic carbonization and dilution effects of APP, the synergistic and catalysis effects of MOFs. Through the char structure analysis, the mechanism of the TPU/APP@MOFs composites during the combustion processes was also investigated and proposed. [ABSTRACT FROM AUTHOR]

• The flammability limits of R13I1 + R152a/R600a/R1270 binary mixtures were measured. • The critical flammable volumetric ratios of R13I1 + R152a/R600a/R1270 were obtained. • A generalized equation for the LFL of R13I1 mixtures was provided. • F -number and HOC were calculated and the inhibitory effects of R13I1 were analyzed. Trifluoroiodomethane (R13I1) is a flame retardant with an extremely low global warming potential (GWP) and can be used as a component to improve the flammable characteristics of most promising low-GWP refrigerants. In this paper, the flammability limits of R13I1 + 1,1-Difluoroethane (R152a), R13I1 + isobutane (R600a) and R13I1 + propylene (R1270) binary mixtures were measured at 60 °C and atmospheric pressure with a 12 L flask according to ASHRAE standards. The critical suppression ratios of R13I1 + R152a, R13I1 + R600a and R13I1 + R1270 are 0.45, 2.24 and 0.99, respectively. A generalized equation for the lower flammability limit (LFL) of R13I1 mixtures was provided. With the LFL of the fuel gas in air and the ratio of R13I1 to the fuel gas, the developed generalized equation can calculated the LFL of R13I1 mixtures with a reasonable accuracy. The influence of R13I1 on the flammability of R152a, R600a and R1270 were studied. The LFL increases and heat of combustion (HOC) decreases significantly with the increase of the R13I1 concentration. The flammability inhibition effects of R13I1 decrease in the order: R152a > R1270 > R600a. [ABSTRACT FROM AUTHOR]

Cotton fabrics have high hydrophilicity and low limiting oxygen index (LOI) value, so they are susceptible to fires and bacterial growth, which endanger people's lives and property and limit their further application. To solve the issue, the prepared green flame retardant β-cyclodextrin phosphate ammonium salt (β-CPAS) was first used to prepare flame retardant cotton fabric, which was then treated with hydrophobic agent phosphorylated hexadecanol (HP) to obtain flame retardant and hydrophobic cotton fabrics (FR-H-cotton) by the traditional dip-dry-cure technique. Fourier transforms infrared spectroscopy showed that β-CPAS and HP were covalently bonded to the cotton sample by a P–O–C bond. The treated cotton was self-extinguished under a vertical flame and had an LOI value of up to 31%. Cone calorimeter analysis showed that both the total heat release rate and peak heat release rate of treated cotton were decreased by about 80% than the control sample. Furthermore, the treated samples have excellent hydrophobicity and self-cleaning capabilities because of the presence of long-chain hexadecanol. Interestingly, FR-H-cotton remained excellent flame retardant and hydrophobic properties after 50 laundering cycles. This green and multifunctional cotton fabric has excellent potential for future market applications. [ABSTRACT FROM AUTHOR]

Lithium metal batteries (LMBs) show great promise for achieving energy densities over 400 Wh·kg−1. However, highly flammable organic electrolytes are a long-lasting problem that triggers safety hazards and hinders the commercial application of LMBs. Here, a nonflammable diluted highly concentrated electrolyte (DHCE) with ethoxy(pentafluoro)cyclotriphosphazene (PFPN) as a diluent is developed to simultaneously achieve high safety and cycling stability of high-voltage LMBs. The optimal DHCE not only ensures reversible Li deposition/dissolution behavior with a superior average Coulombic efficiency (CE) over 99.1% on lithium metal anode (LMA), but also suppresses side reactions and stress crack on the LiCoO2 (LCO) under high cut-off voltage. The newly developed DHCE exhibits high thermal stability, showing complete nonflammability and reduced heat generation between the electrolyte and delithiated LCO/cycled LMA. This work offers an opportunity for rational designing nonflammable electrolytes toward high-voltage and safe LMBs. [ABSTRACT FROM AUTHOR]

The widespread utilization of bamboo in the field of building and construction has sparked growing interests in conducting research on fire performance of bamboo. This study investigated fire performance of bamboo treated with flame retardants that possess water-soluble and environmental friendly characteristics. The synergistic effect of APP and P-N-B complexed flame retardant on flame resistance were evaluated, while absorption capacity and moisture absorption rate were also evaluated in relation to impregnation duration and solution concentration. The results indicated that absorption capacity increased with impregnation duration and solution concentration. It was observed solution concentration had a significant impact on moisture absorption for both APP and P-N-B complexed series. The ideal impregnation duration and solution concentration were found to be 6 h and 30%, respectively. Both APP and P-N-B complexed series significantly improved the fire performance of bamboo, but the latter exhibited a superior effect due to its synergistic combination of P, N and B. The FPIs of APP and P-N-B complexed series increased by factors of 2.4 and 4.1 compared to the untreated one. Both facilitated the formation of stable char layers and exerted their influence in gaseous phase through release of non-combustible gas for fuel dilution and free radicals mitigation. [ABSTRACT FROM AUTHOR]

To improve the flame retardancy of cotton fabrics, a non-halogen and non-formaldehyde polymeric flame retardant (ACAPOC) was synthesized by a solvent-free method. ACAPOC was grafted onto cellulose, and the resulting –N–P(=O)–O–C bonds displayed p-π conjugation, hydrolysis resistance, and greater stability than P–O–C covalent bonds. A mechanistic study showed that ACAPOC affected the thermal degradation pathway of cotton fabrics, which promoted fibers to dehydrate into carbon by generating phosphoric acid or polymetaphosphoric acid through thermal decomposition, interfering with the combustion process. In addition, the non-combustible gases produced by decomposition also diluted the combustible gases, which comprehensively affected the combustion heat cycle. ACAPOC had unobvious effect on crystal structure and surface morphology of cotton fabrics, but greatly reduced the combustion efficiency. ACAPOC-25% underwent 50 LCs in conformity to AATCC 61-2013 3A standard, which can be considered as durable flame-retardant cotton fabrics. Moreover, damage to physical properties barely affected practical application. Taken as a whole, ACAPOC is a low-cost, easy-to-synthesize and efficient flame retardant for cotton fabrics, which may also be applied to other materials such as synthetic fibers. [ABSTRACT FROM AUTHOR]

In this study, thiol-functionalized ladder-like polysesquioxanes end-capped with methyl and phenyl groups were synthesized via a simple sol-gel method and characterized through gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and thermogravimetric analysis (TGA). Additionally, epoxy blends of different formulations were prepared. Their structural, flame-retardant, thermal, and mechanical properties, as well as volatile organic compound (VOC) emissions, were determined using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), TGA, scanning electron microscopy (SEM), limiting oxygen index (LOI), cone calorimetry, and a VOC analyzer. Compared to epoxy blends with flame retardants containing elemental phosphorus alone, those with flame retardants containing elemental phosphorus combined with silicon and sulfur exhibited superior thermal, flame-retardant, and mechanical properties with low VOC emissions. SEM of the residual char revealed a dense and continuous morphology without holes or cracks. In particular, LOI values for the combustion of methyl and phenyl end-capped polysilsesquioxane mixtures were 32.3 and 33.7, respectively, compared to 28.4% of the LOI value for the blends containing only phosphorus compounds. The silicon–sulfur–phosphorus-containing blends displayed reduced flammability concerning the blends using a flame retardant containing only phosphorus. This reflects the cooperative effects of various flame-retardant moieties. [ABSTRACT FROM AUTHOR]

Ozone, widely recognized as an environmentally friendly gas, is extensively used in various textile industry applications. These include pre-treatment processes like bleaching and desizing, as well as creating pattern and vintage effects, wastewater clarification, and surface modification. This study focuses on ozone as a novel solution to a specific challenge: addressing the reduction in flame retardancy properties experienced by flame-retardant (FR) polyester fabrics during post-treatment processes in the production line. Experimentation involved subjecting the fabrics to ozonation and exploring different combinations of ozone flow rates and treatment durations. Mechanical and functional properties of the fabrics were examined, with flammability tested according to International Maritime Organization (IMO) standards. Notably, treatment with a 5 L/min ozone flow rate, a 7.01 g/h ozone concentration ratio, and a duration of 10 min showed significant improvements in IMO values, ensuring compliance with required standards. Furthermore, treated samples underwent comprehensive tests for fastness and strength, yielding results within acceptable ranges. Fourier-transform infrared (FT-IR) and thermogravimetric analysis (TGA) measurements were conducted to evaluate the impact of ozonation. FT-IR results indicated that the presence of C-H groups associated with dyestuff contributed to decreased flame retardancy in the original fabric post-dyeing. However, these groups were effectively eliminated through ozonation, thereby enhancing the fabric's flame retardancy. [ABSTRACT FROM AUTHOR]

The inherent flammability of polymeric materials poses a potential threat to life and the environment. From a perspective of material renewability and environmental concern, some phosphorus-rich biomass compounds have been considered as effective replacements for conventional intumescent-based flame retardants. In this work, with the aim of suppressing the potential fire hazard of highly flammable polypropylene in a sustainable strategy, a green and facile method was proposed to synthesize ZIF-67 and further used to synergistically improve the performance of phytic acid-based intumescent flame retardants. Diverging from conventional solvothermal synthesis strategies, ZIF-67 was directly prepared with polymer matrix via a solvent-free reactive extrusion method with a notable space time yield. The reaction-to-fire properties were comprehensively investigated under forced combustion bench-scale fire conditions using a cone calorimeter with an external heat flux of 50 kW m−2. It was found that flame retardancy behaviors remain competitive when replacing 10 mass% of expandable graphite with phytic acid component. With the addition of ZIF-67, the heat release (53% reduction), smoke production (22% reduction), char structure stability (35% increment), and specific extinction area (19% reduction) behaviors were further improved due to the development of compact phospho-carbonaceous networks during combustion. Considering these excellent synergistic improvements, it provides a new potential direction to efficiently fabricate biomass-based flame retardants. [ABSTRACT FROM AUTHOR]

Cellulose fabric testing for flame-retardant studies is frequently necessary in various textile applications. Natural cellulose material from ramie (Boehmeria nivea) is being promoted as an alternative raw material for the development of fire-resistant fabrics. This research aims to optimize the coating process of ramie fabric using a phosphorus-based flame retardant (FR) to enhance its flame-retardant characteristics. The FR treatment involves bleaching the fabric with H2O2; followed by fabric finishing using a formula comprising 3% (v/v) hydroxymethyl resin; phosphoric acid (2%); and two formulations of the flammable agent Flamatic DM-3072N: 40% (v/v) and 50% (v/v), applied using the pad-dry-cure method. The flame-retardant properties of the treated fabric are evaluated through flammability testing based on the ASTM D6413-08 standard, limiting oxygen index (LOI) analysis, and micrograph surface structure analysis with SEM. The results indicate that ramie fabric treated with the FR-50% material exhibits superior fire resistance, preventing fire spread on the fabric with a char length of 15–30 mm and a LOI value of 29. These findings highlight the potential of FR-treated ramie fabrics for various industries, including the automotive and protective clothing industries. [ABSTRACT FROM AUTHOR]

Inadequate fire resistance of polymers raises questions about their advanced applications. Flexible polyurethane (PU) foams have myriad applications but inherently suffer from very high flammability. Because of the dependency of the ultimate properties (mechanical and damping performance) of PU foams on their cellular structure, reinforcement of PU with additives brings about further concerns. Though they are highly flammable and known for their environmental consequences, rubber wastes are desired from a circularity standpoint, which can also improve the mechanical properties of PU foams. In this work, melamine cyanurate (MC), melamine polyphosphate (MPP), and ammonium polyphosphate (APP) are used as well-known flame retardants (FRs) to develop highly fire-retardant ground tire rubber (GTR) particles for flexible PU foams. Analysis of the burning behavior of the resulting PU/GTR composites revealed that the armed GTR particles endowed PU with reduced flammability expressed by over 30% increase in limiting oxygen index, 50% drop in peak heat release rate, as well as reduced smoke generation. The Flame Retardancy Index (FRI) was used to classify and label PU/GTR composites such that the amount of GTR was found to be more important than that of FR type. The wide range of FRI (0.94–7.56), taking Poor to Good performance labels, was indicative of the sensitivity of flame retardancy to the hybridization of FR with GTR components, a feature of practicality. The results are promising for fire protection requirements in buildings; however, the flammability reduction was achieved at the expense of mechanical and thermal insulation performance. [ABSTRACT FROM AUTHOR]

• Flammability limits of azeotropic mixtures consist of R1243zf are tested for the first time. • A brief mechanism for flame-retardant effect of R13I1, R227ea and R134a is analyzed. • CSCs of R1243zf mixtures are tested and compared with calculation results by 3 methods. 3,3,3-trifluoropropene (R1243zf) is a low climate change effect refrigerant that has great development potential. However, R1243zf is flammable and its safety classification is A2 as per ISO standard 817. To reduce its risk of flammability, the method of using mixed refrigerants in practical applications is an effective approach. In this paper, an experimental system was established according to the ASHRAE standard 34 to measure the flammability limits of four azeotropic mixtures containing R1243zf. First, the critical suppression ratio (CSR) of R13I1/R1243zf was tested out that is 0.353. Further measurements were made to determine the lower flammability limits (LFLs) and critical suppression concentrations (CSCs) of three ternary mixtures consisted of R1243zf, thermodynamic performance enhancer (RE170) and flame retardants (R13I1, R134a or R227ea), at various compositions. The experimental non-flammable proportions of R1243zf/RE170/R13I1, R1243zf/RE170/R134a, and R1243zf/RE170/R227ea were 31.81 %, 5.49 %, and 22.42 %, respectively. Besides, a comparison was made between the experimental data and the predicted results by means of three different theoretical methods (the equal effect method, thermal balance method, and group contribution method). The fresh experimental results will provide practical guidance for the applications that utilize the R1243zf blends in low flammability risk. [ABSTRACT FROM AUTHOR]

In order to improve the inherent flammability of polylactic acid (PLA) and make this new biodegradable material more widely used, B-modified ZSM-5 (B/Z5) was designed as synergistic agent of intumescent flame retardant (IFR), composed of ammonium polyphosphate (APP) and pentaerythritol (PER), and introduced into PLA/IFR (PLAs) to fabricate PLAs/B/Z5 composites by melt extrusion. The flame retardancy, surface morphology, and thermal stability of the composites were investigated by TG, LOI, UL-94, CCT, and SEM. The addition of B/Z5 makes the decomposition temperature of T5% as well as T10% of PLAs reduction in nitrogen atmosphere and carbon layer form in advance. UL-94 test shows the composites reach V-0 rating. LOI value also steadily increases, and the maximum value is 36.0% with B actual loading of 5.26% (recoded as 14B/Z5) in B/Z5. The PHRR decreases by 75% from 417.77 kW/m² for pure PLA to 103.19 kW/m2 for PLAs/14B/Z5, and THR reduces from 92.78 to 19.26 MJ/m2, which decreases by about 80% and the char yield reaches 50%. This study provides a simple and green method for the preparation of high flame-retardant PLA, which has a broad practical application prospect. [ABSTRACT FROM AUTHOR]

To address the flammability drawbacks of nylon 56 and expand the application range of bio‐based nylon 56, melamine cyanurate (MCA) was employed through self‐assembly in a solvent with graphitic carbon nitride surface treatment. Modified MCA (CNMCA)composition and morphology were investigated. CNMCA created with surface treatment and polyamide 56 (PA56) prepared with unmodified MCA had their flame retardant functions and mechanical properties investigated and compared. x‐ray diffraction (XRD) and Fourier transform infrared (FT‐IR) spectroscopy confirmed the successful microencapsulation of g‐C3N4 on the MCA surface. Further characterization of the unmodified MCA and CNMCA was performed using scanning electron microscopy (SEM). The SEM images revealed a significant reduction in the degree of agglomeration in CNMCA compared to conventional MCA, resulting in a more uniform dispersion in the PA56 matrix. Additionally, PA56/CNMCA achieved a UL94 V‐0 rating and a limiting oxygen index (LOI) value of 30.1%. Notably, compared to pure PA56, PA56/CNMCA30 exhibited the most promising synergistic effect, leading to a separate reduction of 45.45% in the total heat release rate (THR) and 13.62% in the total smoke release (TSR). Consequently, with the same flame retardant addition (10 wt%), the CNMCA flame retardant showed superior dispersion in the bio‐based nylon 56 matrix compared to traditional MCA. Due to the physical isolation of g‐C3N4, the synergistic effect of MCA and graphitic carbon nitride imparted better mechanical properties and flame resistance to nylon 56. Highlights: MCA/g‐C3N4 hybrids were prepared and applied in bio‐based nylon 56 for the first time.The MCA/g‐C3N4 hybrid has better dispersion than MCA.PA56/MCA/g‐C3N4 flame retardant composites have better flame retardant and smoke suppression properties than PA56/MCA. [ABSTRACT FROM AUTHOR]

Novel double DOPO‐grafted phthalonitrile flame retardant (DOPO‐DBAPh) has been successfully synthesized via solution reaction with amino‐substituted phthalonitrile monomer, bisphenol A, paraformaldehyde and 9, 10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) as initial materials. The molecular structure of DOPO‐DBAPh was investigated by FT‐IR and 1H‐NMR spectrum. Then, the DOPO‐DBAPh was added into epoxy (EP) to construct DOPO‐DBAPh/EP fire‐retarding composites by casting forming method. The effect of different proportions of DOPO‐DBAPh/EP fire‐retarding composites on the microstructure, thermal, mechanical, flame retardancy and combustion behavior was investigated. It was found that the DOPO‐DBAPh/EP fire‐retarding composites have a high glass transition temperature (Tg = 156∼179°C), and also have excellent thermal stability (T5% = 331.4∼365.4°C) and high flexural strength (96.1∼139.8 MPa). When DOPO‐DBAPh content is 5 wt%, the vertical burning grade and limiting oxygen index (LOI) of DOPO‐DBAPh/EP composites reached V‐0 and 29.6%, respectively. Furthermore, the cone calorimeter testing results showed that the addition of DOPO‐BAPh can obviously inhibit the decomposition rate of cured substance at high temperature and accelerated the formation of dense carbon layer. When DOPO‐BAPh content was 20 wt%, the total heat release rate (THR) and peak heat release rate (PHRR) of the DOPO‐DBAPh/EP fire‐retarding composites were decreased by 38.55% and 35.81% compared with that of cured EP. In a word, this work presents a good way for synthesizing economical and highly efficient flame retardant for use in the preparation of EP‐based fire‐retarding composites with excellent comprehensive performance. Highlights: Novel phosphorus‐nitrogen flame retardant (DOPO‐DBAPh) is developed.5 wt% DOPO‐DBAPh significantly improves the fire safety of EP resin.The DOPO‐DBAPh/EP composites exhibit good thermal and mechanical properties. [ABSTRACT FROM AUTHOR]

For many years, efforts have been made to reduce the flammability of unsaturated polyester resins (UPRs), which are often used in the rail, shipbuilding, and construction industries. Without modification, they often fail to meet fire safety standards. Despite a rich history of flame retardants (FRs) applied to UPRs, researchers seek new solutions that will provide lower flammability and smoke density, as well as attaining a lower environmental impact from the composites. The objective of the study is to highlight the most important recent research on promising nano FRs in order to promote their further development. Mechanisms of action of several groups of nano FRs, such as clay-based, carbon-based, transition metal compounds, layered double hydroxides, polyhedral oligomeric silsesquioxanes, and others, including bio-based, have been studied. Particular emphasis has been laid on nano FRs applied to UPRs, and their influences on thermal stability, flammability, and mechanical properties. Moreover, the environmental impact and toxicity of nano FRs have been discussed. Results have proved that nano FRs applied at low loadings may significantly improve thermal stability, with a simultaneous increase or only a slight decrease in mechanical properties. However, attention on related environmental issues has highlighted the necessity of carefully selecting novel nano FRs. [ABSTRACT FROM AUTHOR]

Limited by flammability, wood and wood-based materials face challenges in distinguishing themselves as structural materials or finishing materials. Once burning, they can produce toxic gases detrimental to humans and the environment. Therefore, it is critical to make clear whether fire-retardant wood construction materials are insusceptible to fire and not the sources of toxic gases. This study aimed to evaluate flame-retardant plywood from the aspects of flammability and the toxic gas and smoke generation during combustion. The flame-retardant plywood was manufactured by impregnating a flame-retardant resin in line with International Maritime Organization (IMO) standards. The research results indicate that seven out of the eight kinds of toxic gases listed by the IMO, other than CO, were not detected during the combustion of the flame-retardant plywood. While CO was detected, its quantities under three test conditions are below the corresponding thresholds. Therefore, unlike synthetic resin products, flame-retardant plywood is a promising finishing material that can reduce the damage from toxic gases in the event of a fire. In the smoke generation tests, the mass reduction rate of flame-retardant plywood increased from 13% to 18% and then to 20% as the test condition became more severe. Under the same circumstances, the average maximum specific optical density also followed an upward trend, whose values (75.70, 81.00, and 191.20), however, still met the IMO standard of below 200. This reflects that the flame-retardant plywood is competent as a finishing material. Further, flammability was evaluated, and the critical flux at extinguishment (CFE), total heat release (Qt), and peak heat release rate (Qp) were determined to be 49.5 kW/m2, 0.21 MJ, and 0.66 kW, respectively, which all did not reach the corresponding thresholds given by the IMO. To sum up, flame-retardant plywood has satisfactory flame-retardant performance and meets fire safety standards, showing the potential to be an attractive finishing material for building and construction. [ABSTRACT FROM AUTHOR]

A series of pentaerythritol derived flame retardant additives (FRs labeled FR1, FR2, FR3, and FR4) were synthesized and blended with thermoplastic polyurethane (TPU) to enhance its flame retardancy. The chemical structures of the FRs were established by FTIR, 1H, 13C and 31P NMR spectroscopy. The flammability of the TPU blends was analyzed through UL-94 vertical burning and limiting oxygen index (LOI) test. It is found that for FR4-TPU blends with 2% of phosphorus content, the LOI value reached up to 31.2%, and no melt dripping with a V-0 rating was obtained by UL-94, indicating its superior flame retardant properties. Thermogravimetric analysis (TGA) of TPU blends showed that the char yield increases from 3.9% in neat TPU to 20% with the addition of 2% of FR3 in TPU. Based on findings from scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), a possible mechanism for the flame retardant property of blends has been proposed. The improved flame retardant properties of TPU blends can be attributed to the formation of a continuous and highly entangled char. This work provides a suitable approach for synthesizing promising phosphorus-based flame retardants from readily available raw materials that can be used to enhance the flame retardancy of TPU. [ABSTRACT FROM AUTHOR]

The paper describes the preparation of polyamide 6 with reduced flammability by anionic in situ polymerization of ε-caprolactam in the presence of flame retardants, a method not described in the literature. Selected inorganic and brominated organic flame retardants were characterized by thermogravimetric analysis. Polymerization tests were used to test the compatibility of flame retardants with the components of the initiation system of anionic polymerization. Based on their results, polyamide plates for the preparation of test specimens were prepared by the method of polymerization casting in a mold. The content of water-extractable portions did not exceed 3%, i.e., the conversion of monomer into polymer took place to a high degree. The presence of flame retardants both inorganic and brominated organic in the polymer matrix did not affect the thermal stability, the content of the crystalline phase and also the mechanical properties. Samples containing brominated organic flame retarders were classified as V-0 according to the UL94 methodology. [ABSTRACT FROM AUTHOR]

In recent years, the poor weather resistance and aging resistance of additive flame retardants have caused researchers to pay attention to reactive flame retardants. A novel P‐N coacting epoxy curing agent with intrinsic flame retardancy was designed and synthesized. The mechanical properties, crosslinking curing properties and flame‐retardant properties of intrinsic flame‐retardant epoxy resin were characterized. The results show that the cross‐linking curing performance of hexa (3,5‐diamino‐1,2,4 triazolyl)‐cyclotriphosphonitrile) (VCP) is lower than that of DDM. This is due to the decrease in cross‐linking density caused by the VCP ring molecular structure. Therefore, the mechanical properties of the epoxy resin cured with VCP decreased, but the flame‐retardant properties of the material significantly improved. The limiting oxygen index of the VCP/EP flame retardant epoxy thermosets was 27.3%, reaching the UL 94 V‐1 level. The peak heat release rate and total heat release rate of the VCP/EP flame retardant epoxy thermosets were significantly reduced. The flame retardancy mechanism was studied by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and x‐ray photoelectron spectroscopy. The results show that the intrinsic flame‐retardant P‐N coacting epoxy resin has excellent curing and flame‐retardant properties. [ABSTRACT FROM AUTHOR]

Flax fabric textile is of great interest as bio‐fiber reinforcement in composites, which has gained popularity due to the high demand for sustainable materials. Despite its sustainability, flax is inherently flammable. This study demonstrates a two‐step polyelectrolyte complex (PEC) coating that renders flax fabric self‐extinguishing. The PEC coating consists of polyethylenimine (PEI) and sodium hexametaphosphate (PSP), cured with a citric acid buffer. Sonication employed during the curing process improves the infiltration of the coating into the flax fibers and maintains the fabric's hand. When comparing non‐sonicated and sonicated flax samples, the latter achieves self‐extinguishing behavior and passes the vertical flame test. Pyrolysis‐combustion flow calorimetry reveals that this PEI/PSP coating (with sonication) reduces the peak heat release rate and total heat release by 40% and 67%, respectively. The intumescent mechanism is predominantly observed in the condensed phase, as suggested by differential scanning calorimetry and X‐ray photoelectron spectroscopy. The results demonstrate that the two‐step PEC treatment with sonication effectively reduces the flammability of flax fabric, making it a promising option for the development of functional fibers, particularly for bio‐composite reinforcement. [ABSTRACT FROM AUTHOR]

The presence of massive amounts of toxic volatiles and smoke during combustion is a very serious problem facing epoxy resin (EP) composites. Therefore, flame retardants (FRs) can simultaneously enhance flame retardancy and reduce the release of smoke and fatal gases. Herein, a novel sulfur–phosphorous reactive flame retardant (SPMS) was synthesized for epoxy resin. The high efficiency of smoke suppression and flame retardancy of the EP/SPMS-APP hybrid was investigated using a cone calorimeter, a vertical burning test, and limited oxygen index measurements. Compared with those of pure EP, the composite with 20 wt% SPMS-APP reduced the peak heat release rate (pHRR), the peak smoke production rate (SPR), and total smoke production rate (TSR) by 82%, 94%, and 84%, respectively. The results showed a remarkable suppressed effect of alleviating the fire hazard of EP using a sulfur–phosphorus flame retardant. [ABSTRACT FROM AUTHOR]

In this study, a DOPO-based reactive flame retardant (DRFR) was synthesized and used as the second diphenol structure for preparation of flame-retardant rigid polyurethane foam (FR-RPUF). DRFR, as a phosphorus/nitrogen-containing diphenol, was prepared from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 4-hydroxy benzaldehyde, and benzidine. FR-RPUF was synthesized from polyether polyol (DaltoFoam TA® 14066) as the first hydroxyl-rich structure, DRFR as the second diphenol, and 4,4′-diphenylmethane diisocyanate through the one-pot method. For comparison, a pure rigid polyurethane foam (pure RPUF) was also synthesized without DRFR. The thermal stability of pure RPUF and FR-RPUFs was investigated by using thermogravimetric analysis (TGA). According to thermogravimetric analysis results, the temperature at 5 mass% loss (T5%) increased from 222 to 238 °C for sample containing 2 mass% of DRFR. Also, the char residue at 700 °C was enhanced by introducing DRFR. Flame retardancy and burning behavior were determined by the limiting oxygen index (LOI) and vertical burning test (UL-94). The LOI value of FR-RPUF sample containing 3 mass% DRFR achieved 21.5%, and the UL-94 test improved from no rating for pure RPUF to V-1 rating for FR-RPUFs. Compared with the pure RPUF, the resultant FR-RPUFs indicated better fire resistance and thermal stability. The dynamical mechanical thermal analysis results revealed that the storage modulus for FR-RPUFs is higher than pure RPUF, which attributed to the good interaction between DRFR and PU matrix. [ABSTRACT FROM AUTHOR]

Wood-based functional materials have developed rapidly. But the flammability significantly limits its further application. To improve the flame retardancy, the balsa wood was delignified by NaClO2 solution to create a cellulose scaffold, and then alternately immersed in CaCl2 ethanol solution and NaHCO3 aqueous solution under vacuum. The high porosity and wettability resulting from delignification benefited the following mineralization process, changing the thermal properties of balsa wood significantly. The organic-inorganic wood composite showed abundant CaCO3 spherical particles under scanning electron microscopy. The peak of the heat release rate of delignified balsa-CaCO3 was reduced by 33% compared to the native balsa, according to the cone calorimetric characterization. The flame test demonstrated that the mineralized wood was flame retardant and selfextinguish. Additionally, the mineralized wood also displayed lower thermal conductivity. This study developed a feasible way to fabricate a lightweight, fire-retardant, self-extinguishing, and heat-insulating wood composite, providing a promising route for the valuable application of cellulosic biomass. [ABSTRACT FROM AUTHOR]

Transparency is an important property for polymer flame retardants, especially epoxy resin (EP) flame retardants, and flame-retardant epoxy resins that maintain a high transparency and low chromatic aberration play important roles in the optical, lighting, and energy industries. Herein, a DOPO-based flame retardant 6,6′-((sulfonylbis(4,1-phenylene))bis(oxy))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) with a high transparency and low chromatic aberration was prepared via the classical Atherton–Todd reaction and named SBPDOPO. Its chemical structure was characterized with Fourier IR spectroscopy and NMR spectroscopy. An EP loaded with 7 wt% SBPDOPO passed the UL-94 V-0 rating with an LOI value of 32.1%, and the peak heat release rate, total heat release, and total smoke production were reduced by 34.1%, 31.6%, and 27.7%, respectively, compared with those of pure EP. In addition, the addition of SBPDOPO improved the thermal stability, residual mass, and glass transition temperature of the EP. On this basis, the EP containing 7 wt% SBPDOPO maintained a high transparency and low color aberration, with a transmittance of 94% relative to that of pure EP and a color aberration ΔE of 1.63. Finally, the flame-retardant mechanism of SBPDOPO was analyzed, which demonstrated that it exerted both gas-phase and condensed-phase flame-retardant effects, and that SBPDOPO/EP had high potential for application scenarios in which both flame retardancy and transparency are needed. SBPDOPO/EP has great potential for applications requiring both flame retardancy and transparency. [ABSTRACT FROM AUTHOR]

• The flammability limits of R134a/R1270, R134a/R170 and R170/R1270 were measured. • R134a demonstrates a significant flame-retardant effect at volume ratios above 0.75. • The flame color and propagation speed of refrigerants were compared and analyzed. Hydrocarbons (HCs) are considered promising alternative refrigerants due to their excellent thermodynamics, transport properties, and environmental friendliness. However, hydrocarbons are flammable. Conversely, R134a is a widely used non-flammable refrigerant but was listed in the Montreal Protocol-Kigali Amendment due to its relatively high global warming potential (GWP). Therefore, in order to reduce the GWP of R134a and inhibit the flammability of hydrocarbon refrigerants, this study investigated the flammability characteristics of mixed refrigerants R134a/R1270, R134a/R170, and R170/R1270. The flammability limits of different concentrations of R170/R1270, R134a/R1270, and R134a/R170 were measured under standard conditions, and the inhibition mechanism of R134a was briefly analyzed. Additionally, the flammability limits of R170/R1270, R134a/R1270, and R134a/R170 were predicted using the polynomial fitting method. Subsequently, the flame propagation speed and the flame color of R1270 and R170, with and without R134a, were compared and analyzed. Furthermore, the cycle performance of R134a/HCs was calculated. The research results are expected to provide guidance for the safe and effective utilization of R1270, R170, and their mixtures in refrigeration systems. [ABSTRACT FROM AUTHOR]

A novel phosphorus‐based maleimide, tris[4‐(2,5‐dioxopyrrol‐1‐yl)phenyl] phosphite (TDPPI), was employed as a flame retardant in epoxy with moderate transparency, enhanced thermal stability, and improved mechanical strength. SEM studies ascertained the uniform dispersion of TDPPI and its compatibility with the epoxy. Differential scanning calorimetry showed that the epoxy compounded with 2.5 wt% of TDPPI achieved 100% curing with the glass transition temperature of 43.8°C. The thermogravimetric study revealed that the presence of 2.5 wt% of TDPPI in epoxy increased the residual mass found at 600°C by 23%. The epoxy thermoset compounded with 2.5 wt% of TDPPI passed the Underwriter's Laboratory (UL‐94) test with V‐1 classification and achieved the limiting oxygen index of 30.7% with a reduced burning rate of about 58.7%. At 1.5 wt% of the TDPPI, the resulting epoxy thermoset exhibited an enhancement in the tensile strength (23%), Young's modulus (37%), flexural strength (9%), and Izod impact strength (37%) relative to the neat epoxy. In conclusion, 2.5 wt% of TDPPI is adequate for imparting flame retardancy to epoxy composites with improved mechanical strength because of the maleimide‐phosphorus synergistic effect. Highlights: TDPPI is a phosphorus and maleimide containing flame retardant.TDPPI improves thermal stability, flame retardancy and mechanical strengths.Only 2.5 wt% of TDPPI is required for epoxy to achieve high flame retardancy.Maleimide presence lowers phosphorus requirement for epoxy flame retardancy.TDPPI is a promising new flame retardant material for epoxy. [ABSTRACT FROM AUTHOR]

The synthesis and application of the bio‐derived flame retardant can meet the current requirements for the high‐efficient and sustainable development of flame retardants. Therefore, using phytic acid (PA), 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO), and piperazine as raw materials, a PA‐derived flame retardant (PAPDOPO) was prepared. Fourier transform infrared spectroscopy and x‐ray diffraction techniques were applied to characterize the structure of the PAPDOPO. In the prepared flame‐retardant epoxy resin (FEP), PAPDOPO showed high flame retardancy. When 4% PAPDOPO was added into epoxy resin (EP), the prepared FEP (EP‐PAPD‐4) passed the V‐0 level in the UL‐94 test, and the limited oxygen index value of EP‐PAPD‐4 reached 35.3%. Microcombustion calorimetry test was also applied to demonstrate the performance of PAPDOPO. The peak heat release rate of EP‐PAPD‐4 was reduced by 30.4% compared with that of the pure EP. Due to the low addition amount of PAPDOPO in FEP, the mechanical properties of the FEP using PAPDOPO as flame retardant were hardly decreased compared with pure EP. [ABSTRACT FROM AUTHOR]

Reducing the flammability of kapok fiber (KF) is an important strategy to increase its applicability. In this work, the phosphorylation of KF with ammonium dihydrogen phosphate (ADP) was used to reduce its flammability, the conditions of phosphorylation reaction were studied in detail, and the chemical groups, crystalline structure, thermal stability, heat release capability, flammability and charring ability of phosphorylated KF were analyzed. KF showed significantly higher phosphorylation level than cotton, and its phosphorylation greatly depended on ADP and urea dosage, reaction temperature and time, and pH. Urea addition, pH 6, 150 ℃ and 1 h rendered high phosphorylation with acceptable whiteness. Phosphorylated KF exhibited good char-forming, low heat release and excellent flame retardant performances during thermal degradation and combustion as evidenced by thermogravimetric, microcalorimetric, vertical combustion and combustion residue morphology analyses. The residue rate of phosphorylated KF subjected to thermal degradation exceeded 50% in nitrogen, and 25% in air. This investigation demonstrates that phosphorylated KF is an intrinsically flame retardant material. [ABSTRACT FROM AUTHOR]

A fully bio-based flame retardant PNF was prepared based on phytic acid, nicotinamide and iron salts in aqueous solution by a green and convenient ionic reaction, and then blended with polylactic acid (PLA) to improve its properties. The results demonstrated that the PLA composite containing 4 wt% PNF(PLA/4PNF) had a flame retardancy rating of UL 94 V-0 and an oxygen index of 25.3%. In addition, the peak heat release rate (PHRR) and total heat release (THR) of PLA/4PNF were reduced by 27.0% and 27.7%, respectively, compared to pure PLA, and the flame retardancy index (FRI) was increased by 210%, demonstrating that PNF could effectively improve the flame retardancy of PLA. Moreover, the thermal conductivity of PLA/4PNF increased by 284% compared to pure PLA, making the material require higher heat to reach the combustion state. DSC and mechanical property tests showed that PLA/4PNF had 31.3% higher crystallinity, 5.2% higher heat deflection temperature and 10.0% higher flexural modulus compared to pure PLA, indicating that PNF effectively improved the mechanical properties and heat resistance of PLA. The research in this article broadens the application of bio-based flameretardant PLA in the field of electronic appliances and office equipment. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) is a thermoplastic resin widely used in various industrial applications. However, the flammability of PP is a severe drawback that lowers operational safety. This study demonstrates the development of flame‐retardant PP. The co‐adding with various solid acids and a hindered N‐alkoxy amine (NOR116 – Flamestab® NOR 116 FF) affects the combustion behavior of PP in a vertical flame test. The co‐adding of silica alumina (SA) and NOR116 with PP promoted the melt drip, suppressed upward combustion heat, and shorter the combustion time. The decomposition products of NOR116 induced the cleavage of the main chain of PP, and it quenched the radicals on the surface of the SA particles because SA has abundant acidic sites and large pores, facilitating the adsorption of a substantial quantity of NOR116. The molecular weight of PP was controlled to 103 ~ 104 before the combustion to achieve an increase in the melt flow ability and suppress the upward combustion. Furthermore, a small amount of a halogen‐based flame retardant was incorporated into the PP/SA/NOR116 sample, and the specimens could instantly self‐extinguish on the gas phase by radical trap. [ABSTRACT FROM AUTHOR]

In this paper, a single-component intumescent flame retardant di-(3-aminopropyltriethoxysilane) spirocyclic pentaerythritol diphosphate (PDAP) was synthesized, imparting flame retardancy to polylactic acid (PLA), which using melt blending process. The chemical structure and thermal stability of PDAP were characterized by test methods such as Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The fire retardancy of PLA/PDAP was evaluated by test methods such as limiting oxygen index (LOI) and vertical burning test (UL-94). The thermal stability of PLA/PDAP was studied by TGA and thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR). According to the results of laser Raman spectroscopy (LRS) and FTIR, the possible flame retardant mechanism of PLA/PDAP was discussed. With only 20 wt% addition of PDAP, PLA/PDAP could achieve 11.98% char residues at 800 °C. The LOI value of PLA/PDAP achieved 37%, UL-94 test reached V-0 rating. And higher fireproof performance with 62.1% reduced peak heat release rate (PHRR), 36.8% reduced total heat release rate (THR) and 19.5% reduced average effective combustion heat (av-EHC) value than PLA. The results show that PDAP has remarkable flame retardant effect on PLA, which provides an excellent research case for flame retardant modification of PLA plastic products. [ABSTRACT FROM AUTHOR]

The phosphorous‐based flame retardant additives poly(m‐phenylene methylphosphonate) (PMP) and resorcinol bis(diphenyl phosphate) (RDP) are reacted with bisphenol F and aniline–based benzoxazine (BF‐a). DSC, rheological analysis, FT‐IR, and soxhlet extraction reveal the covalent incorporation of both FR additives—initiating phenols in PMP structure as well as free phenols generated via transesterification reaction in the case of RDP. In contrast to PMP, RDP elongates the processing window but decreases the thermo–mechanical properties. Both additives increase the resistance in reactions against small flames with solely a phosphorous loading of 0.3 wt%, resulting in a V‐0 rating and an improvement in the OI value by up to 2% for RDP and 4% for PMP. Both FRs reduce the heat release rate but increase the smoke production and the smoke toxicity in the case of RDP. [ABSTRACT FROM AUTHOR]

Paraffin is a potential thermal energy storage material, but leakage and flammability are the two major problems affecting its storage and safe use. Here, a novel flame retarded paraffin/epoxy resin composite was developed by using paraffin, epoxy resin and hollow metal organic framework (W‐UiO66‐PPA) as thermal energy storage material, supporting material and flame retardant, respectively. The thermal energy storage and flame retardancy performances were examined with differential scanning calorimetry, vertical burning, limiting oxygen index and cone calorimeter tests. The results show that the paraffin/epoxy resin retains intact without leakage when the content of paraffin reaches 40 wt%, and this material exhibits high melting latent heat and remarkable thermal recycling property. In addition, the flame retarded paraffin/epoxy resin shows excellent flame retardancy, which is attributed to the following three aspects: (1) the hollow structure with open vertices of W‐UiO66 is capable of absorbing and collecting the combustible gasses produced by the combustion of epoxy resin; (2) the Zr and W elements of W‐UiO66 can facilitate catalytic charring and form a dense char layer; (3) phosphorous‐containing free radicals are able to capture OH· and O· free radicals during the combustion of paraffin and epoxy resin, thus interrupting the combustion chain reaction. On the whole, the flame retarded paraffin/EP possesses excellent thermal energy storage, thermal recycling, and flame retardancy properties. Our work provides a fantastic inspiration for the rational design of other flame retarded form‐stable phase change materials. [ABSTRACT FROM AUTHOR]

In order to improve the flame retardancy of polyvinyl chloride (PVC) used for wires and cables, zinc borate (ZB) was added to PVC to prepare PVC composites, and its flame retardancy and mechanical properties were studied. The mechanical properties test showed that with the increase of ZB content, the tensile properties of PVC composites decrease dgradually. However, when the ZB content was less than 6%, the tensile properties of PVC composites decreased slightly, which still met the requirements of relevant standards. The flame retardant test showed that the flame retardant of PVC composites increased with the increase of ZB content. When the content of ZB was 6%, the comprehensive properties of PVC composite (4#) were excellent. Compared with the composite without ZB, the flame retardancy of the 4# sample was significantly improved, the oxygen index reached 40.1%, the vertical combustion grade reached FV-0, the smoke density decreased to 72, the HCl release decreased to 41 mg/g, the peak heat release rate (PHRR) was decrease by 19.9%, the total heat release (THR) was decreased by 36.5%, and the total smoke production (TSP600 s) was decreased by 69.7%. The tensile strength of the composite was decreased by 10.8%, and the elongation at break was decreased by 12.7%. [ABSTRACT FROM AUTHOR]

Balancing the flame retardant properties and mechanical performance is important for flame retardant composites. In this research, the polylactic acid (PLA)/fiber composite is prepared by treating jute woven fabric with phosphorus‐containing organosilicon compound (PCOC) and adding intumescent flame retardant (IFR) to PLA using a film‐stacking procedure, which is named flame retardant PLA (FRPLA)/PC‐F. The flame retardancy and mechanical properties of PLA/fiber composites were studied and analyzed. Mechanical/flame retardant index (M/F index) was developed to compare the comprehensive properties of the composites. The limited oxygen index (LOI) test results show the LOI value of FRPLA/PC‐F reaches 34.1%, 14.1% higher than untreated PLA/fiber composite (PLA/F). In the cone calorimeter test, the pk‐heat release rate (HRR) value of FRLA/PC‐F decreases from 549 to 388 kW/m2 compared with PLA/F. In addition, the char yield of FRPLA/PC‐F increases from 1.9% (PLA/F) to 18.6%. The scanning electron microscope images of the char yield for FRPLA/PC‐F obtained from cone calorimetry test shows a continuous network structure with the fibrous skeleton completely wrapping by the dense and uniform char layer, which plays a barrier effect that inhibits the release of volatile substance and the transfer of heat. Meanwhile, FRPLA/PC‐F exhibits 28% and 19% improvement in tensile strength and impact strength compared with PLA/F due to the boost of interfacial adhesion between fiber and PLA. The M/F index of FRPLA/PC‐F is 1.15, which is the highest among all the composites, proving the best comprehensive properties and practical applicability. The results in this manuscript above make a great development, which is attractive in the design of PLA/fiber composites with great comprehensive performance. [ABSTRACT FROM AUTHOR]

In the current study, aluminum phytate (AlPt) is used with huntite–hydromagnesite (HH) in plasticized poly(lactic acid) (PLA) in order to improve the fire-retardant performance of the composite. The flame retardant, thermal, and mechanical properties of the composites are investigated using the limiting oxygen index (LOI), horizontal and vertical burning test (UL-94), mass loss calorimeter, thermogravimetric analysis, tensile, and impact tests. According to the test results, the fire-retardant performance of the composite was improved when HH and AlPt were used together. The highest LOI value (33.8) and UL-94 rating of V0 were achieved with the addition of 5 mass% AlPt in the presence of 55 mass% HH. Further, the addition of AlPt did not change the flammability properties. AlPt showed its adjuvant effect predominantly in the condensed phase via improved char formation with enhanced barrier properties. Tensile and impact strength reduced as the added amount of AlPt increased due to the hydrolytic degradation of PLA during the extrusion process. [ABSTRACT FROM AUTHOR]

Polymers are widely employed in many areas, e.g. transport, packaging, electronic devices, etcetera. Among them, acrylonitrile–butadiene–styrene (ABS) is one of the most employed polymers due to its mechanical properties, its ease to mechanize and recyclability. Nevertheless, according to the fire properties, ABS behaviour is usually worse than other polymers, therefore, they have to be upgraded with flame retardant additives. To characterize the fire behaviour of a certain material is necessary to address several typology of tests, providing relevant properties such as thermal conductivity, flammability and heat released. However, researchers may not always be able to run all tests due to the lack of apparatus or samples. Therefore, it is necessary to seek bibliographic sources. As one might expect, for a given material, the property values should be similar, regardless of who performs the test. However, sometimes slightly different results are obtained, which may be due to different causes, such as differences in test set-up and in material composition/manufacture. These differences in properties may lead researcher to doubt which data to use. This paper presents the results of different types of tests using neat ABS polymer. Additionally, these results are compared with the data from literature, discussing the similarities/differences and offering a more comprehensive characterization of ABS. The laboratory techniques included in this work are: thermogravimetric analysis, differential scanning calorimetry, laser flash analysis, smoke density, cone calorimeter, fire propagation and flammability. [ABSTRACT FROM AUTHOR]

Epoxy resin (EP) has excellent comprehensive properties, but its inherent flammability limits its further application in high‐end industries. The present study focuses on the preparation of an efficient phosphorus/silicon‐containing flame retardant for improving the flame retardancy and smoke suppression of EP. The intermediate product ED was first obtained by the addition reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) with eugenol, and then the target flame retardant DPSi‐ED was synthesized by the Williamson etherification reaction between ED and dichlorodiphenylsilane. The flame retardant was further incorporated into EP/4,4′‐diaminodiphenylmethane (DDM) system to prepare the modified epoxy thermosets. The flame‐retardant performance and mechanism were investigated by limiting oxygen index (LOI) test, vertical combustion test, cone calorimetry, thermogravimetric analysis‐infrared spectroscopy (TG‐IR), and so forth. At the same phosphorus content (0.5 wt%), EP/DPSi‐ED thermosets exhibited superior flame‐retardant properties to EP/ED thermosets. Moreover, EP/DPSi‐ED7 achieved a LOI of 35.3% and V‐0 rating in UL‐94 testing, and compared to EP/ED7, its peak heat release rate (pHRR) and total smoke production (TSP) were reduced by 31.5% and 10.9%, respectively. The phosphorus and silicon elements synergistically contributed to the formation of a stable char layer, which acted as a physical barrier to effectively enhance the flame‐retardant properties of the thermosets. Meanwhile, the incorporation of DPSi‐ED containing flexible SiO bonds and rigid DOPO groups to some extent also improved the mechanical properties of the cured EP. Hence, this study provides an effective strategy for the preparation of bio‐based phosphorus/silica‐containing high‐efficiency and smoke‐suppressing flame retardants. [ABSTRACT FROM AUTHOR]

To alleviate the fire hazard of epoxy resin (EP), an efficient flame retardant (ADM) containing phosphophenanthrene and thiazole groups is synthesized and used as co-curing agent for 4,4′-diaminodiphenyl methane to prepare EP/ADM composites. EP/4 mass% ADM composites with phosphorus content of only 0.25 mass% reach UL-94 V-0 rating and the limiting oxygen index value is high to 35.8%. The results reveal that the peak heat release rate, total smoke production, and total heat release of EP/4 mass% ADM composites are reduced by 24%, 14.4% and 16.7%, respectively, in comparison with those of pure EP. The improvement in flame retardancy is mainly attributed to the decomposition of DOPO which produces HPO• and PO• to capture the reactive radicals in the gaseous phase. The thiazole group releases hindered amine groups and inactive gas with a dilution effect in the gaseous phase thus further enhancing the effect of the phosphophenanthrene group. Besides, ADM helps to increase the glass transition temperature (Tg) of EP/ADM composites, which is 176 °C for EP/4 mass% ADM composites, which is higher than the value (172 °C) of EP. [ABSTRACT FROM AUTHOR]

Monterey pine is a renewable biomass resources with structural and chemical characteristics, but is limited by its flammability, poor mechanical properties, and subpar thermal conductivity (TC). Herein, a thermal conductive and flame retardant the multifunction epoxy resin (MEP) prepolymer was injected into the Monterey pine and subsequently cured. The results showed that impregnated MEP Monterey pine, maintained its original cellular structure under applied loads compared to pristine Monterey pine, thus, giving the composite wood better mechanical integrity than its neat counterpart, which served as thermally conductive pathways within the composites. The TC was measured to be 0.12 Wm−1 K−1 for pristine Monterey pine. Whereas, the infiltrated MEP/wood composite yielded a TC of 0.94 Wm−1 K−1 which correlates to a 683.3% enhancement. Besides, the tensile strength of the prepared composites in the longitudinal and radial directions were observed to be 75.0 and 21.7 MPa, and increased by 63.4% and 152.3% compared to that of pristine Monterey pine, respectively. Combustion tests revealed that the Monterey pine/MEP composites self‐extinguished after ignition and departing from the flame source while the pristine Monterey pine did not. It was deduced that the TC, fire retardancy, and mechanical performance of Monterey pine were simultaneously improved by injecting the multifunctional epoxy resin prepolymer, which provide a wide application potential in heat dissipation furniture field. Highlights: The multifunction epoxy enhanced the multiple performance of Monterey pine.The wood composite yielded a high thermal conductivity.Monterey pine/MEP composites managed to self‐extinguish after ignition. [ABSTRACT FROM AUTHOR]

The properties including combustibility, rigidity, thermal conductivity, and the color of the fiber sample influence the flammability characteristics of composite materials. Although the influence of phosphorus‐based fire retardants on the flammability characteristics of glass fiber‐based composite materials has been well studied, there is a need to better understand the effects of these fire retardants on the flammability characteristics of carbon fiber‐based composites. In the current study, four different commercially available phosphorus compounds (melamine polyphosphate (MPP), 9, 10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene10‐oxide (DOPO), aluminum diethyl phosphinate (AlPi), and zinc diethyl phosphinate (ZnPi)) are used. The flammability test results indicate that UL‐94 V rating maintains to burn to clamp with the addition of MPP, DOPO, and ZnPi in all concentrations. The highest UL94 V rating of V0 is obtained with the addition 10 wt% AlPi. An increase in LOI value is observed in samples containing MPP, AlPi, and DOPO. The highest LOI value of 41.5% is observed with the addition of 20 wt% AlPi. According to the MLC results, the lower peak heat release rate (pHRR) and total heat evolved (THE) values are obtained with the addition of all studied phosphorus compounds. The lowest pHRR (157 ± 10 kW/m2) and THE (44 ± 5 MJ/m2) values are obtained with the use of 20 wt% MPP and DOPO, respectively. The highest fire performance index (FPI) is achieved with the use of AlPi. Apart from DOPO which shows its effect predominantly in the gas phase, the studied phosphorus compounds exert flame retardant action both in the condensed and gas phases. [ABSTRACT FROM AUTHOR]

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Developing highly efficient and multifunctional epoxy resins (EPs) that overcome the shortcomings of flammability and brittleness is crucial for pursuing sustainable and safe application but remains a huge challenge. In this paper, a novel biomass-containing intumescent flame retardant containing a rigid–flexible and multi-siloxane bridge structure (DPB) was synthesized using siloxane; 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO); and biomass vanillin. DPB could facilitate the formation of a carbon residual with an intumescent structure, which effectively blocked the propagation of heat and oxygen. As a result, the peak heat release rate (pHRR) and total heat release (THR) of DPB/EP-7.5 decreased by 38.8% and 45.0%, respectively. In terms of mechanical properties, the tensile and flexural elongations at break of DPB/EP-7.5 increased by 77.2% and 105.3%, respectively. Impressively, DPB/EP-7.5 had excellent dielectric properties, with a dielectric constant of 2.5–2.9. This was due to the Si-O bonds (multi-siloxane bridges) contained in DPB/EP, which can quench the polarization behavior of the hydroxyl group. This paper provides a facile strategy for the preparation of multifunctional EP, which will pave the way for the promotion and application of EP in the high-end field. [ABSTRACT FROM AUTHOR]