Flame Retardant Mechanism Research Articles

Preparation of super toughened flame-retardant polylactic acid with an in situ hyperbranched structure by reactive blending with a phosphorus-containing copolyester and hexamethylene glycidyl cyclotriphosphazene

Achieving both super toughness and flame retardancy in polylactic acid (PLA) materials hinges on resolving the interface compatibility issues between flame retardants, toughening agents, and PLA, as well as overcoming potential antagonisms between these components. Here, we present an approach employing hyperbranched structures to simultaneously enhance the toughness and flame retardancy of PLA materials. Our strategy involved the reactive blending of PLA with a quaternary bio-based phosphorus-containing copolyester (PPE) featuring side hydroxyl groups and hexamethylene glycidyl cyclotriphosphazene (HGCP). The multi-epoxy groups of HGCP reacted with the hydroxyl and carboxyl groups present in PPE and PLA, resulting in the formation of hyperbranched PLA-PPE copolymers. The hyperbranched copolymers provided great interfacial compatibilization and low viscosity, synergistically promoting the melt-dripping flame-retardant mechanism facilitated by PPE, aiding in the rapid removal of heat and combustible material from the pyrolysis zone. Consequently, the PLA/PPE/HGCP blends exhibited super toughness, achieving a maximum notched impact strength of 70.2 kJ/m2. Additionally, the blends demonstrated a 27 % LOI and can pass the UL-94 V-0 rating. Moreover, all the blends are biodegradable in a Proteinase K solution. This research underscores the efficacy of utilizing hyperbranched structures as a promising strategy for the development of PLA materials with simultaneous enhancement of processability, toughness, and flame retardancy.

Facile preparation of heptazine-covered Fe2O3 and its synergistic effect on the enhanced flame retardance of silicone rubber composite

The flammability of silicone rubber (SR) significantly limits its broad use in areas that require high flame retardancy. In this study, heptazine-covered Fe2O3, which exhibits effective flame retardancy, was prepared using simple ball milling and heat treatment, which are advantageous for large-scale production. The prepared filler was incorporated into SR. The addition of 7.02 wt% FM filler increased the thermal degradation onset temperature at 5 % weight loss from 492.5 °C for neat SR to 502.7 °C (FM 1:1 composite). Moreover, the peak heat release rate and peak smoke production rate of the FM 1:1 composite significantly decreased by 43.15 % and 68.42 %, respectively, indicating a significant enhancement in the fire safety and smoke suppression of the FM composites. The chemical, morphological, and electronic structures of the FM fillers, pyrolysis gas production, and char residue were thoroughly investigated to reveal the possible flame-retarding mechanisms of the SR composites.

Enhancing flame retardancy in 3D printed polyamide composites using directionally arranged recycled carbon fiber

Combining recycled carbon fiber (rCF) and 3D printing technology has shown great potential for fabricating functional prototypes and production parts used in the aerospace and automotive industries. However, it is still a challenge to design flame-retardant 3D printed parts with high mechanical properties and flame-retardant rating. In the work, a flame-retardant polyamide (PA)-based composite for material extrusion 3D printing was prepared by utilization of rCF, polyhedral oligomeric silsesquioxanes (POSS), and 9,10-Dihydro-9-oxa-10-phosphaphenanthrene (DOPO)-based flame retardant. The 3D-printed composites have high thermal stability, mechanical properties, and excellent flame retardancy with a V-0 rating. With the benefits of material extrusion 3D printing, directionally arranged rCF in 3D printed composites could effectively inhibit the fire spread, extend the time to ignition (TTI), reduce the total heat release (THR) and total smoke release (TSR) of 3D printed composites. The directional flame-retardant mechanism is mainly the thermal conductivity mechanism of the condensed phase and the promotion of stable ordered carbon layer formation. It provides a promising path for designing high-performance flame-retardant materials.

Engineering sulfonated carbon black for flame-retardant and smoke-suppressive polycarbonate with well-preserved mechanical performances

To cope with the practical demands of high-performance polycarbonate (PC) and explore the application of carbon black (CB) in flame retardant field, a sulfonated carbon black (CB-SS) was synthesized and applied to flame retardant PC in this work. Compared with PC/CB composite, PC/CB-SS composite displays better overall performances under the same flame retardant addition. The PC/3CB-SS composite with 3 wt.% of CB-SS achieves a vertical burning test (UL-94) V-0 rating with a limiting oxygen index (LOI) of 29.5%, and its peak heat release rate (PHRR) and total smoke release rate (TSR) are respectively reduced by 17% and 6% relative to those of PC/3CB with 3 wt.% of CB. The flame retardancy mechanism is proposed by analyzing the char residue obtained from cone calorimetry test, which confirms the synergistic flame-retardant effect between sodium sulfonate and CB in condensed phase. Moreover, PC/3CB-SS shows much better mechanical properties than PC/3CB, and its elongation at break is increased by 223% compared with that of PC/3CB. This is mainly due to the more even dispersion of CB-SS within PC and the stronger interfacial force between CB-SS and PC. This work provides an effective approach for the creation of fire-retardant and smoke-suppressive PC composites with well-preserved mechanical properties, contributing to expanding the industrial applications of PC.

Boosting Flame Retardancy of Polypropylene/Calcium Carbonate Composites with Inorganic Flame Retardants.

This study investigates the effects of inorganic flame retardants, zinc borate, and magnesium hydroxide, on the thermal, morphological, flame retardancy, and mechanical properties of polypropylene (PP)/calcium carbonate composites for potential construction industry applications. Polypropylene/calcium carbonate (50 wt.%) composites containing 5 and 10 wt.% flame retardants were prepared using a batch mixer, followed by compression moulding. The results demonstrated enhanced thermal stability, with the highest char residue reaching 47.2% for polypropylene/calcium carbonate/zinc borate (10 wt.%)/magnesium hydroxide (10 wt.%) composite, a notably strong outcome. Additionally, the composite exhibited an elevated limited oxygen index (LOI) of 29.4%, indicating a synergistic effect between zinc borate and magnesium hydroxide. The proposed flame retardancy mechanism suggests that the flammability performance is driven by the interaction between the flame retardants within the polypropylene/calcium carbonate matrix. Magnesium hydroxide contributes to smoke suppression by releasing water, while zinc borate forms a protective glassy foam that covers the burning surface, promoting char formation and acting as a physical barrier to heat transmission and fire spread. Scanning electron microscopy confirmed good dispersion of the additives alongside calcium carbonate within the polymer matrix. Despite the addition of up to 10 wt.% flame retardants, the composites maintained high-notched impact strength.

Deeper insights into flame retardancy of polymers by interpretable, quantifiable, yet accurate machine-learning model

Fire-safety polymer materials are essential in modern society such as electronics, aerospace, new energy. The quantification and prediction of flame retardancy, determined by the chemical composition and the burning process, has always been a bottleneck challenge. Previous empirical design rules and the existing models show large deviations for predicting flame retardancy and are often unexplainable. Here, this study proposes an interpretable model that can quantify the groups contribution of flame-retardancy and predict the flame retardance of intrinsically flame-retardant polymers. The machine learning model simultaneously considers the group structures and their flame-retardant mechanism in both the gas phase and condensed phase, achieving high prediction accuracy (89.8% for the training set and 83.8% for the testing set). It also quantifies the contribution values of various flame-retardant groups (halogen-containing structures, phosphorus-containing structures, phosphorus-nitrogen-containing structures, aromatic ring-containing structures, etc.) in both phases for the first time. The running script that integrates the model has also been open-sourced, providing an emerging strategy for transitioning flame-retardant research from empirical methods to scientific design.

Construction and application of B/P/N durable flame retardant crosslinking system on cotton fabric

The inherent flammability of cotton fabrics necessitates the implementation of flame retardancy to prevent fires. In this study, a B/P/N cross-linking flame retardant system was developed using phosphoric acid, boric acid, and glycerol. The cross-linking system was ammoniated and catalyzed by urea and dicyandiamide to enhance water solubility and fiber bonding strength. Following treatment, the limiting oxygen index of the cotton fabric increased from 18.0 % to 40.5 %, while the damage length in vertical flammability testing decreased from 30.0 cm to 4.8 cm. Thermogravimetric testing revealed an increase in residual char content at 750 °C in a nitrogen atmosphere from 9.7 % to 31.9 %, proving improved thermal stability. Furthermore, the maximum heat release rate and total heat release of the treated samples decreased by 86.7 % and 36.5 %, respectively, compared with pure cotton fabrics. Finally, possible flame retardant mechanisms were inferred from XPS and TG-IR data, demonstrating efficacy in both solid phase and gas phase.

Miscanthus floridulus-based intumescent flame retardant by green self-assembly for fully biological EP composites with commendable flame retardancy, smoke suppression and mechanical properties

The design of fully biological epoxy resin (EP) composites with high performance is highly desirable driven by green and sustainable development due to their renewable and sustainable nature. Herein, an efficient intumescent flame retardant based on Miscanthus floridulus (MF-based IFR) was devised for bio-epoxy composites by a green self-assembly method. The resulting composites with 15 wt% MF-based IFR demonstrated outstanding flame retardancy, effective smoke suppression, and favorable mechanical properties. The enhanced flame retardancy demonstrated the V-0 rating of UL-94 and the 26.4 % of limiting oxygen index (LOI) due to the dual-phase flame-retardant mechanism. Compared to pure EP, the EP composite with 15 wt% MF-based IFR exhibited reductions of 71.90 %, 61.85 %, 55.0 %, and 60.94 % in peak heat release rate (pHRR), total heat release rate (THR), smoke release rate (SPR), and smoke growth rate (TSP), respectively. Additionally, compared to unmodified MF, the composites with 15 wt% MF-based IFR displayed increasing of 3.35 %, 11.26 %, and 10.24 % in tensile, bending, and impact strengths, respectively, attributed to the enhanced interface compatibility. This study provides a straightforward, cost-effective, and efficient strategy for producing fully bio-based epoxy composites with high performance, expanding their potential applications.

Fully biobased approach for sustainable flame retardancy, antibacterial and anti-UV modification of silk fabric

The versatile modification of silk fabric using a fully biobased approach is intriguing. In this study, phytic acid and vanillin, which are plant extracts, were utilized to synthesize reactive vanillin phytate ester for modifying silk fabric to achieve durable flame retardancy, antibacterial and anti-UV performance. The multifunctional properties, thermal resistance, smoke and heat suppression capacity, flame-retardant durability and mechanism of modified silk fabrics were investigated. The vanillin phytate ester imparted high antimicrobial and UV resistance to silk fabric, achieving a 97 % inhibition rate against Escherichia coli and reaching an “excellent” level of UV protection. The modified silk fabric also possessed the self-extinguishing capacity, with a limiting oxygen index value as high as 33.5 %. There was also a significant reduction of 71.7 % in peak heat release and 40 % in smoke release compared with those of the original silk. After undergoing 20 washing cycles, the modified silk fabrics also self-extinguished and passed the vertical burning test, and such good washing resistance was achieved by the Schiff base cross-linking of vanillin phytate ester on the silk fabric. An intumescent flame-retardant mechanism was also identified by char residue analyses, which was driven by the synergistic charring action of phosphate groups and aromatic structures.

Single overall ‘H-shaped’ multifunctional compound achieves fire safety, durability, enhanced strength, and smoke suppression of cotton fabrics

Challenges currently faced by phosphorus-based flame retardants for cotton fabrics include reduced fabric strength after treatment, high smoke release during combustion, formaldehyde release from commercial phosphorus-based flame retardants and poor flame retardant durability after treatment. In the present work, a P/N/B synergistic flame retardant TBST is synthesized using phosphoric acid, cyanuric acid, boric acid, pentaerythritol, etc. The phosphorus‑nitrogen‑boron atomic ratio is 2:3:1, and it is successfully prepared on cotton fabric to prepare TBST/Cotton. When the weight gain rate is 29.8 %, the LOI value is 41.6 ± 0.3 %, indicating that TBST/Cotton has excellent flame retardant performance. At the same time, in the vertical flame test, the length of residual carbon is 5.6 cm. In addition, the THR and HRR are reduced by 58.4 % and 91.9 % respectively compared to Cotton, indicating that TBST/Cotton has excellent combustion performance. In addition, compared to the residual carbon content of Cotton at 710 °C, the residual carbon content of TBST/Cotton in nitrogen increased by 27.79 %. For a 30 % increase in weight, the increase in longitudinal mechanical strength is 23.1 %. Inferred the decomposition mechanism and flame retardant mechanism of TBST/Cotton. TBST/Cotton has the advantages of good flame retardant durability and enhanced mechanical properties, and the reinforcement mechanism of TBST has been speculated.

Recent Advances in Fire-Retardant Silicone Rubber Composites.

Silicone rubber (SR), as one kind of highly valuable rubber material, has been widely used in many fields, e.g., construction, transportation, the electronics industry, automobiles, aviation, and biology, owing to its attractive properties, including high- and low-temperature resistance, weathering resistance, chemical stability, and electrical isolation, as well as transparency. Unfortunately, the inherent flammability of SR largely restricts its practical application in many fields that have high standard requirements for flame retardancy. Throughout the last decade, a series of flame-retardant strategies have been adopted which enhance the flame retardancy of SR and even enhance its other key properties, such as mechanical properties and thermal stability. This comprehensive review systematically reviewed the recent research advances in flame-retarded SR materials and summarized and introduced the up-to-date design of different types of flame retardants and their effects on flame-retardant properties and other performances of SR. In addition, the related flame-retardant mechanisms of the as-prepared flame-retardant SR materials are analyzed and presented. Moreover, key challenges associated with these various types of FRs are discussed, and future development directions are also proposed.

Waterborne Intumescent Fire-Retardant Polymer Composite Coatings: A Review.

Intumescent fire-retardant coatings, which feature thinner layers and good decorative effects while significantly reducing heat transfer and air dispersion capabilities, are highly attractive for fire safety applications due to their effective prevention of material combustion and protection of materials. Particularly, the worldwide demand for improved environmental protection requirements has given rise to the production of waterborne intumescent fire-retardant polymer composite coatings, which are comparable to or provide more advantages than solvent-based intumescent fire-retardant polymer composite coatings in terms of low cost, reduced odor, and minimal environmental and health hazards. However, there is still a lack of a comprehensive and in-depth overview of waterborne intumescent fire-retardant polymer composite coatings. This review aims to systematically and comprehensively discuss the composition, the flame retardant and heat insulation mechanisms, and the practical applications of waterborne intumescent fire-retardant polymer composite coatings. Finally, some key challenges associated with waterborne intumescent fire-retardant polymer composite coatings are highlighted, following which future perspectives and opportunities are proposed.

Novel phosphorous-containing epoxy thermosets with improved anti-flammability, smoke suppression, and dielectric properties

As one of the most commonly used thermosetting resins, the flammability of epoxy resins (EPs) has become a key factor limiting the expansion of their application range. Herein, a novel phosphorous-containing epoxy monomer (EDPPO) was synthesized using diallyl amine and diphenyl phosphoryl chloride as the starting materials. Subsequently, EDPPO was thermally cured with two diamine hardeners, 4, 4′-diaminodiphenyl sulfone (DDS) and 4,4′-dithiodianiline (DTDA). Additionally, commercial diglycidyl ether of bisphenol A (DGEBA)-type epoxy pre-polymers were cured with DDS and DTDA as comparative samples. The cured EDPPO-based thermosets showed excellent flame-retardant properties coupled with smoke suppression. Specifically, the limiting oxygen index (LOI) for the EDPPO/DDS (P content 6.4 wt.%) reached 32.0 %, and the UL-94 vertical burning test reached a V-0 rating. In addition, the PHRR, THR, and TSP values of EDPPO/DDS were 61.6 %, 49.1 %, and 58.5 % lower than those of DGEBA/DDS, respectively. The flame retardant mechanism analysis indicated that the excellent flame retardancy for cured EDPPO-based thermosets was attributed to the combined modes of action in condensed (promoting the charring capacity) and gaseous phases (quenching the active radicals). More importantly, EDPPO/DDS and EDPPO/DTDA exhibited lower dielectric constant and dielectric loss than DGEBA/DDS and DGEBA/DTDA. This work provided novel phosphorous-containing epoxy thermosets with improved anti-flammability, smoke suppression, and dielectric properties.

Self-crosslinking phosphorus-containing durable flame retardants for cotton fabrics

The phosphorus-containing flame retardant that can enter the interior of cotton fiber and has self-crosslinking ability was designed and synthesized. The flame retardant contains two components, 2-(1-(dimethoxy phosphoryl)-2,5, 8-Triazectridecyl) phosphonate starch (PTPS) and 4-(hydroxymethyl)-10-((3-((5-(hydroxymethyl)-10-((3-((tris(hydroxymethyl)phosphonio)methyl)ureido)methyl)-2,6,8,12,14,18-hexaaza-4,10,16-Triphosphanonadecane (BPTP). The structure of PTPS and BPTP were detected by NMR and FTIR, and the results showed that the synthesis of PTPS and BPTP was successful. During the treatment, cellulose was first endowed with -NH groups. Then PTPS molecule and BPTP molecule were grafted onto cellulose through the reaction of P-CH2OH groups and -NH groups. After 50 laundering cycles (NFPA2112–2012 standard), the limiting oxygen indexes (LOIs) of the fabrics treated with 35 wt% CFN-PB and 30 wt% CFN-PB were 28.80% and 27.30%, respectively, and passed the vertical flame test (VFT). Compared with the raw cotton, the peak heat release rate (PHRR), the total heat rate (THR) and the flame growth rate (FGR) of the CNF-PB treatment fabric were reduced by 62.90 %, 29.43 % and 62.91 % respectively. These indicate that the flame retardant PB could be firmly fixed on the fibers and show good flame retardancy durability. In the VFT, and cone calorimetry test, the CFN-PB treated fabric showed the condensed phase flame retardant mechanism.

Modified Epoxy Resin on the Burning Behavior and Mechanical Properties of Aramid Fiber Composite.

Aramid fiber/epoxy resin (AF/EP) composite has been heavily used as an impact protection material due to its excellent mechanical properties and lightweight merits. Meanwhile, it is also necessary to concern the flammability of matrix resin and the wick effect of aramid fiber, which would constitute a fire risk in harsh environments. In this work, a multifunctional flame-retardant modifier (EAD) was incorporated into the AF/EP system to improve the flame retardation. The addition of 5 wt% EAD made the AF/EP composite exhibit a high limiting oxygen index (LOI) value of 37.5%, self-extinguishment, as well as decreased total heat release and total smoke release. The results from thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) demonstrated that the treated composites maintained good thermal stability. Due to the combined action of covalent and noncovalent bonds in the matrix-rich region, the interfacial bonding improved, which endowed AF/EP composite with strengthening and toughening effects. Compared with the control sample AF/EP, the tensile strength and ballistic parameter (V50) of the sample with 5 wt% EAD increased by 17% and 10%, accompanied with ductile failure mode. Furthermore, the flame-retardant mechanism was obtained by analyzing the actions in condensed and gaseous phases. Thanks to good compatibility and interfacial adhesion, the incorporation of EAD solved the inconsistent issue between flame retardancy and mechanical properties, which further expanded the application of AF/EP composite in the protection field.

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

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

Flame retarded lignin-based epoxy resin with excellent antibacterial and anti-corrosion properties modified by coordinated phospho-nitrogen flame retardant

In this paper, epoxidized lignin (HL) and sebacic acid (HSA) were used as the hard and soft segments, respectively, and a kind of reactive coordinated phosphorous-nitrogen flame retardants (DTZ) was designed and synthesized via Zn2+ coordination to fabricate a multifunctional non-bisphenol A lignin based epoxy (EP) composite. The swelling behavior and morphological analysis demonstrated that the crosslinking density of EP increased significantly after adding HL and DTZ. The existence of coordination sacrificial bond of DTZ dissipated more energy when it was subjected to external forces, thereby making 80HSA/14HL/6DTZ maintained a high tensile strength (10.65 MPa) while having little damage to the elongation at break (30.74 %). The limiting oxygen index (LOI) of 80HSA/14HL/6DTZ was significantly higher than that of 100HSA (22.3 %), reaching 36.6 %, and the vertical combustion test (UL-94) reached V-0 level. The morphology of carbon layer and residual carbon analysis showed that HL and DTZ had synergistic effect, and the flame retardancy mechanism of gas phase and condensed phase existed in the combustion process. Simultaneously, the addition of HL and DTZ also endowed the EP composite with excellent corrosion resistance and antibacterial properties.

DOPO chemically modified mesoporous silica composites: Preparation, flame retardancy, and thermodynamic properties

AbstractOrganic flame retardant 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) was used to decorate the pores of mesoporous silica (m‐SiO2) nanospheres to prepare a new composite flame retardant (DK‐SiO2). The content of DOPO in DK‐SiO2 is about 17 wt%. Due to the chemical bonding, DK‐SiO2 not only enhances the flame retardant performance, but also effectively avoids adverse effects of DOPO on the glass transition temperature and mechanical properties of epoxy resin (EP). At 9 wt% loading, the limiting oxygen index of the EP increased from 25.7 to 31.2, and successfully passed the UL‐94 V‐0 rating. Besides, DK‐SiO2 can significantly reduce the peak heat release rate, total heat release, and total smoke production of EP, with reductions of 26%, 32%, and 20.8%, respectively. Compared with the simple blended sample, DK‐SiO2 not only has better flame retardant performance but also shows significant advantages in thermodynamic properties. The glass transition temperature, impact, and tensile strength, as well as storage and flexural modulus have been improved. This excellent flame retardant performance is mainly attributed to the gas‐condensed synergistic flame retardant mechanism between DOPO and m‐SiO2. The good thermodynamic performance is due to the excellent dispersion of DK‐SiO2 nanospheres in the EP.

Preparation of microencapsulated physicochemical composite retardant and study of the flame retardant mechanism

In order to solve the shortcomings of traditional inhibitors, which are easy to be interfered by the outside world during the inhibition process and the active ingredients are easy to be oxidized and invalidated, microencapsulated inhibitors were developed. In this study, we prepared microencapsulated inhibitors of varying wall-to-core ratios using a composite phase of polyethylene glycol 20,000 (PEG-20000) and octenyl amyl succinate (OSAS) as the wall material and a lauryl glucoside (APG-12) and butyl hydroxyanisole (BHA) phase as the core material. After thoroughly mixing the microcapsule inhibitor with coal samples, simultaneous thermal analyzer (TG/DSC) and a temperature-programmed system were used to evaluate the resisting qualities of the produced microencapsulated inhibitors. The results of the temperature programmed experiment showed that the overall CO release from the blocked coal samples was less than that of the original coal. According to thermogravimetric results, the most effective inhibition occurred when the wall/core ratio of the microcapsule inhibitor was 4:1. This also resulted in a reduction of the maximum coal weight loss rate from 1.34 to 0.96 %/min and an increase in the maximum coal weight loss temperature from 477.4 to 507.6 °C. The microencapsulated inhibitor melts in the wall at 57.4 °C, enabling temperature-sensitive intelligent control of core release. Following heating the raw and inhibited coal samples to 100 and 200 °C, respectively, Fourier infrared spectroscopy was conducted. At these temperatures, the amounts of ether bonds increased by 20.4 and 22.6 %, and the number of free hydroxyl groups decreased by 12.8 and 2.7 %, respectively, in the inhibited coal samples. Finally, molecular dynamics theory was applied to investigate the inhibitory mechanism. The prepared microcapsule retardant effectively inhibited the spontaneous combustion reaction of coal, suggesting this microcapsule inhibitor could be manufactured as a novel inhibitor for coal spontaneous combustion.

In-situ polymerization of phosphorus/nitrogen flame-retardant coating for polyester/cotton blend fabrics with superior durability

The durable flame-retardant functional coating of polyester/cotton (T/C) blend fabrics is both interesting and challenging. In this study, a novel in-situ polymerization strategy for phosphorus/nitrogen-based flame-retardant on T/C blend samples was developed through the polycondensation of tetramethylolphosphonium sulfate, dicyandiamide, and anionic cyclic phosphate ester. The chemical structure of the polycondensation compounds, as well as the surface morphology, combustion behavior, flame-retardant capacity, washing durability and flame-retardant mechanism of the coated T/C blend fabrics, were investigated. The coated T/C blend fabrics demonstrated excellent self-extinguishing performance, with the damaged length decreasing to as low as 8.0 cm and the LOI reaching 28 %. Moreover, the peak heat release rate of the coated T/C blend fabrics decreased by 39.7 %. The superior flame retardancy can be attributed to the enhanced dehydration and carbonization by phosphate groups in the condensed phase, as well as the quenching effect and diluting effect in the gas phase. Additionally, the coated T/C blend fabrics exhibited remarkable washing durability and still achieved self-extinguishing after 65 washing cycles, and the in-situ deposition of insoluble three-dimensional polycondensation compounds onto the T/C blend fabrics was beneficial. The flame-retardant coating had a minor impact on the whiteness, tensile strength and breathability of the T/C blend fabrics.