Combustion Tests Research Articles

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.

DETERMINATION ON NITROGEN CONTENT OF ANTIBACTERIAL COTTON FABRIC TREATED WITH CHITOSAN

The study aims to evaluate the nitrogen content on antibacterial cotton fabrics treated with chitosan using four different quantitative determination methods: field-emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDX), dyeability of antibacterial treated samples based on color strength (K/S), elemental analyses via combustion tests, and antibacterial ability under dynamic contact conditions or the dynamic shake flask test. The nitrogen content was analyzed under the effects of molecular weight (MW) of chitosan (2.6 kDa and 187 kDa), crosslinkers including citric acid (CA) and dimethylol dihydroxyethyleneurea (DMDHE), and washing cycles. The findings from these measurements not only determined the nitrogen content of antibacterial cotton fabric but also elucidated the bonding mechanism between cellulose and chitosan in the presence of crosslinking compounds. Consequently, the antibacterial activity of cotton fabrics treated with chitosan could be indirectly assessed through the nitrogen content obtained from the amine groups of finishing compounds.

Highly hygroscopic needle-punched carbon fiber felt with high evaporative cooling efficiency and fire resistance for safe operation of ultrahigh-rate lithium-ion batteries

The effective thermal management of lithium-ion batteries is the key to ensuring their fast charging-discharging, safe and efficient operation. Herein, inspired by transpiration-driven water transport in plants, we report a highly hygroscopic needle-punched carbon fiber felt (HS/CFF) with high evaporative cooling efficiency and fire resistance for the safe operation of lithium-ion batteries working at ultrahigh-rate conditions. The three-dimensional fiber skeleton structure constructed by needle punching in the carbon fiber felt enables effective water transport and storage in HS/CFF, without any water leakage. At an ultra-high discharge rate of 10 C, HS/CFF can reduce the maximum temperature of commercial lithium-ion batteries by 18 °C, and can keep the battery temperature below 60 °C. During 500 cycles of charge-discharge, HS/CFF maintains stable evaporative heat dissipation performance, which helps to improve the safety of lithium-ion batteries and extend their service life. Moreover, HS/CFF remains non-combustible even under exposure to a flame (600-700 °C) for 10 min, and the HS/CFF can be reused after the burning test, with the original excellent heat dissipation effect unchanged. This flexible, fire-resistant cooling material offers a promising avenue for low-energy intelligent thermal management of lithium-ion batteries and other heat-generating electronic devices.

Vanillin-derived co-curing agent for enhanced flame retardancy and mechanical properties in epoxy resin

Herein, we present the synthesis and characterization of a novel phosphorus-containing epoxy co-curing agent, ANVD, fabricated via a one-pot method utilizing vanillin, 1,5-diaminonaphthalene, and DOPO as raw materials. Structural analysis conducted through FTIR and NMR spectroscopy confirmed the composition of ANVD. Differential scanning calorimetry (DSC) results indicated ANVD has significant contribution to the curing crosslinking of DGEBA, resulting in a slightly decreased Tg value for EP/ANVD compared to EP/DOPO, albeit still notably higher. Thermogravimetric analysis (TGA) revealed a reduction in the T5% and Tmax values of EP/ANVD, yet ANVD’s superior char-forming ability increased char residue mass at elevated temperatures. Combustion tests showcased the outstanding flame retardancy of EP/ANVD, with EP/ANVD-5 exhibiting a limiting oxygen index (LOI) value of 33.2 % and achieving a V-0 rating in the UL-94 test. Furthermore, EP/ANVD-5 displayed a notable decrease of 38.6 % and 32.1 % in pHRR and av-HRR, respectively, compared to pure EP, surpassing EP/DOPO with equivalent phosphorus content. Analysis of decomposition products in both condensed and gas phases revealed ANVD’s role in forming dense and continuous expanded char layers during combustion, releasing phosphorus radicals and non-combustible gases, thus exhibiting dual-phase flame retardant effects. Additionally, EP/ANVD-3 exhibited enhanced mechanical properties, with tensile strength and modulus increasing from 68.5 MPa and 0.75 GPa to 76.5 MPa and 0.86 GPa, respectively, compared to pure EP. Overall, the introduction of the bio-based flame retardant ANVD presents promising opportunities for the utilization of bio-based materials in flame retardancy applications.

Flame Retardant Rigid Polyurethane Foam Derived from Biobased Polyols and Water as Co-Blowing Agent: Synergistic Effect of Expanded Graphite and Boron Nitride

Using a bio-based polyol system one-shot free-rising method, bio-based flame-retardant rigid polyurethane foam (FR-RPUF) was prepared. Environmentally friendly blowing agent (Cyclopentane) and co-blowing agent water along with expanded graphite (EG) and boron nitride (BN) were used as admixtures to develop a synergistic flame-retardant composite at a variable ratio of EG and BN respectively. The flame retardancy of the composite was evaluated using various techniques like burning tests, UL 94, and cone calorimetry. At the same time, the morphological aspects and functional groups were analyzed by scanning electron microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR) respectively. The FR-RPUF synthesized using EG and BN at a ratio of 1:1 has impressive flame-retardancy and smoke-suppressing properties, with a "V-1" rating in the UL-94 vertical burning testing. Additionally, EG/BN- FR-RPUF has a compressive modulus of 4.92MPa, making it suitable for discontinuous panel applications.

High performance poly(lactic acid)/poly(ether-block-amide) blend-based bionanocomposites containing carbon nanotubes and/or organoclay

High-performance poly(lactic acid) (PLA) blend-based composites were fabricated with a poly(ether-block-amide) (PEBA) elastomer acting as the blend counterpart. It was confirmed that a compatibilizer (ADR) enhanced the interaction between PLA and PEBA. Carbon nanotubes (CNTs) and organoclay (30B) were added individually and simultaneously into the blend to produce bionanocomposites. Morphological results showed that CNTs were mainly dispersed in PEBA domains, whereas 30B was mainly localized at the interfacial region of PLA and PEBA phases. The selective localization of added CNTs and 30B led to significant modification of the properties of the compatibilized PLA/PEBA blend. The brittleness and flammability of PLA were evidently improved after forming the bionanocomposites. Differential scanning calorimetry results revealed that CNTs and 30B assisted the crystallization of both PLA and PEBA in the composites, with CNTs providing superior nucleation efficiency to 30B. Thermogravimetric analysis revealed the thermal stability enhancement of the blend after adding CNTs and/or 30B, with up to 16 °C increase at 20 wt% loss with inclusion of 2 phr 30B. Addition of CNTs and/or 30B improved the blend's anti-dripping performance during burning tests, and CNT exhibited better anti-dripping efficiency. Ductility of PLA was drastically improved after forming the compatibilized blend, and further improved with incorporation of CNTs and/or 30B (increased from 9 % for neat PLA to 252 % for the hybrid composite containing CNT/30B). The impact strength of 1 phr CNTs-added composite was about 3 times that of PLA. Rheological properties indicated the (pseudo)network formation of added filler(s), leading to a significant reduction in electrical resistivity, up to six orders of magnitude with addition of 3 phr CNTs.

Experimental investigation of combustion characteristics of ammonia with sub-bituminous coal in a pilot circulating fluidized bed combustor

Recent research on power plant technology has focused on employing ammonia as a supplementary fuel with coal to reduce carbon dioxide emissions from coal-fired power plants. However, most of this research has concentrated on pulverized coal systems, with fewer studies on circulating fluidized bed (CFB) combustion systems. Additionally, no research has analyzed combustion and environmental impacts under varying operational conditions with a fixed ammonia co-firing ratio. This study advances the development of coal–ammonia co-firing technology for use in CFB power plants by conducting experiments on a 50 kWth CFB combustion test rig. The co-firing characteristics were evaluated by progressively increasing the ammonia co-combustion rate to 20%, calculated on a high calorific value basis relative to sole coal combustion. Furthermore, this research explored the variations in operational conditions during 20% ammonia co-firing to assess their effects on the temperature distribution within the combustor and the composition of the exhaust gases. The findings elucidate the combustion efficiency, thermal behavior, and emission profiles associated with coal–ammonia co-firing, thereby guiding the optimization of operational strategies to minimize the carbon footprint of CFB power plants.

Study on the combustion characteristics and reaction mechanism of aluminum/alcohol-based nanofluid fuel

Enhancing the volumetric energy density of fuels is a crucial approach in the exploration of efficient energy sources. As a commonly used high-energy additive, Aluminum nanoparticles (Al NPs) holds broad application prospects. This study delves into the effects of Al NPs on the combustion characteristics of methanol and ethanol fuels through in-depth analysis of single droplet combustion and spray combustion experiments involving alcohol-based nanofluid fuels. The experiments revealed that adding Al NPs significantly enhances fuel combustion efficiency, shortening both the combustion life and ignition delay time. Spray combustion tests demonstrated that adding 2 wt% Al NPs increased the maximum and average flame propagation speeds of ethanol fuel spray by 48.93 % and 47.94 %, respectively, while the maximum explosion pressure rose from 0.66MPa to 0.83MPa, with a reduced time to reach peak explosion pressure by 106ms. Based on the SEM and XRD characterization results of the combustion residues and the analysis of flame morphology, a physical model of the alcohol-based nanofluid fuel spray combustion flame was established. Numerical simulations of the gas-phase kinetics model showed that the generation rates of radicals such as H, O, and OH were significantly increased with the addition of Al NPs, intensifying the combustion reaction. The findings provide a theoretical basis for future fuel design and combustion performance optimization.

Combustion and energy performance of multiple aluminum-based alloy particles

The long ignition delay time, high ignition temperature and agglomeration prevent the aluminum (Al) particles from fully releasing the chemical energy stored within them during combustion. Al-based alloy fuels with high energy density and excellent combustion performance have become a potential candidate for replacement with pure Al. Therefore, understanding the combustion and energy performance of Al-based alloys is beneficial for the development of Al-based energetic materials. Herein, the combustion and energy performance of pure Al and three Al-based alloys were comparatively investigated by means of a thermal analysis system, an ignition and combustion test apparatus, and a variety of physicochemical property characterizations. The results showed that all three Al-based alloys contained at least one intermetallic compound. Al-boron (B) and Al-magnesium (Mg)-B alloys had higher theoretical energy densities than pure Al, while Al-Mg did not. The thermal oxidation properties of all three alloys were significantly better than those of pure Al. Compared with pure Al, the three alloys showed higher burning rate, shorter ignition delays, more vigorous combustion, and higher burnout at room pressure in air. This is still true after adding AP. According to the compositions of the condensed combustion products, the possible chemical reactions during the combustion of the alloys were speculated. Grasping the combustion mechanisms of the alloys is challenging due to the relative lack of thermodynamic data on intermetallic compounds. Finally, a comprehensive comparison of the combustion processes of pure Al and alloys was made. Although the Al-Mg alloy does not have the same theoretical energy density as pure Al, the more outstanding combustion performance and fewer two-phase flow losses may make up for the gap in theoretical energy density.

Preparation and performance of hydrotalcite and montmorillonite composite as flame retardant in asphalt pavement

The increasing use of tunnel bitumen pavements has led to a corresponding rise in fire hazards. To improve the fire safety of these pavements, a novel flame retardant material has been developed, which incorporates carbonate intercalated magnesium aluminum hydrotalcite (MALC) and calcium-based montmorillonite (MMT) to form intercalation composites. The resulting MALC/MMT composite, along with 4,4’-methylenebis(isocyanate) (4,4’-MDI), was added in specific proportions to the bitumen, producing a flame retardant modified bitumen. The flame retardant performance was assessed through aging and combustion tests. The results indicate that the most effective flame retardant performance was achieved with a MALC:MMT ratio of 2:1 and a composite dosage of 5%. This study presents a straightforward and effective method for developing a novel inorganic flame retardant.

Combustion Test for the Smallest Reciprocating Piston Internal Combustion Engine with HCCI on the Millimeter Scale

Micro reciprocating piston internal combustion engines are potentially desirable for high-energy density micro power sources. However, complex subsystem functions hinder the downsizing of reciprocating piston internal combustion engines. The homogeneous charge compression-ignition (HCCI) combustion mode requires no external ignition system; it contributes to structural simplification of the reciprocating piston internal combustion engines under a micro space constraint but has not been adequately verified at the millimeter scale. The study used a millimeter-scale HCCI reciprocating piston internal combustion engine fueled by a mixture of kerosene, ether, castor oil, and isopropyl nitrate for combustion investigation. The test engine with a displacement of 0.547 cc is the smallest reciprocating piston internal combustion engine known to have undergone in-cylinder combustion diagnosis. It is observed that the HCCI combustion mode at the millimeter scale can realize stable combustion with excellent cooperation for the thermodynamic cycle under appropriate structural and operating conditions, which is essentially not inferior to those in conventional-sized reciprocating piston internal combustion engines. This finding helps the next step of scaling down reciprocating piston internal combustion engines.

Experimental and Numerical Studies on the Fire Performance of Thin Sustainable Wood-Based Laminated Veneers

Wood and wood-based products are abundantly used, especially in structural applications, due to the impetus for sustainable development. The present work helps highlight the fire performance of plywood, one of the most used wood-based laminated structural components, under three different heat fluxes of 35 kW/m2, 50 kW/m2, and 65 kW/m2. The effects on the various fire reaction properties, namely, time to ignition, heat release rate, peak heat release rate, time to peak heat release rate, time to flameout, total burn time, and mass loss, were observed and reported. The times to ignition (42.2% and 35.4%), peak heat release rate (27.7% and 18.9%), flameout (22.2% and 28.6%), burn time (10.6% and 16.1%), and residual mass (25% and 53.3%) were reduced with the increase in heat flux from 35 kW/m2 to 65 kW/m2, respectively, whereas the peak heat release (21.7% and 2.4%) and ignition temperature (6.5% and 6.6%) were observed to increase. The vertical burning test (UL-94) illustrated the plywood samples to have a V-1 rating, with self-extinguishing capabilities. A numerical predictive model has also been developed based on the Fire Dynamics Simulator to predict the time to ignition, time to flameout, and heat release rate trend along with the peak heat release rate—it is shown to have good agreement with the experimental results, with an average correlation coefficient of 0.87.

Functionalized flattened bamboo board: In-situ immersion assembly of flame-retardant, waterproof and anti-mold composite coatings

The flattened bamboo board (FB) represents a promising innovation in the bamboo industry. To address the challenges of flammability and hygroscopicity, composite coatings consisting of melamine (MEL), phytic acid (PA), cerium ions (Ce3+), and sodium laurate (La) are assembled on the FB surface through an in-situ impregnation strategy. The resulting MEL/PA-Ce3+@La FB exhibits exceptional flame retardancy. It achieves a V-0 rating in the vertical burning test (UL-94) and boasts a high limiting oxygen index (LOI) value of 38.5 %. The coated FB exhibits superhydrophobicity, evidenced by a water contact angle of 156.5°, which can be attributed to the in-situ growth of PA-Ce3+ complexes (for constructing micro/nanoscale coarse structures) and the modification with La (for reducing surface energy).This superhydrophobic surface imparts both self-cleaning and anti-mold properties to the coated FB. Moreover, the coated FB exhibits excellent mechanical stability, withstanding 36 cycles of sandpaper abrasion and tape peeling without losing its hydrophobicity. In summary, this work provides an innovative strategy for the bamboo processing industry to produce flattened bamboo boards with combined flame retardancy, superhydrophobic and anti-mold properties. Such versatility holds significant potential to facilitate the utilization of flattened bamboo boards in the construction and decorative materials industries.

Excellent flame-retardant polycarbonate composites with improved notched impact toughness via introducing imine-functionalized polysiloxane

Polycarbonate (PC) is known to suffer from damage over time, particularly in low-temperature settings besides its inherent flammability, where it can develop notches and lose its impact toughness. To address these issues, we synthesized schiff-based polysiloxane containing the benzene substituted with methoxy (referred to as PSOMe-X, X being the number of methoxy substitution on the benzene ring). Interestingly, by merely increasing the number of methoxy substitutions in PSOMe-X, the PC/PSOMe-X composites demonstrated significantly improved comprehensive performance. The PC/PSOMe-3 composite successfully passed the UL-94 (vertical burning test for Flammability of Plastic Materials for Parts in Devices and Appliances developed by Underwriters Laboratories) V-0 rating, and the limiting oxygen index (LOI) was increased to 29.9 %. This improvement was accompanied by a notable reduction in the peak heat release rate (PHRR) by 64 % and total smoke generation (TSP) by 18 %. Meanwhile the notched impact strength of the PC/PSOMe-3 composite was improved by 190 % at room temperature and 72 % at −25 °C. The mechanism for improved flame retardancy and impact tougheness for PC/PSOMe-X composites were unveiled.

Development and characteristic research on new thermal insulation and anti-permeability grouting material for tunnels in cold regions

The surrounding rock of tunnels in cold regions are susceptible to the freeze–thaw cycle resulting from the combination of low temperatures and moisture during tunnel service. The phenomenon will not only lead to the expansion of pores and fissures in the surrounding rock of the initial tunnel, but also destroy the integrity of the rock. This destruction will have a serious impact on tunnel structure and rail transit operation safety. At present, the commonly used thermal insulation measures have some problems such as maintenance difficulties, low economic efficiency, and safety hazards. Therefore, it is urgent to develop a kind of tunnel maintenance grouting material with insulation and anti-permeability, which has the characteristics of simple operation, easy preparation and application. We independently developed a composite grouting material composed of polyurethane (PU), epoxy resin (E-51) and acrylic powder (PMMA). Through the material combustion test, magnesium hydroxide was selected as the flame retardant additive. Moreover, we measured the thermal conductivity, water absorption, apparent density, porosity and strength characteristic parameters. The thermal insulation and anti-permeability characteristics of the composites were also analyzed. The results indicated that the thermal conductivity of the new composite grouting material is 6.3% lower than the PU before adding flame retardant. Compared with the PU with flame retardant, the water absorption decreased by 74.4% and the ultimate strength increased by 33.3%. For the area with an average temperature lower than − 10 °C, we recommend the ratio scheme of E-51: 3%; PMMA: 15%. For the area with high water content in the surrounding rock of the tunnel, we recommend the ratio scheme of E-51: 15%; PMMA: 3%. This study provides new ideas for material preparation and tunnel insulation methods for anti-freezing measures in tunnels during their operational period in cold regions.

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.

Vanillin-based flame retardant enables polylactic acid high-efficiency fireproof, anti-UV and oxygen barrier for food packaging

Polylactic acid (PLA) is widely known for its biocompatibility, biodegradability, and high transparency. However, it still has varied limitations such as flammability, UV sensitivity, and poor oxygen barrier properties. To address these issues, a bio-based compound, hexasubstituted cyclotriphosphazene (HVP), was synthesized by using vanillin and hexachlorocyclotriphosphazene to enhance the overall performance of PLA. The resulting PLA/HVP composites demonstrated improved mechanical strength and UV resistance. Specifically, PLA/3HVP, with a 3 wt% HVP loading, achieved a UL-94 V-0 rating and a high limiting oxygen index of 26.5 %. Cone calorimeter tests revealed that PLA/3HVP possessed a significantly longer ignition time and a lower peak heat release rate compared to pure PLA. These burning testing results indicated the enhanced fire resistance. Additionally, the oxygen transmission rate of PLA/3HVP was reduced by 81.1 % compared to pure PLA. When used as food packaging, the weight loss of mangoes covered with PLA/3HVP film was 2.2 % after 7 days, compared to 2.5 % with pure PLA film, highlighting its potential for food preservation applications.

Fabrication of CoFe‐layered double hydroxide for flame retardant and smoke suppression of silicone rubber foam

AbstractIn order to improve the flame retardancy and smoke suppression of silicone rubber foam (SRF), the CoFe‐LDH was fabricated by coprecipitation method and used as flame‐retardant ingredient in SRF. The influence of CoFe‐LDH on the flame retardancy, combustion behavior, and thermal stability of SRF was investigated. The results demonstrate that SRF containing only 1.0 phr CoFe‐LDH can pass V‐0 rating in the vertical combustion test, with a limiting oxygen index of 28.6%. The total heat release and total smoke production are 22.2% and 61.1% lower than that of SRF, respectively. Moreover, CoFe‐LDH can improve the thermal stability of SRF in the high temperature range, and the char residue at 900°C of SRF/LDH composite is obviously higher than that of pure SRF. In addition, to further understand the flame‐retardant mechanism of CoFe‐LDH, the micromorphology of the char residue and the gaseous products during heating for SRF and SRF/LDH composite were analyzed. The results indicate that CoFe‐LDH exhibits excellent flame‐retardant effects in both condensed and gaseous phases for its functions of catalysis, carbonization, and nonflammable gas release. This study provides a more efficient and convenient strategy for the flame retardant and smoke suppression research of SRF.

Synthesis of boron-based High-Energy composite microspheres via the Co-Flow microchannel method

Boron-based metastable intermolecular composites (MIC), renowned for their swift energy release and elevated thermal output, exhibit significant promise for utilization in domains such as gunpowder, propellants, and powdered fuel ramjet fuels. The work successfully accomplished the safe and efficient preparation of B/Bi2O3 microunits by utilizing co-flow microchannel technology. The choice of the optimal binder, F2603, for this system was determined by simulation analysis. The practicality of the microchannel platform was then verified using Fluent. SEM analysis demonstrated that an amount of 10 % F2603 resulted in the formation of spherical particles. In terms of physical properties, boron treated with 10 % F2603 exhibits a reduction in its angle of repose from 35° of the raw material to 15°, along with a significant enhancement in hydrophobicity. Furthermore, the MICs lower the reaction temperature of raw boron from 840℃ to 770℃. In the constant volume combustion test, the MIC output pressure increased by 33.3 %. In the constant pressure combustion test, the MIC ignition delay time was reduced from 0.7262 s to 0.5566 s. The structural characteristics of the system decrease the distance for mass and heat transmission across components, resulting in improved overall performance. The study unequivocally demonstrates the efficacy of co-flow microchannel technology in swiftly, effectively, and securely producing energetic molecules. It establishes a solid foundation for future industrial manufacturing.

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.