Flammability Tests Research Articles

Exploring the thermal conductivity of green filamentous algae natural fibre: an experimental investigation

Abstract The use of non-renewable resources in thermal insulation has significant environmental impacts. Another major problem faced by the ecosystem is the invasive growth of water weeds. Making sustainable products from waterweeds helps to prevent its overgrowth that disrupts the balance of the ecosystem. This study explores the viability of Green Filamentous Algae (GFA) as an eco-friendly thermal insulation material. GFA was collected from water bodies, cleaned, and processed into two forms: untreated (UTD) and alkali-treated (TD). Experimental investigations were conducted to evaluate the physical properties of GFA, including density, self-ignition temperature, water absorption, moisture absorption, flammability, and thermal conductivity. Results show that the untreated GFA had a density of 402.52 kg/m³, while the treated GFA exhibited a slightly lower density of 392.32 kg/m³. The self-ignition temperature for both untreated and treated GFA was measured between 275°C and 280°C. The water absorption capacity was higher in treated GFA (654.7%) compared to untreated (493.83%). Moisture absorption capacity was 15.14% for untreated GFA and 17.47% for treated GFA. Flammability tests revealed a burning rate of 20.026 mm/min, placing GFA in the combustibility classification 1 (CC1). Thermal conductivity values were found to be 0.308 W/mK (UTD) and 0.273 W/mK (TD), making treated GFA a promising candidate for sustainable insulation applications. This study demonstrates the potential of GFA as a bio-based insulation material and highlights future improvements to enhance its moisture resistance and thermal performance.

Anti-flammable, anti-fouling, anti-bacterial treatment of cotton fabrics with MOF-based hybrid coatings for highly efficient oil-water separation

A flame-retardant and hydrophobic coating was deposited on the surface of the cotton fabric via a two-step spray deposition technique. Specifically, the coating was composed of flame retardant components (guanidine phosphate) and hydrophobic species (Ti-MOF and bis(3-aminopropyl)-terminated poly(dimethylsiloxane) (PDMS)) and crosslinked with glutaraldehyde. The limiting oxygen index (LOI) of the coated cotton fabrics increased from 18.0 % to 32.0 % (15#) and 26.5 % (15#-Ti-PDMS) relative to that of the original cotton fabric, and the coated cotton fabrics also self-extinguished in the UL-94 flammability test. Compared with that of the original cotton fabric, the PHRR of the coated fabrics was significantly lower, reaching 80 %. The coated cotton fabrics (15# and 15#-Ti-PDMS) had good antibacterial properties against Staphylococcus aureus (S. aureus). In addition, 15#-Ti-PDMS had high hydrophobicity, good washing and abrasion resistance and good water-oil separation performance. Its water contact angle was 146°. The water contact angle remained above 130° after 10 laundering cycles and 50 scratch cycles. Even under strongly acidic and basic conditions, the water-oil separation efficiency of 15#-Ti-PDMS was greater than 99 %, and it was still greater than 90 % after 10 cycles. Therefore, a simple and effective method for preparing flame-retardant, hydrophobic and antibacterial cotton fabrics was developed.

Comparative study of virgin and recycled polyethylene terephthalate and polypropylene intermingled thermoplastic composites

AbstractIn this study, a comparative analysis of the use of recycled PET (R‐PET) in synthetic and natural fiber blended composites was made. PET, R‐PET, and PP yarns were folded with reinforcing fibers by commingling technique and then fabrics were prepared using weaving technology. Hot compression molding technology was used for composite fabrication. Tensile and impact characterization revealed the significant influence of reinforcing and TP fibers on mechanical properties. R‐PET matrix glass fiber reinforced composites exhibited 41.77% higher tensile strength than virgin PET and 20.41% higher than PP. In terms of tensile strength for linen reinforced samples, R‐PET shows an impressive 181% improvement over virgin PET and 154% over PP. According to the drop weight test results, glass fiber reinforced R‐PET matrix sample exhibited a peak load value 53% higher than that of the virgin PET matrix, although it was 9.47% lower than the PP matrix. In linen fiber reinforced samples, R‐PET demonstrated a 57.73% improvement over virgin PET but lower by 9.47% compared to the PP matrix. During this time, DSC, TGA, FTIR, and flammability tests were also performed on the composite samples. The results showed that R‐PET has easy processability as a matrix material and provides better wetting of the reinforcing fibers. For this reason, it has been shown that R‐PET matrix samples provide better mechanical properties than both PET and PP matrix samples. It has also been determined that R‐PET is a more suitable matrix material compared with natural fiber reinforced composites.Highlights Commingled yarns were used for preparing composites. R‐PET yarns were used as matrix in preparing glass and linen reinforced composites. R‐PET was compared with virgin PET and PP yarns. R‐PET showed great potential in easy preparation of TP composites. Composites made with R‐PET showed improved thermal and mechanical properties.

Flammability and Mechanical Testing of Sandwich Composite for Rolling Stock Structural Applications

Components made of composite materials are being increasingly used in the construction of rolling stock. Currently, the use of components made of composite materials as train structural elements is increasingly being considered. Non-structural components made of composites are most often found inside rail vehicles (e.g., the interior lining), while structural components made of sandwich composite materials can be used for the roof, sidewalls, and underframe constructions. This article provides a description of an innovative sandwich composite developed for a metro’s underframe, as well as the production process and preparation of the composite specimens. The main parts of the work are flammability and mechanical (static and fatigue) tests of the innovative sandwich composite. The scope of the flammability tests included the testing of the fire properties using the radial plate method, the optical density of smoke, and the content of toxic gases. The mechanical strength of the sandwich composite was examined during a flexural (three-point bending) test and a fatigue strength under a given dynamic load. The results presented in the article are very significant, both in terms of flammability and the mechanical strength tests. In order to produce large-size train components, appropriately large patches of component layers of the composite are required; this may pose production problems.

Effects of Anchovy, Mussel, and Shrimp Powders on the Flame Retardancy of Bacterial Cellulose

ABSTRACT This study aims to fabricate bacterial cellulose with improved flame retardancy by applying anchovy, mussel, and shrimp powders. The elemental analysis confirmed that raw marine powders contained nitrogen and sulfur elements which could play important roles in enhancing the flame retardancy of bacterial cellulose. Thermogravimetric analysis revealed the improved thermal stability of bacterial cellulose following entrapping and crosslinking of the marine powders. The fabricated bacterial celluloses with marine powders had similar levels of flame retardancy as that of bacterial cellulose treated with a commercial flame-retardant, sodium metasilicate nonahydrate, which was confirmed by the vertical flammability test and limiting oxygen index. The char morphology analysis revealed intumescent char on the surface of the samples, confirming the effect of marine powders on the flame retardancy of bacterial cellulose. Moreover, the marine powders were entrapped and crosslinked with bacterial cellulose nanostructures, and the chemical and crystalline structures of bacterial cellulose were retained. This study proposes an efficient method to improve the flame retardancy of bacterial cellulose by introducing marine powders via the combined entrapment and crosslinking method.

Flame retardant epoxy vitrimers employing a Meldrum's acid-functionalized and phosphorus-containing bisphenol compound as the cross-linking agent for conventional epoxy

In addition to recycling and reprocessing features, designs of vitrimers possessing critical properties required for conventional cross-linked polymers are of interest. In this work, a newly designed Meldrum's acid (MA)-functionalized and phosphorus-containing bisphenol compound (P-MADV) compound is synthesized. Employing P-MADV as a curing agent, simultaneous formation of permanent and dynamic covalent linkages through one-pot reaction has been achieved in formation of flame retardant epoxy resin vitrimers. The newly synthesized P-MADV compound is an effective cross-linking agent for commercially-available epoxy resins for synthesis of flame-retardant epoxy vitrimers through the conventional cross-linking conditions and processes. The cross-linked epoxy vitrimer passes the flame test under UL 94V-0 specification contributed from the phosphorus-containing groups. The flame retardant vitrimer also exhibits a storage modulus of 1.2 GPa at 50 °C and a Tg (tanδ peak) of 185 °C, which are comparable to the values found with conventional phenolic novolac-cross-linked epoxy resin (storage modulus: 1.6 GPa; Tg: 155 °C). Without addition of catalysts for dynamic bond exchanging reaction, the cross-linked epoxy vitrimer shows stress relaxation time of 397 s at 230 °C and an activation energy of stress relaxation of 97.8 kJ mol−1. The dynamic features warrant the epoxy vitrimer being recyclable under thermally pressing at 230 °C and 16 MPa for 1 h. The recycled samples exhibit thermal and mechanical properties being comparable to the pristine resin. This work has demonstrated an attractive approach for preparation of flame retardant epoxy resin vitrimers in viewpoints of both manufacturing processes and resins properties.

Electromagnetic interference shielding, mechanical, and flame retardant behaviors of Ti3C2Tx-MXene/glass fabric epoxy hybrid composites

This study investigates the manufacturability and electromagnetic shielding effectiveness (EMI-SE) of Ti3C2Tx/MXene-coated glass fabric laminated composites for aerospace applications. MXene-coated fabrics were produced using a dip-coating method. The effects of varying dipping counts (5 and 10) and different configurations of fabric arrangements on the EMI-SE of the composites in the X-band range (8.2–12.4 GHz) were investigated. Glass fabrics with 5 and 10 dips showed average surface resistances of 38.56 Ω/sq and 23.17 Ω/sq, respectively. In both the 5- and 10-dip composite sets, the total EMI-SE increased with the number of MXene-coated glass fabric layers in the composite. The 5MXC5 and 10MXC5 specimens, with conductive fabric in all layers, had average total shielding effectiveness (SET) of −18.75 dB and −23.21 dB, respectively. These values are 147.05 % and 205.80 % higher than the neat glass fiber-epoxy composite (C1). Flammability, bending, ILSS, and hardness tests were conducted on these composites. Increasing the MXene content reduced the burning rate, with 10MXC5 exhibiting a 26.31 % lower burning rate compared to C1. However, higher MXene content slightly decreased bending and ILSS values. Optical microscope examination of the fracture surfaces revealed that this decrease was due to delamination damage.

Dynamic mechanical analysis, flammability and quasi-static test on Kevlar/basalt-epoxy hybrid composite laminates

Dynamic mechanical analysis, flammability and quasi-static test on Kevlar/basalt-epoxy hybrid composite laminates

Mechanical Properties and Flammability Analysis of Wood Fiber Filled Polylactic Acid (PLA) Composites Using Additive Manufacturing

ABSTRACT Natural fibers, such as wood fibers, can substitute for synthetic fibers in various applications due to their low environmental impact, cost-effectiveness, and outstanding mechanical properties as rapid-growing materials and renewable resources. This paper aims to investigate the mechanical properties of 20% wood fiber as a reinforcement material in polylactic acid (PLA) using an additive manufacturing approach. The samples were fabricated using 3D printing techniques. The relevant parameters included the orientation of printing in X, Y, and Z directions, with the percentage of infill set to be 100%. The findings indicated that bio-composites and their adopted printing orientations confirmed the significant effects on the mechanical properties. Pure PLA possessed superior properties in all directions compared to wood/PLA. The highest values were 50.33 MPa for tensile strength and 94.36 MPa for flexural strength, both achieved in Y orientations. However, composites showed an improvement in tensile and flexural moduli in X orientation with 1395.40 MPa, and 2937.72 MPa for Young and flexural modulus, respectively. In the flammability test, wood/PLA bio-composites were ignited easily with reduced smoke production compared to the neat PLA. Wood/PLA bio-composites exhibited high stiffness, and their mechanical properties were influenced by many factors, such as percentage of weight fraction, wood type, and printing orientations.

Development of sustainable flame-retardant bio-based hydrogel composites from hemp/wool nonwovens with chitosan-banana sap hydrogel

Flame retardant (FR) finishing is crucial for developing protective textiles, traditionally relying on halogen, phosphorus, and phosphorus-nitrogen chemistries, which have limitations like toxicity and fabric stiffening. Innovative approaches such as nanotechnology, plasma treatments, and natural resource-based finishes are being explored to achieve sustainable FR textiles. This study presents the development and comprehensive characterization of hydrogel composites made from nonwoven fabrics composed of various hemp/wool blends (70/30, 80/20, and 90/10). The nonwoven fabrics were treated with a chitosan hydrogel incorporating banana sap to enhance their properties. Scanning electron microscope (SEM) examined the surface morphology and structural integrity of the composites, while Fourier transform infrared spectroscopy (FTIR) identified chemical interactions and functional groups. Differential scanning calorimeter (DSC) revealed thermal properties, water absorbency tests demonstrated hydrophilicity, mechanical testing assessed tensile strength, and vertical flammability tests evaluated fire resistance. SEM and FTIR revealed a successful coating of chitosan hydrogel with banana sap inclusions onto the hemp/wool nonwoven fabric, forming a composite structure. DSC analysis suggests higher chitosan content and hemp fiber ratio (like 70/30) lead to increased thermal stability of hydrogel composites. Higher chitosan concentrations in the hydrogel significantly improve the flame-retardant properties of hemp/wool nonwoven fabrics by reducing char length and enhancing protective char layer formation, with banana sap further promoting charring. These results indicate that the developed composite can be effectively used in flame-retardant textiles.

Multi-scale ceramic self-extinguishing fire retardant coating based on scale armor layer

Currently, designing an efficient and broadly applicable (suitable for foams, wood, steel, plastic) fire-retardant coating remains a significant challenge. This work introduces a multi-scale micro-nanostructured hybrid fireproof coating. The composite features basic fillers that include ceramic glass microspheres, while its interior comprises an inorganic aerogel made from nano black phosphorus and silicon dioxide nanofibers for reinforcement, with a phosphorus-containing acrylic polymer serving as the base. Upon exposure to elevated temperatures, the coating’s surface transforms into a solid char layer resembling scale armor, effectively functioning as a robust fire barrier to protect the underlying substrate. The coating treated rigid polyurethane foam achieved an exceptionally high Limiting Oxygen Index of 45 %, outperforming comparable products. In terms of flame retardancy and smoke suppression, this innovative coating significantly reduces Peak Heat Release Rate (50.3 %) and Total Smoke Production (54.9 %). Notably, it exhibits rapid self-extinguishing capabilities within seconds during butane flame tests at temperatures exceeding 1100 °C, demonstrating remarkable resistance to high-temperature flames. This research offers a straightforward methodology for developing high-performance fireproof coatings, with promising applications across various industrial settings.

Influence of Plant Additives on Antimicrobial Properties of Glass-Fabric-Reinforced Epoxy Composites Used in Railway Transport.

The aim of this research was to explore the innovative use of natural additives, containing phytochemicals with proven antimicrobial effects, in the production of epoxy-glass composites. This study was based on information regarding the antimicrobial effects of phytochemicals present in Cistus incanus, Zingiber officinale, and Armoracia rusticana. The additives were subjected to a gas chromatography (GC) analysis to determine their composition, and, subsequently, they were used to prepare resin mixtures and to produce epoxy-glass composites. Samples of the modified materials were tested against E. coli, S. aureus, and C. albicans. In addition, flammability and durability tests were also performed. It was found that the strongest biocidal properties were demonstrated by the material with the addition of cistus, which caused a reduction of microorganisms by 2.13 log units (S. aureus), 1.51 log units (E. coli), and 0.81 log units (C. albicans). The same material also achieved the most favorable results of strength tests, with the values of flexural strength and tensile strength reaching 390 MPa and 280 MPa, respectively. Public transport is a place particularly exposed to various types of pathogens. Currently, there are no solutions on the railway market that involve the use of composites modified in this respect.

Enhanced flame retardancy and thermal insulation of epoxy resins composites incorporated with ammonium polyphosphate and ionic liquids loaded CuO-ZnO hollow spheres

Epoxy resin, as a thermosetting polymer material with good performance, has been limited in application due to its high flammability. In this investigation, porous CuO-ZnO hollow spheres (CZHS) were prepared by a hydrothermal method. By incorporation with ionic liquids loaded CuO-ZnO hollow spheres (CZHS@Ils) and ammonium polyphosphate (APP) into epoxy resin (EP) matrix, a new composite flame retardant material, named as EP/7.5APP/1.5CZHS@ILs, was developed for improvement of their thermal insulation and flame retardancy. The thermal conductivity of EP/7.5APP/1.5CZHS@ILs was measured to be 0.0197 W m −1 K −1, which is lesser than that of APP incorporated epoxy resin (EP/APP), demonstrating good thermal insulation capability. The flame retardancy were assessed using the limiting oxygen index (LOI) test, the Vertical flame testing (UL-94) test, and the cone calorimeter (CC) test. The results obtained from LOI test show that the EP/7.5APP/1.5CZHS@ILs has good flame retardancy with a LOI value of up to 28, better than that of pure EP which has a LOI value of 19.2. Moreover, a V-0 level of the EP/7.5APP/1.5CZHS@ILs was observed from the UL-94 test. The peak heat release rate (PHRR) was reduced to 257.9 kW m−2, which is 74.8 % lower than that of the pure EP. Such results are attributed to the synergy effect of CZHS@ILs and APP which offers the epoxy resin excellent flame retardancy. Taking advantages of the excellent thermal insulation, flame retardancy and better mechanical properties, the as-resulted EP/7.5APP/1.5CZHS@ILs may hold great potential for future thermal insulation and flame-retardant applications of energy saving building.

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.

Characterization of fresh biowastes for biogas production and environmental health in Niger Delta, Nigeria

BackgroundEnvironmental pollution is a public health problem in Niger Delta, Nigeria. Therefore, the aims of the present study were to: identify the major fresh biowastes in Bayelsa State, Niger Delta; quantify the biogas yields from mono-digestion and co-digestion of identified biowastes; determine the first day of biogas production during hydraulic retention time; assess pH variations during anaerobic digestion; and evaluate biogas flame colours.MethodsFifteen communities in Bayelsa State were randomly selected, and on-the-spot assessment and quantification of the biowastes found in each community were carried out daily per week. Mono-digestion of 20 kg of each biowaste and co-digestion of 10 kg of animal waste with 10 kg of plant waste were carried out respectively under anaerobic conditions. Cumulative biogas yield and pH were measured using a pH meter and weighing scale respectively. Biogas flame colours during combustion were visually assessed.ResultsExactly 120.61 metric ton of fresh biowastes was found to be generated per week in Bayelsa State, Niger Delta. Industrial biowastes were the highest [47.6 tonnes, (39.46%)], followed by abattoir biowastes [33 tonnes (27%)], market and roadside sellers biowastes [25.5 tonnes (21.14%)], and farm biowastes [14.51 (12.03%)]. Biogas yields (kg) were: 0, 0, 0, 0, 0, 17, 14, 2, 18, 16, 17, 15 and 1 kg for palm oil mill effluent (POME), orange fruit waste (OFW), pineapple peels (PP), plantain peels, cassava mill effluent (CME), rumen digesta (RD), cow dung, sewage, PP-RD, plantain peels-cow dung, POME-rumen digesta, OFW-cow dung, and CME-sewage respectively. The first day of biogas production for RD, cow dung, sewage, PP-RD, plantain peels-cow dung, POME-RD, OFW-cow dung, and CME-sewage was on the 6th, 32nd. 56th, 1st, 26th, 18th, 25th, and 60th day of hydraulic retention time respectively. A dominant blue flame colour mixed reddish yellow or orange flames were found during biogas combustion. A slight increase in pH was found in all the biodigester media.ConclusionsIn the present study, a variety of biowastes yielding various quantities and qualities of biogas were identified in Bayelsa State, Niger Delta. The study’s findings have provided evidence-based data that might be explored as a road map and catalyst for policy creation against inadequate biowaste management and as sustainable alternatives to the expensive liquefied petroleum gas. The potential of current research study to be scaled up for commercial use is implicated in the present study.

Fabrication of Laminated Electrospun Fire˗Resistant Phosphorylated Poly(Vinylalcohol) Membrane for Enhanced Firefighter Safety

AbstractThe current study focuses on the creation of breathable and fire˗retardant fibrous membranes using phosphorylated poly(vinylalcohol) (PPVA) via the electrospinning method, with a specific interest in their application for structural firefighter clothing. Poly(vinylalcohol) (PVA) was phosphorylated to enhance its inherent flame resistance. Optimization of reaction conditions, including time and temperature, was conducted to achieve a solution suitable for electrospinning. The flame resistance of PPVA was confirmed through vertical flammability tests, with thermogravimetric analysis indicating a significant increase in carbonaceous char formation during PPVA decomposition compared to unmodified PVA. The limiting oxygen index also exhibited a notable increase from PVA to PPVA. Furthermore, the study established optimal operating conditions for producing uniform fibers, considering parameters such as polymer concentration, feed rate, tip to collector distance, and applied potential difference. The PPVA membrane demonstrated superior water vapor transmission rates compared to PVA, indicating enhanced breathability. The entire fabrication process utilized an environmentally friendly water‐based solvent. Additionally, a moisture‐cum‐thermal barrier layer (MCTB) was developed by laminating the PPVA fibrous membranes with microporous polytetrafluoroethylene and further with needle punch‐spunlaced OPAN fabric. Experimental assessments of the MCTB layer revealed satisfactory breathability and thermal performance, surpassing the standard requirements of 35 cal/cm2 for structural firefighting configuration.

Phytic acid-induced durable fire-proof and hydrophobic complex coating for versatile cotton fabrics.

To address the current development requirements for multifunctional cotton fabrics, a phytic acid-induced flame-retardant hydrophobic coating containing nitrogen (N), phosphorus (P), and silicon (Si) was grafted on the surface of cotton fabrics using a facile step-by-step immersion method. The limiting oxygen index value improved to 31.2%, decreasing to 26.7% after 50 laundering cycles, while the fabric remained self-extinguishing effect in the vertical flammability test and showed a water contact angle of 126.1°. Cone calorimetry test showed that the modified fabric could not be ignited at the irradiation heat flux of 35kW/m2. When the irradiation heat flux was raised to 50kW/m2, there was a significant decline in the peak heat release rate of the modified cotton fabric, which decreased by 43.2% to a remarkably low value of 114.0kW/m2, indicating excellent flame-retardant properties. The analysis of the flame-retardant mechanism uncovered that the modified coating exhibited a significant dual flame-retardant mechanism involving both the gaseous phase and the condensed phase. Additionally, the oil-water separation tests revealed that the separation efficiency of the modified cotton fabrics was as high as 97.1% and remained around 96% after 10cycles, which made them reusable for the clean-up of hazardous chemicals.

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.

Experimental and numerical studies of NO reduction by ammonia in different methane flame positions

Blending ammonia with methane for combustion can reduce carbon emissions and improve the flame characteristics of ammonia combustion. However, blending ammonia with methane can easily lead to high concentrations of NOx emissions. This study investigates the impact of different ammonia and methane blending methods on the flame structure and NOx emission by experiments and CFD numerical simulation. The results indicate that simultaneous injection of ammonia and methane through the central fuel tube significantly alters the combustion flame structure and leads to high concentrations of NOx emission. As the ammonia ratio increases, the flame structure transitions from a bright flame to a layered flame with an inner yellow conical small flame surrounded by a light-colored outer flame. When the ammonia ration increases from 0 % to 20 %, NOx emission increase from 15 ppm to 323 ppm, nearly 22 times higher. When ammonia is injected into the methane flame from flame side, the flame above the injection position appears as an orange flame, and a significant reduction in NOx emission is obtained. When the ammonia ratio is 20 % and injected at heights of 20 mm 40 mm, and 60 mm above the fuel exit, the outlet NOx concentrations are 183 ppm, 140 ppm, and 153 ppm respectively, this represents reductions of 43.3 %, 56.6 %, and 52.6 %, respectively. The numerical simulation results indicate that the injection of ammonia leads to the formation of higher concentrations of NH2 and super-vapor H2O, resulting in an orange color flame. The gas temperature and oxygen concentration play a crucial role in NOx emissions. NOx emission is lowest when ammonia is injected into the higher temperature, lower oxygen environment at 40 mm.

A system with efficient flame retardant and antibacterial properties for the development of exceptional durable functional cotton fabrics

Phosphorus-based flame retardants are widely employed in the study of flame retardancy for cotton fabrics due to their halogen-free nature and high efficiency. The addition of nitrogen and other elements can further enhance flame retardant properties through synergistic effects. However, the synthesis of flame-retardant multifunctional additives based on phosphoramidic ammonium salts has been scarcely reported. In this study, a halogen-free and formaldehyde-free phosphoramidite ammonium salt was synthesized as a synergistic flame retardant multifunctional additive. This compound, with phosphorus as the primary flame retardant element and a nitrogen-containing guanidine group, was used to modify cotton fabrics. The treated fabrics exhibited enhanced flame retardant and antibacterial properties. Notably, cotton fabrics treated with a 17.9 % weight gain showed a damaged length of 4 cm in the vertical flame test, and the LOI value increased to 41.5 %, remaining at 27.3 % even after 50 washing cycles. The results of the cone calorimeter test (CCT) revealed that the peak heat release rate (PHRR) and total heat release (THR) of treated cotton were 30.35 kW/m2 and 5.46 MJ/m2, respectively, representing reductions of 87.04 % and 36.07 % compared to untreated cotton. Physical performance tests indicated only a slight decrease in the strength and whiteness of the cotton fabrics, while softness increased after treatment. Moreover, the treated cotton fabric exhibited excellent antibacterial properties, with antibacterial rates of 99.26 % against E. coli and 98.54 % against S. aureus.