Flame suppression mechanism of aluminum dust cloud by melamine cyanurate and melamine polyphosphate

A bacterial cellulose composite separator with high thermal stability and flame retardancy for high-performance lithium ion batteries

Separators play a crucial role in enhancing the safety of lithium-ion batteries (LIBs); however, commercial polyolefin separators exhibit poor thermal stability and are flammable. This study investigates the use of green, environmentally friendly, and renewable bacterial cellulose as a substrate for developing a composite separator (BHM/5). The BHM/5 separator, comprising bacterial cellulose, an inorganic mineral nano-hydroxyapatite (HAP) and flame-retardant melamine polyphosphate (MPP), is fabricated via freeze drying and high-temperature pressing. The developed composite separator demonstrates superior thermal stability and excellent flame retardancy compared with commercial polyolefin separators while maintaining structural integrity at 200 °C and exhibiting self-extinguishing properties after ignition. Furthermore, the BHM/5 separator exhibits a high porosity of 74 % and a substantial electrolyte uptake of 459 %, achieving an ion conductivity of 1.44 mS/cm. As a result, the cell of the LiFePO4-Li system assembled demonstrates an initial discharge capacity of 131.35 mAh·g-1 at a current density of 1C and a capacity retention of 95.4 % after 150 cycles.

Synthesis and Characterization of Sodium Lignosulfonate-Based Phosphorus-Containing Intermediates and Its Composite Si-P-C Silicone-Acrylic Emulsion Coating for Flame-Retardant Plywood

Through the substitution reaction between 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and sodium lignosulfonate (LS), a novel phosphorus-containing sodium lignosulfonate (DAL) was successfully synthesized via the solvothermal method and used as a multifunctional flame retardant to prepare a novel silicone-acrylic emulsion (SAE) composite Si-P-C coating. The structure of DAL was determined by X-ray diffraction (XRD), attenuated total reflection infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (solid-state 13C NMR and 31P NMR). The results demonstrated that incorporating an appropriate dosage of DAL (0.9 g, 1.5 wt %) into SAE-based composite coatings enhances flame retardancy and reduces heat release and smoke production during burning. The peak heat release rate (p-HRR) decreases from 236.7 to 120.3 kW·m-2, total smoke production (TSP) decreases by 71.1%, and the flame-retardant index increases from 1.00 to 4.58. Meanwhile, the coating is transformed into a dense and nonflammable vitreous polyphosphate barrier layer during the firing process to prevent heat or mass transfer. Furthermore, the pyrolysis kinetics identify that the 3D Z-L-T model governs the coatings' pyrolysis, and the appropriate DAL makes the pyrolysis Eα climb from 300.98 to 331.30 kJ·mol-1 at 358-439 °C. Hence, this study presents a new synthesis method of multifunctional flame retardant DAL, studies the excellent properties and cross-linking mechanism of DAL-doped SAE-composite Si-P-C coatings, and explores a halogen-free, low-carbon, and clean eco-technology strategy.

Melamine induced changes in histopathology of the main organs and transcriptional levels of MAPK signaling genes in kidneys of female mice

Melamine is an important chemical raw material used in industries, which has potential health risks to animals and humans. Current research mainly focuses on the toxic effects of high-dose melamine ingestion. However, there are few reports on whether melamine at the current limited standard dose has adverse effects on various tissues and organs, and whether there are sensitive target genes for risk evaluation. For this, 24 female Kunming mice were fed 0, 1.8-, 3.6-, and 7.2- mg/kg/d melamine via drinking water for consecutive 28 days, respectively. The morphological changes of the ovarian, hepatic, and renal tissues were firstly observed. The results demonstrated that the histopathology of ovary, liver, and especially in kidney had been altered by melamine intake in female. And then, the transcriptional levels of MAPK signaling genes including p38, ERK1, ERK2, JNK1, and JNK2 in kidneys were investigated by real-time PCR. The data showed that ERK1 and p38 mRNAs expressions were up-regulated significantly by melamine, suggesting that ERK1 and p38 transcriptional levels in the kidney might to be considered as candidate targets for lower-dose melamine toxicity. This study not only provides potential targets for the diagnosis and prevention of melamine damage, but also helps to assess the health risks of the current minimum allowable levels of melamine in food and environment.

Flame retardant chloroprene rubbers with high tensile strength and elongation at break via dual cross-linked networks

The tensile strength and elongation at break of rubbers are mutually restrictive factors. Design and preparation of chloroprene rubber (CR) with high tensile strength, high elongation at break and excellent flame retardancy at the same time is challenging. Melamine cyanurate (MCA) is for the first time discovered to be a reactive flame retardant for CR. The tensile strength of C-M36 (with 3 wt% ZnO and 36 wt% MCA) vulcanizate is 2.5 times that of C-M0 (only with 3 wt% ZnO) vulcanizate, while the elongation at break of C-M36 vulcanizate is 1.3 times that of ZnO cross-linked C-M0 vulcanizate. At the same time, the limiting oxygen index of C-M36 (39%) is 1.22 times that of C-M0 (32%). FTIR and the vulcanization tests confirm that the reaction between CR and cyanuric acid occurs under the catalysis of a base (melamine), and the cyanuric acid molecules are grafted onto the molecular chain of CR. Two types of crosslinking networks are formed in CR vulcanizate, namely the traditional covalent bond crosslinks and the triple hydrogen crosslinks formed between cyanuric acid and melamine. Thus, the flame-retardant CR/MCA vulcanizate with high strength and high elongation at break is obtained. This research will strongly promote the industrial application of CR.

Melamine cyanurate served as a reactive flame retardant crosslinker for chloroprene rubbers.

Melamine induces reproductive dysfunction via down-regulated the phosphorylation of p38 and downstream transcription factors Max and Sap1a in mice testes

Melamine poisoning incidents and potential health risks raise global attention. Recent studies imply that melamine exposure is related to male reproductive dysfunction, however, the underlying mechanisms are unclear. In this study, 32 male Kunming mice were administered with 0, 12.5, 25, and 50 mg/L melamine via drinking water for 13 weeks, respectively. Sperm quality, testicular morphology, and the mRNA expression levels of MAPK family members p38, ERK5, ERK1/2, JNK1/2/3 and their downstream transcription factors GADD153, MAX, MEF2C, CREB, c-Myc, JunD, c-JUN, Sap1a, p53, ATF-2, Elk1, and Nur77 in testes were investigated. The results revealed that low-dose melamine exposure reduced sperm quality, altered the testicular histological structure, and reduced the mRNA expression levels of p38, ERK1/2, MAX and Sap1a in the testes. The p38 and phosphorylated-p38 expressions analysis further suggested that the down-regulated phosphorylation of p38 and downstream transcription factors MAX and Sap1a play key roles in male reproductive dysfunction caused by melamine. Altogether, our study provides a new insight to elucidate the underlying mechanisms by which melamine induces male reproductive toxicity, and to evaluate the health risks of melamine.

Investigation on thermokinetic suppression of ammonium polyphosphate on sucrose dust deflagration: Based on flame propagation, thermal decomposition and residue analysis

In this investigation, ammonium polyphosphate (APP) is applied to suppress the deflagration of sucrose dust. Through the systematic research on flame propagation images and temperature, decomposition behavior of powder samples and the compositions of deflagration residue, the suppression performance and mechanism of APP on sucrose deflagration are profoundly summarized. Timing diagrams show that APP contributes to reduce deflagration flame brightness, increases ignition delay time and flame fault area. The minimum inerting concentration of APP for sucrose deflagration is determined to be 8 %. From the collected deflagration flame temperature curves, it is confirmed that APP can delay peak temperature arrival time, weaken temperature fluctuation, and decrease peak values of flame temperature and temperature rising rate. Through the analysis on thermal decomposition of samples and deflagration residue, it is reflected that APP has superior composite suppression effect. It can not only absorb reaction heat, but also decrease deflagration exotherm to improve thermal stability of sucrose particles. Thus, the easily oxidized components in sucrose are protected, and deflagration intensity is effectively weakened. This work provides a new solution for prevention and suppression deflagration of dust waste in sugar industry.

Moderation of Al dust explosions by micro- and nano-sized Al2O3powder

Adding solid inertants to combustible dust is one measure to prevent and mitigate dust explosions. Al₂O₃ at four particle size distributions was used to determine the minimum ignition energy (MIE) and maximum explosion pressure (P_max) of aluminum dust and thus examine the effect of particle size on the inerting efficiency. It was interesting to observe that nano-sized Al₂O₃ powder showed excellent promise as a solid inertant, having inerting efficacy superior to that of micro-sized Al₂O₃. In addition to thermal inhibition, nano Al₂O₃ contributed to explosion moderation by binding Al particles together forming larger-sized aggregates that reduce dispersion in the dust clouds, and thus alleviate explosion hazards. Ignition sensitivity increased when micro-sized Al₂O₃ was admixed at 5 or 10% with 1000-1500 g/m³ Al mixtures, an effect apparently caused by a 20% decrease in effective particle size distribution brought on by the Al₂O₃ addition. Generally, increasing the amount of admixed Al₂O₃ increased MIE and decreased P_max of Al dust clouds, and decreasing the particle size of Al₂O₃ resulted in better inerting performance on moderating both the likelihood of the ignition and the consequence of the explosion.

Suppression of Aluminum Dust Explosion by Ca(H2PO4)2/RM Composite Powder with Core–Shell Structure: Effect and Mechanism

A Ca(H2PO4)2/RM composite powder suppressant with core–shell structure was prepared with modified red mud (RM) as the carrier and Ca(H2PO4)2 as the loaded particles, using a solvent–antisolvent process, in an attempt to suppress aluminum dust explosion more effectively. The suppression effects of the Ca(H2PO4)2/RM composite powder suppressant for aluminum dust flame propagation and for explosion overpressure were tested in a vertical glass tube test apparatus and a 20 L explosion vessel. The results show that the Ca(H2PO4)2/RM composite powder suppressant was more effective in suppressing aluminum dust flame propagation and explosion overpressure than either Ca(H2PO4)2 or RM powder alone. Finally, the suppression mechanism of the Ca(H2PO4)2/RM composite powder suppressant was analyzed. On the one hand, a large amount of burning heat was absorbed through the decomposition of Ca(H2PO4)2 and the melting phase transformation of the decomposition product; on the other hand, the strong isolation provided by the RM helped limit flame propagation. The strong adsorptivity of RM allowed this material to adsorb the radicals from the explosion reaction perfectly.

Suppression of wood dust explosion by ultrafine magnesium hydroxide

The suppression effects of ultrafine Mg (OH)₂ powders with different particle sizes and mass fractions on explosion flame of wood dust are experimentally studied in a half-closed vertical experimental duct. Flame structures and characteristic parameters, including flame light emission images, propagation velocity, temperature, during the flame propagation of wood dust explosion are recorded by high-speed photography and fine thermocouple. Thermal decomposition behaviors of wood dust and Mg(OH)₂ powders are studied using synchronous thermal analyzer. Chemical structures of residual dust samples after the explosion are characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The experimental results show that explosion flame of wood dust is obviously suppressed by physical and chemical effects of Mg(OH)₂ powders, and the suppression effect of nano-Mg(OH)₂ is better than that of micron-Mg(OH)₂ under same mass fractions. By analyzing multiple characteristics of nano-powders, the advantages of nano-Mg(OH)₂ over micron-powders are further investigated.

Melamine and cyanuric acid in foodstuffs from the United States and their implications for human exposure

We determined the concentrations of melamine, ammeline, ammelide, and cyanuric acid in meat, fish and seafood, cereal products, beverages, cooking oil, and vegetables (n = 121) collected from Albany, New York, United States. In addition, food packaging (n = 24) and animal feed (n = 12) were analyzed to determine the sources of melamine and its derivatives in foods. Among the six categories of foods analyzed, median concentrations of ∑melamine (sum of melamine and its three derivatives) in meat (23.6 ng/g fresh weight; fw) and cereal products (20.9 ng/g fw) were significantly (p < 0.05) higher than those in other food categories (<5.03 ng/g fw). Cyanuric acid and melamine were the major compounds, accounting for 51% and 26% of the total ∑melamine concentrations, respectively. ∑melamine was found ubiquitously in food packaging (median: 36.2 ng/g fw) and animal feed (56.5 ng/g fw), which are two important sources of melamine found in foodstuffs. The median estimated daily dietary intakes (including concentrations reported for dairy products in our previous study) of melamine and cyanuric acid were in the ranges of 13.4-72.7 and 75.4-347 ng/kg body weight/day, respectively, for various age groups. Dairy products, cereal products, and meat were major sources of dietary melamine (~76%) and cyanuric acid (~95%) exposure. The calculated hazard quotients for dietary exposure to melamine and cyanuric acid were well below 1.0, which suggested minimal risk from current exposures.