Fire retardant mechanism of PA66 modified by a “trinity” reactive flame retardant

A “trinity” reactive flame retardant (TRFR) was successfully synthesized from pentaerythritol, phosphorus oxychloride (POC), and p-aminobenzoic acid in two steps. The flame retardant polyamide 66 (PA66) was prepared by polymerizing TRFR with PA66 salt; the structural changes during the heating process, the morphology, and composition after combustion of flame retardant PA66 were analyzed. Fourier transform infrared, scanning electron microscopy, and Raman analysis results showed that the TRFR structure on flame retardant PA66 decomposed at the temperature of 25–550 °C, forming compounds containing phosphorus, carbon, and nitrogen, respectively. These compounds promoted the dehydration of the combustion surface to form char, increased the char formation rate, and produced nonflammable gases, resulting in a dense, porous, noncombustible carbon layer. The carbon layer may isolate oxygen and heat, thereby preventing the polymer from sustainability of combustion. When the TRFR salt content was 3%, TRFR flame retardant PA66 has excellent flame retardancy with limited oxygen index value of 29 and UL94 of V-0 rating. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47488.     

Preparation of organic–inorganic intumescent flame retardant with phosphorus,nitrogen and silicon and its flame retardant effect for epoxy resin

According to the requirement of fire life cycle assessment (LCA), chitosan ethoxyl urea phosphate (CEUP), an organic–inorganic intumescent flame retardant (IFR) containing phosphorus, nitrogen, and silicon, was synthesized by the reaction of chitosan, phosphorus pentoxide, and urea. FTIR, ¹H NMR, SEM, and XRD were employed to characterize the compounds. As a result, CEUP was successfully prepared with higher thermal stability, favorable to enhance fire resistance. Combined with OMMT, the organic/inorganic IFR was applied as EP flame-retardant agents. The combustion behavior of EP composite was investigated by LOI, UL-94, CCT, SEM, TGA, and TG-IR. It was observed that using 15% CEUP and 3% OMMT (EP3), LOI value reached 34.8% and passed the UL-94 V-0 rating, while THR and TSP of EP composite reduced 65 and 72% compared with pure EP. The char residue of EP composite was up to 22.4%. The thermal decomposition mechanism was traced from 100 to 600°C by TG-IR. It was suggestive that CEUP decomposition commenced at 100°C to create phosphoric acid and sublimation of urea occurred at 300°C. EP3 exhibited a strong thermal stability, namely even at 600°C, the volatile substances were detectable. Dense and expanded carbon layer was confirmed in SEM images.     

Burnin issues — choosing the right flame retardant

Nearly all plastics are based on hydrocarbons and are combustible.For use where safety is essential — such as aircraft, building/construction, public transport and increasingly in housings for electrical/electronics equipment — they must be rendered incombustible, or at least difficult to ignite and burn. Certain thermoplastics, such as PVC and modified PPO, are to some extent inherently resistant to burning, but may need to be supplemented by additives. John Murphy reviews the options.     

Electrochemical properties of nanometer-sized 0.6Li2MnO3·0.4LiNi0.5Mn0.5O2 composite powders prepared by flame spray pyrolysis

Nanometer-sized 0.6Li₂MnO₃·0.4LiNi_0.5Mn_0.5O₂ composite cathode powders are prepared directly by high-temperature flame spray pyrolysis. The precursor powders and the powders post-treated at 800 °C exhibit mixed-layered crystal structures comprising layered Li₂MnO₃ and layered LiNi_0.5Mn_0.5O₂ phases. The discharge capacity of the precursor powders decreased from 193 mAh g^?1 to 96 mAh g^?1 by the 9th cycle, corresponding to a capacity retention of 49.7%. Post-treatment at 800 °C increases the capacity retention of the post-treated composite powders to 94.6% after 50 cycles, corresponding to a decrease in the discharge capacity from 225 to 213 mAh g^?1. The post-treated composite powders that contain a high amount of the Li₂MnO₃ phase have a high initial discharge capacity and good cyclability.     

Synthesis of a novel organic–inorganic hybrid flame retardant based on Ca(H2PO4)2 and hexachlorocyclotriphosphazene and its performance in polyvinyl alcohol

To optimize the poor thermal stability and flammable of polyvinyl alcohol (PVA), a novel environmental-friendly organic–inorganic hybrid flame retardant Ca(H₂PO₄)₂@HCCP was successfully designed and synthesized via surface treatment technology and used to advance the flame retardancy of PVA. The thermogravimetric analysis implied that Ca(H₂PO₄)₂@HCCP can enhance significantly the thermal stability and char forming ability of PVA. Combustion results demonstrate that Ca(H₂PO₄)₂@HCCP could effectively suppress the melt dripping of PVA in the process of combustion. The presence of Ca(H₂PO₄)₂@HCCP can sharply reduce peak heat release rate and the total heat release up to 75% and 22.9%, respectively, in the microscale combustion calorimeter measurement. The results manifested that Ca(H₂PO₄)₂@HCCP could endow PVA with superior flame retardancy. Moreover, char residues analysis explained the flame retardant mechanism in condensed and gas phase, which is mainly attributed to the strong catalytic char formation, free radical trapping, and gas barrier effect. Therefore, the green flame retardant has great applications prospect in fire safety.     

Phase equilibria in the CaO·SiO2Na2O·SiO2Na2O·Al2O3·6SiO2 system

Equilibrium phase relations in the system CaO·SiO₂Na₂O·SiO₂Na₂O·Al₂O₃·6SiO₂ at 40–80 wt% Na₂O·Al₂O₃·6SiO₂ composition range have been experimentally studied at temperatures between 800 °C and 1200 °C. The liquidus temperature was determined with differential scanning calorimetry. The equilibrated samples were quenched with pressurized nitrogen, and examined with electron probe X-ray microanalysis and X-ray diffraction for identification of microstructure and phase relations. Five primary phase fields, CaO·SiO₂, Na₂O·SiO₂, Na₂O·2CaO·3SiO₂, 2Na₂O·CaO·3SiO₂ and Na₂O·Al₂O₃·6SiO₂ were established. The ternary eutectic point of CaO·SiO₂, Na₂O·2CaO·3SiO₂ and Na₂O·Al₂O₃·6SiO₂ was determined to be at 1030 °C with the composition of 29.0 wt% CaO·SiO₂, 12.0 wt% Na₂O·SiO₂ and 59.0 wt% Na₂O·Al₂O₃·6SiO₂. Peritectic reaction of Na₂O·2CaO·3SiO₂, 2Na₂O·CaO·3SiO₂ and Na₂O·Al₂O₃·6SiO₂ occurred at 930 °C with the composition of 13.0 wt% CaO·SiO₂, 29.0 wt% Na₂O·SiO₂ and 58.0 wt% Na₂O·Al₂O₃·6SiO₂. The liquidus surface projection of the ternary system has been constructed in the composition region important for the bottom ash application.     

Novel epoxy/expandable graphite halogen-free flame retardant composites−preparation, characterization, and properties

In this work, expandable graphite (EG) was grafted using a coupling agent, 3-isocyanatopropyltriethoxysilane (IPTS). EG has a -O-C₂H₅ (-OEt) functional group which reacts with a polymer matrix through the sol-gel reaction. EG was functionalized by the coupling agent to form a covalent bonding between organic and inorganic phases, increasing the compatibility between the fillers and polymer, and thereby enhancing the thermal stability of the composites. FT-IR and X-ray photoelectron spectroscopy (XPS) were adopted to characterize the grafting reaction between IPTS and EG. Thermogravimetric analysis (TGA), the derivative of thermogravimetric weight (DTG) and the difference between the thermogravimetric weights (TG△) were employed to calculate the thermal stability of the composites. The limiting oxygen index (LOI) was utilized to classify the composites by flame retardancy. A scanning electron microscope (SEM) was applied to observe their morphology, and the behavior of expansion was discussed after the materials were burnt. TGA/MS was used to analyze the gas products during thermal degradation. The results demonstrate that functionalized EG can improve the thermal stability of composites and increase the flame retardancy.     

Soft chemistry preparation of layered Al0.3V2O5·5H2O

A novel layered compound Al_0.3V₂O₅·5H₂O was successfully prepared and characterized using powder X-ray diffraction, Thermal analysis, scanning and transmission electron microscopes. The new layered Al_0.3V₂O₅·5H₂O has like-nanowires shape and the layered structure was stable until 400 °C. At higher temperature (500 °C), it decomposes to orthorhombic Al_xV₂O₅ and triclinic AlVO₄.     

A Study of Ionic Conductivity of Glasses in the PbCl2–PbO · B2O3 and PbCl2–2PbO · B2O3 Systems

The steady-state electrical conductivity of oxychloride glasses in the PbCl₂–PbO · B₂O₃ and PbCl₂–2PbO · B₂O₃ systems is investigated. In the temperature range from 190 to 380°C, the dependence of log on the reciprocal of the temperature exhibits a linear behavior. The nature of charge carriers is studied using the Hittorf technique. It is demonstrated that protons and chlorine ions are charge carriers in solid glasses. The concentration dependence of the transport numbers of chlorine ions is examined by the Tubandt method. The contribution of the electronic component to the total electrical conductivity is estimated with the use of the Liang–Wagner technique. The concentration dependences of the electrical conductivity and the transport numbers of chlorine ions are interpreted in terms of the microinhomogeneous glass structure associated with the selective interaction of components during synthesis of glasses.     

Improvement in the non-linear electrical characteristics of the SnO2·Co2O3·Ta2O5 varistor material with Pr6O11 additive

The electrical and microstructural properties of SnO2-based varistor ceramic sample were improved by addition of Pr6O11. It was found that the introduction of Pr6O11 can lead to a great improvement in the threshold voltage and the non-linear electrical properties of SnO2-based varistors. As the amount of Pr6O11 increased from 0.00 to 0.5 mol%, the mean grain size decreases from 16.64 to 7.58 μm, the relative dielectric constant (at 1 kHz) increases from 1243.2 to 4534.6, the non-linear coefficient increases from 15.44 to 18.25 and the break down electrical field increases from 275.3 to 880.5 V/mm. The structure-property relationship is discussed systematically.     

Crystallization behavior of iron- and boron-containing nepheline (Na2O·Al2O3·2SiO2) based model high-level nuclear waste glasses

This study focuses on understanding the relationship between iron redox, composition, and heat-treatment atmosphere in nepheline-based model high-level nuclear waste glasses. Glasses in the Na₂O–Al₂O₃–B₂O₃–Fe₂O₃–SiO₂ system with varying Al₂O₃/Fe₂O₃ and Na₂O/Fe₂O₃ ratios have been synthesized by melt-quench technique and studied for their crystallization behavior in different heating atmospheres—air, inert (N₂), and reducing (96%N₂–4%H₂). The compositional dependence of iron redox chemistry in glasses and the impact of heating environment and crystallization on iron coordination in glass-ceramics have been investigated by Mössbauer spectroscopy and vibrating sample magnetometry. While iron coordination in glasses and glass-ceramics changed as a function of glass chemistry, the heating atmosphere during crystallization exhibited minimal effect on iron redox. The change in heating atmosphere did not affect the phase assemblage but did affect the microstructural evolution. While glass-ceramics produced as a result of heat treatment in air and N₂ atmospheres developed a golden/brown colored iron-rich layer on their surface, those produced in a reducing atmosphere did not exhibit any such phenomenon. Furthermore, while this iron-rich layer was observed in glass-ceramics with varying Al₂O₃/Fe₂O₃ ratio, it was absent from glass-ceramics with varying Na₂O/Fe₂O₃ ratio. An explanation of these results has been provided on the basis of kinetics of diffusion of oxygen and network modifiers in the glasses under different thermodynamic conditions. The plausible implications of the formation of iron-rich layer on the surface of glass-ceramics on the chemical durability of high-level nuclear waste glasses have been discussed.     

(NH4)2C2O4·H2O和NH4HC2O4·0.5H2O 单晶的培养研究

利用六次甲基四胺缓慢水解产生的NH3和草酸反应,扩散法培养出(NH4)2C2O4·H2O和NH4HC2O4·0.5H2O两种单晶.     

Ca2B2O5·H2O的热分解过程研究

采用水热法制备了片状Ca_2B_2O_5·H_2O水合硼酸盐前驱体,利用XRD、FI-IR及SEM等手段对样品进行了表征,利用TG-DTA热重分析法对Ca_2B_2O_5·H_2O的脱水热分解进行了分析。结合热分析结果和不同温度下焙烧产物的物相表征结果,研究上述硼酸钙的热分解过程,结果表明,热分解过程大致分为三个阶段:第一阶段硼酸钙失去表面的吸附水,第二阶段硼酸钙失去结晶水形成无定形的无水硼酸钙,第三阶段无水硼酸钙由无定形转化为结晶。     

氯化钡(BaCl_2·2H_2O)

正1)性质。无色单斜晶系结晶。冷结晶为扁平菱形,热结晶为无定形。工业品为白色片状或粉状结晶。结晶水在空气中稳定,加热到113℃时失去结晶水。易溶于水,溶解度随温度的升高而增大。有乙醇及氯离子(如氯化钙)存在时,溶解度显著降低。在乙醇及酸中的溶解度比在水中的溶解度小。在无水乙醇中失去结晶水,但并不溶解。不溶于丙酮。氯化钡的水溶液具苦咸味,并且因含氯离子而具有较强的腐蚀性。工业氯化钡有毒、不易燃、不易爆。     

分要对Na2O·CaO·2P2O5玻璃水解性的影响

运用化学分析和ＳＥＭ－ＥＤＸＡ等测试方法，研究了Ｎａ２Ｏ·ＣａＯ·２Ｐ２Ｏ５玻璃的分相形貌、分相组成与水解性关系。研究结果表明：玻璃分相形貌对玻璃的水解性有决定作用。分相有利于玻璃的生物活性．     

Hydrothermal synthesis and characterization of nanorods “LixV2−δO4−δ·H2O”

Nanorods “Li_xV_2−δO_4−δ·H₂O” were hydrothermally synthesized with starting agents LiOH·H₂O and V₂O₅, and reducing agent hydrazine monohydrate (NH₂NH₂·H₂O) under alkaline condition at 160 °C. The samples were characterizated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The nanorods obtained have diameters from 80 to 100 nm with length up to several micrometers. Molecular coordination and assembly mechanism can be assumed to explain the formation of one-dimensional nanorods.     

Facile construction of polypyrrole microencapsulated γ-Fe2O3 for simultaneously enhancing the flame retardancy and smoke toxicity suppression of intumescent flame-retardant epoxy resins

For effectively strengthening the comprehensive properties of intumescent flame-retardant epoxy resins (EPs), a microencapsulating γ-Fe₂O₃ by polypyrrole (PPy) named PPy-Fe₂O₃ was synthesized and used as a synergist to simultaneously enhance the flame retardancy, smoke toxicity suppression and mechanical strength of EP composites containing diaminodiphenylmethane modified ammonium polyphosphate (DDP). The results demonstrate that the mixture of PPy-Fe₂O₃ and DDP exhibits a surprising synergistic effect on strengthening the comprehensive properties of EP composites. Specifically, EP composite containing 0.2 wt% PPy-Fe₂O₃ and 9.8 wt% DDP achieves the UL94 V-0 rating with a limiting oxygen index (LOI) value of 35.5%, while 10 wt% DDP only imparts a UL94 V-1 rating and a LOI value of 34.0% to EP. Furthermore, 0.2 wt% PPy-Fe₂O₃ shows a 11.0% reduction in peak smoke production rate and a 12.3% reduction in peak heat release rate of the EP/DDP system. The enhanced fire security of EP/DDP/PPy-Fe₂O₃ is attributed to the formation of more phosphorus-rich structures retained in the char, thus reducing the release of harmful gases including NH₃, CO, and CO₂, and generating more incombustible gases including H₂O to weaken burning intensity. Meanwhile, the satisfactory compatibility of PPy-Fe₂O₃ with epoxy matrix imparts a superior mechanical strength to EP composites.