Comparative performance of carbon nanotube and nanoclay on thermal properties and flammability behavior of amorphous polyamide/SEBS blend

Multiwall carbon nanotubes (CNT) or montmorillonite clay (MMT-30B) were added to a poly(hexamethylene isophthalamide-co-terephthalamine) (an amorphous polyamide - aPA) and styrene-ethylene/butylene-styrene graphitized with maleic anhydride (SEBS) blend, in different concentrations, in order to investigate the morphology, thermal properties and flammability behavior. Different nanoparticle localizations in the phase blend were observed through transmission electronic microscopy. CNT nanoparticles are localized in SEBS phase, and MMT-30B nanoparticles in aPA phase. No significant changes were observed on transition temperatures and thermal stability with both nanoparticle additions. However, a slight increase on storage modulus for clay nanocomposites and a slight reduction for carbon nanotube nanocomposites were observed, due to their different phase localizations. Regarding flammability, CNT nanocomposites showed better performance as a flame retardant when compared to samples with MMT-30B. Although the MMT-30B nanocomposites could not be classified according to the UL-94 criteria, no dripped flaming particles were observed, due to the a char barrier formation on the polymer surface. The CNT nanocomposites were classified according to the UL-94 criteria as V-2. The CNT's selective localization on the SEBS phase decreases its heat-release rate, but no interconnected network structure was formed in the matrix to suppress the dripping flaming particles.     

Ignition mechanism of flammable dust and dust mixtures: An insight through thermogravimetric/differential scanning calorimetry analysis

Understanding flame propagation mechanism and thermal behavior of flammable dusts is of crucial importance, since they strongly affect the flammability and explosion parameters. In a previous work, we found that the volatile point of anthraquinone/nicotinic acid mixtures can be lower than the one of the pure dusts, suggesting a synergistic effect. In this work, thermogravimetric and differential scanning calorimetry analyses of anthraquinone/niacin mixtures were carried out both in open and closed cup, to explain the observed synergistic behavior. FTIR analysis on solid residue and evolved gaseous species showed that the mixtures change compositions during the thermal treatment, without undergoing any chemical transformation. The thermal behavior of dust mixtures reveals the presence of a eutectic point, resulting in a volatiles production at lower temperature and accelerating the flame propagation.     

可燃工质氨的燃烧及阻燃机理的研究

当前环境问题日益突出,天然工质氨作为环保性制冷剂再次引起科学界的广泛重视。但NH₃存在可燃可爆性问题,在实际应用中存在着一定的安全隐患。采用量子化学密度泛函理论计算方法,在M06-2X/6-311+G（d,p）的计算水平上,对NH₃的燃烧及阻燃机理开展研究,得到反应过程的微观反应路径。研究表明,NH₃可通过三种方式发生燃烧微观反应,一是发生自身裂解反应,生成H自由基;二是与氧气发生碰撞反应,生成OOH自由基;三是与活性自由基发生碰撞反应,生成新的活性自由基,NH₃可与H、O、OH自由基反应,反应能垒较低。此外,还计算了两种典型的阻燃基团F和CF₃对可燃分子NH₃的微观阻燃路径,验证其阻燃效果。本文从微观分子的角度考察了可燃工质氨的燃烧及阻燃机理,为新一代低温室效应工质的燃烧及阻燃机制提供了参考。     

Flame Retardance and Smoke Suppression of Poly(vinyl chloride) Using Multicomponent Systems

Metal-based organic complexes (MBO) are a class of FRSS additives that comprise a transition metal and an organic ligand that cleaves at an elevated temperature thereby releasing the metal in a reactive state. They help in the formation of char and thus act as an effective smoke suppressant. Use of MBO complexes as flame retardant smoke suppressants, phosphate ester as a flame retardant and active filler as endothermic material is reported here as multicomponent FRSS systems. MBOs used in the present study are the chelates of pentanediono. They were used alone as well as in combination with aluminum trihydrate (ATH) as filler were used to impart flame retardancy and smoke suppression to poly vinylchloride. Their performance was measured in terms of flammability, smoke generation, char formation and evolution of combustion gases. MBOs of molybdenum and chromium were found to be very efficient flame retardant smoke suppressants.     

Lipid‐derived monomer and corresponding bio‐based nanocomposites

Fatty acid based monomer and corresponding hybrid polymer layered silicate nanocomposites have successfully been prepared by using in situ polymerizations. The hybrid materials were prepared by adding different ratios of nanoclay during free radical homopolymerization of 2‐(acryloyloxy)ethyl stearate (AOES) monomer and copolymerization of AOES with styrene. AOES monomer was synthesized by treating stearic acid with 2‐hydroxyethyl acrylate. The formation of AOES monomer, homopolymer and copolymer was confirmed by ¹H NMR spectroscopic analysis. Further analysis and characterization of the nanocomposites were carried out by XRD, transmission electron microscopy, AFM and attenuated total reflectance Fourier transform infrared spectroscopy. TGA of the polymer nanocomposites was also carried out to evaluate their thermal stability, while flammability tests were conducted to investigate the effect of layered silicate on flame retardancy. Nanofiller addition into the polymer matrix substantially improved the thermal properties and fire retardancy of the composites. © 2016 Society of Chemical Industry     

Graphic Manifestation of the Ability of Selected Alkaline Earth Chlorides to Impart Flame-Retardancy to Cotton Fabric

Optimum percent quanties of selected alkaline earth chlorides used for imparting flame-retardancy to cotton fabric have been chosen from one of the author's ACS-presented articles. Based on the afore mentioned data and gathering information concerning their physicochemical specifications from scientific literature the related graphical representations were obtained. The results illustrate a reasonable dependence in lowering the ability of the alkaline earth chlorides on their higher stabilities that is, the optimum percent of the applied chlorides decreased according to the metals position in the periodic table. Therefore a better understanding has been achieved and deduced.     

Self induced buoyant blow off in upward flame spread on thin solid fuels

Upward flame spread experiments were conducted on long thin composite fabric fuels made of 75% cotton and 25% fiberglass of various widths between 2 and 8.8 cm and lengths greater than 1.5 m. Symmetric ignition at the bottom edge of the fuel resulted in two sided upward flame growth initially. As flame grew to a critical length (15–30 cm depending on sample width) fluctuation or instability of the flame base was observed. For samples 5 cm or less in width, this instability lead to flame blow off on one side of the sample (can be either side in repeated tests). The remaining flame on the other side would quickly shrink in length and spread all the way to the end of the sample with a constant limiting length and steady spread rate. Flame blow off from the increased buoyancy induced air velocity (at the flame base) with increasing flame length is proposed as the mechanism for this interesting phenomenon. Experimental details and the proposed explanation, including sample width effect, are offered in the paper.     

国内外床垫阻燃性标准比较

文章通过对比欧盟、美国以及中国在法律、法规以及标准中对床垫阻燃性的要求,分析中国与这些先进国家在床垫阻燃性要求上的差距,以期为我国床垫阻燃性的标准提供有益的参考,为人民的生命安全提供有力的保障。     

氧指数的热平衡分析

本文从热平衡在熄火时的条件,应用层流扩散火焰简化模型,分析氧指数与体系的各种物理、化学因素间的关系,来理解物质的阻燃特性。     

A Comparative Study of the Explosion Characteristics of IPN and IPN/JP‐10 Mixtures in Air Aerosols

This article presents a comparison of the explosion characteristics of mixtures of isopropyl nitrate (IPN, (CH₃)₂CHONO₂) and JP‐10 (C₁₀H₁₆, tricycle [5.2.1.0^2,6] decane) in air aerosols. The explosion pressure, flame temperature, maximum rate of pressure rise, maximum rate of temperature rise, and lower flammability limits (LFLs) were measured for two sets of IPN and mixed IPN/JP‐10 in air aerosols at different concentrations and Sauter mean diameters (SMDs) of 19 μm and 34 μm, respectively, and the values were compared with the experimental results of JP‐10/air aerosols with SMDs of 20 μm and 35 μm (from our previous research). Experiments were also performed to study various concentrations at various ignition energies for the IPN/air aerosols and the explosions of binary mixture aerosols with various mass ratios of IPN and JP‐10. The experimental results indicated that for the IPN/air and JP‐10/air aerosols with a mean SMD of ∼34 μm, the maximum peak pressure and maximum peak temperature of the IPN/air aerosols were greater than those of the JP‐10/air aerosols. The maximum rate of pressure rise of the IPN/air aerosols reached a maximum value of 395.3 MPa/s at a mean SMD of ∼34 μm, and the pressure increased more abruptly in the IPN/air aerosols than in the JP‐10/air aerosols. The LFLs of the IPN/air aerosols occurred with a total concentration of 197 g/m³ at a mean SMD of 19 μm and a total concentration of 233 g/m³ at a mean SMD of 34 μm, whereas the LFLs for the JP‐10/air aerosols with SMDs of 20 μm and 35 μm were less than 47 g/m³ and 40 g/m³, respectively. The experimental results presented here also showed that the maximum peak pressure was 1.07 MPa at a binary liquid mass ratio of IPN:JP‐10 (%) of 72 : 28 and a mean SMD of ∼34 μm.