In situ preparation of intrinsic flame-retardant urea formaldehyde/carbon nanotubes nanocomposite foam: structure and reinforcing mechanism

ABSTRACT

Urea-formaldehyde (UF)/carboxylated carbon nanotubes (CNTs-COOH) nanocomposite foams were prepared via in-situ polymerization. Chemical bonding and hydrogen bonding interactions formed between CNTs-COOH and UF matrix. UF resin adhered onto the ektexine of CNTs-COOH and grafting ratio of 496.41% was achieved. UF/CNTs-COOH foam showed smaller cell size, narrower cell size distribution and lower water absorption compared with UF foam. Introduction of 0.25 wt% CNTs-COOH resulted in 58.43% increase in compressive strength. CNTs-COOH were pulled out with surface covered with UF resin under stress and the failure mode was the destruction of matrix around interfacial layer. UL-94V-0 rating was achieved for the composite foams.     

军用涤纶长丝面料热转移印花及功能整理研究

介绍涤纶长丝面料分散染料热转移印花工艺,包括工艺流程、主要技术创新、产品应用等方面。阐述涤纶长丝面料阻燃涂层整理技术,并讨论阻燃剂用量、涂层增重量对整理效果的影响。总结防热红外侦察整理、防雷达波侦察整理、多功能迷彩面料生产及要点。文章表明,化纤长丝纺织产品的发展与国防建设是密切相关、相互促进、相辅相成的。以化纤长丝为基材生产的系列化军用产品是建设强大国防的重要保障。不断深化化纤长丝面料的功能性深度加工具有非常重要的意义。     

Flame propagation enhancement by plasma excitation of oxygen. Part II: Effects of O2(aΔg)

The isolated effect of O₂(a¹Δ_g) on the propagation of C₂H₄ lifted flames was studied at reduced pressures (3.61 kPa and 6.73 kPa). The O₂(a¹Δ_g) was produced in a microwave discharge plasma and was isolated from O and O₃ by NO addition to the plasma afterglow in a flow residence time on the order of 1 s. The concentrations of O₂(a¹Δ_g) and O₃ were measured quantitatively through absorption by sensitive off-axis integrated-cavity-output spectroscopy and one-pass line-of-sight absorption, respectively. Under these conditions, it was found that O₂(a¹Δ_g) enhanced the propagation speed of C₂H₄ lifted flames. Comparison with the results of enhancement by O₃ found in part I of this investigation provided an estimation of 2-3% of flame speed enhancement for 5500 ppm of O₂(a¹Δ_g) addition from the plasma. Numerical simulation results using the current kinetic model of O₂(a¹Δ_g) over-predicts the flame propagation enhancement found in the experiments. However, the inclusion of collisional quenching rate estimations of O₂(a¹Δ_g) by C₂H₄ mitigated the over-prediction. The present isolated experimental results of the enhancement of a hydrocarbon fueled flame by O₂(a¹Δ_g), along with kinetic modeling results suggest that further studies of C_nH_m + O₂(a¹Δ_g) collisional and reactive quenching are required in order to correctly predict combustion enhancement by O₂(a¹Δ_g). The present experimental results will have a direct impact on the development of elementary reaction rates with O₂(a¹Δ_g) at flame conditions to establish detailed plasma-flame kinetic mechanisms.     

Synthesis and application of a new functionalized resin for use in an on-line,solid phase extraction system for the determination of trace elements in waters and reference cereal materials by flame atomic absorption spectrometry

The synthesis and characterization of the resin Amberlite XAD-4 functionalized with 2,6-pyridinedicarboxaldehyde and its application in an on-line system for the preconcentration of cadmium, cobalt, copper, lead and manganese prior to determination using flame atomic absorption spectrometry (FAAS) is proposed. Metal ions retained on the modified resin were eluted using 1.0 mol L⁻¹ HNO₃ solution and aspirated directly to the nebulizer–burner system of a FAAS instrument using a flow injection system. Detection limits (3σ) were determined to be 0.13 μg L⁻¹ for Cd, 0.29 μg L⁻¹ for Cu, 0.23 μg L⁻¹ for Mn, 0.58 μg L⁻¹ for Co and 2.19 μg L⁻¹ for Pb using a 10 mL of water sample loading volume. The limits of detection would be 100 times higher with units of μg kg⁻¹ for the solid samples in which their dilution ratios as (volume/weight) were 100. Enrichment factors ranged from 23.6 to 28.9 (for Co and Mn, respectively). The proposed method was successfully applied to determination of the analytes in natural water samples and certified reference materials.     

Fast reactions with nano- and micrometer aluminum: A study on oxidation versus fluorination

The use of fluorine as an oxidizing agent in aluminum (Al)-based thermite reactions yields higher peak pressures and an increase in gas production compared with oxygen-containing oxidizers, such as molybdenum trioxide (MoO₃). Thus fluorination reactions have the potential to excel in situations that require high pressures and flame speeds. This study compares the combustion behaviors of Al/Teflon, Al/MoO₃/Teflon, and Al/MoO₃ in an effort to determine the effects that the replacement of oxygen with fluorine has on the reaction dynamics in both open and confined burning configurations. Data were collected from pressure sensors and high-speed imaging. The mass percent of Al was varied from 10 to 90% to study the effects of composition. The composites were then further tested at the optimum stoichiometry using either 50 nm or 1-3 μm Al to examine the effect of Al particle size. The addition of Teflon in an open configuration hinders the reaction due to a loss of liberated gas. Confining the reaction enables the trapped gases to enhance convection, yielding increased flame speeds. For confined conditions, the reactions containing Teflon exhibit higher peak pressures but lower flame speeds than the reactions with MoO₃. These results imply that a direct relationship between generated gas pressures and flame speeds does not generally exist when comparing different oxidizers. The theoretically predicted relationship for the relative flame speed versus relative particle size based on the melt-dispersion mechanism agrees with experimental data for all Al particle sizes and for the fluorination reaction. Particle synthesis parameters are suggested that could be controlled to enable micrometer-scale Al particles to achieve the performance of nanoscale Al particles. This is of significant practical importance, because nanoparticles are 30 to 50 times more expensive than the micrometer particles.     

阻燃聚氨酯软质泡沫塑料中氯含量的测定

叙述了阻燃聚氨酯软质泡沫塑料中氯含量的测定方法:在助燃剂存在下,氧瓶燃烧使聚氨酯软质泡沫塑料中的有机氯转化为HCl,用稀NaOH吸收,使用硫氰酸汞分光光度法测定聚氨酯软质泡沫塑料中阻燃剂的氯含量。该方法简单快捷、精确度高,回收率为99.64%～102.41%。     

纯生物质纤维素气凝胶的制备及其阻燃性能

为有效推进纺织领域资源循环利用、增强绿色低碳循环发展,以废棉纱为原料制备再生纤维素气凝胶,并在水相环境驱动下,将浸提自废弃农林作物的生物质茶多酚沉积于该气凝胶表面,开发纯生物质节能保温用阻燃纤维素气凝胶(BTCA),并分别采用极限氧指数仪、热重分析、热重红外联用仪、拉曼光谱等分析了BTCA的热稳定性、热分解气固相产物及...     

阻燃抗静电尼龙6中炭黑的选择及处理

为了赋予尼龙６（ＰＡ６）优良的抗静电性,选择了四种结构不同的导电炭黑（ＣＢ）进行研究比较,并筛选了合适的表面处理剂对填充ＣＢ进行表面处理。实验结果表明：由ＴＥＭ观察到的具有空壳结构的导电ＣＢ较实心结构的导电ＣＢ用量少,导电性能更优良;经表面处理的ＣＢ填充ＰＡ６,不仅加工性能得到有效地改善,而且显著地减少了因填充ＣＢ对ＰＡ６阻燃及力学性能的不利影响     

高分子复合材料用膨胀型阻燃涂层

论述高分子复合材料用膨胀型阻燃涂层的作用机理 ,应用效果及今后需进一步研究的问题     

EVA/MWNTs复合材料的阻燃性能

综述了近几年来乙烯-乙酸乙烯酯共聚物/多壁碳纳米管（EVA/MWNTs）纳米复合材料的研究进展,介绍了其制备方法,详述了其热解行为及阻燃性能（包括热释放速率、引燃时间、成炭性）,并对其阻燃机理进行了深入的讨论。比较了MWNTs、有机黏土、层状双氢氧化物等不同纳米填料的阻燃性能,分析了对MWNTs进行不同处理（包括纯化、使用高密度聚乙烯进行表面涂覆改性、研磨）对相应纳米复合材料的热稳定性及可燃性的影响。