十溴二苯醚与水合硼酸锌对环氧树脂固化物阻燃耐热性的影响

用氧指数（ＬＯＩ）测定和差示扫描量热（ＤＳＣ）法研究了十溴二苯醚（ＦＲ—１０）与水合硼酸锌（ＺＢ）对环氧树脂固化物阻燃耐热性的影响。结果表明随ＦＲ—１０用量的增加，环氧树脂固化物ＬＯＩ增加，按气相和凝聚相机理发挥阻燃作用。ＺＢ在环氧树脂固化物中有较好的阻燃作用，用量０．７５ｐｈｒ时可使ＬＯＩ增加１．２，但继续增加用量，直到１０倍，ＬＯＩ仅增加１．１，并发现ＺＢ用量较大的样品，在燃烧时有明显的熔融超前现象。ＺＢ和ＦＲ—１０配用时加强了阻燃效果，在Ｂｒ／Ｂ＜１时，环氧树脂固化物的ＬＯＩ降低，在３时ＬＯＩ增加，Ｂｒ／Ｂ为０时不熔滴，１时溶滴最严重，随Ｂｒ／Ｂ增加溶滴变小，由于影响热降解，因此使阻燃协同效应未体现出来，加入配合阻燃剂虽降低了固化物的耐热性，但不影响正常使用     

硬质聚氨酯泡沫塑料的阻燃技术

综述了提高硬质聚氨酯泡沫塑料阻燃性的方法，介绍了常用添加型阻燃剂的作用和特点以及常用的结构改性提高阻燃性的技术途径。     

磷系阻燃剂在聚氨酯泡沫塑料中的应用

介绍了磷系阻燃剂在聚氨酯泡沫塑料中的应用,概述了硬质和软质聚氨酯泡沫塑料阻燃技术。探讨了阻燃剂配方的最优化设计,提出了合成磷酸酯阻燃剂和软质聚氨酯泡沫塑料阻燃方面的新设想。     

燃料柴油中金属离子的测定

采用AAS法测定燃料柴油中钠、铅、铜、钾、钙等主要金属杂质的含量。采用了制备二次亚沸水及提纯化学试剂 ,富集样品中的杂质等技术。改善和控制环境影响微量元素分析的因素 ,采用原子吸收分光光度法中的火焰法和石墨炉。高灵敏度石墨原子化器的检出下限达 2× 10 - 11g铜、铅。     

Effect of type of substitution in 4,4′‐bis‐(diaminodiphenyl) methane hardener on cure kinetics,mechanical, and flame retardant properties of tetrafunctional epoxy resins

The nature of the substituent in 4,4′‐bis‐(diaminodiphenyl) methane (DDM) hardener on the cure kinetics, mechanical, and flame retardant properties of N,N,N′,N′‐tetraglycidyl diaminodiphenyl methane (TGDDM) resin is investigated in comparison with unsubstituted DDM and widely used 4,4′‐bis‐(diaminodiphenyl) sulfone hardeners. Dynamic differential scanning calorimetry (DSC) and cure rheology studies showed that the substitution decreased the reactivity of the amine. An electron‐withdrawing chlorine substituent was found to be more effective than an electron‐releasing methyl group in reducing the amine reactivity. Substituted and unsubstituted DDM hardeners showed two peaks in their DSC thermograms that were due to steric hindrance in the former and deficiency of amine in the latter. Substitution showed its effect on the mechanical properties and glass‐transition temperature. The flexural modulus was increased; however, the Izod impact and glass‐transition temperature were decreased in substituted amine systems. The limiting oxygen index results showed higher flame retardancy in the chlorine substituted hardener system compared to other hardener systems that were studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 480–491, 2006     

Determining factor for the blowoff limit of a flame spreading in an opposed turbulent flow, in a narrow solid-fuel duct

This study clarified the blowoff mechanism for a flame spreading in an opposed turbulent flow in narrow solid fuel ducts. To clarify this mechanism, two experiments were conducted. The first experiment was to investigate the influence of ambient pressure and fuel duct size on the blowoff limit. The results indicated that the flow velocity at the point when blowoff occurred, Vg,t, increased with ambient pressure. This tendency could not be confirmed by a well-known expression for the Damköhler number, which is defined as the ratio of the characteristic flow time to the characteristic chemical time. Subsequently, to clarify the determining factor for the blowoff, the second experiment, which observed the flow field near the flame leading edge, was conducted. The results show that the flow separation in front of the flame leading edge, which provided sufficient residence time of oxidizer and gaseous fuel, is necessary for the flame to spread in an opposed oxidizer flow. From the results, it is found that the oxidizer friction velocity, u_∗, which is an indicator of the turbulent momentum transfer, is the determining factor for the flame blowoff limit. When the friction velocity is larger than a critical value, flame blowoff occurs in the fuel duct, due to the absence of flow separation.     

Flame retardant mechanism of polyamide 6-clay nanocomposites

The thermal and flammability properties of polyamide 6/clay (2 and 5% by mass fraction) nanocomposites were measured to determine their flame retardant (FR) performance. The gasification process of the nanocomposite samples at an external radiant flux of 50 kW/m² in a nitrogen atmosphere was observed, and the residues collected at various sample mass losses were analyzed by thermogravimetric analysis, transmission electron microscopy, and X-ray diffraction to determine the content of the residue and to understand the FR mechanism of the nanocomposites. The analysis of the floccules of blackened residues shows that up to 80% by mass of the residues consists of clay particles and the remainder is thermally stable organic components with possible graphitic structure. Furthermore, clay particles are stacked in the carbonaceous floccule residues and the d-spacing of the clay platelets is in the range of 1.3-1.4 nm as compared to the well exfoliated original sample. The accumulation of the initially well-dispersed clay particles in the sample on the burning/gasifying sample surface are due to two possible mechanisms. One is recession of the polymer resin from the surface by pyrolysis with the de-wetted clay particles left behind. Another mechanism is the transportation of clay particles pushed by numerous rising bubbles of degradation products and the associated convection flow in the melt from the interior of the sample toward the sample surface. Numerous rising bubbles may have another effect on the transport of clay particles. Bursting of the bubbles at the sample surface pushes the accumulated clay particles outward from the bursting area and forms the island-like floccules instead of forming a continuous net-like structure of a clay filled protective layer. Therefore, both PA6/clay nanocomposite samples did not produce sufficient amounts of protective floccules to cover the entire sample surface and vigorous bubbling was observed over the sample surface which was not covered by the protective floccules.     

Extinguishing class B fires with dry chemicals: Scaling studies

In a continuing study of flame extinguishment,^1,2,3,4 we report on scaling studies for dry chemicals on larger heptane diffusion flames (0.29 m² and 2.32 m² pans). We demonstrate again that small particle sizes extinguish most effectively. Extinguishment is related to heat absorption by decomposing or vaporizing particles. We show that the limiting particle size for each dry chemical—that is, the maximum size which completely decomposes or vaporizes in the flame—is independent of flame size for the systems studied. We broaden and apply the concept of latent or maximum effectiveness^2,3 to pan fires of all sizes. Finally, we describe and characterize an aerodynamic effect in the transport of powders, where large particles with their higher momentum entrain and drag smaller, more effective particles into the flame.We also show that extinction curves, involving the ratio of real-to-latent extinction weight and the proportion of small to large particles, have predictable shapes and predictable quantitative levels for most dry chemicals. We have developed the real-to-latent concept along with scaling equations for agent mixtures and for a wide spectrum of agents and particle sizes.     

Extinction of a premixed flame by a large variation in axial velocity

Unsteady flame propagation in a tube is examined by introducing a mean velocity variation larger than the burning velocity to a stabilized flame for a period longer than the reaction time scale. In our previous work, stabilized propane-air flames were classified as either one-dimensional or two-dimensional flames. The eventual extinction during the velocity increase was categorized as either acoustic extinction or boundary layer extinction. In this work, the effects of a nonunity Lewis number were estimated through experiments with a methane-air flame; the eventual extinction during the velocity decrease was investigated in more detail; and the growth of the extinction boundary layer was analyzed with a transient one-dimensional model of the flame stretch. In our experiments, the Lewis number did not affect the existence or characteristics of the critical velocity and the characteristic time for boundary layer extinction. An additional critical velocity was found, however, for acoustic extinction when the Lewis number was smaller than unity. In the transient one-dimensional model, the velocity transition along the flame was calculated with a continuity equation and an axial momentum equation. The spatial gradient of the burning velocity and the extinction criterion were simplified with the experimental results and some theoretical studies. The analysis shows that the unsteady flame stretch at the flame edge during a large axial velocity variation is the prevailing cause of the growth of the extinction boundary layer. These results provide some evidence that flame stretch affects the behavior of the flame edge; they also suggest the cause of the finger flame. The findings help explain the unsteady behavior of premixed flames near a flammability limit.