膨胀型阻燃剂阻燃环氧树脂的阻燃性能及影响因素

研究了季戊四醇磷酸酯三聚氰胺盐微胶囊化的多聚磷酸铵（KDIFR）、三聚氰胺-甲醛树脂微胶囊化的多聚磷酸铵（MAPP）和多聚磷酸铵（APP） 3种膨胀型阻燃剂,及引入硼、铝元素对膨胀型阻燃环氧树脂(EP)阻燃性能的影响,采用极限氧指数法和水平燃烧法测试材料的燃烧性能。结果表明,3种阻燃剂中APP的阻燃效果最好,当APP/EP为0.3（质量比,下同）时,其极限氧指数为32.2 %,达到难燃级水平;在EP/APP中引入铝元素或硼元素可使阻燃效果提高,硼、铝共存时阻燃效果更加突出,加入APP总量0.8 %的硼酸铝可使EP/APP的自熄时间由48 s降为24 s;热分析结果表明,APP热分解吸热恰与EP的热降解产物燃烧放热相匹配,这是使EP/APP的阻燃性能提高的主要原因;在EP/APP中引入硼和铝元素可明显促进EP/APP成炭,起到协同阻燃作用。     

载铜蒙脱土对聚氯乙烯材料阻燃性能的研究

通过离子交换反应将铜离子负载在无机层状蒙脱土上,采用十六烷基三甲基溴化铵对载铜蒙脱土进行有机改性,并将其作为阻燃剂添加到软质聚氯乙烯(PVC)材料中。利用X射线衍射对PVC/有机改性载铜蒙脱土的结构进行表征。结果表明,PVC分子链插层进入有机改性载铜蒙脱土层间形成插层型结构,且蒙脱土的层间距达到3.69 nm。热重分析、极限氧指数、垂直燃烧和烟密度测试结果表明,有机改性载铜蒙脱土有效改善了PVC的热稳定性,大幅提高了其阻燃性能。载铜蒙脱土的用量仅为PVC用量的3 %时,垂直燃烧即可达到V0级。     

微气孔球形药常压传火速度的测试方法

为了简便快速地测试微气孔球形药的常压传火速度,对靶线法、半圆槽法、直管法等传火速度测试方法进行了对比,研究了测试管材料的种类、外界气流、测试管长径比等条件对常压传火速度的影响规律。结果表明,在几种测试方法中直管法操作简便,偏差小,且不受外界气流的影响;随着测试管长径比的增加,直管法测得的传火速度逐步提高;采用底部开口状态测试管得到的测试结果比底部封闭的测试管得到的结果偏大近50%;采用透明的玻璃管作为测试管可以研究传火速度和药粒的点传火现象。采用透明玻璃管测试常压状态下微气孔球形药的传火速度是可行的。     

氢氧化镁生产现状及市场分析

氢氧化镁是一种重要的镁化工产品。综述了氢氧化镁的生产技术(水镁石磨细法和化学合成法)以及改性研究,重点介绍了氢氧化镁的化学合成法以及改性研究的热点。分析了国内外氢氧化镁的市场与消费情况,指出全球氢氧化镁的最大消费途径是废水处理和烟气脱硫,其次是阻燃剂;阻燃剂是氢氧化镁消费增长最为迅速的领域。提出了氢氧化镁的生产技术成本问题,并展望了其发展前景。     

A hybrid intumescent fire retardant coating from cake- and eggshell-type IFRC

In this study the applicability of flame retardant mixed with a carbon source (such as pentaerythritol) for the intumescent fire retardant coating (IFRC) daubed on the top of a piece of plywood was investigated. There are three kinds of flame retardants used in this study: (1) artificial mesophase graphite powder (MGP), (2) sericite (Al₄(OH)₄(KAlSi₃O₁₀)₂), and (3) graphite. The desirable sizes of graphite, MGP and sericite were obtained by sieving. The graphite, MGP and sericite were characterized using a scanning electron microscope (SEM) and an energy dispersive spectrum (EDS). The IFRC, which consisted of 19.8% of flame retardant (or flame retardant mixed with carbon source), 15% of dehydrate agent, 18% of foaming agent, 7.2% of resin binder, and 40% of solvent, was prepared and daubed on the top of plywood. The fire protection capability of IFRC was tested using a flammability 45° tester. A conventional IFRC (with the carbon source) was also prepared to study the effect of adding the mixture of flame retardant and carbon source on the fire protection capability of IFRC. The microstructures of the conventional IFRC, the IFRC with flame retardant, and the hybrid IFRC (with flame retardant and carbon source) were inferred and demonstrated using SEM micrographs of the cross-section of three kinds of burnt IFRC. Most interestingly, the fire protection capability of the hybrid IFRC exceeds that of the conventional IFRC even though the percentage of carbon in the burnt hybrid IFRC is less than that in the burnt conventional IFRC.     

Effects of charge temperature and exhaust gas re-circulation on combustion and emission characteristics of an acetylene fuelled HCCI engine

In this work, experiments were conducted on a homogeneous charge compression ignition (HCCI) engine with acetylene as the sole fuel at different power outputs. Initially, the intake air was heated to different temperatures in order to determine the optimum level at every output. Charge temperatures needed were in the range of 40-110 °C from no load to a BMEP (Brake Mean Effective Pressure) of 4 bar. Subsequently, exhaust gas re-circulation (EGR) was done at the identified charge temperatures and brake thermal efficiency was found to improve. At high BMEPs, use of EGR led to knocking. Thus, fine control over charge temperature and EGR quantity is needed at these conditions. Nitric oxide and smoke levels were very low. However, HC levels were high at about 1700-2700 ppm. Brake thermal efficiencies were comparable to or even better than the compression ignition mode of operation.     

Flame structure of LPG-air Inverse Diffusion Flame in a backstep burner

The present experimental study characterizes the turbulent LPG Inverse Diffusion Flame (IDF) stabilized in a backstep burner in terms of visible flame length, dual flame structure, centerline temperature distribution, and oxygen concentration. The visible flame length for a fixed fuel jet velocity is found to reduce with increase in air jet velocity. Besides this, the effect of air and fuel jet velocities on visible flame length is interpreted using a new parameter, Global Momentum Ratio (GMR). Interestingly, GMR seems to be correlating well with the visible flame length for the air and fuel velocity ranges considered in the present study. Moreover, the dual flame structure of IDF is identified with the help of CH-chemiluminescence signature. The existence of dual flame structure of IDF is confirmed further with the centerline temperature and oxygen concentration measurements.     

Acrylic-based fire-retardant coatings for steel protection: Employing the concept of in situ ceramization

Traditional intumescent coatings are widely used as passive fire-protective coatings for steel structures as they are capable of expanding in the range of 20–50 times the original thickness thereby providing excellent insulation. However, the fragile nature of such residue and susceptibility to thermo-oxidation given their carbonaceous nature are key problematic issues. The concept of in situ ceramization is explored in this work as a means to form inorganic cohesive char with improved rigidity and thermo-oxidative stability. Coating samples were prepared by incorporating ammonium polyphosphate, talc, Mg(OH)₂, and polydimethylsiloxane as additives into acrylic resin at different weight fractions. Thermal analysis and x-ray diffraction have confirmed the reactions between the additives to form various crystalline magnesium phosphate phases, and to a small extent, silicon phosphate, thereby ensuring the thermo-oxidative stability of the residue. This is reiterated by the fire performance tests (by exposing the coatings to a temperature profile in a furnace similar to ISO 834 fire curve). Despite the advantages of rigid char and its thermo-oxidative stability as a result of formation of inorganic phosphates, the lack of swelling has resulted in relatively poor insulation capabilities of the char, and subsequently, compromised the fire protection times (that are in the range of 45–55 min). However, pyrolysis flow combustion calorimeter results of the coatings are promising and have shown a significant drop of up to 70% in the peak of heat release rate values as compared to neat resin.     

Effect of expandable graphite and ammonium polyphosphate on the thermal degradation and weathering of intumescent fire-retardant coating

This research aims to study the effect of ammonium polyphosphate and expandable graphite on the intumescent coating formulations (ICF). The coating presented in this research article is based on carbon source expandable graphite (EG), blowing agent melamine, acid source ammonium polyphosphate (APP), epoxy resin as a binder with polyamide amine. The stability of the developed coating was verified at 950°C for 1-hour fire test. The results showed that the coating is stable and well bond with the steel substrate. The char was characterized by using FESEM, XRD, FTIR, DTA, TGA, XPS, Py-GCMS and Weathering Test. The morphology of the char was studied by SEM of the coating after furnace fire test. XRD and FTIR show the presence of graphite, borophosphate; boron oxide and sassolite in the residual char. TGA and DTG disclosed that EG improved the residual mass of coating. XPS analysis showed the char residue of IF5-APP-EG contains carbon and oxygen contents 47.50 and 40.70, respectively. Py-GCMS analysis described that the IF5-APP-EG released less gaseous compounds. The weathering test illustrated that's the char expansion of coatings samples was decreased due to the presence of a humid environment and UV light. The IF5-APP-EG showed the maximum char expansion, lower substrate temperature and high residual weight among the studied formulations.     

High-efficiency ammonium polyphosphate intumescent encapsulated polypropylene flame retardant

The flame retardant polypropylene containing the micro-envelope core-shell structure flame retardant, which encapsulated ammonium polyphosphate into melamine-formaldehyde resin and sodium silicate through in situ polymerization was prepared with polyamide 6, added as a carbon-forming agent. The composition of ammonium polyphosphate, encapsulated ammonium polyphosphate with melamine-formaldehyde resin and the micro-envelope core-shell structure flame retardant were characterized. The fire safety and thermal stability were investigated and showed an improvement including limiting oxygen index, thermogravimetric analysis, vertical burning tests, and microscale combustion calorimeter. The burned compounds were also studied to confirm the burning mechanism. The results showed the flame retardant performance had been greatly improved, while polyamide 6 had better char-forming effect. Besides, the water solubility of flame retardants and their influence on the mechanical properties of polypropylene were also investigated. The results on the effects of additives demonstrated a high efficiency flame retardant to polypropylene. A core-shell flame retardant that sodium silicate and melamine-formaldehyde resin-coated ammonium polyphosphate had been constructed. The effect of the built flame retardant system on the combustion performance of polypropylene was studied from the mechanism and performance. The LOI of the most flame retardant polypropylene reached 28.6%, and UL-94 reached the V-0 level.