绿色环保型氢氧化镁阻燃剂

介绍了阻燃剂的种类和发展趋势,并重点介绍了氢氧化镁阻燃剂的阻燃机理、特点、应用和发展。指出氢氧化镁阻燃剂是一种新型的、对环境友好的无机阻燃剂。     

The fire retardant behaviour of huntite and hydromagnesite - A review

Naturally occurring mixtures of hydromagnesite and huntite have found important industrial use. Their endothermic decomposition over a temperature range similar to that of commonly used polymers and their release of water and carbon dioxide, has led to such mixtures being successfully used as fire retardants. They have replaced aluminium hydroxide and magnesium hydroxide in many applications. The current understanding of the thermal decomposition mechanism of both minerals and their combination in natural mixtures has been reviewed and related to their fire retardant action. Both minerals contribute to the reduction in flammability of polymers although the extent of these interactions has not been fully investigated. However, the fire retardant mechanism of these minerals appears more complicated than either aluminium hydroxide or magnesium hydroxide.     

硅橡胶复合材料阻燃研究进展

将功能填料引进到硅橡胶及其复合材料中可以获得特定功能的硅橡胶复合材料,已经成为近些年研究热点。目前阻燃剂种类繁多,但是性能比较单一,这已经不能满足人们的需要。人们在关注硅橡胶复合材料阻燃性能的同时,也考虑与其它性能兼备以及成本等问题。因此,本文综述了铂化合物、磷系阻燃剂、阻燃涂层、阻燃填料和微胶囊化阻燃剂等阻燃体系下硅橡胶复合材料的阻燃研究现状,总结了不同阻燃剂的阻燃机理,并且给出了其今后的改进方法,最后对硅橡胶复合材料阻燃研究的发展做了展望。     

Production of carbonates and hydrates and their use as flame retardant fillers

Flame retardant fillers are of growing importance as they do not give the high smoke and corrosive gas emissions associated with some other flame retardants The basic characteristics of a flame retardant filler are described, together with the manufacture of the principal commercial types. Experimental results are presented to demonstrate that their flame retardant effect is more complex than predicted by a simple endothermic decomposition model.     

Structural and thermal interpretation of the synergy and interactions between the fire retardants magnesium hydroxide and zinc borate

The mechanism of cooperative action of commercial fire retardants is interpreted as resulting from specific chemical reaction and phase changes. This investigation focuses on the thermally initiated interactions between two forms of commercially available fire retardant compounds. The fire performance of a polyolefin with a metal hydroxide fire retardant, magnesium hydroxide, can significantly reduce the heat release rate through absorption of heat during conversion to its metal oxide. Formation of water, followed by vaporisation, decreases heat and dilutes volatiles from polymer degradation. The second form of fire retardant compounds are zinc borates (2ZnO·3B₂O₃·3H₂O and 4ZnO·B₂O₃·H₂O), that undergo dehydration with increasing temperature. Differential thermal analysis and wide-angle X-ray spectroscopy indicated that various structural changes occurred during heating. Endothermic transitions were observed for all components, while zinc borate (2ZnO·3B₂O₃·3H₂O) showed an exothermic crystallisation transition at relatively high temperature. The exotherm was modified by the development of a new crystalline phase, magnesium orthoborate (3MgO·B₂O₃) that formed on reaction with magnesium oxide (MgO) at temperatures greater than 500 °C. Formation of crystalline zinc oxide (ZnO) was also detected. From zinc borate (4ZnO·B₂O₃·H₂O), ZnO was primarily formed. No new crystalline phases were observed in the presence of MgO over the temperature range investigated.     

A review of candidate fire retardants for polyisoprene

Polyisoprene elastomer, as natural rubber (NR) or manufactured synthetically (IR), is used in rubber compounds for applications such as tyres, dampers and suspension elements. NR/IR compounds without fire retardants have a low resistance to burning, and emit large quantities of dense smoke. This is because polyisoprene readily decomposes upon heating, by random chain scission, vaporising into a mixture of small aromatic chemical species, which ignite readily and form smoke particles with negligible char residue formation. The effects of commonly used additives on the thermal decomposition and burning of polyisoprene are reviewed; whilst cross-linking agents have significant effects on physical and ageing properties, they have little effect on thermal decomposition and burning. Fillers such as carbon black and silicas reduce the fuel content by dilution of the polymer and the formation of a stabilising residue.Potential approaches for fire retarding IR are reviewed, identifying two main approaches; halogenated additives, or high loadings of aluminium hydroxide (ATH), neither of which are satisfactory. Other potential approaches are identified, including the use of phosphorus and nitrogen based additives as intumescent char formers, and with zeolites as char catalysts. Alternative inorganic fire retardants to ATH are identified for use, and zinc hydroxystannate and zinc borate are considered as synergists with ATH. Expandable graphite (EG) is identified for use in other elastomers and has potential for polyisoprene. Nano-scale fire retardants such as montmorillonite clay and multi-walled carbon nanotubes are reported typically as a secondary additive to hydrated fillers, but have yet to make a successful transition to industrial processing.     

A facile strategy to fabricate intumescent fire-retardant and smoke suppression protective coatings for natural rubber

As flammable natural rubber (NR) becomes more ubiquitous in industrial fields, there is a growing need for safe and effective flame retardant treatments through efficient techniques. Remarkably, our developed highly efficient natural tannic acid (TA)-based intumescent flame-retardant system (AGT) has the unique function in the rubber flame retardant aspect. Meanwhile, the developed coating method through polyurethane elastomer (PU) both as adhesive medium and a carbonforming agent can not only minimize the influence of flame retardant on the desirable intrinsic properties of base polymer and also maximize the efficiency of flame retardant. The flame-retardant coating (AGT/PU) exhibits highly efficient flame retardant performances reflected by a 31.9% reduction in peak heat release rate and a 27.3% reduction in total heat release and a 26.2% reduction in total smoke production with 50 wt% loading in 1 mm thick coating due to synergistic flame retardant effects. More importantly, the excellent flame retardancy performance are obtained by the PU@AGT10, as reflected in flame retardancy index (FRI) value of 11.88 makes it as excellent flame retardancy performance. While many physically mixed flame retardants are usually seriously detrimental to mechanical properties of NR, the influence of AGT/PU coating on mechanical properties of NR decreases obviously because fire retardant just directly impacts on PU adhesive layer rather than NR matrix, and the reinforcement function of graphene is also much significant. Moreover, the coating method requires just less flame retardant to achieve high flame retardant effect for NR. These findings suggest that significant opportunities for flame retardant polymer materials in industry.     

Development of additives possessing both solid-phase and gas-phase flame retardant activities

Effective additives are required to impart a measure of fire retardancy to polymeric materials used in a variety of applications. Traditionally, these have been gas-phase active additives, most commonly organohalogen compounds or solid-phase active agents, often organophosphorus compounds. Organosphosphorus flame retardants are often very effective but may suffer from a cost disadvantage when compared with their organobromine counterparts. Organohalogen flame retardants are usually quite effective but their use is a subject to several environmental concerns. The development of additives that could simultaneously promote both types of fire retardant action could make available flame retardants that are both more cost effective and more environmentally friendly than those currently in use. Several sets of compounds with the potential to display both solid-phase and gas-phase flame retardant activities have been prepared and evaluated.     

Improvement on fire behaviour of water blown PIR-PUR foams: use of an halogen-free flame retardant

A new flame retardant, i.e. expandable graphite (EG), has been used in polyisocyanurate-polyurethane (PIR-PUR) foams in order to improve fire behaviour of such foams. In order to obtain a completely halogen-free material, water-blown PIR-PUR foams have been prepared thus avoiding the use of hydrochlorofluorocarbons or hydrofluorocarbons. The influence of several EG amounts on physical-mechanical properties and fire performances of such foams has been analysed. The results obtained show that the use of EG affects significantly physical and mechanical properties, such as compression strength and thermal conductivity, particularly at very high EG content (25 wt.%), as it often happens in presence of fillers. The fire performances have been investigated by mean of cone calorimeter apparatus and oxygen index test; the results obtained show that the fire behaviour of PIR-PUR foams could be significantly improved by use of EG; in particular it has observed a dramatically decrease of rate of heat release even for relative low EG amount (15%).     

Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants

The mechanism and kinetics of thermal degradation of materials developed from cellulose fiber and synergetic fire retardant or expandable graphite have been investigated using thermogravimetric analysis. The model-free methods such as Kissinger–Akahira–Sunose (KAS), Friedman, and Flynn–Wall–Ozawa (FWO) were applied to measure apparent activation energy (E_α). The increased E_α indicated a greater thermal stability because of the formation of a thermally stable char, and the decreased E_α after the increasing region related to the catalytic reaction of the fire retardants, which revealed that the pyrolysis of fire retardant-containing cellulosic materials through more complex and multi-step kinetics. The Friedman method can be considered as the best method to evaluate the E_α of fire-retarded cellulose thermal insulation compared with the KAS and FWO methods. A master-plots method such as the Criado method was used to determine the possible degradation mechanisms. The degradation of cellulose thermal insulation without a fire retardant is governed by a D3 diffusion process when the conversion value is below 0.6, but the materials containing synergetic fire retardant and expandable graphite fire retardant may have a complicated reaction mechanism that fits several proposed theoretical models in different conversion ranges. Gases released during the thermal degradation were identified by pyrolysis–gas chromatography/mass spectrometry. Fire retardants could catalyze the dehydration of cellulosic thermal insulating materials at a lower temperature and facilitate the generation of furfural and levoglucosenone, thus promoting the formation of char. These results provide useful information to understand the pyrolysis and fire retardancy mechanism of fire-retarded cellulose thermal insulation.

     

Thermal properties of compounds possessing both solid-phase and gas-phase flame retardant potential

Effective additives are required to impart a measure of fire retardancy to polymeric materials used in a variety of applications. Traditionally, these have been gas-phase active additives, most commonly organohalogen compounds, or solid-phase active agents, often organophosphorus compounds. Organosphosphorus flame retardants are often very effective but may suffer from a cost disadvantage when compared with their organobromine counterparts. Organohalogen flame retardants are usually quite effective but their use is subject to several environmental concerns. The development of additives that could simultaneously promote both types of fire retardant action could make available flame retardants that are both more cost effective and more environmentally friendly than those currently in use. Several sets of compounds including bromoanilino triazine derivatives and bromoaryl phosphates with the potential to display both solid-phase and gas-phase flame retardant activity have been prepared and evaluated by a variety of thermal methods.     

Flame retardancy of silicone-based materials

This review describes some recent works related to the development of the flame retardation of silicone elastomers and/or applications of silicones as flame retardant agents in other polymers. First, the thermal degradation of silicones themselves is discussed, focussing on depolymerization mechanisms, effect of structure, heating conditions, and effect of additives (i.e. less than 5 wt% fillers) on thermal degradation of silicones. Then, the influence of several types of mineral fillers (of up to 80 wt% content) as ceramization agents of silicones is presented. Finally, the introduction of (functionalized) silicones as flame retardants into other polymers is described.     

Evaluation of various fire retardants for use in wood flour-polyethylene composites

Wood-plastic composites represent a growing class of materials used by the residential construction industry and the furniture industry. For some applications in these industries, the fire performance of the material must be known, and in some cases improved. However, the fire performance of wood-plastic composites is not well understood, and there is little information regarding the effectiveness of various fire retardants in the public domain. We used oxygen index and cone calorimeter tests to characterize the fire performance of wood flour-polyethylene composites, and compared the results with unfilled polyethylene and solid wood. We then evaluated the effect of five additive-type fire retardants on fire performance. Generally, magnesium hydroxide and ammonium polyphosphate improved the fire performance of WPCs the most while a bromine-based fire retardant and zinc borate improved fire performance the least.     

阻燃剂对5Ah锂离子软包电池倍率性能和安全性能的影响研究

在电解液中加入不同含量(5 %,10 %,20 %)的阻燃剂,研究了其对LiNi _0.4Co_0.2Mn_0.4 O₂三元材料作为正极材料组装的5 Ah锂离子软包电池的倍率性能、过充性能和短路性能的影响. 实验结果表明,电解液中5 %体积含量的阻燃剂使软包电池在1C和2C放电时,具有最好的倍率性能;当阻燃剂的体积含量提升到20 %,在过充时,电池表面温度升高的最少;在短路实验时,电池不起火、不爆炸.     

The application of hydrated mineral fillers as fire retardant and smoke suppressing additives for polymers

The characteristics of hydrated mineral fillers are discussed with reference to their use as fire retardant additives for polymers. Particular consideration is given to their mode of action and criteria which influence their performance, both in reducing polymer flammability and in suppressing smoke evolution during combustion. Methods for reducing their adverse effect on mechanical properties of the host polymer are also highlighted.     

Nanomorphology and reaction to fire of polyurethane and polyamide nanocomposites containing flame retardants

The reaction to fire of polymer nanocomposites (thermoplastic polyurethane and polyamide-6) containing two different nanofillers (organoclay and carbon nanotube) has been investigated. Polymer nanocomposites exhibit significant reduction of peak of heat release rate but the nanomorphology (exfoliation, intercalation and presence of tactoids) does not play any significant role, although a reasonable level of nanodispersion is necessary to achieve good flame retardancy in specific cases (mass loss calorimetry experiment). Modelling aspects for the time to ignition are also proposed in the paper. It is shown that the approach ‘nanocomposite’ gives the best results combined with conventional flame retardants (phosphinate and phosphate) and leads to synergistic effects. The aspects of nanodispersion of the nanoparticle with the flame retardant (microfiller) are fully commented in the paper using TEM and solid state NMR. Mechanisms of action are finally proposed explaining the synergy when conventional flame retardants are combined with nanoparticles.     

Synergistic effect of carbon nanotubes and decabromodiphenyl oxide/Sb2O3 in improving the flame retardancy of polystyrene

Brominated flame retardant polystyrene composites were prepared by melt blending polystyrene, decabromodiphenyl oxide, antimony oxide, multi-wall carbon nanotubes and montmorillonite clay. Synergy between carbon nanotubes and clay and the brominated fire retardant was studied by thermogravimetric analysis, microscale combustion calorimetry and cone calorimetry. Nanotubes are more efficient than clay in improving the flame retardancy of the materials and promoting carbonization in the polystyrene matrix. Comparison of the results from the microscale combustion calorimeter and the cone calorimeter indicate that the rate of change of the peak heat release rate reduction in the microscale combustion calorimeter was slower than that in the cone. Both heat release capacity and reduction in the peak heat release rate in the microscale combustion calorimeter are important for screening the flame retardant materials; they show good correlations with the cone parameters, peak heat release rate and total heat released.     

Characterization of fire retardant polymer blends by temperature resolved in-source pyrolysis mass spectrometry

The characterization of fire retardant polymer blends by temperature resolved in-source pyrolysis mass spectrometry (PYMS) is demonstrated with a few examples. Electron impact (EI) and electron capture negative ionization (ECNI) were used to identify the thermal degradation products of polymer blends containing brominated fire retardants. PYMS (EI mode) offers an analytical instrument for a fast analysis of unknown mixtures of polymers and for the presence of fire retardant additives. Under electron impact conditions, in vacuo, low-molecular weight additives like fire retardants mainly evaporate from the polymer matrix. PYMS (EI mode) has been used for the characterization of addition polymers like polystyrene and acrylonitrile-butadiene-styrene copolymer, and for condensation polymers like the polyester poly(butylene terephthalate). Applying electron capture negative ionization, at low argon pressure in the ionization chamber, a more realistic pyrolysis situation is created because the premature loss of volatile additives is suppressed. The selectivity of ECNI for electron accepting groups like bromine makes it possible to study the influence of brominated compounds on the degradation processes in the melt. This is demonstrated by our studies on polystyrene and acrylonitrile-butadiene-styrene copolymer. High-molecular weight pyrolysis products in the m/z range of 1000 - 2000 are detected for p-bromopolystyrene and for a blend of high impact polystyrene with the fire retardant system decabromodiphenyl ether/antimony(III) oxide. In addition to the formation of antimony bromides shown in earlier studies, the emission of the synergist antimony(III) oxide as a dimeric cluster (Sb₄O₆) or as a reduced Sb₄ cluster is observed under PYMS conditions.     

Effect of fire retardant on flammability of acrylamide and 2-acrylamido-2-methylpropane sodium sulfonate copolymer composites

Poly[acrylamide-co-(2-acrylamido-2-methylpropane sodium sulfonate)] superabsorbents and superabsorbent composites (SAPCs) with zinc borate and/or melamine as fire retardants were synthesized. Water absorbencies decreased inversely to added amount of fire retardant. Thermal stability of SAPC/zinc borate increases with increasing zinc borate. Incorporating melamine improved thermal stability of the SAPC until 300 °C. Flammability analysis demonstrated that wood surface coated with SAP or SAPC emulsions extended time to ignition of the wood. Peak heat release rate and total heat release are smallest in specimens coated with SAPC/30% melamine. Wood coated with SAPC incorporating 20% zinc borate/10% melamine mixture gave the longest time to ignition at 4½ min.     

阻燃高分子复合材料中氢氧化镁的制备及其表面改性

以氢氧化镁为代表的无卤阻燃剂,由于其具有良好的阻燃、抑烟性能及环保特点,已日益得到学术界和产业界的重视.在实际应用过程中,人们发现阻燃剂的形貌对其阻燃性能具有较大影响,因此本文重点综述了化学沉淀法制备不同形貌及尺寸的氢氧化镁和各影响因素对其制备的影响,以及当前氢氧化镁表面改性的一些新方法,如:大分子改性等,使得其在复合加工过程中,能与高分子材料具有良好的相容性.