Studies of phosphonate‐containing bismaleimide resins. I. Synthesis and characteristics of model compounds and polyaspartimides

Two phosphonate‐containing bismaleimide (BMI) [(4,4′‐bismaleimidophenyl)phosphonate] monomers with different melting temperatures and similar curing temperatures were synthesized by reacting N‐hydroxyphenylmaleimide with two kinds of dichloride‐terminated phosphonic monomers. The BMI monomers synthesized were identified with ¹H‐, ¹³C‐, and ³¹P‐nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. The phosphonate‐containing BMI monomers react with a free‐radical initiator to prepare phosphonate‐containing BMI polymers and also with various aromatic diamines to prepare a series of polyaspartimides as reactive flame retardants. The polymerization degrees of polyaspartimides depend on the alkalinity and nucleophility of diamines as chain extenders. Differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA) were used to study the thermal properties of the phosphonate‐containing BMI resins such as the melting temperature, curing temperature, glass transition temperature (T_g), and thermal resistance. All the phosphonate‐containing BMI resins, except the BMI polymers, have a T_g in the range of 210–256°C and show 5% weight loss temperatures (T_5%) of 329–434 and 310–388°C in air and nitrogen atmospheres, respectively. The higher heat resistance of cured BMI resin relative to the BMI polymer is due to its higher crosslinking density. Since the recrosslinking reactions of BMI polymers and polyaspartimides occur more easily in an oxidation environment, their thermal stabilities in air are higher than are those in nitrogen gas. In addition, the thermal decomposition properties of polyaspartimides depend on the structures and compositions of both the diamine segments and the BMI segments. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1919–1933, 2002     

New developments in speciality polymers: polymeric stabilizers

Many new speciality polymers have been developed in the last few years. In this paper polymeric stabilizers (antioxidants, flame retardants and ultraviolet stabilizers) will be discussed. Polymeric antioxidants of the hindered-phenol type, copolymers of 2,6-ditertiarybutyl-4-vinyl(or isopropenyl)phenol with styrene, methyl methacrylate, or more importantly butadiene or isoprene have been prepared; hydrogenation of the latter copolymers gave copolymers of the two polymerizable phenolic antioxidants with ethylene or ethylene/propylene. The polymeric antioxidants have been blended with diene polymers and selected polyolefins and have improved the long-term oxidative stability of these polymers. Polymeric flame retardants have been prepared by copolymerizing styrene and/or acrylonitrile with acrylates and methacrylates of aliphatic bromine-containing alcohols or bromine-containing phenols. Polymers with polymer-bound flame retardants have a higher limiting oxygen index compared with the original polymer. A new class of polymerizable ultraviolet stabilizers has also been developed; these stabilizers are styryl, α-methylstyryl, acryloyl and methacryloyl derivatives of 2(2-hydroxyphenyl)2H-benzotriazoles. These monomers have been copolymerized with styrene, acrylates and methacrylates. 2(2-Hydroxyphenyl)2H-benzotriazoles substituted in the 4 position of the benzotriazole ring with hydroxyl, acetoxy or carboxyl groups suitable for incorporation into polyesters, polycarbonates, polyamides and epoxy resins have also been synthesized. All 2(2-hydroxyphenyl)2H-benzotriazole ultraviolet absorbers and the polymers into which they are incorporated have high light absorbency with γ_max between 330 and 350 nm and extinction coefficients in some cases as high as 4.5 × 10⁴ 1 mol^?1 cm^?1.     

The flammability of polyacrylonitrile and its copolymers III. Effect of flame retardants

This paper extends previously reported work ^1,2 and describes the influence that a range of selected flame retardants have on the burning behaviour and pyrolyses of homo-and copolymers of acrylonitrile. Various inorganic and organic phosphorus and nitrogen- or sulphur-containing, halogen-containing (in the absence and presence of halogen or antimony (III) oxide) and nitrogen-containing flame retardants and red phosphorus were studied using LOI, TGA, DSC and residual char measuring techniques. Flame retardancy relates directly to char-forming tendency for all retardants and their ability to reduce the dominance of flammable volatiles formed during the first stage of acrylic polymer pyrolysis. Ammonium phosphates are particularly effective flame retardants for the selected copolymers. Possible mechanisms of retardant activity are discussed, including the char-forming tendency of antimony–bromine combiniations.     

Flammability testing of pure and flame retardant-treated cotton fabrics

A Controlled-atomosphere cone calorimeter was used to investigate the burning of pure and flame retardant-treated cotton fabrics. The condensed-phase flame retardants used were Morguard (containing ammonium dihydrogen phosphate and diammonium hydrogen phoisphate) and Nochar (containing ammonium sulfate and a sodium salt). The fabrics were tested at 25 kW m^?2 incident heat flux in environments containing 15–30% oxygen. The flame retardants increased the time to ignition, residue yield, and CO and CO₂ yields. The flame retardants decreased the peak and average mass loss rates, the peak and average heat release rates, the effective heat of combustion at peak heat release rate, and the propensity to flashover. The effect of oxygen concentration on the burning of pure and flame retardant-treated cotton fabrics has also been investigated. The flame retardants had better performance when the treated fabrics burned in the lower oxyge concentrations. The result of this study indicate that the controlled-atmosphere cone calorimeter is a good tool for studying the effect of flame retardant and oxygen concentration on the burning of materials.     

Flammability behavior of unsaturated polyesters modified with novel phosphorous containing flame retardants

Two phosphorous containing reactive flame retardants namely Triallyl phosphate (TAP) and diethylene glycol modified tetra‐allyl phosphate (DTAP) are synthesized and incorporated successfully in commercial Unsaturated polyester (UPR) in various amounts (5, 10, and 15 phr) to yield flame retardant unsaturated polyester (FRUPR) composites. The structures of reactive flame retardant monomers are confirmed by FTIR, ¹H‐NMR, and³¹P‐NMR spectroscopy. Further, FRUPR composites are characterized for their mechanical, thermal, and flame retardant properties. It is observed that tensile strength and hardness of composites are enhanced with the addition of flame retardants; however, flexural strength and impact resistance are lowered. Differential Scanning Calorimetry (DSC) study reveals that there is a significant increase in glass transition temperature with the addition of flame retardants suggesting the formation of dense and crosslinked structure in FRUPR composites. Thermal stability and the flame retardant properties are also observed to be improved with the increase in concentration of flame retardant in UPR as evidenced from Thermo‐gravimetric analysis (TGA). Beyond 10 phr concentration of flame retardants, all composites show V‐0 rating on UL‐94 test. Also, increase in phosphorous content in composites leads to gradual improvement in limiting oxygen index values. POLYM. COMPOS., 38:1483–1491, 2017. © 2015 Society of Plastics Engineers     

Flame resistance and foaming properties of NBR compounds with halogen‐free flame retardants

Acrylonitrile butadiene rubber (NBR) foams compounded with various halogen‐free flame retardants were prepared. The influence of nonhalogen flame retardants on the flame resistance and foaming properties of the NBR compounds were investigated. The foaming properties (expandability 980%–1050%, closed‐cell structure) of NBR compounds with expandable graphite (EG) and ammonium polyphosphate (APP) flame retardants were similar to the NBR base compounds which contained primarily aluminum hydroxide (ATH). The heat release capacity (HRC) ranged from 10 to 74 J/g‐K, the average heat release rate (A‐HRR) ranged from 8 to 60 kW/m², and the total heat release (THR) ranged from 2.6 to 7.3 MJ/m² for the nonhalogenated NBR foams with closed‐cell structure and were significantly decreased upon increasing the amounts of flame retardants. This reduction is attributed to the hard char formation and production of water from the interaction with ATH. The limiting oxygen index (LOI) and time to ignition (TTI) show opposite results. The smoke density (0.050–0.037) of the NBR foams with EG flame retardant was decreased when compared to the NBR foam (0.107). The EG flame retardant was more effective than the phosphorus/nitrogen flame retardants in reducing the HRR and smoke density. The use of both ATH and EG is very effective in improving flame resistance. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Ecological issue of polymer flame retardancy

The use of polymer flame retardants has an important role in saving lives. The main flame retardant systems for polymers currently in use are based on halogenated, phosphorous, nitrogen, and inorganic compounds. All of these flame retardant systems basically inhibit or even suppress the combustion process by chemical or physical action in the gas or condensed phase. Conventional flame retardants, such as halogenated, phosphorous, or metallic additives, have a number of negative attributes. An ecological issue of the application of conventional flame retardants demands the search of new polymer flame retardant systems. Among the new trends of flame retardancy are intumescent systems, polymer nanocomposites, preceramic additives, low‐melting glasses, different types of char formers, and polymer morphology modification processing. The brief explanations on the three major types of flame retardant systems (intumescent systems, polymer nanocomposites, and polymer organic char formers) are the subject of this overview. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2449–2462, 2002     

高分子材料无卤阻燃剂的研究现状

综述了高分子材料无卤阻燃剂的种类和阻燃机理,重点介绍了无机物阻燃剂、无卤膨胀型阻燃剂、有机硅阻燃剂等无卤阻燃剂的开发和在高分子材料中的应用研究现状并,对无卤阻燃剂的发展方向进行了展望。     

高分子体系阻燃剂的研究新进展

使用阻燃剂可避免火灾中聚合物燃烧所带来的危害,但常用的阻燃剂存在阻燃效率低、燃烧时烟雾大或对复合材料的力学性能产生不良影响等缺点。本文介绍了新技术(包括纳米技术、微胶囊化技术)在高分子阻燃体系中的应用及研究现状,并对其阻燃机理进行了阐述。通过分析阻燃剂的发展趋向预测了阻燃高分子材料发展的一些新趋向。     

Flame retardance and origin of bismaleimide resin composites with green and efficient aluminum phosphates

Developing green and high efficiency inorganic flame retardants is the trend of preparing flame retarding polymer composites. Aluminum phosphates (t‐hAP) with uniform, small dimension, and hexagonal structure were facilely synthesized, which have similar size (1–2 μm) but different structures from commercial spherical‐like aluminum phosphate (cAP). The flame retardance of bismaleimide (BD)/t‐hAP and BD/cAP composites were intensively investigated. t‐hAP is proved to have much better flame retarding effect than cAP, but also exhibits advantages over Mg(OH)₂ and Al(OH)₃. With only 5 wt % addition of t‐hAP into BD resin, the peak and total heat releases as well as total smoke production significantly reduce 42.3, 47.8, and 67.3%, respectively; besides, better data are obtained as the loading of t‐hAP increases to 10 wt %. These attractive data result from three effects induced by t‐hAP. Besides the better protection role of sheet structure, the strong hydrogen bonding between t‐hAP and BD resin endows the composite with good dispersion of t‐hAP and high crosslinking density; moreover, t‐hAP releases H₂O and NH₃, diluting flammable gases during combustion. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41089.     

Synthesis of brominated acenaphthylenes and their flame-retardant effects on ethylene–propylene–diene terpolymer

Bromoacenaphthylenes and their condensates as flame-retardant reagents were synthesized by bromination of acenaphthylene using ZnCl₂? CF₃COOH or FeCl₃ as catalysts and subsequent dehydrobromination. The chief components were identified as bromoacenaphthylene monomers when ZnCl₂? CF₃COOH were used, and as their condensates (mostly trimers) in the case of FeCl₃. Their performance as flame-retardant reagents for ethylene–propylene–diene terpolymer (EPDM) was evaluated by measuring the oxygen index of finished compounds, and flammability by a vertical flammability test based on UL-94-VO. Both the monomers and the condensates demonstrated high flame-retardant effectiveness. The high efficiency was attributed to their excellent dispersity in the base polymer and their characteristic thermal decomposition behavior. In TGA, they decomposed in a very wide range of temprature (ca.200–560°C), which covers the decomposition range of EPDM. This was attributed to the existence of bromines of different thermal stabilities in one molecule.     

Decabromobiphenyl oxide–aluminum hydroxide system as a flame retardant for styrene–butadiene rubber

Styrene–butadiene rubber (SBR) was treated with decabromobiphenyl oxide (DBBO) and/or aluminum hydroxide [Al(OH)₃] as a flame retardant. The flammability of the resulting system was determined by the limiting oxygen index method. The effect of the added flame retardants on the maximum torque (MH), curing rate, and tensile properties was also evaluated. The results showed, particularly, that DBBO was a more effective flame retardant than was Al(OH)₃. On the other hand, this brominated compound reduced the modulus of elasticity while its effect on the maximum torque was insignificant. Moreover, the addition of DBBO was found to decrease the curing rate of SBR. In contrast, Al(OH)₃ significantly increased the maximum torque and also markedly reduced the modulus of elasticity. Moreover, the effect of the treatment with Al(OH)₃ on the curing rate was found to be insignificant. The flammability measurement of the SBR treated with different mixtures of the two flame retardants indicated that the two compounds reacted slightly antagonistically. The addition of Al(OH)₃ to DBBO in a mixture that was applied to SBR remedied some negative impacts on the mechanical properties when DBBO was added separately to the rubber. The value of the maximum torque of SBR increased and the curing rate slightly increased as well. Meanwhile, the values of the modulus of elasticity were not affected. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2134–2139, 2000     

Halogeno‐modified polystyrene: monomer reactivity ratios,thermal behaviour and flammability

Chemical modification based on incorporation of flame retardants into polymer backbones was used in order to reduce flammability of polystyrene (PSt). The halogeno‐substituted styrenes: 4‐chlorostyrene (ClSt), 4‐bromostyrene (BrSt) and 2,3,4,5,6‐pentafluorostyrene (5FSt) were applied as reactive flame retardants. Homo‐ and copolymers of these halogeno‐substituted styrenes and styrene (St) were synthesized with various feed ratios using free radical bulk polymerization with azobisisobutyronitrile as a initiator. This yielded series of (co)polymers with various amounts of included ClSt, BrSt and 5FSt (5–50 mol% of modified St). Copolymer compositions were determined using ¹H NMR spectroscopy. The relative reactivity ratios of the used comonomers were determined by applying conventional linearization methods. The Jaacks (J) method was used for systems including BrSt and ClSt monomers whereas the Fineman–Ross method was additionally used to confirm the values of reactivity ratios of St–5FSt. The reactivity ratios of comonomer pairs obtained from J plots were 0.75 and 0.38 (St–ClSt), 1.65 and 0.46 (St–BrSt), 0.44 and 0.42 (St–5FSt). Glass transition temperature and thermal stability of obtained (co)polymers were determined using differential scanning calorimetry and thermogravimetric analysis (TGA), respectively. The thermal degradation kinetic of PSt, PClSt, PBrSt and P5FSt was studied applying TGA. Kinetic parameters such as thermal decomposition activation energy (E) and frequency factor (A) were estimated using Ozawa and Kissinger models. The resulting activation energies estimated using these two methods were quite close. The values of activation energy (kJ mol^?1) increased in the following order: PClSt (E(O) = 216.1) < PSt (E(O) = 219.9) < PBrSt (E(O) = 224.7) < P5FSt (E(O) = 330.9). A pyrolysis combustion flow calorimeter was applied as a tool for assessing the flammability of the synthesized (co)polymers. © 2014 Society of Chemical Industry     

无卤阻燃剂合成及应用研究进展

从绿色环保的角度出发,对比了含卤阻燃剂对环境的危害和无卤绿色阻燃剂的低毒、低烟和高效阻燃的特点,介绍了磷系阻燃剂、膨胀型阻燃剂、硅系阻燃剂、无机金属阻燃剂以及生物基阻燃剂的合成方法及其在相关高分子材料中的应用研究进展。分析表明,磷氮等复配阻燃剂和合成新型的P,N,Si等多元素一体的阻燃剂,不仅阻燃效果好,对基体材料的其它性能影响也小。尤其是生物基阻燃剂,满足对绿色环保和可持续发展的需求,将成为未来阻燃剂开发的热点。     

PA6的填充阻燃研究进展

简单分析了PA6的阻燃途径,详细综述了近年来填充型阻燃剂在PA6中的应用,包括含卤阻燃剂、无卤阻燃剂及有机高分子阻燃剂等,讨论了各自的阻燃机理,最后预测了应用于PA6的阻燃剂未来发展趋势。     

Study of Heat Shrinkability and Flame Retardancy of Poly(ethylene vinyl acetate)/Epichlorohydrin Blends

Greater cure time (crosslinking) and greater elastomer content increases the shrinkability as well as flame retardancy of the blends. Additive flame retardants hamper the heat shrinkability of the blend to some extent depending on various factors. The depression of shrinkability due to interference of flame retarding agent is less for cured sample and elastomer‐rich blend compared to uncured and plastic‐rich blend, respectively. At high temperature the shrinkability is higher, but the sacrifice of shrinkability in the presence of flame retardants increases with increase in temperature, for a particular blend. The highest flame retardancy is obtained in presence of Sb₂O₃/Chlorohor and TPP/Zn metaborate.     

阻燃剂氢氧化镁的国内研究进展

综述了氢氧化镁的改性方法及其在高分子聚合物材料阻燃中的应用的国内研究进展,介绍了氢氧化镁与其他阻燃剂在阻燃高分子聚合物一同应用时的协同效应。     

Ecological Aspects of Polymer Flame Retardation

Abstract

The practical application of commercial polymer flame retardant can no longer meet alone the present requirements either in terms of effectiveness or hazard. The most effective flame retardants so far are halogen, phosphorous, antimony and heavy metal based compounds which however have the most environmental impact either while they perform their action or when burned in incineration of waste containing fire retardant polymeric materials.

The practical search of new ecologically-friendly flame retardants requires cooperation between industrial and academic research. This presentation is devoted to only some of new trends in this very important task: Polymer Char Formers, Low-rflelting Glasses Systems, Morphological Modifications.     

Effect of hydrated fillers and red phosphorus on the limiting oxygen index of poly(ethylene‐co‐vinyl actate)‐poly(vinyl butyral) and low density polyethylene‐poly(ethylene‐co‐vinyl alcohol) blends

The limiting oxygen index (LOI) values of EVA‐PVB and low density polyethylene (LDPE)‐poly(ethylene‐co‐vinyl alcohol) (EVOH) polymer blends containing hydrated filler‐type flame retardants and red phosphorus were measured. When used as the sole flame retardant, magnesium hydroxide [Mg(OH)₂] and alumina trihydrate (ATH) performed best in EVA and PVB, respectively. Magnesium hydroxide addition had a limited effect on the LOI of plasticized PVB, and addition of red phosphorus made little difference. This result is attributed to a mismatch between the decomposition temperature of Mg(OH)₂ and the temperature at which the PVB plasticizer vaporizes. Otherwise, low‐level addition of red phosphorus significantly improved LOI values. The presence of hydroxyl groups on the polymer backbone had a beneficial effect with respect to LOI values in ATH‐filled blends. An LOI value of 30 was achieved in EVOH with as little as 32% of ATH and 3% of red phosphorus. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

Preparation of flexible,self‐extinguishing silicone foams

Flexible, self‐extinguishing silicone foams (SFs) with a relatively low density (0.25–0.45 g/cm³) were obtained from a mixture of α,ω‐(dihydroxy)polydimethylsiloxanes, water, flame retardants (melamine and/or expanded graphite), and polyisocyanates [poly(diphenylmethane isocyanate)]. These compositions were crosslinked at room temperature with branched polymethylhydrosiloxanes with the structure (MeSiO_1.5)₃ (MeHSiO)₁₀₂(Me₃SiO_0.5)₅ in the presence of tin octoate as a catalyst. The SFs were modified by the addition of linear or graft carbofunctional polysiloxanes containing γ‐hydroxypropyl groups. Only the SFs prepared by means of a dehydrocondensation reaction had a good homogeneity of pores, whereas the foams formed with two kinds of blowing agents (hydrogen and carbon dioxide, generated in the reaction of water with isocyanate groups) had lower densities but a poor homogeneity of pores. Unmodified SFs showed a tensile strength of 20 kPa or less, whereas the foams formed with the addition of poly(diphenylmethane isocyanate) and water had a tensile strength of 23–25 kPa. The SFs with 15 and 30% contents of melamine or expanded graphite had tensile strengths in the ranges 38–45 and 51–54 kPa, respectively. All of the prepared SFs were combustible materials. The SFs without the addition of flame retardants had a limiting oxygen index of approximately 21%, whereas the SFs with a 30% content of fire retardant had self‐extinguishing properties and a limited oxygen index of 41–43%. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011