Red phosphorus acts as second acid source to form a novel intumescent-contractive flame-retardant system on ABS

A novel halogen-free flame retardant prepared by poly(p-ethylene terephthalamide) and ammonium polyphosphate (APP) on acrylonitrile–butadiene–styrene (ABS) resin has a good flame retardancy when loading is 30 %; but, once the mass fraction is <30 %, the system does not maintain outstanding flame retardancy. To improve the efficiency of this kind of flame retardant and LOI values, higher thermal stability acid source-red phosphorus is introduced. It is found that a little quantity of red phosphorus will improve the flame retardancy of ABS remarkably and will change the process of charring; when the mass fractions of APP, PPTA, and red phosphorus are only 15, 5, and 2 %, respectively, though the LOI of flame-retardant ABS is 27, UL-94 vertical burning test still reach V-0. Thermogravimetric analysis data show that red phosphorus changes the thermal degradation behavior of IFR-ABS system, shrink digital photo display system, and yield more stable residue at higher temperature; Fourier transform infrared results and scanning electron microscopic micrographs show that red phosphorus can catalyze the charring and form much denser char to improve the flame-retardant performance of the materials.     

Mechanism of flame retardant action of red phosphorus in polyacrylonitrile

The mechanism of flame retardant (FR) action of red phosphorus in polyacrylonitrile combustion was investigated by thermogravimetry, flash-pyrolysis GC-MS, and combustion methods. Red phosphorus was found to increase the thermal stability in air of polyacrylonitrile and to induce a char residue increment on this substrate. Both these effects disappeared when pyrolysis was carried out under nitrogen flow. Flash-pyrolysis GC-MS experiments showed that red phosphorus does not alter the pyrolysis product distribution of polyacrylonitrile, which implies that there is no specific interaction between polyacrylonitrile and red phosphorus. These data also showed that polymeric red phosphorus decomposes to volatile white phosphorus (P₄) during pyrolysis. These observations allow us to propose a simple model for the mechanism of FR action of red phosphorus on polyacry-lonitrile at the molecular level. Combustion data for polyacrylonitrile-red phosphorus mixtures are in agreement with the proposed mechanism of FR action.     

Preparation and characterization of microcapsulated red phosphorus and its multi-step thermal oxidation processes based on kinetic approach

Aluminium hydroxide/melamine–formaldehyde resin microcapsulated red phosphorus (MRP) was successfully prepared by two-step processes. The microcapsulated red phosphorus was characterized with Fouriertransform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Meanwhile its water absorption, thermostability were also determined. The results show that the MRP exhibited lower water absorption and higher thermostability compared with red phosphorus (RP) itself. Moreover, the thermal oxidative decomposition kinetics of MRP was investigated by TG/DTG and DTA in air atmosphere using non-isothermal experiments. The results show that the MRP’s decomposition consisted of two steps. And the apparent activation energies E_α was determined by applying both the Ozawa–Flynn–Wall (OFW) and Kissinger, Akahira and Sunose (KAS) methods. It was found that the dependence of E_α on α is complex. Both of the steps in this study fitted Sestak–Berggren (SB) model in overall reaction controlled kinetics and the corresponding model parameters, n, m, A were obtained. The simulated curves were fitted to experimental curves by plotting dα/dt vs. temperature at different heating rates.     

Substituents effect on thermal electrocyclic reaction of dihydroazulene–vinylheptafulvene photoswitch: a DFT study to improve the photoswitch

Thermal cyclization for a series of substituted vinylheptafulvenes (VHFs) to dihydroazulenes (DHAs) was studied at PBE0 method of density functional theory in the gas phase and in the acetonitrile solvent (through PCM). Judicious control of the thermal reaction through substituent is quite necessary to design thermally robust DHA–VHF photoswitches. For most of the substituents, DHA was predicted thermodynamically stable over VHF except for amino (in gas phase and solvent) and hydroxyl (in acetonitrile), where DHA isomers were calculated thermally unstable compared to VHF. Activation barriers for thermal electrocyclic reaction in both media showed positive correlation with Taft’s σ _R values at positions 7 and 5, however, a negative correlation was observed at position 4 and 6. The latter unprecedented behavior is proposed to arise from the delocalization of negative charges on the seven membered ring. Activation barriers for amino-substituted VHFs were generally lower than expected from Taft’s σ _R. A fluoro group at the position 7 was quite effective in imparting very high activation barrier (31.73 kcal mol^?1) for the thermal cyclization in the gas phase. However, in the acetonitrile solvent, the highest activation barriers were observed for electron withdrawing CHO (28.10 kcal mol^?1) and NO₂ (28.13 kcal mol^?1) groups at positions 7.     

A mechanistic study of flame retardance of novel copolyester phosphorus containing linked pendant groups by TG/XPS/direct Py-MS

The flame retardant mechanism of the copolyester phosphorus containing linked pendant groups was investigated by thermogravimetric （TG）, X-ray photoelectron spectroscopy （XPS） and direct insertion probe pyrolysis mass spectrometry （DP-MS） technique. TG results show that the incorporation of phosphorus containing unit linked pendant groups can destabilize the copolyester due to the cleavage of P-CH2 bond, and phosphorus containing units cannot promote the char-formation of the copolyester during the thermal degradation of the copolyester. XPS spectra indicate that with the increase of the temperature, the P-CH2 bonds of the copolyester break down gradually, the concentration of phosphorus in the condensed phase products decrease gradually and the chemical state of phosphorus does not change in the temperature of 250-380 ℃. Direct pyrolysis MS suggests that the P-CH2 bonds cleavage occurs at pendant groups and species containing phosphorus can volatilize into the gas phase. A flame retardant mechanism is proposed for the gas phase mode of action of the halogen-free copolyester phosphorus containing linked pendant groups.     

团簇尺寸对奇数和偶数磷团簇离子信号强度差异的影响

磷原子形成的奇数和偶数团簇离子的信号存在明显的强度差异. 当团簇离子尺寸n>25时, 奇数团簇离子的信号强度一般会远远超过其邻近的偶数团簇离子. 为更好地理解团簇尺寸对这一现象的影响, 本文通过真空中激光溅射红磷的方法, 利用质谱对磷团簇离子进行了研究和分析. 结果表明这种方法可以产生较大尺寸(n~500)的磷团簇离子. 进一步对团簇离子的强度分布进行分析表明: 随着正负离子团簇尺寸的增加, 奇/偶数离子强度差异都会逐渐减小. 根据它们的变化趋势, 可以预测: 当n>1000时, 奇/偶数离子强度交替的现象可能会消失. 这一结果正反映出团簇在从原子演变到凝聚态物质过程中的桥梁作用.     

The influence of an N-alkoxy HALS on the decomposition of a brominated fire retardant in polypropylene

This work studies the effect of an N-alkoxy HALS on the thermal decomposition of a brominated phosphate ester fire retardant. We have monitored the fate of the fire retardant in the presence of the N-alkoxy HALS during thermal decomposition using TGA, FTIR, TD-GC-MS, NMR and ESR methods. We have shown that the two additives interact in the condensed phase at temperatures below the onset of polymer decomposition to produce 1,3-dibromo-2,2-bis(bromomethyl)-propane as the main decomposition product. It is believed that this molecule is the key to the fire retardant action of the brominated phosphate ester because it readily decomposes to the effective gas phase flame inhibiting agent, HBr.     

热裂解气相色谱质谱法分析聚合物中红磷

采用单击热裂解(PY)模式和逸出气体分析(EGA)程序升温两种热裂解模式对红磷样品进行定性分析,利用气相色谱分离技术对红磷进行分离,根据红磷的特征质谱31,62,93,124及特征丰度比,质谱法分析不同材料中的红磷含量。单击热裂解模式下,材质和添加剂有可能对红磷造成干扰,改进后的EGA热裂解模式能排除红磷检测中材质和添加剂的干扰,并采用改进后的EGA裂解程序测定自制阳性样品中红磷的含量。结果表明:通过优化裂解温度和气相色谱条件可以有效改善红磷的分析结果,红磷质量浓度在100~500 mg/kg范围内具有良好线性,加标回收率在90.7%~97.7%,相对标准偏差(RSD)为1.6%~2.3%,定量限为81.27 mg/kg。     

Numerical study of nitrogen desorption by rapid oxygen purge for a medical oxygen concentrator

Efficient desorption of selectively adsorbed N₂ from air in a packed column of LiX zeolite by rapidly purging the adsorbent with an O₂ enriched gas is an important element of a rapid cyclic pressure swing adsorption (RPSA) process used in the design of many medical oxygen concentrators (MOC). The amount of O₂ purge gas used in the desorption process is a sensitive variable in determining the overall separation performance of a MOC unit. Various resistances like (a) adsorption kinetics, (b) column pressure drop, (c) non-isothermal column operation, (d) gas phase mass and thermal axial dispersions, and (e) gas-solid heat transfer kinetics determine the amount of purge gas required for efficient desorption of N₂. The impacts of these variables on the purge efficiency were numerically simulated using a detailed mathematical model of non-isothermal, non-isobaric, and non-equilibrium desorption process in an adiabatic column. The purge gas quantity required for a specific desorption duty (fraction of total N₂ removed from a column) is minimum when the process is carried out under ideal, hypothetical conditions (isothermal, isobaric, and governed by local thermodynamic equilibrium). All above-listed non-idealities (a?Ce) can increase the purge gas quantity, thereby, lowering the efficiency of the desorption process compared to the ideal case. Items (a?Cc) are primarily responsible for inefficient desorption by purge, while gas phase mass and thermal axial dispersions do not affect the purge efficiency under the conditions of operation used in this study. Smaller adsorbent particles can be used to reduce the negative effects of adsorption kinetics, especially for a fast desorption process, but increased column pressure drop adds to purge inefficiency. A?particle size range of ??300?C500???m is found to require a?minimum purge gas amount for a given desorption duty. The purge gas requirement can be further reduced by employing a pancake column design (length to diameter ratio, L/D<0.2) which lowers the column pressure drop, but hydrodynamic inefficiencies (gas mal-distribution, particle agglomeration) may be introduced. Lower L/D also leads to a smaller fraction of the column volume that is free of N₂ at the purge inlet end, which is required for maintaining product gas purity. The simulated gas and solid temperature profiles inside the column at the end of the rapid desorption process show that a finite gas-solid heat transfer coefficient affects these profiles only in the purge gas entrance region of the column. The profiles in the balance of the column are nearly invariant to the values of that coefficient. Consequently, the gas-solid heat transfer resistance has a minimum influence on the overall integrated N₂ desorption efficiency by O₂ purge for the present application.     

密胺树脂/硼酸锌双层包覆微胶囊化红磷的制备及其在阻燃聚烯烃中的应用

描述了采用密胺树脂和硼酸锌连续双层包覆微胶囊化红磷(MRP)的最新制备方法。采用红外光谱、电子能谱和透射电镜等分析手段对其进行了表征，并证实红磷已被完全包覆。实验数据表明：经包覆的MRP的热稳定性获得了明显改善，吸水率和磷化氢的发生量均大大减少。MRP作为阻燃助剂应用于聚烯烃阻燃材料表现出了良好的阻燃效果。实时红外和热失重测量以及扫描电镜观察表明：其阻燃机制是红磷受热时与树脂反应促进了含磷膨胀炭层的形成，从而提高了材料的热稳定性，碳层起到了隔氧、隔热作用，而且主要在凝聚相中发挥其阻燃作用。     

Reactions of elemental phosphorus and phosphine with electrophiles in superbasic systems: XVIII. Phosphorylation of 1-(chloromethyl)naphthalene with the elemental phosphorus

1-Chloromethylnaphthalene reacts with white and red phosphorus, and also with the “activated red phosphorus,” the complex organophosphorus polymer of unknown structure obtained by irradiation of a solution of white phosphorus in benzene by the ⁶⁰Co source, in a system including KOH water solution, dioxane or benzene, and a phase transfer catalyst (22–98°C, argon), to form bis(1-naphthylmethyl)-and tris-(1-naphthylmethyl)phosphine oxides, and also (1-naphthylmethyl)phosphonous-and bis(1-naphthylmethyl)-phosphinic acids. The yield and the ratio of the reaction products depend on reaction conditions as well as on the nature of phosphorylating agent. It is shown that the reactivity of the “activated red phosphorus” is not worse than that of the white phosphorus and significantly exceeds the reactivity of the usual technical red phosphorus.     

Thermal decomposition of silver carbonate

Conflicting results have been reported by different workers on the thermal decomposition of silver carbonate, Ag₂CO₃. In the present study, the decomposition mechanism was elucidated by various analytical methods; gas analysis (differential thermal gas analyses) in helium, carbon dioxide and oxygen flows with and without a P₂O₅ trap or a KOH trap, DTA-TG in a carbon dioxide flow and high-temperature X-ray diffraction analysis in a carbon dioxide flow. The gas evolution at ca. 200?C consisted of carbon dioxide. A simultaneous evolution of carbon dioxide and oxygen occurred at ca. 400?C. Two endothermic peaks (ca. 189 and 197?C) without weight change during the heating in a carbon dioxide atmosphere were due to the phase transition of silver carbonate from the normal viaΒ toα phase. The reverse transition occurred during the cooling.     

Synergistic effect of red phosphorus, novolac and melamine ternary combination on flame retardancy of poly(oxymethylene)

New flame retardant system for poly(oxymethylene) (POM) has been studied. The combination of red phosphorus with novolac and melamine was found to act as an effective flame retardant of POM. The base POM exhibited very low limiting oxygen index (LOI) value of 15.3, while the flame retarded POM gave remarkably high LOI value of 37.5 and UL94 V-1 ranking without dripping at 0.8 mm thickness. The results of cone calorimetry, thermogravimetry and FTIR analysis suggested that the flame retarding mechanism is the intumescent char formation in the condensed phase. Novolac having a phenolic hydroxyl group is miscible with POM, and in the flaming process, red phosphorus yields phosphine and its acidic product such as phosphoric acid due to hydrolysis and oxidation reactions. In addition, all of novolac, melamine and phosphine are able to readily react with formaldehyde generated from POM during burning to give the reinforced and cross-linked char network through the polyaddition and polycondensation reactions. Therefore, the red phosphorus/novolac/melamine ternary combination system could synergistically promote the high flame retardancy of POM without the flaming drips.     

The size dependent shift of the surface plasmon absorption band of small spherical metal particles

It has been previously established that the surface plasmon of small spherical silver particles, which are embedded in a noble gas matrix, shifts to higher energies (blue shift) as the mean diameterD of the particles decreases (100 Å>D>20 Å). This blue shift has also been found for supported silver particles, and quite recently we observed it by elastic light scattering in the gas phase. This latter experiment proves unambiguously that the blue shift in small silver particles is not induced by interactions with the environment, the presence of which is clearly recognized in less inert matrices such as O₂ or CO. From self-consistent calculations of the surface response of planar jellium surfaces one would expect a red shift, which is also directly confirmed by a few calculations for selected jellium spheres. The contradiction between the observed blue shift for small particles and the predicted red shift for jellium spheres disappears, if one accounts for thed-electrons of silver in a very simple approximation.     

新型侧基含磷共聚酯的阻燃和热降解动力学

利用动态热重分析法(TG)研究了聚酯(PET )及侧基含磷共聚酯(FR-PET)在不同升温速率下的热稳定性及热降解动力学, 并通过极限氧指数法(LOI)考察了FR-PET的阻燃性能; 采用Flynn-Wall-Ozawa方法分析了PET和FR-PET的热降解表观活化能; 利用Coast-Redfern方法通过对不同机理模型的选取, 确定了PET和FR-PET热降解动力学机理及其模型, 得出了主降解阶段的非等温动力学方程及热降解速率曲线图. 研究结果表明, 侧基含磷单元的引入提高了聚酯的阻燃性能, 侧基上的P—C和P—O键易断裂, 从而降低了聚酯的热稳定性. PET和FR-PET的热降解表观活化能(0.1≤α≤0.85)分别为194-227和184-209 kJ/mol; PET和FR-PET热降解反应均属于受减速形α-t曲线控制的反应级数机理, 其机理函数为f(α)=3(1-α)2/3(0.1≤α≤0.85). 侧基含磷单元的引入对PET的主降解阶段的热降解速率并无实质上的影响. 侧基含磷共聚酯的凝聚相阻燃作用有限, 可能以气相阻燃机理为主发挥阻燃作用.     

Preparation and characterization of microcapsulated red phosphorus and kinetic analysis of its thermal oxidation

Microcapsulated red phosphorus (MRP) with aluminum hydroxide/phenolic resin coating layer was prepared by a two-step coating process. The results of Fourier-transform infrared spectroscopy and scanning electron microscopy show that red phosphorus (RP) is coated by aluminum hydroxide and phenolic resin. MRP absorbs less water and is more thermally stable than RP. The thermal oxidation kinetics of MRP was investigated by TG/DTG/DTA under air atmosphere using non-isothermal experiments with the heating rates ranging from 10 to 25°C/min. The values of the apparent activation energy E _a were 168 ± 9 kJ/mol as determined by the isoconversional Ozawa–Flynn–Wall method and 164 ± 12 kJ/mol according to the Kissinger?Akahira?Sunose method. Based on Málek’s procedure the kinetic reaction follows the ?esták–Berggren model with f(α) = α0.34(1 ? α)^0.94 (α is RP conversion) and pre-exponential factor A = 3.11 × 10¹² s^–1. The simulated curves were fitted with experimental curves constructed by plotting dα/dt vs temperature at different heating rates.     

Thermal decomposition of 1,3,3-trinitroazetidine in the gas phase, solution, and melt

1,3,3-Trinitroazetidine (TNAZ) was synthesized using the alternative approach based on the transformation of 3-oximino-1-(p-toluenesulfonyl)azetidine in the reaction with nitric acid through intermediate pseudonitrol. The thermal decomposition of TNAZ in the gas phase, melt and m-dinitrobenzene solution in a wide concentration range (5–80%) was studied by manometry, volumetry, thermogravimetry, IR spectroscopy, and mass spectrometry. In the gas phase in the temperature range from 170 to 220°C the thermal decomposition proceeds according to the first-order kinetic law with the activation energy 40.5 kcal mol^?1 and pre-exponential factor 10^15.0 s^?1. The major gaseous reaction products are N₂, NO, NO₂, CO₂, H₂O, and nitroacetaldehyde, and trace amounts of CO and HCN are formed. The rate-determining step of the process is the homolytic cleavage of the N-NO₂ bond in the TNAZ molecule. In melt at 170–210 °C the thermal decomposition proceeds with the pronounced self-acceleration and the maximum reaction rates are observed at conversions 53.9–67.4%. The solid decomposition products accelerate the reaction. It is most likely that the autocatalysis of TNAZ decomposition in the liquid phase is due to the autocatalytic decomposition of 1-nitroso-3,3-dinitroazetidine, which is formed by the thermal decomposition of TNAZ. In m-dinitrobenzene TNAZ also decomposes with self-acceleration. The higher the concentration in the solution, the more pronounced the self-acceleration. Additives of picric acid moderately accelerate the thermal decomposition of TNAZ, whereas hexamethylenetetraamine additives exert a strong acceleration.     

Influence of phosphorus valency on thermal behaviour of flame retarded polyurethane foams

This paper reports decomposition/pyrolysis studies of polyurethane (PU) rigid foams containing phosphinate, phosphonate or phosphate as flame retardant in order to study the effect of phosphorus oxidation state on their gas and/or solid phase action. The flame retardants analyzed were aluminium phosphinate (IPA), dimethylpropanphosphonate (DMPP), triethylphosphate (TEP) and ammonium polyphosphate (APP), which differ in oxidation state and/or decomposition temperature. Gases evolved during TGA analyses as well as solid residues have been studied by means of MS and FTIR.The results show that phosphorus flame retardants which significantly lose weight at temperatures lower than those of neat PU foams act in the gas phase irrespective of their valency: indeed, they are completely volatilized before polymer decomposition starts and thus no interaction between flame retardant and polymer can be expected. The effect of phosphorus oxidation state becomes important when flame retardant decomposition takes place in the same temperatures range as neat polymer. In this case, it seems that at lower P oxidation state (+1) a combined gas and solid phase action takes place while at higher P oxidation state (+5) only solid phase action was observed.     

Determination of pesticides in aqueous samples by solid-phase microextraction in-line coupled to gas chromatography—mass spectrometry

A multiresidue method was developed for the determination of nitrogen- and phosphorous-containing pesticides (amines, anilides, phosphorothioates, and triazines) by solid-phase microextraction (SPME) in-line coupled to gas chromatography—mass spectrometry (GC/MS). The 85-µm polyacrylate fiber was first dipped into the aqueous sample for a given time and then directly introduced into the heated injector of the gas chromatography—mass spectrometer, where the analytes are thermally desorbed. The method was evaluated with respect to the limit of detection, linearity, and precision. The limit of detection [selected ion monitoring (SIM) mode] depends on the compound and varies from 5 to 90 ng/L. The method is linear over at least 3 orders of magnitude with coefficients of correlation usually ≥0.996. In general, the coefficient of variation (precision) is <10%. The partitioning of the analyte between the aqueous phase and the polymeric phase depends on the hydrophobicity of the compound as expressed by the octanol—water partitioning coefficient P _ow. The addition of sodium chloride has a strong effect on the extraction efficiency. This effect increases with decreasing hydrophobicity (increasing polarity) of the compound. The triazines atrazine, simazine, and terbuthylazine were first identified and quantified in water samples from the effluent of sewage plants by SPME-gas chromatography—nitrogen—phosphorus detection (GC/NPD). For such a complex matrix GC/NPD is not sufficiently selective for an unambiguous identification at low levels (<1 ppb) of pesticides. Selectivity may be enhanced by using SMPE-GC/MS in the SIM mode with three characteristic ions for each pesticide. This method allows an unequivocal identification and quantification at low levels of pesticides in environmental samples. At a target limit of detection below 100 ng/L, SPME-GC/MS represents a very simple, fast, selective, and solvent-free multimethod for the extraction and determination of these nitrogen- and phosphorous-containing pesticides from aqueous samples.     

利用气相色谱顶空装置测定红磷储存过程中生成的磷化氢

采用气相色谱法测定了高温加速老化的红磷生成的磷化氢,用外标法定量。该方法的检测限达到0.001 μg/L,加标回收率大于97%,其相对标准偏差为2.35%~6.52%。研究了微量水和铁离子等在红磷产生磷化氢过程中的作用,结果表明：水是工业红磷产生磷化氢的必要条件,它为红磷生成磷化氢提供质子氢;随着红磷样品中水分的增加,它的氧化反应速度加快,磷化氢的生成量增加;但当水分含量达到一定数值时,磷化氢的增长幅度减缓;微量的铁盐影响红磷的氧化反应,不同酸的铁盐对反应的影响效果不同;亚铁氰化钾对抑制含铁盐红磷样品产生