Synthesis,characterization, and modification of 2-allylphenoxyorganocyclotriphosphazene copolymers

The monomer 2-allylphenoxyorganocyclotriphosphazene I with phenoxy (or 2,2,2-trifluoroethoxy) side group was synthesized on reacting hexachlorocyclotriphosphazene with phenol (or 2,2,2-trifluoroethanol) and 2-allylphenol with phase-transfer catalysis in a dichloromethane/alkaline solution. The synthesis had a large yield (>80%) and narrow product distribution and proceeded under mild condition. The radical copolymerization of I with II (styrene, methyl methacrylate, and vinylbenzyl chloride) using azobis(isobutyrylnitrile) (AIBN) as an initiator was investigated. Reactivity ratios and Alfrey–Price parameters for copolymers were obtained. Organophosphazene monomer I was less reactive than II . The thermal stability of the copolymer with phenoxy side group was greater than that with 2,2,2-trifluoroethoxy side group. The incorporation of organophosphazene units into an organic polymer backbone decreased the glass transition temperature and increased the thermal stability of the copolymers. Tensile measurement showed that Young's modulus tended to decrease and the polymer became softer and ductile when the incorporated amount of I increases. © 1996 John Wiley & Sons, Inc.     

Corrosion and thermal characterization of styrene based copolymers

Films from copolymers with resistance to wear, corrosion and thermal degradation as well as other important functions have been applied in many fields. It is known that the introduction of anionic hydrophilic groups in the polymer enhances its adhesion to substrates and protective function. In the present work, copolymers of styrene with acrylic, methacrylic and itaconic acids were prepared by polymerization in toluene with benzoyl peroxide initiation (BPO) and have been tested as anticorrosive films. The copolymers were analyzed by FTIR and TGA methods. Polarizing microscope images were employed to characterize the anticorrosive properties of the formed films. All copolymers produced in this work show strong adhesion to the substrate.     

Thermal analysis of a cylindrical lithium-ion battery

This work investigates the heat generation characteristics of a cylindrical lithium-ion battery. The battery consists of the graphite, LiPF₆ of the propylene carbonate/ethylene carbonate/dimethyl carbonate (PC/EC/DMC) solution, and spinal as anode, electrolyte and cathode, respectively. The coupled electrochemical–thermal model is developed with full consideration of electrolyte transport properties as functions of temperature and Li ion concentration. A truly conservative finite volume numerical method is employed for the spatial discretization of the model equations. Three types of heat generation sources including the ohmic heat, the active polarization heat and the reaction heat are quantitatively analyzed for the battery discharge process. The ohmic heat is found to be the largest contribution with around 54% in the total heat generation. About 30% of the total heat generation in average is ascribed to the electrochemical reaction. The active polarization contributes the least comparing to the ohmic heat and reactions heat. The results also show that the Li ion concentration and its gradient in electrolyte are the main factors giving the effect on the heat generations of active polarization and electrolyte electric resistance. The raised temperature in the battery discharge is positive related with the thickness of both separator and electrodes.     

Nonisothermal Co-Polymerizing Behavior and Thermal Properties of Methylacyloxylpropyl-POSS with Styrene

The methylacryloylpropyl-polyhedral oligomeric silsesquioxanes (MAP-POSS) was introduced into the PSt by copolymerization. The copolymerizing kinetics was investigated by non-isothermal DSC. The mechanical loss peak temperature T _p and thermal properties were determined by DMA and TGA. The results show that the compatibility of MAP-POSS with styrene is very well and can copolymerization. The relationship of polymerization E _a and conversion α be obtained. The copolymerization reactions can be described by the autocatalytic ?esták-Berggren (S-B) equation. The T _p was increased about 13°C than pure PSt, and up to a maximum of 110.8°C when the MAP-POSS contents is 10 wt%.     

Thermal analysis and mechanical characterization of maleimide‐functionalized benzoxazine/epoxy copolymers

Maleimide‐functionalized benzoxazine is copolymerized with epoxy to improve toughness and processibility without compromising the thermal properties. The incorporation of maleimide functionality into the benzoxazine monomer results in a high performance polymer. All three possible polymerization reactions are confirmed using Fourier transform infrared (FT‐IR) spectroscopy. While maleimide‐functionalized benzoxazine has a glass transition temperature, T_g, of 252°C, a further 25°C increase of T_g is observed when copolymerized with epoxy. The flexural properties are also measured, and the copolymers exhibit a flexural modulus of 4.2–5.0 GPa. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1670–1677, 2006     

Liquid-solid-liquid phase-transfer catalysis in sequential phosphazene reaction: kinetic investigation and reactor design

The reactor design and kinetics of the substitution reaction of hexachlorocyclotriphosphazene, (NPCl₂)₃, with phenol to synthesize the partially substituted (phenoxy)chlorocyclotriphosphazene was investigated by using triphase catalysis in an organic phase/alkaline solution. Two reactors, the slurry reactor and the fixed-bed reactor were proposed to evaluate a liquid-solid-liquid triphase reaction. The design problems of these reactors were evaluated to obtain the best performance. A cross type “+” Teflon magnetic stirrer was put in the bottom of the slurry reactor that can reduce the liquid flow rate to prevent solid catalyst to flow out of the reactor. Because the mass-transfer rate for the first and second degree of the substitution of the series phosphazene reaction were slow, they reacted in situ with sodium phenolate in the interior of the resin to form the two to five degrees of the substituted products. The kinetic parameter of the phosphazene reaction was influenced by the particle diffusion of the reactant. The effectiveness factor and Thiele modulus of the system and the diffusivity of the reactants were also obtained. The relationship of the coverage of catalyst onto the interfacial area between the two phases with the reaction-rate constant was studied.     

POSS/PS纳米复合微球的制备与热性能研究

采用乳液共聚法合成了POSS/PS纳米复合微球,研究了反应条件对复合材料热性能的影响.结果表明,合成的微球形态规则、尺寸分布较均匀,微球具有核壳型结构,尺寸可调,微球尺寸可控制在50nm左右.通过共聚引入刚性POSS结构,使得POSS/PS纳米复合材料的玻璃化温度显著高于纯PS,耐热性明显改善.     

Geometrical influence of ABn monomer structure on the thermal properties of linear-hyperbranched ether-ketone copolymers prepared via an AB+ABn route

A series of poly(ether ketone) copolymers were prepared by nucleophilic aromatic polymerization reactions of 4-fluoro-4′-hydroxybenzophenone, 2, in the presence of varying percentages of AB_n monomers based on a triarylphosphine oxide platform, 1a (2F), 1b (4F), and 1c (6F), where A=OH and B=F. As expected, the crystallinity of the samples decreased with an increasing AB_n content. However, the tetrahedral geometry of the phosphine oxide-based AB_n monomers proved to be much more efficient at lowering the melt temperature of the copolymers than was the corresponding ketone-based AB_n monomer, 3,5-bis(4-fluorophenylbenzoyl)phenol, 4, that possesses a structure more similar to that of 2. Polymerization of 2 in the presence of as little as 5 mol% of bis-(3,4,5-trifluorophenyl)-(4-hydroxyphenyl)phosphine oxide, 1c (6F), afforded a completely amorphous polymer with a glass transition temperature of 168 °C that was soluble in hot NMP and DMSO. The copolymers also exhibited excellent thermoxidative stability with a number of samples displaying 5% weight loss temperatures, in air, well in excess of 500 °C.     

Thermal runaway prediction for impregnated activated carbons from isothermal DSC measurements

Isothermal DSC measurements are used to extract the kinetics of the reaction between activated carbon, which has been impregnated with K₂CO₃, and air at elevated temperature. For the carbon studied here, the reaction takes place in two apparently independent processes. In the first process, the surface functional groups react with the carbon and with air, and in the second process the remaining carbon reacts with air. The impregnate causes the dramatic acceleration of the reaction compared to the reactivity of the pure base carbon in air. The reaction of the surface functional groups with air obeys the following reaction for the fractional degree of conversion, dα₁/dt=γ₁ exp(−E_a1/k_BT) α₁^m (1−α₁)ⁿ, with m and n approximately equal to −0.95 and 0.5, respectively. The reaction of the remaining carbon with air follows zero-order reaction kinetics. The obtained reaction kinetics can fit the results of isothermal DSC measurements over a wide range of temperature and scanning DSC measurements over a wide range of sweep rates, without any adjustment of parameters. The reaction kinetics, among other experimentally-derived parameters, were then used to calculate the temperature-time profiles for samples of carbon held in stainless steel mesh cylinders of various diameters within a heated constant-temperature oven. These calculations are shown to agree well with experiments at numerous temperatures for two cylinder radii using the same set of kinetic parameters used to fit the DSC results. Some of the temperatures and radii were selected such that thermal runaway of the carbon sample would occur, and the simulations modeled the time and temperature of this runaway accurately. Therefore, it should now be possible to simulate the temperature-time response of this particular impregnated carbon to conditions of high-temperature storage, such as those of the IATA oven exposure test or to storage within a shipping container exposed to a particular thermal history.     

硝酸胍型产气药热分解动力学研究

采用TG-DSC技术研究了受热条件下硝酸胍型产气药的热稳定性、分解动力学和贮存期,并利用Kissinger法、Ozawa法计算了硝酸胍型产气药的热分解表观活化能(Ea)、指前因子(A)和速率常数(k),结果表明Kissinger法与Ozawar法所得动力学参数较为相近。采用恒温法预估了其使用寿命。     

氢氧化镁纳米棒的热分析干燥动力学研究

在不同干燥介质温度（333～513K）和不同物料床层厚度（0．5～7mm）的恒定干燥条件下,得到氢氧化镁纳米棒的干燥曲线和干燥速率曲线。采用热分析动力学技术对干燥动力学实验数据进行处理后,得到氢氧化镁纳米棒的干燥微分机理函数为f（1-MR）=2MR（-MR）^1/2,干燥积分机理函数为g（1-Mg）=（-lnMR）^1/2,干燥方程为Mn=exp[-（kt）^2],干燥速率方程为-dMR/dt=2kMR（-lnMR）^1/2,干燥速率常数为k=Aexp[-Ea／RT]=Aexp[-Ev（1＋CLL）／RT];指前因子A=10．741min^-1,界面蒸发活化能Ev=10．671kJ/mol,经验常数CL=100．000m^-1。     

壳聚糖与MAA接枝共聚反应及产物热性能研究

用硝酸铈铵引发壳聚糖(Cs)与甲基丙烯酸(MAA)接枝共聚，研究了接枝共聚反应产物组成与单体及引发剂浓度的关系，以及Cs接枝前后的热性能。结果表明，接枝共聚物的接枝率、接枝效率、均聚物含量，以及总转化率随单体及引发剂浓度的增加而呈现先增加后下降的趋势。同时，由于接枝聚合，使Cs大分子原来的结晶结构受到破坏，导致热稳定性有所下降。     

旋光性和带官能团的三元共聚物--香茅醇、苯乙烯和甲基丙烯酸甲酯的合成与表征及动力学研究

深入研究了一系新型的三元共聚物合成，包括两个给电子单体，即单茅醇（旋光性）和苯乙烯，一个接受电子单体，甲基丙烯酸甲酯，用BPO为自由基引发剂，二甲苯为溶剂，在80℃下反应2h.该体系符合理想动力学特征，总活性自由能为33KJ／mol,用H－NMR分析了三元共聚物的结构，7－8δ的峰为苯基质子峰，3．4－4δ的峰为含甲氧基质子峰，7－7．5δ为乙醇基质子峰，此外，用FTIR光谱分析，在波长2900cm^-1,1750cm^-1和3400cm^-1分别是苯基，甲氧基，和乙醇基的峰，进入共聚物组分的单体通过Kelen-Tudos方法确定，反应比率的值为r1(MMA)=0.9,r2(苯乙烯＋香茅醇）＝0．02。     

High-Temperature Bulk Copolymerization of Methyl Methacrylate and Acrylonitrile: III. Thermal Polymerization

The thermally initiated copolymerization of methyl methacrylate and acrylonitrile has been studied in the bulk phase. Experiments for estimating reactivity ratios were conducted at 120°C and 140°C. Feed composition constraint approaches were used to design the reactivity ratio experiments. The error in variables model (EVM) method was employed to evaluate the reactivity ratios and analyze the error. The results showed that the reactivity ratios did not vary significantly with temperature up to 140°C for both thermally initiated and experiments with initiator. Full conversion range experiments were also conducted at 140°C. The rate of reaction, copolymer composition, M¯ _n , M¯ _w , and glass transition temperatures of samples were measured.     

肥煤的热抽提及其抽提物的性能研究

主要考察了肥煤在不同温度及不同溶剂下的热抽提性能,并对热抽提物性质进行了分析。实验结果表明,提高热抽提温度,肥煤热抽提率增大,并在其软化点附近达到最高值,而后随温度的升高而降低;增大溶剂极性,肥煤热抽提率也显著升高。热重和红外分析显示了热抽提物结构的变化,其基本无灰的特点有望成为煤洁净利用的突破口。     

Random copolymers of propylene with 1,5-hexadiene containing only cyclopentane units in main chain and tailoring structure and mechanical properties of the copolymers

In the presence of [Ph₃C][B(C₆F₅)₄] and Triisobutylaluminium, dimethyl pyridylamidohafnium complex exhibited remarkable catalytic activity in the copolymerization of propylene with 1,5-hexadiene, affording high molecular weight copolymers with unimodal molecular weight distributions. More noticeably, the resultant copolymers contain absolutely cyclo-group in the polymer chains without pendent vinyl groups and crosslinking. The solid state structures and properties of the homogeneous copolymers were studied by examining melting behavior, wide-angle X-ray scattering, and tensile deformation. Chain microstructures were analyzed by ¹³C NMR spectra, and further confirmed by the measurement of reactivity ratios of the two monomers. These copolymers display a random distribution of the comonomer, and crystallinity decreases with increasing comonomer content. The copolymers contain variable amounts of comonomeric units, showing desired physical properties ranging from thermoplastic to elastoplastomeric to elastomeric.     

Thermal decomposition of tetrachloroethylene with excess hydrogen

Tetrachloroethylene (C₂Cl₄) was used as a model of highly chlorinated carbon to investigate the thermal decomposition process of chlorocarbons in pyrolytic reaction environment. The pyrolytic reaction of tetrachloroethylene has been conducted in an isothermal tubular flow reactor at 1 atm. total pressure with reaction temperatures 600–850 °C between 0.3 and 2.0 s under excess H₂ reaction atmosphere. Complete decay (99%) of the parent reagent was observed at temperature near 850 °C with 1 s reaction time. Major products observed were C₂HCl₃, C₂H₂Cl₂, C₂H₃Cl and HCl at below 775 °C. The number and quantity of chlorinated products decrease with increasing temperature. Formation of non-chlorinated hydrocarbons, C₂H₄, C₂H₆, CH₄ and C₂H₂ increases as the temperature increases above 800 °C. The poor carbon mass balances (<50%) were given over a wide temperature range, although the decomposition rate of C₂Cl₄ increases rapidly at higher temperature. They are as expected due to formation of high molecular weight compounds, highly chlorinated species and soot which were not detected by GC analysis of this work quantitatively. The important pyrolytic reaction pathways to describe the important features of reagent decay, intermediate product distributions and carbon mass balances, based upon thermodynamic and kinetic principles, were suggested. The main reaction pathways for formation of major products along with preliminary activation energies and rate constants were given.     

反应烧结碳化硅材料的抗热震性能研究

通过对比不同温差热震后材料的残余强度 ,对反应烧结碳化硅材料的抗热震性能进行了研究。结果表明 :反应烧结碳化硅材料的抗热震性能与显微组织密切相关 ,低游离硅含量与小粒径的反应烧结碳化硅材料具有较好的抗热震断裂性能 ,而高游离硅含量或大碳化硅粒径的材料具有相对优异的抗热震损伤性。对反应烧结碳化硅材料的抗热震性与显微组织的关系进行了探讨。     

聚硅氧烷/聚醚聚氨酯弹性体的合成与表征

以聚二甲基硅氧烷(PDM S)与聚丁醚(PTM G)为混合软段与4,4'-二苯甲基二异氰酸酯(M D I)、1,4-丁二醇(1,4-BD)制备出一系列的聚氨酯共聚物。用FT IR、DM A、TGA以及AFM分别对共聚物的结构、热性质以及表面形态进行了表征。结果表明,共聚物含有复杂的微相分离结构,而且与纯聚氨酯相比,含硅氧烷的聚氨酯比纯聚氨酯具有更好的热稳定性。