Synthesis and polymerization of maleimide-type new macromonomer with polystyrene having controlled chain length

A new reactive and functionalized polystyrene with a maleimide moiety at the one polymer end was synthesized with N-(4-(1-chloroethyl)pheyl)maleimide (CEPMI)/SnCl₄/tetra-butylammonium chloride (TBAC) initiating system. The polymer obtained with the CEPMI/SnCl₄/TBAC initiating system under the condition of [TBAC]/[SnCl₄] = 1 was to be maleimide-type macromonomer with polystyrene having controlled molecular weight of polystyrene (VI). VI could be polymerized with anionic and radical initiators to give new type graft polymer (poly[N-(4-ethylphenyl)maleimide]-graft-polystyrene) with controlled chain length with respect to side chains.     

Study on the volumetric expansion of benzoxazine curing with different catalysts

A systematic investigation on the volumetric expansion of four benzoxazine systems, which are benzoxazine, benzoxazine/tertiary amine, benzoxazine/organic acid, and benzoxazine/epoxy resin/tertiary amine, was done. By using gravitometric and dilatometric methods, etc., studies on volumetric shrinkage, isothermal cure shrinkage, and density versus cure time plots were done. The cure reactions of these benzoxazines were carried out at 140 and 160°C. The results show that all benzoxazine systems exhibit apparent volumetric expansion after polymerization, that is, the densities of monomers are larger than are those of polymers at room temperature. But, meanwhile, they exhibit volumetric shrinkage while curing isothermally. The results also show that the higher the cure temperature is, the larger the cure shrinkage of the benzoxazines will be and that the extent of the cure shrinkage of the benzoxazines with the aid of catalysts is larger than is that of thermal polymerization systems. The reason for this is that, accelerated by catalysts, the polymerization rate become faster and the extent of polymerizatiom becomes larger. It is obvious that catalysts can make a notable impact on the cure reaction of benzoxazines. Therefore, the dimension of the volumetric expansion of benzoxazine is associated with its polymerization mechanism, molecular structure, and extent of polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1107–1113, 2002; DOI 10.1002/app.10267     

游离氧化钙对水泥浆体体积膨胀的影响机制

硬化水泥桨体由于水泥中游高氧化钙水化会导致体积膨胀。研究发现,浆体的体积膨胀除与ｆＣａＯ的含量和活性有关外,还与浆体的结构和性能密切ｆＣａＯ水化形成Ｃａ（ＯＨ）２时,不仅固相体积增加,而且空隙体积亦增加,而且空隙体积亦增加。ｆＣａＯ在浆体硬化结构形成之后水化,且其水化产物成堆聚集时才会导致浆体体积膨胀。     

Visible light induced polymerization of maleimide-vinyl and maleimide-allyl ether based systems

The photoinitiated polymerization reaction of maleimide-vinyl ether and maleimide-allyl ether under visible light in the presence of several visible photoinitiating systems have been investigated. Remarkable high rates of polymerization with nearly 100% of conversions are obtained. Photoinitiator free polymerization of maleimide-allyl ether systems exhibits also a quite good efficiency, comparable to that of maleimide-vinyl ether. Photoinitiators working through hydrogen abstraction like camphorquinone were shown to be able to initiate very well the visible curing of maleimide-allyl ether. The curing of a maleimide-allyl or vinyl ether formulation can be achieved within 1 s in the presence of a 4-component photoinitiating system under low light intensity. The role of a large variety of photoinitiating systems and the mechanisms involved in the initiation step are discussed.     

Light-induced crosslinking polymerization of a novel N-substituted bis-maleimide monomer

The photoinduced polymerization of a N-alkyl substituted bis-maleimide (MI) has been studied by real-time infrared spectroscopy. The polymerization of the neat monomer proceeds rapidly and extensively because of both its great absorbance in the UV-range, and the presence on the alkyl chain of easily abstractable hydrogen atoms, which are needed to produce the initiating radicals. Such photoinitiator-free resin was found to be less sensitive to oxygen inhibition than typical UV-curable acrylate resins, the peroxyl radicals formed being capable to propagate the chain reaction. This N-substituted bis-maleimide was also successfully used as monomeric photoinitiator to induce the crosslinking polymerization of acrylate monomers through the free radicals formed upon its photolysis.     

A volumetric technique for measuring the coefficient of thermal expansion of hardening cement paste and mortar

Knowledge of the coefficient of thermal expansion (CTE) is of paramount importance for the determination of the cracking risk of concrete structures at early ages. This paper presents a novel technique which is suitable to measure the CTE of hardening materials with high accuracy starting from casting time.The technique consists of casting a small amount of cement paste or mortar into flexible membranes. The specimens are immersed in an oil bath, whose temperature is rapidly changed and then kept constant in repeating cycles. By suspending the sample from a high-precision balance and reading the change of mass after each temperature step, the CTE is calculated with high accuracy from the measured temperature and strain.Results on cement pastes and mortars (water/cement 0.3) showed a good repeatability. In particular, a sudden decrease in the CTE at setting time, followed by a gradual increase as the cement paste self-desiccates, was measured.     

Correction factors for the dynamic measurement of the volumetric mass-transfer coefficient

The experimental determination of the volumetric mass-transfer coefficient based on the use of an oxygen electrode requires a mathematical model of the experimental system and a parameter estimation method to obtain a number for the k_ta value. Previous work has resulted in a number of different model structures corresponding to different hypotheses concerning the relevant physical phenomena. Little is known about the impact of a specific choice for the model structure or that of the estimation procedure on the numerical value of the mass-transfer estimate. This impact is investigated here and guidelines are given for the choice of a parameter estimation scheme. In addition, correction factors that measure the impact of a structural choice are given for both the moment and least squares parameter estimation methods. The diagrams may be used in a preliminary phase to make an overall appraisal of the specific experimental conditions and in the estimation phase to reduce computational loads.     

Vibrational spectroscopic investigation of light‐induced polymerization process of epoxy resin,polytetrahydrofuran and spirobislactone

The light‐induced polymerization process of bisphenol F diglycidyl ether (BFDGE), 5,5′‐dicarboxylic‐7,7′‐dioxo‐2,2′‐spirodi(benzotetrahydrofuran) (DCSBL) and polytetrahydrofuran (pTHF‐250) was studied. 4‐[(2‐Hydroxytetradecyl)oxy]phenyl‐phenyliodoniumhexafluoroantimonate, camphorquinone and ethyl 4‐dimethylaminobenzoate were used as a photoinitiator system. The polymerization process was induced by light and monitored using Fourier transform infrared spectroscopy. A novel combination‐initiation polymerization process was proposed: first, cationic copolymerization of BFDGE and pTHF‐250 was initiated by the photoinitiator system and heat was released by this polymerization; then, copolymerization of BFDGE and DCSBL was induced by that heat while pTHF‐250 served as an anionic initiator. Copyright © 2007 Society of Chemical Industry     

磷灰石晶格热膨胀性质的实验研究

本文采用高温粉晶X射线衍射技术 ,对溶胶—凝胶法合成羟基磷灰石 (Hap) ,提拉法合成氟磷灰石 (Fap)和天然沉积型碳氟磷灰石 (CFap)从室温到 95 0℃之间的晶格热膨胀系数进行了测定。实验结果表明 :在测试温度范围内 ,各样品的晶格膨胀系数与温度呈线性关系。Hap的△a/a与△c/c分别为 13 .8× 10 - 6 C- 1 和 15 .3× 10 - 6 C- 1 ,Fap的△a/a与△c/c分别为 15 .8× 10 - 6 C- 1 和 18.2× 10 - 6 C- 1 ,CFap的△a/a与△c/c分别为 15 .3× 10 - 6 C- 1 和 18.5× 10 - 6 C- 1 。在实验温度区间内未发现样品有明显的相变或结构转变现象 ,高温实验后样品的傅立叶变换红外光谱测定证实了这一推断。     

Effect of Chemical Structure of Solid Lipid Matrix on Its Melting Behavior and Volumetric Expansion in Pressurized Carbon Dioxide

Supercritical carbon dioxide (SC-CO₂) technology offers new opportunities for green processing of lipids; however, there is little information of the melting behavior and volumetric expansion of solid lipids in pressurized CO₂. In this study, melting behavior and volumetric expansion of two different solid lipid classes and the effect of the structural differences within the same lipid class on the melting behavior in pressurized CO₂ were investigated. The melting point of the solid lipids decreased linearly with increasing pressures up to a certain level; then, it stayed constant. The highest melting point depression was observed for soybean oil monoacylglycerol (SO-MAG) at 51.5 °C/110 bar, whereas the lowest was for fully hydrogenated soybean oil (FHSO) containing 30% SO-MAG at 55.0 °C/79 bar. Melting point depression depended on lipid class. SO-MAG exhibited a higher melting point depression than FHSO (triacylglycerol form), and its blends with SO-MAG. There was no difference in melting point depression between glyceryl 1,2-distearate and glyceryl 1,3-distearate up to 200 bar (P > 0.05). A positive correlation between the melting point depression and volumetric expansion of solid lipids was observed. The highest volumetric expansion was for SO-MAG in the linear region of the melting point depression curve, achieving 14.4% expansion compared to 9.3% for FHSO (P < 0.05). The highest dT/dP value (0.17 °C bar⁻¹) was obtained for SO-MAG, whereas the FHSO (0.09 °C bar⁻¹) had the lowest one. Findings of this study will help optimize solid lipid-involving SC-CO₂ processes for better protection of heat-sensitive compounds while improving energy efficiency.     

Thermal expansion behavior of composites based on non-axisymmetric ellipsoidal particles

A new model for calculating the coefficients of thermal expansion, CTE, in all three coordinate directions is developed for composites containing non-axisymmetric, ellipsoidal particles, i.e., three-dimensional ellipsoids (a₁ ≠ a₂ ≠ a₃) characterized by two aspect ratios, ρα=a₁/a₃ and ρβ=a₁/a₂. The model makes use of Eshelby's equivalent tensor for the particles and utilizes the methodology from recent papers by Lee et al. The effects of the primary, ρ_α, and secondary, ρ_β, aspect ratios and filler volume fraction (0-6%) on the various CTE for nanocomposites containing aligned inclusions are demonstrated by calculations for a matrix of nylon 6 and a filler of montmorillonite single platelets. The CTE in the longitudinal direction, α11, decreases, as both aspect ratios increase. The CTE in the transverse direction, α22, decreases as ρα increases but increases as ρβ increases. The CTE in the normal direction, α33, is greater than that of the matrix and increases as ρα increases but decreases as ρβ increases.     

Thermal expansion investigation of iron rich glass-ceramic

A theoretical procedure was developed with the aim of obtaining an estimation of the crystallisation fraction in glass-ceramics by means of thermal expansion measurements. The theoretical model was applied to the crystallisation of an iron rich glass composition yielding magnetite and pyroxene as crystalline phases.The crystallisation mechanism was investigated by means of DTA, XRD, FTIR, TEM; the thermal expansion by Differential Dilatometer. A relationship between the weight fraction of crystal phase and the linear thermal expansion coefficient was obtained. The values of the fraction of crystal phase, evaluated by means of dilatometric measurements, showed a good agreement with the results obtained by means of density variation and XRD analyses.The crystallisation kinetic of the iron rich glass, at 630 and 700 °C, was also investigated by dilatometry and the variation of CTE as a function of the crystallisation time explained in terms of increasing of the apparent viscosity of the residual glass.     

PVC装置聚合单元扩能分析

详细叙述了齐鲁石化公司氯碱厂PVC装置产量由18.6万t/a改扩到23.0万t/a的情况,在分析了影响该装置扩能因素的基础上,提出了以“同步进料,带压出料”为主的改造方案,改造后聚合系统每天投料由原设计的16釜增加到19釜,设计操作时间内的生产能力可达到23.7万t/a,通过采用冷同步进料（含釜外脱氧）和带压出料等措施缩短了非反应时间和反应周期。     

Thermal expansion behavior of composites based on axisymmetric ellipsoidal particles

A new model for calculating the coefficients of thermal expansion, CTE, in all three coordinate directions is developed for composites containing aligned, axisymmetric elliptical particles, i.e., characterized by a single aspect ratio, that in the limit approximate the shapes of spheres, fibers and discs. This model is based on Elshelby's method but employs a somewhat different formulation than used in prior papers; a main advantage of the current approach is that it can be readily extended to composites based on ellipsoidal particles with no axes of symmetry, i.e., all three major axes are different, as recently demonstrated for modulus. CTE predictions for the simple case of axisymmetric particles are illustrated by calculations for glass particles in the shape of spheres, fibers and discs in an epoxy resin and are compared to those from the popular Chow theory. For spherical-shaped particles, the CTEs in all directions are the same and decrease modestly as the volume fraction of filler particles increases. As the particle aspect ratio increases from unity, the thermal expansion becomes anisotropic. The coefficient of longitudinal linear thermal expansion always decreases with increasing aspect ratio and filler loading due to the mechanical constraint of the filler. For aligned axisymmetric particles, the coefficients of linear thermal expansion are always the same in two directions. The values in the transverse direction may be higher or lower than that of the matrix depending on the values of aspect ratio and filler loading; these regions are mapped out for this particular set of matrix and filler properties. The two-dimensional constraints on matrix expansion caused by discs versus the one-dimensional effects of fibers cause quantitative differences in behavior for the two shapes.     

一种大相对分子质量膨胀单体的制备

主要从高分子材料设计角度研究一种固化时具有适当膨胀性或较低收缩率的材料。对膨胀聚合反应研究发现，带有膨胀基团双环原酸酯的材料在阳离子引发剂存在下开环时具有膨胀特性。我们采用一种简单的方法制备了带有活泼羟基的双环原酸酯4-羟甲基-2，6，7-三氧杂二环(2，2，2)辛烷，首次进行了双环原酸酯4-羟甲基-2，6，7-三氧杂二环(2，2，2)辛烷和大分子未封端聚醚预聚物的反应，得到了具有较大相对分子质量的两端带有双环原酸酯膨胀基团的长链大分子膨胀单体。在阳离子引发剂的作用下，该物质于130℃能够发生开环聚合反应，膨胀率平均为0．43％。     

Influence of dissolved hydrocarbons on volumetric oxygen mass transfer coefficient in a novel airlift contactor

Hydrocarbon compounds are sparsely soluble in aqueous systems but, nonetheless, their presence can influence significantly mass transfer behavior in gas-liquid systems. water-p-xylene and water-p-xylene-naphthalene mixtures were employed in order to determine the influence of dissolved hydrocarbons on mass transfer of oxygen from air bubbles to water. The surface renewal-stretch model has been modified for predicting the volumetric mass transfer coefficient, (K_La)_h, in the presence of surface contaminant molecules, including hydrocarbon compounds and surfactants. Theory and experimental oxygen transfer results were found to be in satisfactory agreement with average absolute deviation of 15%. Pendant drop and contact angle measurements by axisymmetric drop shape analysis were carried out to determine the reduction in surface tension of water due to the addition of p-xylene and naphthalene. Molecular orientation caused by instantaneous attraction of the polar moieties of the organic compounds toward the water interface has been found to be the main cause of reduction in surface tension. It was predicated that changes in gas-liquid mass transfer behavior resulted from surface contamination and that the significant parameter was the reduction in surface tension.     

Flow modeling in electrochemical tubular reactor containing volumetric electrode: Application to copper cementation reaction

The aim of the present work is to study the electrolyte flow characteristics in a tubular reactor containing a volumetric electrode, acting as turbulence enhancer, applied in our previous works to copper removal by cementation process. The hydrodynamic behavior of the electrolyte within the reactor under study has been determined using the residence time distribution (RTD) experimentally determined by a pulse tracer technique.     

复合氧化物材料的负热膨胀机理

介绍了相转变、桥氧原子的横向热振动、刚性多面体的旋转耦合、固体内压转变、相界面弯曲、阳离子迁移等六种模式的负热膨胀机理。并对其应用前景和发展趋势进行了预测     

Effects of volumetric efficiency on the performance and emissions characteristics of a dual fueled (gasoline and LPG) spark ignition engine

In this study, effects of variation in volumetric efficiency on the engine emissions characteristics with different LPG usage levels (25%, 50%, 75%, and 100%), on an engine operated with new generation closed loop, multi-point, and sequential gas injection system were investigated. For this purpose, experiments were carried out under constant engine speed (3800 rpm) and different load (5%, 30%, 60%, 90%) conditions. The variations in volumetric efficiency, air-fuel ratio, brake thermal efficiency, brake specific fuel consumption, brake specific energy consumption, and exhaust gasses were examined. The volumetric efficiency decreased considerably at the use of 25% LPG level. As for the 50%, 75% and 100% LPG usage, volumetric efficiency decreased in proportion to LPG usage level. Air-fuel ratio decreases with the increase in LPG usage level and the minimum air-fuel ratio value was obtained at 100% LPG usage. At the use of mixture containing 25% LPG, brake specific fuel and energy consumption decreased while the brake thermal efficiency was maintained. Positive results were obtained at all LPG usage levels in terms of exhaust emissions. Best results were achieved at using 100% LPG for exhaust emissions.     

膨胀剂对混凝土抗裂防渗的贡献

通过常规实验和基础实验，采用对比的方法，研究了膨胀剂的适宜掺量和对水泥砂浆强度的影响。结果表明，加入膨胀剂能补偿部分收缩，有效抑制或减少裂缝的产生，提高混凝土的耐久性；试验条件下试验所用膨胀剂的适宜掺量应小于6％：对补偿收缩混凝土，其限制膨胀率应作为第一性指标。