水性聚氨酯分散液的研究进展

评述了水性聚氨酯分散液的作用和重要性,综述了水性聚氨酯分散液的研究进展,对水性聚氨酯分散液的合成制备方法进行了归纳总结,认为在制备水性聚氨酯过程中,同时利用异氰酸酯基和不饱和双键的反应活性,形成互穿聚合物网络体系是目前合成制备水性聚氨酯分散液的主要思路和方法,最后,对水性聚氨酯分散液的应用发展趋势进行了展望。     

水性聚氨酯脲-丙烯酸酯膜的表面性能

用预聚物分散－原位聚合法合成了聚氨酯脲－丙烯酸酯（ＰＵＡ）水分散液。用ＡＴＲ－ＦＴＩＲ和ＥＳＣＡ技术表征了ＰＵＡ水分散液在玻璃基材上成膜后的表面结构和组成,测定了不同液体在ＰＵＡ膜表面上的接触角及ＰＵＡ膜的耐磨性。结果表明,ＰＵＡ成膜时与空气接触面和与玻璃接触面的表面组成和耐磨性接近于聚氨酯脲（ＰＵＵ）的表面特性。此外,在ＰＵＡ膜中ＰＵＵ和聚丙烯酸酯的组成呈“双向梯度”分布,即在沿膜的２个表面方向     

Rheological behavior of waterborne polyurethane/starch aqueous dispersions during cure

Isothermal rheological behaviors of waterborne polyurethane (WPU)/starch aqueous dispersions during cure were investigated with a small-amplitude oscillatory shear flow experiment to evaluate their crosslinked structure and to predict their mechanical properties, for the first time. An abrupt increase in the elastic storage modulus (G′), the viscous loss modulus (G″), the complex dynamic viscosity (η^*) and the loss tangent (tan δ) was observed during the curing process of the dispersions, as a result of the formation of a fractal polymer gel. The gel point (t_gel) was determined from the intersection in tan δ vs curing time for different constant shear frequencies, where tan δ was frequency independent and all curves crossed over, indicating the validity of the Winter–Chambon criterion for the complex system. The values of the power law exponent (n) and the gel strength (S_g) at the gel point indicated that with an increase of starch content the crosslinked WPU/starch gels underwent a transition from weak fractal to strong elastic ones. Moreover, the WPU/starch composite sheets, obtained from the aqueous dispersions with relatively high S_g values, also exhibited the increased tensile strength (σ_b) and Young's modulus (E). Their structure–mechanical properties relationship and the phase transitions of dispersed starch–dual-phase continuity–starch matrix were revealed. This work confirmed that the rheological characters could be used to predict the mechanical properties of the WPU materials blended with natural polymer.     

利用互溶溶剂交替浸取强化植物提取过程

利用互溶溶剂交替浸取的方法,在室温下对中药大黄进行了浸取实验。实验结果显示,利用水和乙醇对大黄进行交替浸取能够极大的提高提取速率。水和乙醇的浸泡能够可逆的改变大黄颗粒的尺度和微观结构,经过水浸润的大黄颗粒体积增大,且颗粒表面呈现明显的多孔状结构。在使用互溶溶剂进行交替浸取时,微尺度上溶液组成分布的不均会引起局部湍流,从而极大的加强传质过程。     

新型TMPLA水性聚氨酯分散体的合成及助成膜性能

合成了新型扩链剂三羟甲基丙烷月桂酸单酯(TMPLA)并制备聚氨酯水分散体(n-PUD),取代小分子成膜助剂辅助高玻璃化温度(T_g)聚丙烯酸酯乳液(PA)成膜,以制备高性能超低挥发性有机化合物(VOC)含量水性木器涂料。研究了软/硬段质量比、NCO/OH及TMPLA/BDO摩尔比对n-PUD助成膜性能的影响。结果表明:随软/硬段质量比和NCO/OH摩尔比降低,PUD的助成膜能力增强;TMPLA引入能显著提高n-PUD的助成膜能力,优选TMPLA/BDO摩尔比4/2,NCO/OH摩尔比1.3,软/硬段质量比55/45时,n-PUD/PA按质量比25/75复配乳液在不加成膜助剂条件下能够在5℃形成连续透明成膜,制备的水性木器涂料VOC含量低至30 g·L^-1。     

Polystyrene ionomer aqueous dispersion. I. Process and mechanism of the phase inversion of emulsification

Aqueous dispersions of lightly sulfonated polystyrene (SPS) that was neutralized by ammonia liquor were prepared. The variations of the conductivity and viscosity of SPS ionomer solution during the emulsification process and the effect of ionic contents on the phase inversion in the emulsification process were studied. The turning points in conductivity curve and the maximum viscosity were considered as the characters of phase inversion in the process of emulsification. The mechanism of phase inversion was inferred. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1671–1675, 1998     

药物合成反应中四氯化碳的应用及替换研究进展

综述了四氯化碳在药物合成反应中的应用,总结了在药物合成反应中四氯化碳溶剂替换研究工作.     

Methodology for advanced measurement accuracy of the overall volumetric oxygen transfer coefficient with application to hydrocarbon–aqueous dispersions

Accurate quantification of the overall volumetric oxygen transfer coefficient (K_La) is essential for the success of aerobic bioprocesses. In hydrocarbon‐based bioprocesses where K_La is depressed at higher viscosities, this is particularly critical. In this study an accessible methodology for K_La determination has been developed and validated for alkane‐based systems under a wide range of process conditions. Critical to measurement accuracy in around 90% of the K_La values was the incorporation of the response lag. Neglect of the response lag resulted in errors greater than 5% above K_La = 0.3K_p to K_La = 0.6K_p (where K_p is the inverse response lag or probe constant), at least 1.5‐fold to 3‐fold lower than the analogous K_La in water. Further, K_p varied significantly with both alkane concentration and chain length. A sensitivity analysis confirmed ? 25% to 90% error in K_La with 30% over‐ and under‐estimation of K_p respectively. When incorporating K_p values specific to the process conditions, accurate K_La values were confirmed in 0 to 20% (v/v) C_10–13 and C_14–20 aqueous dispersions over 600 to 1200 rpm agitation. Copyright © 2012 Society of Chemical Industry     

紫外光固蓖麻油改性聚氨酯水分散体的研究

制备了蓖麻油封端的聚氨酯水分散体,成膜于四氟乙烯板上,在紫外光照射下,通过水性光引发剂引发,制备得到聚氨酯涂层。通过FT-IR,DSC,凝胶量,耐水,耐溶剂性以及硬度测试对水分散体的物化性能,光固化前后涂膜的结构和性能进行了研究。结果表明,蓖麻油改性聚氨酯在紫外光照下发生了交联反应:固化后涂层的凝胶量较固化前有所增加,涂层的吸水率大幅度下降,铅笔硬度由3H提高至6H,耐甲乙酮拭擦次数增加了158次。     

Newly UV-curable polyurethane coatings prepared by multifunctional thiol- and ene-terminated polyurethane aqueous dispersions mixtures: Preparation and characterization

A series of newly developed UV-curable polyurethane coatings were prepared by blending multifunctional thiol- and ene-terminated polyurethane aqueous dispersions. The composition, structure, solution stability and mechanical properties of the title coatings were characterized in detail by FT-IR, photo-DSC and DMA measurements. It was found that the resulting polyurethane coatings showed good solution stability and high photopolymerization activity even after a long time (i.e. 1 month). The incorporation of a waterborne polyurethane chain into the both multifunctional thiols and ene monomers promoted their solution stability and avoided any reaction between thiols and ene groups as a result of their high reacting activity in non-aqueous systems. UV-cured films prepared by this method were found to exhibit excellent physical properties with improvements over what can be attained directly with current UV-curable urethane-acrylate based systems. This method allows for the preparation of high performance UV-curable polyurethane aqueous coatings based on thiol-ene chemistry systems.     

The chain extension of anionic prepolymers in the preparation of aqueous poly(urethane–urea) dispersions

Anionic polyurethane prepolymers end‐capped with isocyanate groups were dispersed and chain‐extended in aqueous media using three different extension agents: hydrazine, 1,2‐ethylene diamine (EDA) and 1,2‐propylene diamine (PDA). Two types of prepolymer were used. The first was prepared from isophorone diisocyanate (IPDI), α,α‐dimethylol propionic acid (DMPA) and poly(propylene oxide) diol (PPO) and the second from α,α,α′,α′‐tetramethyl‐1,3‐xylylene diisocyanate (m‐TMXDI), poly(caprolactone) diol (PCL) and DMPA. The colloidal particles which formed in the dispersion process and the constituent poly(urethane–urea) chains were characterised by a combination of dynamic and static light scattering, gel permeation chromatography and FTIR spectroscopy. Using EDA as the extender, a study was made of how the degree of extension depended on the molar ratio of amine to isocyanate groups, [NH₂]/[NCO] (= R_{A, I}). It was found that using a stoichiometric balance of isocyanate and amine groups did not lead to high degree of extension, and better chain extension was obtained at lower R_{A, I} values. In a comparative study using stoichiometric balances of isocyanate and amine groups, the degrees of extension obtained using PDA and EDA were approximately the same, while hydrazine was the least effective. Force–extension studies were carried out on samples prepared from films cast from the aqueous poly(urethane–urea) dispersions in order to assess the influence of chain‐extender type and stoichiometry on bulk properties; values of Young's modulus, tensile strength and maximum extension are reported. Copyright © 2003 Society of Chemical Industry     

Newly UV-curable polyurethane coatings prepared by multifunctional thiol- and ene-terminated polyurethane aqueous dispersions: Photopolymerization properties

A novel approach toward the preparation of newly UV-curable polyurethane coatings composed of multifunctional thiol- and ene-terminated polyurethane aqueous dispersions is presented. By a synergistic combination of polyurethane dispersions synthesis and thiol-ene chemistry, strategies for the preparation of newly UV-curable polyurethane coatings are developed. Photo-DSC, real-time FTIR, DMA and tensile tests measurements are used to investigate the photopolymerization and mechanical behaviors of newly UV-curable polyurethane coatings. The newly polyurethane coatings have 1.5 times higher polymerization rate and final 99% functional groups conversion in air conditions compared to current urethane-acrylate based UV-curable polyurethane dispersions coatings. UV-cured polyurethane films prepared by this method are also found to exhibit increase in Young's modulus and tensile strength at break by 25% and 10%, respectively. These experiment facts suggest that the incorporation of thiol-ene chemistry to the polyurethane dispersion coatings increase their polymerization rate, producing a high degree of cross-linking. This confirms the preparation of the targeted novel UV-curable polyurethane coatings and reveals the dramatic effect that changes in incorporation of thiol-ene chemistry can have on the photopolymerization behaviors of UV-curable polyurethane dispersions coatings systems.     

错流萃取糠醛水溶液溶剂比的研究

本文研究了原料／溶剂（体积比）对错流萃取糠醛的影响，通过四级错流萃取试验并采用相分配系数法用UNIQUAC模型进行模拟计算，确定以溶剂比2．5：1错流萃取糠醛较合适，且模拟计算结果与试验结果误差较小。     

Aqueous dispersions of DBSA‐doped polyaniline: One‐pot preparation,characterization, and properties study

Aniline was polymerized in the presence of dodecylbenzene sulfonic acid (DBSA) as a functionalized protonic acid, in an aqueous medium to directly synthesize polyaniline (PANI)‐DBSA particles. DBSA acted as a dopant and a surfactant with stabilizing PANI‐DBSA dispersions by formation of strong hydrogen bonds. The NH⁺…SO interactions between the PANI chains and the DBSA appeared at 1026 cm^?1 in Fourier transform infrared (FTIR) spectrum. Elemental analysis was used to determine the degree of sulfonation (S/N ratio) of PANI chains and resulted that the sulfur‐to‐nitrogen ratio is 0.35. Thermogravimetric analysis (TGA) technique was used to analyze thermal properties of the particles and resulted that the synthesized PANI‐DBSA particles have high thermal stability. The moisture, DBSA and PANI contents of the PANI‐DBSA were estimated from TGA curve, and then the number of aniline repeating units doped with one DBSA molecule was approximately calculated. X‐ray diffraction (XRD) analysis confirmed that a chemical crosslinking reaction occurs between the PANI chains during thermal treatment of PANI‐DBSA. The morphology of PANI‐DBSA powder was investigated by scanning electron microscopy technique and showed that the PANI particles develops from round particles to a smooth surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Temperature effects on the birefringence of nitrocellulose and nitrocellulose/nitroglycerine mixtures

Changes in the optical path difference of nitrocellulose fibres of varying degrees of substitution over the temperature range ?120°C to 130°C are interpreted as due to conformational changes in the primary nitrate group. Changes in path difference of nitrocellulose/nitroglycerine paste fibres over the same temperature range indicate an irreversible annealing effect and a change in the nitrocellulose structure. Propellants made from nitrocellulose and nitroglycerine show similar changes and it is concluded that submicroscopic fibrils are present even though no fibres are visible. When fibres are visible they show a banded structure, the nature of which is discussed.     

Gamma-irradiation of 7-ketocholesterol in aqueous dispersions and liposomes

7-Ketocholesterol in aqueous sodium stearate dispersions or incorporated into liposomes was exposed to gamma radiation at 0–4°C to a dose of 50 kGy. Substrate degradation was noted in all systems, but occurred to a much greater extent in dispersions (≈90%) than in liposomes (0–25%). The difference in degree of degradation is attributed to dissimilarities in the micro-environment of 7-ketocholesterol in the two systems. The principal decomposition product was identified as 7-ketocholestanol, a compound that can arise from hydrogenation of the double bond of the starting material. Also detected, but in lower concentration, were the epimeric 7-hydroxycholesterols resulting from the reduction of the original carbonyl function. Both 7-ketocholestanol and the epimeric 7-hydroxycholesterols are believed to be secondary species generated by the interaction of the starting material with the primary radiolysis products of water. In addition, many minor degradation products were noted but not identified.     

Urea/NaOH aqueous solution as new solvent of aeromonas gum

Aeromonas (A) gum, an acidic heteropolysaccharide, formed aggregates easily in NaCl aqueous solution. A novel solvent of the A gum, which can prevent aggregation, was found to be 0.20M urea/0.25M NaOH aqueous solution. The weight‐average molecular weight (M_w), radius of gyration (〈s²〉^1/2), and intrinsic viscosity ([η]) of the samples were determined in 0.20M urea/0.25M NaOH aqueous solution at 25°C by light scattering (M_w, 〈s²〉^1/2) and viscometry ([η]). The values of M_w, 〈s²〉^1/2, and [η] were close to those in 0.20M lithium chloride/dimethylsulfoxide, in which the A gum exists as a semiflexible single chain, implying the same conformation for the A gum in 0.20M urea/0.25M NaOH aqueous solution. The results revealed that 0.20M urea/0.25M NaOH aqueous solution is a good solvent, which effectively avoids the aggregates of the A gum in aqueous solution. Moreover, it can be used to investigate the solution properties and chain conformation of water‐insoluble polysaccharides or the polysaccharides that are easily aggregated in aqueous systems. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1710–1713, 2005     

Reaction mechanism of coal hydrogenation: 1. Two-ring solvent system

Taiheiyo coal was hydrogenated in naphthalene, tetralin and decalin under 10 MPa (initial pressure) of hydrogen or nitrogen with stabilized nickel as catalyst at 400 °C for 15 min. Preasphaltene, asphaltene and oil conversions and the conversion of the solvents were measured. The hydrogen absorbed by coal from molecular hydrogen and from the donor solvent was calculated. The main reaction route appears to be the direct hydrogenation of coal by molecular hydrogen, with the side reaction via solvent by molecular hydrogen occurring only slightly, when an active catalyst such as stabilized nickel is present.     

取向TS-1分子筛膜的合成与结构引导机理

通过壳聚糖的引导作用, 采用水热法在氧化铝载体上原位合成了b-轴取向的钛硅分子筛(TS-1)膜. 使用XRD、SEM等手段对所合成的TS-1膜进行了表征. 通过漫反射FT-IR和接触角的测定描述了壳聚糖薄膜的表面官能团、壳聚糖薄膜表面与合成液的相互作用. SEM结果表明, 在壳聚糖的引导下可得到b-轴取向的TS-1膜, 而直接在氧化铝载体上只能得到无序的TS-1膜层. XRD的测量结果表现了典型的TS-1结构. 漫反射FT-IR和接触角的测试结果表明, 由于壳聚糖表面官能团的作用, 其表面形成过渡层, 经过成核, 晶核生长得到片状TS-1晶体颗粒, 最后获得多层b-轴取向的TS-1膜.