聚合物多元醇分散体的流变特性

聚合物多元醇分散体(以下简称分散体)是接枝聚醚多元醇、聚醚多元醇和乙烯基单体聚合物的混合物,直接用于制备高回弹、高负载和阻燃的软质和半软质聚氨酯泡沫体,是新一代聚醚多元醇产品[1].分散体用于聚氨酯工业中各种产品的生产,除要求有良好的稳定性外,其最为重要的指标是粘度应小于3000mPa·s和乙烯基单体聚合物的含量(固含量)应大于40%.但分散体的粘度,随固含量的增加呈指数性增加[2].近年来,已有既具高固含量和良好稳定性,又有较低粘度的分散体的研究报道[3].本文在不同的反应条件下,合成了分散体,测定了其流变特性和体系中微粒的大小…     

新型的承载双金属氰化物络合催化剂

用双金属氰化物(DMC)络合催化剂可制得相对分子质量高、相对分子质量分布窄和不饱和度低的聚醚多元醇。为提高DMC催化剂的利用率,降低催化剂和聚醚的生产成本,国外开发了承载的DMC催化剂。它不仅可简化聚醚的后处理工艺,而且使聚醚的连续化大规模生产得以实现,因此代表了DMC催化剂的一个重要发展方向。     

含氟聚醚多元醇的研究进展

与常规羟基聚醚相比,含氟聚醚多元醇可被用来制备具有耐热、耐UV光、耐候、耐腐蚀、耐化学品、耐溶剂、拒油拒水、自清洁、自润滑等优良性能的高分子,因此具有多种潜在应用领域和发展前景。本文综述了国内外含氟聚醚多元醇的制备技术途径、结构类型特点,并阐述了其在聚氨酯弹性体、涂料及其它应用领域的研究进展。指出降低成本、开发绿色高效的制备技术、简化工艺路线、优化工艺条件、研发新产品为未来发展含氟聚醚多元醇的主要研发方向。     

以乙烯基酯树脂为多元醇制备聚氨酯硬质泡沫塑料的研究

研究了用乙烯基酯树脂（ＶＥＲ）直接代替通常的聚醚或聚酯型多元醇制备聚氨酯（ＰＵ）硬质泡沫塑料的可能性。实验结果表明,发泡配方中促进氨酯化反应的催化剂Ｎ,Ｎ－二甲基环己胺能与ＢＰＯ复合形成室温引发体系,加速ＶＢＲ的共聚合反应,影响了ＰＵ硬质泡沫塑料形成过程中的发泡与凝胶反应,导致泡了孔骨架基材的交联密度较低,泡孔结构不规整,并显示出较差的物理性能。以ＡＩＢＮ为引发剂时,反应初期主要进行氨酯化反应;仅     

基于天然高分子的聚氨酯材料

综述了近年来天然高分子低聚糖、纤维素、淀粉、木素及液化木材部分或全部代替聚醚多元醇制备聚氨酯材料的研究进展     

单组分阴离子聚氨酯水乳液结构与性能

聚氨酯乳液;聚醚多元醇;二羟甲基丙酸;单组分阴离子聚氨酯水乳液结构与性能     

杂多酸引发甲氢呋喃开环聚合反应——Ⅶ.以1，1，1—三羟甲基丙烷为分子量调节剂

聚氨酯是由硬段和软段组成,其中的软段主要来源于聚醚或聚酯,通过化学交联反应可改变聚氨酯的力学性能,由过氧化物引发或使用小分子的三醇作为扩链剂对聚氨酯的硬段进行化学交联,所得聚氨酯的性能会变坏;而使用环氧丙烷（PO）与四氢呋喃（THF）的共聚醚三醇来制备在软段化学交联的聚氨酯,所得聚氨酯与由PO－THF共聚醚二醇制备的聚氨酯相比,断裂伸长率有轻微的下降,但抗拉强度得取了很大改善,由此可见,通过聚醚多元醇对聚氮酯的软段进行化学交联,有利于改善其力学性能。     

含有双酚A链段的聚氨酯网络研究

首先合成与表征了一种含有双酚A结构的多元醇,通过添加这种多元醇至聚氧化丙烯聚醚多元醇中合成了含有双酚A链段的聚氨酯网络。通过DSC、FTIR和SEM等方法考察了这类聚氨酯网络的结构形态,研究结果表明,PU网络中的双酚A链段与聚氧化丙烯链段不相容,而且破坏了PU硬段的有序化结构。在聚氧化丙烯聚醚多元醇中添加5－10phr双酚A结构的多醇就能显著地提高聚氨酯网络的拉伸强度、弹性模量和断裂伸长率。     

聚醚/聚酯型软质聚氨酯泡沫的合成研究

以聚醚多元醇(N220、N330)、聚酯多元醇(PNA)和液化二苯基甲烷二异氰酸酯(MDI)为主要原料,采用一步法制备软质聚氨酯泡沫。通过红外光谱、拉伸和回弹实验、热重分析及光学显微镜观察拍摄对泡沫产品的结构、拉伸性能、回弹性、热稳定性及泡孔结构进行了分析,并研究了PNA的加入量及不同催化剂比例对产品性能和泡孔结构的影响。结果表明:PNA的加入量为15%时,泡沫产品的各项性能最佳;当双(二甲胺基乙基)醚(A-1)∶三乙醇胺(TEOA)∶辛酸亚锡(T-9)=0.1∶0.6∶0.2时,泡孔结构均匀、力学性能良好。     

淀粉聚醚多元醇的合成研究

近年来由于石油价格的上涨,严重地限制了聚氨酯工业的发展。因此用价廉易得的再生资源淀粉代替部分化工产品合成聚醚多元醇,减少对石油产品的依赖性,降低成本,对发展聚氨酯工业和给淀粉寻找新的出路,具有十分重要的现实意义和新的战略意义。     

Electron-Beam-Induced Radiation Effects on Siloxane Foam

Summary: Two types of siloxane foam were irradiated by an electron beam at room temperature. Changes in the chemical structure of the samples were determined by Fourier-transform infrared resonance. The gaseous products from the irradiated samples were analyzed by gas chromatography and mass spectroscopy. Electron spin resonance was used to analyze the free radicals, and the compression properties were determined by a universal material tester. The results indicated that the effect of absorbed dose on the mechanical properties of polymethylvinyl siloxane foam was more pronounced than that for polymethylphenylvinyl siloxane foam. The yield of gases evolved from the radiation degradation of polymethylvinyl siloxane foam was higher than that from polymethylphenylvinyl siloxane foam. The free-radical signal from polymethylphenylvinyl siloxane foam was stronger and lasted longer than that from polymethylvinyl siloxane foam after irradiation.     

表面活性剂疏水链长对高温下泡沫稳定性的影响

选用不同疏水链长的α-烯烃磺酸盐(AOS)形成泡沫, 分别用泡沫衰减法和泡沫岩芯封堵法测定不同温度下的泡沫稳定性, 并采用动态表面张力、界面流变、分子模拟等方法研究了表面活性剂在气/液界面的吸附行为和界面吸附层的性质, 分析了高温下泡沫的稳定机制. 实验结果表明, 在高温下, 极性头的“锚定作用”减弱, 表面活性剂疏水链难以在气液界面保持以直立状态吸附, 疏水链碳数大于20的表面活性剂分子难以分立吸附, 其疏水链相互交叉缠绕, 增强了泡沫膜的强度, 减缓了气体通过液膜的扩散, 形成的泡沫在高温下具有较好的稳定性.     

Studies on foam stability by the actions of hydrophobically modified polyacrylamides

Hydrophobically modified polyacrylamide (HMPAM), as a foam stabilizer, was prepared with a cationic surfomer, acrylamide and acrylic acid by free-radical polymerization in aqueous solution. The actions of HMPAM on foam stability have been investigated with the Waring blender method. The results showed the foam containing HMPAM was stabler than that contained polyacrylamide. Moreover, a linear relationship between the logarithm of the half decay time and polymer concentration was observed, and the slope reflects the polymer ability to stabilize the foam.     

Effect of hydrophobically modified SiO2 nanoparticles on the stability of water-based SDS foam

In the present study, SiO₂ nanoparticles were first hydrophobically modified and then added into anionic surfactant sodium dodecyl sulfate (SDS) stabilized water-based foam to improve the foam stability. The foam stability was experimentally evaluated by measuring surface tension, Zeta potential and half-life of the foam. The foam stabilizing mechanism was also studied from a micro perspective by molecular dynamics simulation through analyzing the equilibration configuration and MSD curve of both SDS surfactant and water molecules. The results show that foam exhibits an optimal stability when SiO₂ concentration is 0.35 wt% under a specific surfactant concentration (0.5 wt%) in this work. The addition of SiO₂ nanoparticles with suitable concentration could improve the adsorption between SDS molecules and nanoparticles, thus limiting the movement of SDS and restricting the movement of surrounding water molecules, which is beneficial to enhance the foam stability.     

The effect of filamentous bacteria on foam production and stability

Bacteria have been implicated in the formation of viscous brown foams that can appear suddenly on wastewater treatment plants. Three strains of the filamentous bacterium Gordonia amarae, isolated from wastewater treatment plants, were investigated to determine their effect on foam formation and stabilisation. During the exponential phase of the bacterial growth a biosurfactant was formed, causing a significant drop in the surface tension of the filtered medium and the formation of persistent foam. Foaming tests in the presence and absence of bacteria showed that bacteria increased foam persistence, most probably by reducing the drainage from the lamellae between bubbles. Experiments showed that > or =55% of the three bacterial strains partitioned into the foam produced by the biosurfactant, indicating that their surfaces were hydrophobic. The extent of partitioning was independent of the growth stage, suggesting that the cell surface hydrophobicity did not change with age, or with cell viability. This work shows that, although the G. amarae cells themselves do not cause foaming, they do produce biosurfactant, which aids foam formation, and they stabilise the foam by reducing the rate of drainage from the foam lamellae.     

Influence of Foam Apparent Viscosity and Viscoelasticity of Liquid Films on Foam Stability

The objective of this research work was to study the relationship among the apparent viscosity of bulk foam, the viscoelasticity of liquid films, and foam stability. Bulk foam tests showed that the drainage half-life of AOS foam was higher than that of sodium dodecyl sulfate (SDS) and hexadecyltrimethyl ammonium bromide (CTAB) foams. The results of foam apparent viscosity revealed that the foam apparent viscosity was related to foam quality rather than foam stability. Higher film viscoelasticity modulus could be assigned for α -olefin sulfonate (AOS) films than those for SDS and CTAB ones. The film conductivity tests indicated that AOS liquid films, compared with SDS and CTAB liquid films, could delay the liquid drainage speed under dynamic conditions. Compared with foam apparent viscosity, the viscoelasticity of liquid films appeared to be a key factor in foam stability.     

Effect of organic acid chain length on foam performance in a porous medium

We have systematically studied the effect of organic acid chain length on surface dilatational properties and foam flow performance in a porous medium. Surface dilatational properties were studied by oscillating drop module (ODM). ODM results in deionized water show that sufficient long chain length of organic acid is an essential requirement for high surface dilatational modulus. While, to various salinities, surfactant to acid ratio of achieving high surface dilatational modulus varies. Foam flow tests show that surface dilatational modulus has decisive effect on produced foam size, which partially determines foam flow pressure drop. Both surface dilatational modulus and surface tension determine foam flow pressure drop. Besides, surface loss modulus also contributes to pressure drop. Bulk foam tests show that addition of organic acids with proper chain length can enhance foam tolerance to oil significantly. Compared with alkane chain length, acid with longer chain has good ability in stabilizing foam. At last, foam flooding tests show that surface dilatational modulus and foam tolerance to oil play important roles in foam enhanced oil recovery.     

Investigation on properties of aqueous foams stabilized by aliphatic alcohols and polypropylene glycol

Foams stabilized by nonionic surfactants are usually moderately stable due to high drainage rate and intense bubble coalescence and coarsening. This study aimed to investigate comparatively the foam properties of aliphatic alcohols (methyl isobutyl carbinol (MIBC) and 2-octanol) and polypropylene glycol (PPG400). Experiments were conducted using the FoamScan method at various surfactant concentrations and gas flow rates where the foam volume, liquid content of foam and foam half-life were determined. The results showed that both foamability and foam stability of surfactant solution increased with increasing gas flow rate and surfactant concentration for all tested surfactants. PPG400 was an unusually strong surfactant having the largest surface activity compared with MIBC and 2-octanol, which exhibited the maximum foaming performance and foam stability at all tested gas flow rates and concentrations. The present study suggested that foam properties depended primarily on the type of surfactant and its concentration and secondarily on the gas flow rate. In addition, properties of interface are closely related to that of foam, which is a significant point if one wants to produce foams for specific applications.     

The Effect of Macromolecules on Foam Stability in Sodium Dodecyl Sulfate/Cetylpyridinium Bromide Mixtures

Abstract

The effects of macromolecules, gelatin, and polyvinylpyrrolidone (PVP), on the properties of foam comprising sodium dodecyl sulfate (SDS) and cetylpyridinium bromide (CPDB) have been studied by measurements of foamability, foam stability, surface tension, and solution specific viscosity. The results indicate that foamability and foam stability are significantly improved when macromolecules are added into mixed systems. Both gelatin and PVP associate with SDS/CPDB surfactants and form aggregates. Electrostatic repulsion and steric stabilization between the two sides of the foam lamellae, due to aggregation, and prevention of drainage in the lamellae, achieved by the long chains of macromolecules are the reasons for increasing foamability and foam stability. The interactions between PVP and surfactants is weaker than those between gelatin and surfactants. The strongest association between macromolecules and surfactants occurs when the molar ratio of SDS/CPDB is 1:1. By comparing PVP with gelatin, the former is favored to increase foamability, and the latter is favored to increase foam stability.     

Treatment of low level radioactive liquid wastes using composite ion-exchange resins based on polyurethane foam

Composite ion-exchange resins were prepared by coating copper-ferrocyanide (CFC) and hydrous manganese oxide (HMO) powders on polyurethane (PU) foam. Polyvinyl acetate/Acetone was used as a binder. The foam was loaded with about five times its weight with CFC and HMO powders. The distribution coefficients of CFC-PU foam and HMO-PU foam for cesium and strontium respectively were estimated. Under similar conditions the HMO-PU foam showed higher capacity as well as better kinetics for removal of strontium than CFC-PU foam for Cs. The pilot plant scale studies were conducted using a mixed composite ion-exchange resin bed. About 1000 bed volumes could be passed before attaining a DF of 10 from an initial value of 60–80. The spent resin was digested in alkaline KMnO₄ and the digested liquid was fixed in cement matrix. The matrices were characterized with respect to compressive strength and leach resistance.