分散剂对聚脲多元醇性能的影响

研究了芳香族分散剂S和醇类分散剂D对聚脲多元醇 (PHD)性能的影响 ,并对两种分散剂进行了比较 ,发现这两种分散剂都可以改善聚脲颗粒的分散性、降低聚脲多元醇 (PHD)体系黏度 ,并且发现醇类分散剂D对高固含量 (>2 5 % )的聚脲多元醇 (PHD)也有很好的分散降黏的作用。     

聚脲多元醇的制备

聚脲多元醇PHD的生产工艺复杂 ,在普通实验室和工厂合成较为困难。为了能够更方便地合成PHD ,华南理工大学材料科学研究所通过大量实验寻找出简易制备PHD的工艺 ,并将制得的PHD用于发泡及对其进行各种性能测试 ,结果令人满意。     

尿素基聚脲多元醇制备聚氨酯软泡性能的研究

以自制的尿素基聚脲多元醇(PHD)为原料制备了软质聚氨酯泡沫,考察了PHD的用量对泡沫的发泡性能、物理机械性能以及阻燃性能的影响.结果表明,PHD的加入对普通软质聚氨酯泡沫发泡和凝胶速度都有明显的催化作用,可减少催化剂的用量;当用10～30份的PHD代替普通聚醚多元醇时,泡沫的压缩强度、65%/25%压陷比、回弹率、75%压缩永久变形、拉伸强度、伸长率以及撕裂强度等各项性能均有明显的提高;PHD的加入还可以提高泡沫的阻燃性.     

氨基树脂制备聚脲多元醇

将三聚氰胺进行改性制备氨基树脂即多元胺溶液,再将氨基树脂用于制备聚脲多元醇(PHD),并对其合成原理、合成工艺及其关键影响因素等进行了研究。用红外光谱、NDJ-1型旋转式黏度计、LG10-24型离心机、透射电镜(TEM)、热重分析(TG)等对聚脲分散体进行测试与表征。     

蜜氨基聚脲多元醇对聚氨酯泡沫性能的影响

以自制蜜氨基聚脲多元醇为主要原料制备高回弹聚氨酯软泡,研究蜜氨基聚脲多元醇对泡沫的开孔率、密度、回弹率、压陷硬度、水平燃烧速率和氧指数等方面的影响。三聚氰胺聚脲多元醇为其泡沫提供了优良的泡沫压陷硬度和阻燃性。玻璃化温度和热解温度测试值表明蜜氨基聚脲多元醇为其泡沫提供了优异的热稳定性。     

JS—350聚脲多元醇的研制

研究了脲指数、聚醚、多元胺,反应温度、搅拌速率和异氰酸酯用量对聚脲多元醇性能的影响。通过滴加法由水合多元胺 N-1体系成功地制备了JS-350聚脲多元醇。制得的聚脲多元醇在泡沫密度基本不变的情况下,能提高 HR 泡沫的承载能力和舒适性,填补了国内空白。     

聚脲一氨酯橡胶的制备

通过≥90％的多元醇(分子量1000—6000)和MDI或衍生物(NCO-OH比例≥3.2∶1)的反应以及将预聚体与剩余的多元醇和取代基≥1邻位的芳族二胺一起进行反应-注射模压而制备带有微孔的密封外层的聚脲—氨酯橡胶。预聚体(NCO含量12.4％,25℃下粘度为2.2Pa—s)由92公斤粗MDI(NCO含量32.5％)和446.8公斤聚丙烯甘醇(分子量2000)制备而成。以预聚体为100     

聚脲多元醇的合成研究

在实验室以间歇法制备了聚脲多元醇,在反应体系中加入分散剂S,研究分散剂S对体系粘度、固含量、贮存稳定性的影响,发现分散剂的加入有利于降低反应体系和产品的粘度,提高聚脲多元醇的固含量和稳定性。采用FTIR、DSC、粒径分布仪、TEM等手段分析了聚脲分散体的结构、热性能、分散性及形态。     

聚脲多元醇对聚氨酯泡沫阻燃性的影响

使用含氮结构型阻燃聚脲多元醇和阻燃剂对聚氨酯高回弹泡沫的阻燃性进行研究,考察了配方中聚脲多元醇用量及阻燃剂品种对泡沫烟密度及氧指数的影响。研究结果表明,聚脲多元醇具有显著的抑烟作用,与三聚氰胺、阻燃剂R一起使用时,协同阻燃效应明显,不仅能有效降低泡沫燃烧时的发烟量,还能显著提高泡沫的氧指数。     

聚脲防爆材料的制备及力学性能影响因素的研究

为制备出性能优异的聚脲防爆材料，通过多种配方设计，探讨了软段种类、软段相对分子质量、硬段含量、异氰酸酯指数对聚脲防爆材料力学性能的影响。结果表明，选用相对分子质量为 1 000的聚己内酯多元醇（ PCL）作为软段，硬段含量为 55%，异氰酸酯指数为 1. 05~1. 10时，制备的聚脲防爆材料的综合性能最优。     

Synthesis of a hydrosoluble reversible addition-fragmentation chain transfer agent and application in the preparation of micro/nano-polyacrylamide gel dispersions

A hydrosoluble reversible addition-fragmentation chain transfer (RAFT) agent named S-(2-propionic acid)-S′-(2-methylpropionic acid) trithiocarbonate (PAMPATTC) is successfully synthesized. Then the micro/nano-polyacrylamide gel dispersions are prepared via one-pot RAFT polymerization in water to solve the problems of complicated preparation process and particle size control of common profile-controlling and flooding agents. The structure of the RAFT agent is characterized and confirmed by fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (¹H-NMR). The effects of different reaction conditions on the properties of polyacrylamide gel dispersions are studied. The polymer dispersity index (PDI) of the polyacrylamide gel dispersions is tested by aqueous gel permeation chromatography, confirming the activity characteristics of RAFT polymerization. The rheological characteristics of the polyacrylamide gel dispersions and liner polyacrylamide are characterized. Compared with the liner polyacrylamide at similar viscosities, it is confirmed that the polyacrylamide gel dispersions were closer to Newtonian fluid, especially at high shear rates and the increasing amount of RAFT agent. The viscoelasticity tests under frequency scanning further confirm that the polyacrylamide gel dispersions are successfully synthesized via aqueous RAFT polymerization. The particle sizes are measured to show that the particle size of the polyacrylamide gel dispersions is micro/nano-scale. The micromorphology of polyacrylamide gel dispersions is determined to indicate the irregular spherical structure, confirming that the micro-particles are indeed formed by the aggregation of nano-particles.     

Effect of compounding procedure on mechanical properties and dispersed phase morphology of poly(lactic acid)/polycaprolactone blends containing peroxide

Side feeding technique was applied to poly (lactic acid) (PLA)/polycaprolactone (PCL) blends containing peroxide. Feeding procedures attempted were blanket and split feeding. In the former procedure, all the materials were fed into the main hopper at once. On the other hand, the feeding of materials was split by using main hopper and side feeder in the later procedure. The results indicated that static tensile properties were not dependent on feeding procedure, but the impact strength was superior in the case of the split feeding samples. It is noteworthy that the impact strength of the split feeding sample was considerably affected as it was four times better. Coarse dispersions such as continuous filament and layer dispersions were formed in the blend specimens without peroxide. On the other hand, fine dispersions were formed in the blend specimens containing peroxide which served as compatibilizer in this blend system. Peroxide addition through the side feeder brought about fine dispersions, promoted adhesion at the interface, and increased viscous nature of the PCL phase. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1066–1074, 2007     

The fine dispersion of functionalized carbon nanotubes in acrylic latex coatings

Nanocomposites of a polymer and carbon nanotubes exhibit high electrical and thermal conductivity and enhanced mechanical properties in comparison to the polymer alone. Film formation from latex dispersions is an ideal way to create nanocomposite coatings with the advantages of solvent-free processing and a high uniformity of dispersion. It is shown here that carbon nanotubes functionalised with poly(vinyl alcohol) (PVA) can be blended with two types of acrylic latex to create stable colloidal dispersions without the need for added surfactant or emulsifier. Waterborne nanocomposite films with optical transparency can be formed. Microscopic analysis shows that the PVA-functionalized nanotubes are finely and uniformly dispersed in the polymer matrix.     

Electrophoretic,dynamic, and static light scattering on charged polymer emulsions

Light scattering studies on dispersions formed by phase separation of a polymer-solvent-non-solvent mixture show that the dispersions comprise charged droplets of the polymer-rich phase. The charge number is not large, and data on the electrophoretic-scattering and the dynamic scattering in the absence of an external electric field are both consistent with distribution of charge among the droplets. Data on the dependence of the static scattering on concentration and scattering angle show that the droplets are also disperse in radius. The data are discussed in terms of an interaction potential among the charged droplets relating the electrostatic interactions to the charge number and radius of the droplets, and the ionic strength of the solvent.     

Stability and properties of waterborne polyurethane/clay nanocomposite dispersions

Factors that can affect the stability of waterborne polyurethane (WBPU)/clay nanocomposite dispersions are reported. It is suggested that the dispersion stability depends on the carboxyl acid salt content, clay content, sonication (mechanical forces), and clay surface structure. It was observed that the dispersion stability increased with increasing carboxyl acid salt content after applying sonication (mechanical forces) in clay with OH groups (Cloisite 30B) up to 23.58 mol% DMPA. Encapsulated (WBPU20-30B4-M and WBPU23-30B5-M) clay in PU particles was formed using the above combination. The dispersion with clay encapsulated in PU particles had the longest storage time of all of the dispersions. The zeta potential, particle size, particle size distribution, and viscosity of the dispersions also depend on carboxyl acid salt content, clay content, sonication (mechanical forces), and clay surface structure.     

Three‐phase fluidized distillation

Separation efficiency in distillation operations can be improved by modifying the characteristics of the dispersions formed on the trays. The present work reports on the hydrodynamic and mass transfer characteristics of liquid‐solid‐vapour dispersions formed on sieve trays without downcomers of a distillation column operating under total reflux conditions. Murphree efficiency and the operating limits of distillation using the ethanol‐n‐butanol system are analyzed for a large range of vapour velocities and liquid mixture compositions, utilising wettable PVC particles and non‐wettable silicone, PE, and Teflonr? particles. It was verified that wettable particles show a drastic reduction in the upper operating limit of vapour velocity, but this does not occur for non‐wettable particles. Tray efficiency can be increased when non‐wettable particles are used, mainly for high vapour velocity operations.     

Microwave‐induced enhancement of the dissolution rate of poorly water‐soluble tibolone from poly(ethylene glycol) solid dispersions

In this study, solid dispersions of poorly water‐soluble Tibolone in a poly(ethylene glycol) matrix were prepared with conventional melt mixing and microwave irradiation. The results of the assay content, LC–MS, and ¹H‐NMR indicated that microwave irradiation did not affect drug stability when a relatively low irradiation power (440 W) was used. Fourier transform infrared spectroscopy indicated that there were no hydrogen bonds formed between Tibolone and poly(ethylene glycol), and this affected the drug's crystallinity and its particle size distribution. The dissolution rate of the drug was slightly higher in the case of dispersions prepared by microwave irradiation. This enhancement of the drug dissolution rate was probably due to the lower size of the Tibolone particles in the dispersions prepared by microwave irradiation. The application of microwaves represents a promising alternative to conventional preparative methods of drug dispersions. The main advantage in comparison with conventional melt mixing is that solid dispersions can be prepared in much shorter times. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

An investigation of the elastic properties of viscoelastic clusters of particles: A comparison between two methods

Most industrial process lines involve mixing complex dispersions, which can include non-Newtonian liquids and viscoelastic particles. Knowledge of the parameters of these components may provide a key for understanding how dispersions are formed and how equipment should be designed. One parameter is the shear modulus, which describes the ability of particles to resist mechanical stresses. This parameter may play the main role in the mixing process, when a dispersion is formed by the mechanical influence of a rotor (slice or shear in a rotor-stator mixer). In this work, two methods were chosen for measuring the shear modulus: the evaluation method, based on the Warner-Bratzler cut test, and the oscillatory method. Both methods were used for measuring viscoelastic clusters of particles, and the results were adjusted for the purposes of the comparison. The comparison shows that the shear modulus values obtained from Warner-Bratzler are higher than the values obtained from the oscillatory test for the same conditions. This difference can be explained by differences in the mechanical processes during the experiments.     

Das faserprotein kollagen

The main component of the connective tissue, the collagen, is one of the few fibre proteins. By its three dimensional interlace the stable and flexible structure of the animal skin and the leather produced therefrom is formed. Fibres of collagen can be obtained by dissolving the skin mechanically or by spinning of collagen solutions. From solutions or dispersions of collagen films can be obtained. By a special technological treatment a stable collagen foam can be produced from collagen dispersions. Because of their good physiological compatibility and their biological reabsorption products from collagen are suitable for applications in human medicine.     

硅氧烷改性聚氨酯水分散液

针对聚氨酯水分散液(PUD)胶膜目前存在的耐热、耐水性能的不足,介绍了用聚硅氧烷(PSi)改性的研究进展。综述了硅氧烷改性聚氨酯水分散液(PSi-PUD)的特性、难度及其克服的措施。简略叙述了理论依据。