胶粒聚集程度对ZrO2—MgO超细粉末团聚状态的影响

依据共沉淀过程的动力学分析,研究了共沉淀反应最初阶段胶粒的聚集程度与粉末团聚状态之间的关系。实验结果表明:粉末中的团聚体起源于沉淀反应过程,胶粒的聚集程度决定着粉末的团聚状态。因而,可以通过控制胶粒的聚集特征来控制粉末的团聚状态。根据实验,提出了用以表征粉末中团粒聚集特征的聚集系数的概念。     

Rheometry of aging of colloidal melamine–urea–formaldehyde polycondensates

Aged and whitened melamine–urea–formaldehyde (MUF) resins in a colloidal state were tested with parallel‐plate rheometry to determine the extent of their viscoelastic behavior. Only in advanced colloidal states, and so only when aggregated colloidal clusters occurred, did the resins present clear indications of viscoelastic responses, as illustrated by the crossover of elastic modulus and viscous modulus curves at lower strain percentages. These colloidal clusters were labile microstructures, which, broken by applied shear, justified the known thixotropic behavior of these resins sufficiently advanced by aging or other means. MUF resins already in the colloidal state, but for which colloidal clustering had not yet occurred, behaved exclusively as viscous liquids. Two different cases of physical gelation were observed, reversible physical gelation and irreversible physical gelation, underlying which a true gel situation possibly occurred. Physical gelation due to colloidal superstructures occurred in both, but the difference in the resin average molecular masses revealed if the physical gelation was reversible or irreversible and, therefore, if the liquid/cluster separation was defined as the terminal phase of physical gelation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 655–659, 2005     

溶胶的运动性质

1861年英国化学家首次提出了“胶体”这个名词。胶体是处在一定分散范围的物质的一种存在状态。而不是某一种物质固有的特性。现在,“胶体”是指那些具有高度分散的体系。20世纪初人们把胶体区分为两类：亲液胶体和憎液胶体。胶体的运动性质主要表现在分散相粒子在分散介质中的热运动和在重力场及离心场中的沉降作用。     

Preparation and characteristics of a waterborne preventive stain coating material with organic-inorganic composites

With the goal of developing a waterborne coating material that prevents staining, organic-inorganic composites prepared from colloidal silica and two types of acrylic resin emulsions were investigated as exterior coatings. conventional acrylic resin emulsion and organic silane hybridized acrylic resin emulsion prepared by emulsion polymerization were mixed with colloidal silica to form organic-inorganic comiposite films. The addition of colloidal silica to emulsions yielded films with higher hydrophilicities, as indicated by lower water contact angles for these films in comparison to films without colloidal silica. The water contact angles of organic silane hybridized acrylic resin emulsion/colloidal silica films were lower than those of acrylic resin emulsion/colloidal silica films. Composite films containing colloidal silica particles smaller than 100 nm in diameter showed high hydrophilicities. Observations of the dispersed state of colloidal silicaparticles in organic-inorganic composite films by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated that colloidal silica particles were densely aggregated on the film surface. Outdoor exposure tests of the coating materials prepared from organic silane hybridized acrylic resin and colloidal silica particles with diameters of 7.5 nm showed excellent stain resistance.     

Uniformity of Al2O3-ZrO2 Composites by Colloidal Filtration

Dispersion states of aqueous composite Al₂O₃/ZrO₂ colloidal suspensions were studied by measuring particle size distribution as a function of pH. Mutual dispersion was achieved at pH values of 2.0 to 3.5. Consolidated composites formed by colloidal filtration reflected the uniformity of the colloidal state. The mean flexural strength (896 MPa) of the sintered compacts was 1.6 times that of bodies consolidated by isostatic pressing .     

拟薄水铝石胶溶质量的表征

拟薄水铝石溶胶是FCC催化剂双铝基黏结剂的重要组成部分,影响催化剂强度,然而按照目前质量指标生产的双铝基黏结剂存在黏结性能不稳定的问题。结合现有指标,认为缺少对拟薄水铝石胶溶过程的考察。而且FCC催化剂在制备过程中,从浆液到最终喷雾干燥升温过程明显,因此,通过新的表征方式对拟薄水铝石在胶溶过程和升温过程中的黏度变化,定义了新的参数黏温活化能。结果表明,黏温活化能可以较好反映拟薄水铝的胶溶状态。     

Colloidal macromolecular phenomena. Part II. Novel microcrystals of polymers

Colloidal microcrystalline cellulose, introduced in 1961, now is a successful commercial product with growing world-wide markets. This paper describes some major findings of our continuing research to convert fibrous or fiber-forming polymer systems into new colloidal microcrystalline physical states without going through a homogeneous molecular solution phase. Several novel microcrystalline colloidal products from the following natural and/or synthetic polymeric raw materials are described and compared for the first time: cellulose, amylose, collagen, nylon, and chrysotile mineral silicates. Many previously unpublished electron micrographs are presented. These products demonstrate a new and growing field of colloidal microcrystalline polymer science. They open up increasing opportunities for new polymer products based on the original concept, namely, the unhinging of polymer microcrystals from their natural or synthetic network and then by appropriate mechanical energy, releasing them as discrete, submicron colloidal polymer microcrystals dispersed in various liquid media to form unique gel systems, or reaggregated in the dry state to form porous colloidal particles.     

Comparative kinetics of induced radical autocondensation of polyflavonoid tannins. I. Modified and nonmodified tannins

Comparative kinetics of the radical autocondensation induced by SiO₂ of a polyflavonoid tannin, namely quebracho tannin a mostly profisetinidin/prorobinetinidin tannin, in its natural extract state, sulfited, carbohydrate free, and in its adhesive intermediate form were carried out by electron spin resonance (ESR). The results obtained not only confirmed the existence of strong radical mechanisms of tannin autocondensation in the presence of dissolved SiO₂, but also pointed out new effects of interest in such a reaction. The SiO₂ induced autocondensation proceeds at a faster rate, and radical surge and concentration decay appear to be more marked and more rapid the more colloidal the tannin solution is. This appears to indicate that a colloid-induced intramicellar radical mechanism of the reaction is at work. As a consequence the intensity and rate of the radicals surge and decay decreases passing from more colloidal to less colloidal tannin solutions. Thus, the decay rate decreases passing from natural tannin to adhesive intermediate, to carbohydrate-free tannin, to almost disappear for sulfited tannin. The colloidal state of the solution appears to depend mostly, but not only, on the presence of the polymeric carbohydrates in the extract. © 1996 John Wiley & Sons, Inc.     

Colloidal aggregation of MUF polycondensation resins: Formulation influence and storage stability

Colloidal particle formation followed by their clustering has been shown to be the normal way of ageing of aminoplastic resins, in particular melamine–urea–formaldehyde (MUF) resins. Ageing (or further advancement of the resin by other means such as longer condensation times) causes whitening of the resin. This is a macroscopic indication both of the formation of colloidal particles and of their clustering. Some clustering appears rather early in this process, even when the great majority of the resin does visually appear to be in colloidal state, being transparent. However, it eventually progresses to resins which are mostly in colloidal, clustered state, followed much later by a supercluster formation starting to involve the whole resin. There appears to be clear correspondence between molecular mass increases as obtained by gel permeation chromatography (GPC), low‐angle laser light scattering (LALLS) analysis, and observation by polarizing optical microscopy. LALLS, however, appears to indicate the dimensions of the colloidal particles themselves when the level of colloidal aggregation is rather low, but it indicates the dimensions of the clusters once these are mostly aggregated. The smaller visible colloidal particles, already aggregates, were found by polarizing optical microscopy to be of a mostly elongated, rodlike shape, the length of which was shown to grow much further than their width with resin advancement and ageing. As their dimensions indicate, these are already clusters; this implies that the mainly linear increase of the polycondensate chains influences also the simpler colloidal clusters' growth direction, possibly explaining the resins' lack of tridimensional hardening while still in storage. It also explains why molecules such as free urea and acetals, by disrupting these colloidal aggregation mechanisms, allow both a much longer shelf life of the resin and its better performance in hardening. These findings explained the considerable difference in the behavior and performance of different MUF resin formulations. The ageing of the MUF resins of different preparation procedures appeared then to proceed from (1) clear resin (molecular colloidal aggregation) to (2) superclusters of a whitened, heavily thixotropic resin, which is the beginning of physical gelation to (3) liquid/cluster separation, which is the terminal stage of physical gelation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2690–2699, 2004     

Properties of organic–inorganic composite materials prepared from acrylic resin emulsions and colloidal silicas

To design an organic–inorganic composite material with colloidal silica as the inorganic component, an acrylic resin emulsion and an organic silane hybridized acrylic resin emulsion were prepared by emulsion polymerization. The organic–inorganic composite films were prepared by blending the emulsion and the colloidal silica. The contact angles for water, gloss at 60°, and the transparencies of those films were measured. The dispersion state of colloidal silica in films was observed with a scanning electron microscope (SEM) and a transmission electron microscope (TEM). From these results, the contact angle for water of the organic–inorganic composite film obtained from the silane hybridized acrylic resin emulsion was lower than that of the organic–inorganic composite film obtained from an acrylic resin emulsion. The contact angles for water in organic–inorganic composite films with colloidal silicas were lower than those of the films without the colloidal silicas. The films prepared from silane hybridized acrylic resin emulsion composites with colloidal silicas of less than 100 nm were more hydrophilic. SEM and TEM observations demonstrated that some aggregations of the small colloidal particle silica were densely dispersed on the film surface. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2051–2056, 2006     

Expansion associated with ettringite formation at different temperatures

Expansion of hydrated mixtures made with C₃A, CaSO₄ · 2H₂O, Ca(OH)₂ and SiO₂, at 22, 30, 40, 50, 60°C, was studied to verify if expansion is associated with colloidal ettringite formation or with the solid state conversion of C₄AH₁₃ to monosulfate hydrate in presence of calcium hydroxide. From the results of our investigation it can be drawn the conclusion that mortars expansion is in connection with colloidal ettringite formation and the monosulfate hydrate is formed only when the greatest expansion is ended. The increase in hydration temperature seem to be favorable to the formation of colloidal ettringite.     

Control of pit initiation sites on aluminum foil using colloidal crystals as mask

The electrochemical etching of aluminum foils using a physical mask of colloidal spheres was studied to directly control the initiation sites of pits independent of the surface activation state of the substrate. A two-dimensional array of colloidal spheres used as a mask was prepared by self-assembly on an aluminum substrate. The transfer of the hexagonally ordered pattern of self-assembled colloidal spheres to the aluminum substrate could be achieved by the selective electrochemical etching of an exposed aluminum surface. That is, etch pits were generated only in the triangular void space among the three spheres on the aluminum surface. Based on this process, the dispersibility of the initiation sites of pits was improved clearly in comparison with that for the conventional method. The density of pits could also be controlled by changing the diameter of spheres used as a mask.     

Redispersible dried hydroxyapatite particles with grafted pH-sensitivity polymer brushes of poly(styrene-co-4-vinylpyridine)

Reversible aggregation-redispersion transition of colloidal particles is of considerable importance in colloidal science and various industrial fields. In the present study, stimuli-responsive hybrid hydroxyapatite (HA) particles were prepared with redispersible ability in aqueous solutions even after separation from the “as synthesized” state and subsequent dry heat treatment. We firstly modified HA particles with sodium oleate as chelating agent, then introduced bromoalkyl functional groups through an addition reaction of unsaturated oleate molecule with bromine, and finally grafted polymer brushes of polystyrene-co-4-vinylpyridine onto HA. It was the pH-sensitive polymer shell that had rendered HA particles the redispersible ability, which was attributed to the protonation of the pyridine blocks in acidic solutions. The reversible dispersion-aggregation transition of HA could be controlled by alternating the pH value of aqueous solution. Protonated pyridine blocks had provided enough electrostatic and steric repulsions for colloidal HA to avoid effective collision.     

Colloidal aggregation of aminoplastic polycondensation resins: Urea–formaldehyde versus melamine–formaldehyde and melamine–urea–formaldehyde resins

Colloidal particles formation followed by their clustering have been shown to be the normal way of ageing of aminoplastic resins, namely urea–formaldehyde (UF) resins, melamine–formaldehyde (MF) resins, and melamine–urea–formaldehyde (MUF) resins. Ageing or further advancement of the resin by other means such as longer condensation times causes whitening of the resin. This is a macroscopic indication of both the formation of colloidal particles and of their clustering. It eventually progresses to resins, which are mostly in colloidal, clustered state, followed much later on by a supercluster formation starting to involve the whole resin. The initial, filament‐like colloidal aggregates formed by UF resins have different appearance than the globular ones formed by MF resins. MUF resins present a short rod‐like appearance hybrid between the two. GPC has been shown to detect the existence of colloidal superaggregates in a UF resin, while smaller aggregates might not be detected at all. The star‐like structures visible in the colloidal globules of MF resins are likely to be light interference patterns of the early colloidal structures in the resins. These star‐like interference patterns become more complex with resin ageing or advancement due to the advancement of the resin to more complex aggregates, to eventually reach the stage in which filament‐like and rod‐like structures start to appear. The next step is formation of globular masses that are representative of the true start of physical gelation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1406–1412, 2006     

中国生漆高装饰性能原因的研究

本文讨论了生漆及其精制漆具有高装饰性(丰满度好)的原因,认为漆酚的长侧链、漆膜固化后形成的胶态分散体光学性质不均匀,使漆膜具有高装饰性,找出了一些精制漆工艺的理论依据。     

Influence of chromophoric electron-withdrawing groups on photoinduced deformation of azo polymer colloids

This study investigated the influence of chromophoric electron-withdrawing groups on photoinduced deformation behavior of colloidal spheres of three azo polymers. The colloidal spheres were prepared by using the epoxy-based azo polymers (BP-AZ-CA, BP-AZ-CN, and BP-AZ-NT) through gradual hydrophobic aggregation of the polymers in THF-H₂O media. The colloidal spheres were controlled to have similar average sizes by adjusting both the polymer concentrations in the initial THF solutions and water-adding rates in the preparation processes. The colloids were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The colloid deformation was investigated by irradiating the colloidal spheres in solid state with a linearly polarized Ar⁺ laser beam (488 nm, 130 mW/cm²). For comparison, the colloids were also studied by irradiation with a polarized diode solid state laser beam (532 nm, 130 mW/cm²). Upon the light irradiation, all the colloidal spheres were elongated along the polarization direction of the laser beams. The electron-withdrawing groups showed significant influence on the colloid deformation behavior related with the response to the light irradiation. The colloid deformation was more efficiently induced by irradiation with the laser beams having the intermediate wavelengths between the λ_max and the absorption band tails of the azo chromophores. When the hydrophilic carboxylic group was used as the electron-withdrawing groups, more significant deformation was induced under the same light irradiation condition, which could be attributed to the higher hydrophilicity of the polymer. Above observations can lead to a better understanding of the photoinduced deformation mechanism of azo polymer colloids.     

Preparation and characterization of microdisperse bioavailable carotenoid hydrosols

The application of carotenoids as natural additives in various water-based or water-compatible formulations for the pigmentation of foods and feeds is seriously hampered by their insolubility in aqueous systems. Therefore, in order to develop the full potential of colour strength and to achieve a high degree of bioavailability during gastro intestinal passage, the coarse crystalline material has to be transformed into a microdisperse state. Exemplified with β-carotene, a novel non-mechanical process is described that transforms the carotenoids into a colloidal hydrosol characterized by an average particle size of about 0.1 μm. The process is based on the preparation of a transient high temperature solute state of the carotenoid in a water-miscible solvent, coupled with succeeding rapid aqueous precipitation in the presence of a stabilizing polymer colloid. The obtained hydrosols are characterized by photon-correlation-spectroscopy(size), and microelectrophoresis(colloidal stabilization). The bioavailability was tested by monitoring plasma levels of β-carotene in veal calves.     

Colloidal Crystallization of Polystyrene Induced by a New Drop-Slide Method

Summary  Colloidal crystals of mono-dispersed polystyrene spheres in aqueous solvent were formed by a new drop-slide method. The optical properties of the colloidal crystal array (CCA) were characterized by reflection spectroscopy. The very strong intensity of reflectance was obtained by the new method. The maximum of the diffraction peak is highly symmetric and has a relatively narrow line width of about 52.0 nm when the CCA is in the wet state. An in-situ real time investigation on the formation of the CCA was performed. The reflection maximum was found to be 566.4nm, which blue shifted to 486.5 nm over the first drying phase and finally to a minimum of 432.3nm upon reaching the final stable state. The shifts of peak position were determined to be 4.1 nm / min at the first drying phase. The analysis of the diffraction maximum with calculation shows that the colloidal particles can crystallize into a face-centered-cubic (fcc) structure. The scanning electron micrograph image of the polystyrene spheres after is completely dried shows a face centered cubic formation.     

Asphalt colloidal types differentiated by Korcak distribution

Asphalt in a colloidal context can be considered as a sol, sol-gel or gel type where in all three cases the asphaltene particle plays an important role. Usually the three colloidal types can be differentiated by refinery processes or by rheological properties. The aggregation or clustering of the asphaltene particles (or micelles) from sol to sol-gel and finally to the gel state with a fixed lattice can follow the stochastic process of fractal Brownian motion which can fit a hyperbolic (or Korcak) distribution. A test was carried out using the same mass of various asphalts of different colloidal types for floc formation with a series of n-alkanes (dispersion media) of increasing characteristic lengths. Results from floc formation studies indicate that the value of the size distribution for the gel type is small, is higher for the sol-gel type, and is highest for the sol type. On the other hand, the surface irregularities for all three types of asphalt do not have any correlation. These observed facts are consistent with principles based on the fractal approach.