Aqueous dispersion properties

K. R. Mikeska and W R. Cannon, Non-Aqueous Dispersion Properties of Pure Barium Titanate for Tape Casting, Colloids and Surfaces, 29, 305-21 (1988). 

Nllsen, K.J., The Effect of Moisture on the Surface Chemistry and Non-Aqueous Dispersion Properties of Laser Synthesized Silicon Nitride. Ph.D. Thesis, Rutgers University, (1988). 

Poly etrafluoroethylene is manufactured and sold in three forms granular, fine powder, and aqueous dispersion each requires a different fabrication technique. Granular resins are manufactured in a wide variety of grades to obtain a different balance between powder flows and end use properties (Pig. 1). Pine powders that are made by coagulating aqueous dispersions also are available in various grades. Differences in fine powder grades correspond to their usefulness in specific appHcations and to the ease of fabrication. Aqueous dispersions are sold in latex form and are available in different grades. A variety of formulation techniques are used to tailor these dispersions for specific appHcations. 

The abihty to form aqueous dispersions is a property that gives many quaternary compounds useful appHcations. Placement of polar groups, eg, hydroxy or ethyl ether, ia the quaternary stmcture can iacrease solubiUty ia polar solvents. 

Properties. CoUoidal siUca is a stable aqueous dispersion or sol of discrete amorphous siUca particles having diameters of 1 to 100 nm. SiUca sols do not gel or setde out of solution for at least several years of storage. Aqueous sols that contain up to 50% siUca have been developed (30,31). Particle sizes of approximately 130 nm in diameter are possible (32), but slowly settle out of solution. 

Bacterial Cellulose. Development of a new strain of Acetobacter may lead to economical production of another novel ceUulose. CeUulon fiber has a very fine fiber diameter and therefore a much larger surface area, which makes it physicaUy distinct from wood ceUulose. Its physical properties mote closely resemble those of the microcrystalline ceUuloses thus it feels smooth ia the mouth, has a high water-binding capacity, and provides viscous aqueous dispersions at low concentration. It iateracts synergisticaUy with xanthan and CMC for enhanced viscosity and stabUity. 

Dispersion properties and aqueous solubility of disperse dyes... 

AMMONIUM HALIDE, 293 ANISOTROPY, 38 57 153 174 406 ANNULAR DIE, 311 ANTIOXIDANT, 385 ANTI-SLIP PROPERTIES, 208 ANTISTATIC PROPERTIES, 91 302 426 427 444 447 450 APPEARANCE, 124 186 241 293 AQUEOUS DISPERSION, 103 ARGON, 185 233 235 321 339 433 ARRHENIUS FACTOR, 243 ARTIFICIAL HIP, 52 ARTIFICIAL KNEE, 52 ARTIFICIAL SEAWEED, 455 ASPECT RATIO, 314 419 ATOMIC FORCE MICROSCOPY, 149... 

In the following decades, homo-, co- and terpolymers of VAM with other vinyl esters, (meth)acrylates, and ethylene were developed to give thermoplastic materials with tailored properties that are nowadays produced as solid resins, aqueous dispersions and dispersible powders. 

Copolymers with acrylates (vinyl acrylics) or other vinyl esters are also commonly produced, mostly as aqueous dispersions. They are, independent of the nature of the comonomer, often referred to as copolymers or terpolymers . The presence of comonomers of course heavily influences a number of physical properties like the glass transition temperature and melting point, water solubility or flexibility, to name just a few. 

The properties of polymers processed out of aqueous dispersions are influenced by the particle size and the particle size distribution (Example 3-47). 

The following experiment should demonstrate the influence of particle size and mini-mai fiim-formation temperature (which is connected with the glass transition temperature and therefore with the chemical structure of the polymers) on the properties of fiims, prepared from aqueous dispersions. 

Polymer Selection. The selection of corn starch as the starting material was made due to its low cost, ready availability, multitude of previous derivatization literature work and favorable chemical and physical properties (i.e., inert, readily deriva-tized homopolysaccharide capable of forming high solids content aqueous dispersions with relatively low viscosities). The corn starch used in this study was purchased in bulk from a local food cooperative. Table I gives the proximate analysis of a typical corn starch. 

The ability to form aqueous dispersions is a property that gives many quaternary compounds useful applications. 

Particle Structure - So far, the discussion of non-uniform emulsion polymers has centered around mechanical properties, interpreted in terms of gradations of sequences between set compositional limits. But latexes are aqueous dispersions, and an exploration of particle morphology is equally interesting and important. For instance, can polymer particles be constructed such that particle sequence compositions are located in a desired region of the particle, and what evidence exists that such particle morphologies have been realized ... 

With the advent of advanced characterization techniques such as multiple detector liquid exclusion chromatography and - C Fourier transform nuclear magnetic resonance spectroscopy, the study of structure/property relationships in polymers has become technically feasible (l -(5). Understanding the relationship between structure and properties alone does not always allow for the solution of problems encountered in commercial polymer synthesis. Certain processes, of which emulsion polymerization is one, are controlled by variables which exert a large influence on polymer infrastructure (sequence distribution, tacticity, branching, enchainment) and hence properties. In addition, because the emulsion polymerization takes place in an heterophase system and because the product is an aqueous dispersion, it is important to understand which performance characteristics are influended by the colloidal state, (i.e., particle size and size distribution) and which by the polymer infrastructure. 

Methoxy, hydroxypro-poxy, acetyl, suc-cinyl 5 HPMCAS-L HPMCAS-M HMPCAS-H (Syntapharm) Aqueous dispersion Powder <5 pm Elastic properties, plasticizer not essential Slightly hygroscopic... 

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