Paints colloid particles

The surfaces of colloidal particles are often charged and these changes can arise from a number of sources. Chemically bound ionogenic species may be found on the surface of particles such as rubber or paint latex particles. Charged species may be physically adsorbed if ionic surface active materials, for example, have been added. A charged surface may occur on a crystal lattice. An example is the isomorphous substitution of lower valency cations such as aluminium for silicon in the lattice structure of clays. A further example is the adsorption of lattice ions... 

In colloidal systems, van der Waals forces play a prominent role. When any two particles (neutral or with charges) come very close to each other, the van der Waals forces will be strongly dependent on the surrounding medium. In a vacuum, two identical particles will always exhibit an attractive force. On the other hand, if two different particles are present in a medium (in water), then there may be repulsion forces. This can be due to one particle adsorbing with the medium more strongly than with the other particle. One example will be silica particles in water medium and plastics (as in wastewater treatment). It is critical to understand under what conditions it is possible that colloidal particles remain suspended. For example, if paint aggregates in the container, then it is obviously useless for its intended purpose. 

Consider, for example, colloidal particles, i.e., particles that are too small to display the properties of macroscopic objects, say, <0.01 mm, and too large to behave like atoms and small molecules, approximately >10,000 pm. These colloidal particles move under electric fields, and if they are pigments, electric fields can be used to guide the colloidal particles to deposit upon metals and color them. The hues formed in this way may be more permanent than paint. But why do the particles move The... 

Many paints are colloidal solutions, in which the pigment particles are between 1 and 1,000 nanometers in size. These particles do not come together and form larger particles because colloidal particles carry electrical charges of like sign. They repel each other. 

When suspended colloidal particles form a network through the liquid, viscosity is increased. For silica gels the thickening and thixotropic effects are used in a large number of applications. The silica is mixed with paints, coatings, inks, pharmaceutical and cosmetics with this purpose.34... 

Stability in mixtures of colloidal particles and polymer molecules, dispersed in a solvent, has been the subject of experimental and theoretical investigations for a long time and it has applications in diverse fields such as paint technology, wastewater treatment, emulsion polymerization, biology etc. It has now been well recognized that polymer molecules can be used to induce either stabilization or flocculation (phase separation) in colloidal dispersions. It is important to distinguish between polymers which are adsorbed on the particle surface and those that are free in solution because the two situations usually lead to qualitatively different effects. Stability imparted by adsorbed polymers is known as steric stabilization and the flocculation or phase separation caused by the free polymer is due... 

The addition of polymers can also destabilize a colloidal solution for two reasons. Firstly, when polymers adsorb on more than one colloid and this phenomenon is called bridging. Secondly, when polyelectrolytes neutralize oppositely charged colloids and thereby reduce the electrostatic repulsion between the colloids. In some cases both a destabilization and a stabilization of a solution is desired. One example is the manufacturing of paints, where it is required that the paint is easy to apply on the wall and that it stays on the wall. This can be achieved with a solvent which stabilizes the solution but rapidly evaporates when the paint is applied and makes it possible for the colloidal particles to coagulate. 

There are three chapters in this volume, two of which address the microscale. Ploehn and Russel address the Interactions Between Colloidal Particles and Soluble Polymers, which is motivated by advances in statistical mechanics and scaling theories, as well as by the importance of numerous polymeric flocculants, dispersants, surfactants, and thickeners. How do polymers thicken ketchup Adler, Nadim, and Brenner address Rheological Models of Suspensions, a closely related subject through fluid mechanics, statistical physics, and continuum theory. Their work is also inspired by industrial processes such as paint, pulp and paper, and concrete and by natural systems such as blood flow and the transportation of sediment in oceans and rivers. Why did doctors in the Middle Ages induce bleeding in their patients in order to thin their blood ... 

Particles larger than small molecules may form mixtures with solvents. If gravity does not cause these particles to settle out of the mixture over time, the mixture is called a colloidal system, or colloid. The term colloid can also refer to the colloidal particles.) Colloidal particles are larger than solute particles, and can even be single large molecules such as hemoglobin. A colloidal system can be any combination of phases except gas in gas). Some examples of colloidal systems are an aerosol (liquid or solid particles in a gas like fog or smoke), a. foam gas particles in a liquid like whipped cream), an emulsion (liquid particles in a liquid or solid like milk or butter), or a sol (solid particles in a liquid like paint). 

One of aluminum potassium sulfate s major uses is in the dyeing of fibers and fabrics, where it is employed as a mordant. A mordant is a substance that reacts with a dye, helping it attach more permanently to a fiber or fabric. Aluminum potassium sulfate has also been used in the paper-making industry for many centuries, where it has a variety of applications. For example, it can he used to give paper a tough, shiny surface or to increase the intensity of inks, paints, and dyes used on the paper. Some water treatment plants also use aluminum potassium sulfate in their purification systems. The compound is added to water, where it combines with colloidal particles suspended in water to form larger clumps, which then settle out of the water. Other uses of aluminum potassium sulfate include ... 

To this point, our discussion of the protective action of nonionic stabilizing molecules has been concerned exclusively with hydrosols. Realization that stabilization could similarly be imparted to colloidal particles in nonaqueous media was somewhat later in coming. This comment disregards, of course, the pragmatic technological application of the phenomenon in such products as paints, etc. 

A colloidal sol is a suspension of very small solid particles in a continuous liquid medium. Colloidal sols are quite stable and show the Tyndall effect (light scattering by particles in a colloid). They can be quite stable. Examples include blood, pigmented ink, and paint. Colloidal sols can change their viscosity quickly if they... 

Depending on the molecular weight of the polymer in question, such colloidal particles in paint could be clusters of 2-100 molecules. The difference between small polymer particles and large molecules is not great. 

Individual cells of bacteria are colloidal particles and can form colloidal suspensions in water. Many of the green algae in water are present as colloidal suspensions of individual cells. Milk, mayonnaise, and paint are all colloidal suspensions. Colloids are used in making rubber, glue, plastics, and grease. The formation of a colloidal suspension of butterfat in milk is the process by which mflk is homogenized, so that the cream does not rise to the top. 

Polymers are often applied to promote either stabilization or aggregation. Examples of polymer-induced aggregation are found in water purification, clarification of wine and fruit juices, and in papermaking. Stabilization of colloidal particles by polymers is applied in foodstuffs, paints, and dyes, in the dispersion of particles on magnetic tapes and photographic paper, as well as in many cosmetic and medical salves and lotions. A rather recent development is the use of polymers to reduce or prevent the deposition of protein molecules and biological cells on surfaces in order to avoid biofouling and, hence, improve the biocompatibility of these surfaces. 

In foods and paints and in biological systems such as the living cell, colloids and polymers are often present simultaneously. When the polymers do not adsorb onto the colloidal particles the result is a socalled depletion layer. As we shall see, overlap of depletion layers leads to an attractive depletion interaction between the colloidal particles. The term depletion derives from Latin meaning emptied out . The verb plere is to fill [24]. Thus a pletion force is due to accumulation of some substance between two colloids. The reversal, a depletion force is due to the expulsion of material. 

Chains attached to colloidal surfaces provide powerful forces for stabilization. Colloidal particles that normally coagulate from a solvent dispersion can thus be stabilized by adding a small amount of polymer to the dispersion. Such polymer additives are sometimes known as protective colloids, leading to steric stabilization. Both synthetic polymers and biopolymers such as proteins and gelatin are commonly used in both nonpolar and polar solvents. Industrially they are used in paints, toners, emulsions, suspensions, cosmetics, pharmaceuticals, processed foods, and lubricants. 

VOCs can present special problems in the indoor microatmosphere. A common source of such emissions consists of oil-based paints from which the volatile paint vehicles evaporate as the paint dries. Water-based latex paints even have the potential to emit air pollutants. One such source consists of coalescents added to these paints that enable the colloidal particles in the paint to spread, giving a uniform painted surface. A Presidential Green Chemistry Challenge award was given to... 

Suspensions of colloidal particles are widely used in a number of processing steps in practical applications processing of ceramics (Lewis, 2000), in consumer products, in paints and inks, and in the production ofphotonic band gap crystals for optical applications (Braun, 1999, 2001). Suspensions offer imique advantages because particle interactions can be tuned to achieve desired properties. The result is, suspensions can be produced that are easily pumped, settle rapidly, can be shaped, dried and sintered, and easily consolidated. While the details of how these properties are achieved will vary with the chemistry of the solid and fluid phases of interest, the imderlying physical chemistry of the colloidal state will be common between different materials thus offering general guidelines on how to achieve the desired properties. 

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