Liquid dispersion coatings

Although FEP is available as a liquid dispersion, the commonly used material in liquid dispersion coatings are PFA and PVDF. Both materials are used in various ways such as filled or unfilled. T q)ical fillers for PFA are mica flakes. PVDF can be reinforced with fiberglass cloth or carbon fabric for additional permeation protection. T q)ical thicknesses achieved are up to 80 milli-inches (2 mm). PFA coatings are used with wire mesh reinforcment for additional protection from delamination. 

Selection of pigmented or unpigmented topcoat. Needed for FDA approved products. 

Temperature control. Adequate and precise temperature control in the oven is needed for proper baking of the lining. 

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Nanoparticles are frequently used as a suspension in some kind of solvent. This is a two phase mixture of suspended solid and liquid solvent and is thus an example of a colloid. The solid doesn t separate out as a precipitate partially because the nanoparticles are so small and partially because they are stabilised by coating groups that prevent their aggregation into a precipitate and enhance their solubility. Colloidal gold, which has a typical red colour for particles of less than 100 nm, has been known since ancient times as a means of staining glass. Colloid science is a mature discipline that is much wider than the relatively recent field of nanoparticle research. Strictly a colloid can be defined as a stable system of small particles dispersed in a different medium. It represents a multi-phase system in which one dimension of a dispersed phase is of colloidal size. Thus, for example, a foam is a gas dispersed in a liquid or solid. A liquid aerosol is a liquid dispersed in gas, whereas a solid aerosol (or smoke) is a solid dispersed in a gas. An emulsion is a liquid dispersed in a liquid, a gel is liquid dispersed in a solid and a soils a solid dispersed in a liquid or solid. We saw in Section 14.7 the distinction between sol and gel in the sol gel process. 

Emulsions and suspensions are colloidal dispersions of two or more immiscible phases in which one phase (disperse or internal phase) is dispersed as droplets or particles into another phase (continuous or dispersant phase). Therefore, various types of colloidal systems can be obtained. For example, oil/water and water /oil single emulsions can be prepared, as well as so-called multiple emulsions, which involve the preliminary emulsification of two phases (e.g., w/o or o/w), followed by secondary emulsification into a third phase leading to a three-phase mixture, such as w/o/w or o/w/o. Suspensions where a solid phase is dispersed into a liquid phase can also be obtained. In this case, solid particles can be (i) microspheres, for example, spherical particles composed of various natural and synthetic materials with diameters in the micrometer range solid lipid microspheres, albumin microspheres, polymer microspheres and (ii) capsules, for example, small, coated particles loaded with a solid, a liquid, a solid-liquid dispersion or solid-gas dispersion. Aerosols, where the internal phase is constituted by a solid or a liquid phase dispersed in air as a continuous phase, represent another type of colloidal system. 

The adsorption mechanisms of surfactant at interfaces have been extensively studied in order to understand their performance in many processes such as dispersion, coating, emulsification, foaming and detergency. These interfaces are liquid-gas (foaming), liquid-liquid (emulsification) and liquid-solid (dispersion, coating and detergency). 

Extrusion Coating - The use of liquid silicone rubber in coating application requires less energy than conventional dispersion coating processes. Solventless material, rapid cure time, absence of by-products and the elimination of multiple passes all contribute to the reduced energy demand of the liquid polymer system. 

This method involves magnetization of the sample coated with a liquid dispersion of magnetic particles, and then observing the magnetic medium patterns. Discontinuities in the samples result in indications in the magnetic medium patterns different from normal patterns. The type and origin of the discontinuity along with the pattern of indication are noted below. 

The above polymeric dispersants are essential materials for the preparation of most disperse systems, of which should be mentioned dyestuffs, paper coatings, inks, agrochemicals, pharmaceuticals, personal care products, ceramics, and detergents [1]. One of the most important applications of polymeric surfactants is in the preparation of oil-in-water (O/W) and water-in-oil (W/O) emulsions, as well as solid/liquid dispersions [2, 3]. In this case, the hydrophobic portion of the surfactant molecule should adsorb strongly at the O/W or become dissolved in... 

Most paint formulations consist of disperse systems (solid in liquid dispersions) [2]. The disperse phase consists of primary pigment particles (organic or inorganic) which provide the opacity, colour and other optical effects these are usually in the submicron range. Other coarse particles (mostly inorganic) are used in primers and undercoats to seal the substrate and enhance adhesion of the top coat The continuous phase consists of a solution of polymer or resin which provides the basis for a continuous film that seals the surface and protects it from the outside environment Most modem paints contain latexes which are used as film formers. These latexes - which typically have a glass transition temperature (Tg) below... 

A plastisol is a liquid dispersion of a fine-particle-size polyvinyl chloride in a plasticizer. PVC linings are commonly called vinyls. They are noted for their toughness, chemical resistance, and durability. They are available as solutions, dispersions, and lattices. PVC powders have essentially the same properties as liquids. Polyvinyl chloride plastisol and powder coatings have limited adhesion and require primers. These linings must be heat cured. 

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