Solvent-containing coatings

Among products and processes, the trend to environmentally friendly alternatives has also increased, even though the share of solvent-containing coating materials still dominates the market. Therefore, the article on solvents will remain indispensable for some time to come. The second edition will serve to confirm the book in its role as a standard reference for anyone working with coatings. 

Because branched ketones and aromatic hydrocarbons are used for their cost/performance benefits, they became the solvents of choice for many apphcations. Numerous solvent systems had to be reformulated to comply with Rule 66. This usually meant an increase in cost, sometimes accompanied by performance degradation. Rule 66-type regulations were adopted in many other states and cities as well. Federal specifications for coatings and many other solvent-containing materials also incorporate Rule 66 requirements. 

The wash primer is a special type of vinyl coating. This material contains a poly(vinyl butyral) resin, zinc chromate, and phosphoric acid in an alcohol-water solvent. The coating is so thin it is HteraUy washed onto a freshly blasted steel surface, where it passivates the metal surface by converting it to a thin iron phosphate-chromate coating. The alcohol solvent makes it possible to apply the coating over damp surfaces. The coating forms the first coat of... 

High Solids Costings. High soHds coatings resemble the technology of solvent-free coatings but the compositions contain ca 70% by volume of soHd resin and are modified by reactive diluents, low viscosity multifunctional resins, or backbone stmctures other than the bisphenol A moiety. 

The predominant RO membranes used in water applications include cellulose polymers, thin film oomposites (TFCs) consisting of aromatic polyamides, and crosslinked polyetherurea. Cellulosic membranes are formed by immersion casting of 30 to 40 percent polymer lacquers on a web immersed in water. These lacquers include cellulose acetate, triacetate, and acetate-butyrate. TFCs are formed by interfacial polymerization that involves coating a microporous membrane substrate with an aqueous prepolymer solution and immersing in a water-immiscible solvent containing a reactant [Petersen, J. Memhr. Sol., 83, 81 (1993)]. The Dow FilmTec FT-30 membrane developed by Cadotte uses 1-3 diaminobenzene prepolymer crosslinked with 1-3 and 1-4 benzenedicarboxylic acid chlorides. These membranes have NaCl retention and water permeability claims. 

These are the most important components of paint. Coatings can be either clear or opaque (containing pigments) and either solvent- or water-based. With solvent-based paints, after application, most of the solvent is lost through evaporation. These solvent-based coatings are mostly alkyds (name derived from alkyl/acid) or modified alkyd resins. Normally they contain 30% polymer solids higher solids content is limited by the increasing viscosity of the system. 

Anhydrous ether is recommended since a solvent containing moisture will react to coat the hydride with oxides which will retard its rate of solution. The checkers used ether dried... 

A TLC system comprises three elements. As its name implies, one of the elements is thin layer coated mostly on a glass or plastic plate, which acts as a stationary phase. Such a plate is termed chromatoplate . The most popular materials (adsorbent) used to form the thin layer are silica gel and alumina powder. The other elements are a sample, and a solvent or solvent mixture (developer) which acts as a mobile phase to develop (elute) the sample. A stock solution of sample is prepared in advance of the TLC experiment and applied to the thin layer to form a spot. After removal of solvent contained in the spot, the sample is eluted with an appropriate... 

Bismuth vanadate pigments are used in the manufacture of lead-free, weather resistant, brilliant yellow colors for automobile finishes and industrial paints. They are suitable for the pigmentation of solvent-containing paints, water-based paints, powder coatings, and coil-coating systems. It can be mixed with other pigments... 

DNPH-steroids can be separated by HPLC with several partition systems [31,32] including 1 % /3,/3 -oxydipropionitrile (BOP) on Zipax with eluting solvents containing 0-20% tetrahydrofuran in heptane or 2-methylheptane, or 1% ethylene glycol on Zipax with 3% chloroform in heptane as the mobile phase. Reversed-phase chromatography with 1.0% hydrocarbon polymer (HCP) or 1% cyanoethyl silicone (ANH) on Zipax and methanol-water as the mobile phase can be useful for the separation of several polar steroids. Gradient elution (water to methanol) on octadecylsilane (ODS), Permaphase (chemically bonded on Zipax), also provides a separation of polar DNPH-steroids. The separation of five DNPH-steroids on 1.5% BOP coated on Zipax is shown in Fig.4.13. 

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