Vehicle, in paint

Uses Dispersant/wetting agenl/stabilizer tor solv.-borne pigments, grinding vehicle in paints... 

Pigment. Synthetic organic pigments are inert, stable, coloured substances insoluble in water and organic solvents, such as the oils commonly used as vehicles in paint manufacture. They are used also in the mass coloration of plastics. Physical form is of paramount importance in ensuring maximum colouring power and reflectance. 

The role of the vehicle in paint is to form an adhesive film over the pigment granules that is optically clear, glossy (reflective) or matte (diffusely reflective) as desired, and protective. In this section, the term biitder is used collectively to represent all similar compounds and components. Because of their function, binders may be referred to as film-forming agents, and they function in concert with the solvent system. Film formation, or curing, occurs by several mechanisms ... 

When the problem is to disrupt Ughtly bonded clusters or agglomerates, a new aspect of fine grinding enters. This may be iUustrated by the breakdown of pigments to incorporate them in liquid vehicles in the making of paints, and the disruption of biological cells to release soluble produces. Purees, food pastes, pulps, and the like are processed by this type of mill. Dispersion is also associated with the formation of emulsions which are basically two-fluid systems. Syrups, sauces, milk, ointments, creams, lotions, and asphalt and water-paint emulsions are in this categoiy. 

Synthetic resins are extensively used, e.g., in surface finishes, in the fabrication and repair of boat and motor vehicle bodies, in the manufacture of laminated boards, for electrical components, in pattern making and in paints and varnishes. Non-rubber adhesives made from fish glues and from cotton derivatives (e.g. cellulose acetate) tend not to be sensitizing but, depending upon composition and the manner of use, many other types may pose significant dermatitic and fume hazards. 

All paints consist of a binder (sometimes called a medium) and pigment. Materials consisting of binder only are called varnishes. Most paints and varnishes contain solvent in order to make the binder sufficiently liquid to be applied. The combination of binder and solvent is called the vehicle. Some paints are available without solvent (e.g. solventless epoxies) but these generally require special methods of application (e.g. application of heat) to reduce the viscosity. 

Medium in paints or enamels. The continuous phase in which the pigment is dispersed thus in the liquid paint in the can it is synonymous with vehicle and in the dry film it is synonymous with binder (q.v.). 

When the highest resistance to corrosion and solvent fumes is needed, catalyzed paints are the answer. These come in two parts a clear or colored base finish and a catalyst. Since their pot life is limited (typically eight hours), they must be mixed just prior to use. Brochures with information on their chemical resistance can be obtained from companies that sell industrial finishes. Since the resistance to different chemicals varies from brand to brand, a planner should study several types to find one that will best suit the particular application. These finishes are of the high gloss type. For highest chemical resistance to fumes, a coat of clear finish should be applied on top of the colored one. While the vehicle in the finish is very resistant, the pigments may not be and therefore could discolor. 

The effect of European REACH legislation, which will cover all chemicals used in the European countries, on the paint industry is discussed and proposals made for a possible solution. REACH is the abbreviation for Registration, Evaluation and Authorisation of Chemicals. A case study involving vehicle refinish paints is described. Recommendations made by the industry for an improved REACH are considered. 

P.Y.155 is used to an appreciable extent in industrial finishes that are targeted for commercial vehicles, tractors, and farm implements. In paints, it resists temperatures up to 160°C. 

P.R.68 is used in paints for applications where it performs well, especially in terms of lightfastness. Incorporated in an air drying alkyd resin vehicle, full shades equal step 5 on the Blue Scale for lightfastness. 1 5 Ti02 reductions, however, only score as high as step 2. P.R.68 exhibits excellent resistance to a large number of organic solvents, while it is quite sensitive to alkali and acid, as well as to water. 

It is principally used in painting, and by varnishers, and being comparatively clear and colorless, is especially valuable as tho vehicle for flake white, and other pigments, when it is desired to preserve the brilliancy of their tints. When fresh, it is occasionally employed for culinary purposes, but when rancid, it is purgative. Sometimes also it is employed as a source of light. 

Zinc-white Paint.—Like white lead, tho oxide of zinc requires to be mixed with an oily vehicle, to be applied in painting. As oxide of zinc does not readily form a saponaceous compound with fate or oils like oxide of lead the paint which is prepared with it and ordinary linseed ofl, does not dry or harden for a long time. This peculiarity was at first one of the principal... 

High structure blacks in unvulcanized mbber give higher Mooney viscosities, lower die swell, faster extmsion rates, and better and more rapid dispersion after incorporation. In vulcanized mbber higher modulus is obtained. High structure blacks give lower bulk densities and high vehicle demand in paint systems. 

Paints. Although most drying oils have been replaced as paint vehicles hy latexes and other synthetic resins, oils are still being used to a degree in paint and allied products. In exterior house paints, linseed oil or oxidizing alkyds are used when paint must be applied al temperatures as low as 4 to 5 C, i.c. temperatures at which latexes do not coalesce satisfactorily They also arc used in primers over chalky surfaces where latex paints do nol provide adequate adhesion. 

Paints are commonly divided into oil-base, or solvent systems, and latex, or water-base, paints. These paints are essentially a suspension of inorganic pigments and a resin, or vehicle, in a suitable solvent. Paints protect wood surfaces by forming an ultraviolet absorbing film that adheres strongly to the surface. 

Titanates react with ester groups in paint vehicles, eg, linseed oil, tuna oil, and alkyds, and with hydroxy groups, eg, in caster oil and some alkyds, to prevent wrinkling of paint films (104,447). 

The obtained analytical data allow a conclusion to be drawn about whether the compared paint samples could have originated from the same coat of paint or not. If the reference material (i.e. from the suspect) is not available, only establishment of the kind of paint and the type of paint coat is possible. In the case of automobile paints, it is also possible to find the model of car involved in an accident. Eor this purpose, analytical data are compared with a database containing information about the type of paint coatings (layering, chemical composition of each layer) used in various types and models of vehicles in Europe. Such a collection has existed in Europe since 1995 and is updated every year with information on new products. Experts from many criminalistic laboratories have participated in its creation. Comparison with such a database provides information about the make and model of the vehicle involved in the incident and its year of production. It is thus helpful in identifying the perpetrator s vehicle. It should be emphasised that identifying the make and year of production of a vehicle on the basis of a paint database only applies to vehicles with a factory-new coat of paint. 

The formulation of a paint is a matter of the skill and experience of a paint technologist. It is largely determined by the ratios of the constituents in paints and the nature of the substrate to which the paint is to be applied. For example, a paint for use over concrete pavement will have very different properties from one intended for application to timber floors. Two paints may even be based on the same generic type of vehicle, but the formulation will be quite different in their final composition. 

---