VARNISHES AND PAINTS, PAPER COATINGS

Natural or synthetic materials, which are applied in a viscous liquid state by thin layer at the structures and elements with the film formation for their protection against the harmful influence of the environment, also for decorative design and improving of the hygiene and sanitary conditions, are related to the varnishes and paints. They are divided into basic and auxiliary materials. Paints, varnishes and enamels are the basic materials. Primers and fillers (spacklings), used at the surface preparation for the painting, solvents, diluents are auxiliary materials. Paints are also divided by the next features: type of film-forming substances (oil, glyph, epoxy, lime, silicate, etc.); kind of liquid phase (aqueous and waterless); relation to the water action (water-resistant and water-nonresistant); main purpose (chemically resistant, thermal resistant, electric insulating, etc.) (Table 18.1, Fig. 18.1).

Paints are used for the formation of the opaque coloured decorative and protective films, which hide the texture of material under paining; varnishes, - for creation of transparent colourless coating and finishing of painted surface and also for protecting from mechanical damages. Composition of paints consists of the binding or film-forming substances and colouring agents or pigments. They can contain fillers, due to which it is possible to reduce the content of pigments, and special components which improve technological and operating qualities of materials (hardeners - siccatives, diluents, etc.).

Varnishes are dispersions of natural or synthetic polymers, bitumens, drying oil, in volatile solutions. Plasticizers, siccatives and other admixtures can be added in composition of varnishes.

Enamel paints (enamels) are suspensions of pigments in polymer or oil varnishes; unlike paints, they contain less fillers and have more intensive glance.

Priming paints provide the required adhesion between the cleaned surface and coating. Usually the primer consists of the same materials as paints, but has less content of pigments.

Spacklings (putties) are applied for filling of voids and smoothing of surfaces before painting. They contain not only adhesive substance but also a large amount of filler (usually chalk).

The typical scheme of multilayer coating includes: primer - one layer; spackling - one or several layers; enamel (paint) – several layers; varnish - one layer. The sequence of the materials coating, usually, remains the same, but separate elements of coating can be excluded. For example, if the surface of the painted material is sufficiently flat, without the significant defects and the increased decorativeness of coating is not required; application of spackling and varnish is not required.

Table 18.1

Classification of painting mixtures depending on performance conditions of coating

Date: 2015-12-18; view: 1057