Paint-and-varnish coatings

Other Derivatives and Applications. Copolymerization of DCPD with other unsaturated substances has received wide attention, and several useful appHcations have been developed. With drying oils (qv) thermal copolymerization leads to the production of resinous products, the so-called bodied oils, that give improved drying and result in paint and varnish coatings of greater resistance to weathering. 

Formation and protective mechanisms of antimicrobial polymer coatings are in principal the same as in inhibited paint-and-varnish coats [97],... 

Paint-and-varnish coatings for temporal protection of metal ware are subdivided into wipe-off and detachable. 

A.D. Yakovlev. Chemistry and Technology of Paint and Varnish Coatings Handbook for Higher Educational Institutions, Leningrad, Khimiya, 1989. 

Paints and varnishes (coatings) have two primary functions protection and decoration. Other objectives include information, identification, safety, insulation, vapor barrier, nonskid surface, and control of temperature, light, and dust. A range of product categories with a wide variety of application is therefore available ... 

BS EN 1062-3 (1997). Paints and Varnishes - Coating Materials and Coating Systems for Exterior Masonry and Concrete. Part 3 Capillary Absorption and Permeability to water, British Standards Institute, London. 

Features of Adhesion of Particles to Paint and Varnish Coatings... 

The relationships found for the adhesion of particles to surfaces in air and in hquid media (see Chapters IV-Vl) are valid in the case of particle adhesion to painted surfaces. The distribution of particles of different shapes adhering to paint and varnish coatings likewise follows a log-normal law [194]. 

A lower adhesion of particles to painted surfaces in a liquid medium in comparison with adhesion in air has also been observed for irregularly shaped particles. In air, the median force of adhesion for irregular particles with an equivalent diameter of 70-110 jum was found to vary from 1.3 10 to 3.8 10 dyn in an aqueous medium, the median force for these same particles varied from 1.6 10 to 4.8 10" dyn. The adhesion of particles to paint and varnish coatings in the aqueous medium was 2 orders of magnitude less than in air i.e., the general relationships found previously for adhesive interaction (see Sections 20 and 30) are manifested under these conditions also. 

Properties of Paint and Varnish Coatings Affecting Particle Adhesion. Any... 

In order to solve problems of dust retention, we must determine which properties of paint and varnish coatings determine the adhesion of dust particles. Among these properties we should mention the following roughness, moisture resistance, elasticity, physicochemical properties (hydrophobicity or hydrophil-icity, tackiness), and electrical properties. In view of the variety of forces responsible for adhesion and the differing properties of paint coatings and particle... 

The substrate roughness, which determines the true contact area of dust particles, affects the forces of adhesion in a manner that has been discussed in detail in Chapter V. In order to reduce the forces of particle adhesion, paint and varnish coatings should be rough on a microscopic scale, without any macroscopic asperities. We will now consider the main classes of paint and varnish coatings (on the basis of external appearance) and the possible roughness and the expected adhesion of dust particles to these coatings (Table VIII. 1). 

In some cases, data are available from which we can obtain a relative characterization of particle adhesion to paint and varnish coatings. Such a relative characterization was given in [213] the deposition and removal of the contaminants were performed under identical conditions. The coatings were ranked in decreasing order of adhesion number as follows melamine-alkyd enamel ML-12-18 (98%) penta-phthalate white enamel PF-115 (94%) red alkyd-nitro-enamel EP-51 (64%) grey chlorinated PVC enamel KhV-113 (57%). It will be noted that the chlorinated PVC enamel KhV-113 gave the least retention of contaminants. 

Many paint and varnish coatings, such as chlorinated PVC, polyurethane, and nitrocellulose enamels, have wetting angles somewhere within the limits indicated above. 

Thus we see that hydrophobization of paint and varnish coatings reduces the... 

Methods for Hydrophobization of Paint and Varnish Coatings. All methods for hydrophobizing paint and varnish coatings may be divided into two groups surface and bulk hydrophobization techniques. In either case, the hydrophobization is accomplished by modifying the coating. 

Bulk modification of paint and varnish coatings is achieved by the incorporation of various additives in the paint or varnish. In particle adhesion tests on certain coatings modified by this method, simultaneous measurements of wetting angle were made. The results obtained on chlorovinyl KhV-124 and penta-phthalic PF-115 coatings are listed in Table VIII.3, and those on chlorinated PVC coatings in Table VIII.4. 

The data that we have reviewed illustrate the fact that hydrophobization of paint and varnish coatings reduces the degree of adhesive interaction. The properties of paint and varnish coatings may be changed by either surface or depth (bulk) modification of the coating. 

Changes in Adhesion to Paint and Varnish Coatings because of Electrical Forces. By changing the electrical component of adhesive force, considerable reductions can be achieved in the adhesion of dust to surfaces, in some cases even complete elimination of dust accumulation. Previously (see Section 15) we examined the possibilities of changing the electrical component of particle adhesive force by modifying the properties of the surface. Adhesive forces can... 

Influence of Electrical Resistance of Paint and Varnish Coatings on Adhesion to Coating. Paint and varnish coatings may be either dust repellent or dust retaining, depending on their ability to conduct an electric current, i.e., on the magnitude of their electrical resistance. 

If all Other conditions are the same, we may expect that the forces of dust adhesion from an air stream on the penta-phthalic lacquer will be greater than on the epoxy enamel. Naturally, the hardness of the coating is not constant it changes depending on the ambient air temperature (particularly at excessively high temperatures) and also changes with the time elapsed from the moment of application. These data, however, can be used for a preliminary estimate of the forces of particle adhesion to paint and varnish coatings. 

In evaluating the adhesive properties of paint and varnish coatings, the hardness index must be used along with other indices characterizing the physicochemical properties of the coating material. Such a correlative index is the contact (wetting) angle. 

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