Types of paintwork materials (VKM)

Depending on their purpose and composition paintwork materials (VKM) are commonly divided into: varnishes, paints, enamels, primers and fillers.

Varnishes are solutions of film-forming substances in solvents (or water) which form homogeneous, hard, transparent (except for bitumen varnish) coating after drying. Their composition does not contain pigments and fillers.

Paints are suspensions of pigments in film-forming substances, which form opaque homogeneous coating after drying.

Enamel - suspension of pigments and fillers in varnish, which forms opaque, hard coating of different structure and gloss after drying.

Primer - a suspension of pigments and fillers in a film-forming substance, which forms a homogeneous opaque film after drying.

Putty - mixture of fillers, pigments and film-forming substances, paste-like viscous mass, intended to fill surface defects, give it an even texture.

Composition of paintwork materials

The main components of paintwork materials are film-forming agents, pigments, fillers, plasticizers, solvents, drying agents and additives.

Paintwork film formers is a multicomponent system which forms a continuous film durably adherent to the base surface in the result of physical and chemical processes. Film-forming agents must bind fillers with pigments in paintwork materials, be soluble with organic solvents, ensure good adhesion of the paintwork coating with the substrate and form a solid protective film after drying.

Film forming agents include: polymerization resins (based on acrylates, methacrylates, vinyl chloride, etc.), polycondensation resins (alkyd, polyurethane, epoxy, silicone, formaldehyde), natural resins (rosin, bitumen, asphalt, copals), vegetable oils, tallow oil, fatty acids and cellulose ethers.

Let's consider some types of film formers.

Alkyd resins

Alkyd resins occupy first place among film-forming agents not only in the domestic, but also in foreign paint industry. They are polyethers of branched structure. They are products of incomplete processing of single-base fatty acids and multibase acids and alcohols.

Alkyd resins are classified depending on the alcohol used for their production. There are alkyd resins based on glycerin (glyphthalic), etriol (etriphthalic), pentaerythritol (pentaphthalic) and xylite (xylphthalic).

To make alkyd resin soluble and the paintwork coating water-resistant and elastic, it is modified with fatty acids or vegetable oils. That is why alkyd resins are divided into nondrying and drying. Oil content can be very different, up to 70%. They are extra-fat (up to 34% of oil), lean (from 35 to 45%), medium-fat (46 - 55% of oil) and fat (from 56 to 70%). Pentaphthalic alkyd resins have the best protective properties when their oil content is about 60 - 65%, and glyphthalic resins - at 50%. It is also necessary to know that at a given oil content the water permeability and film drying rate depends very much on the type of vegetable oil used. The relationship can be described as follows (in descending order): tung oil > oleoresin oil > linseed oil > dehydrated castor oil > soybean oil > sunflower oil.