Basic knowledge of coating
The concept of coatings
Coating is a material which is applied on the surface of an object through a specific application method to form adhesive, fixed and continuous film. Coating can protect, decorate or have other special functions to the coated object. Coating consists of film-forming material, pigments, filler, solvent and additives. The composition may vary according to the performance requirements, for example, there is no pigment or filler in varnishes, while there is no solvent in powder coating.
Composition of coating
1. Primary film former:
Mainly grease or resin, the main film-forming material refers to the material which is spread on the surface of an object to dry to film. It is the main substance which makes the coating adhesive to the surface to form continuous film. Synthetic resin is often used as the raw material in modern coating industry, like alkyd resin and acrylic resin. It is the main component of coating.
2. Secondary film former:
Pigments, filler and dyestuff are secondary film formers. Pigment: fine powder substance which makes coating to have color or covering ability, adjusts coating viscosity, increase film thickness, improve mechanical and filling performances and enhance durability and abrasive resistance of the paint film. According to the nature of pigments, they can be divided into: inorganic pigment, organic pigment and extender. Pigment has tinting and covering power, filler has filling function and dyestuff has tinting but not covering power.
3. Assistant film former:
Additives. Their dosage in coating is very small but they can improve coating performance. Examples include disperser, levelling agent, defoamer, thickener, etc.
4. Volatile matter
Solvent is substance which can dissolve other substance to form homogeneous solution. It has great influence on the viscosity, gloss, levelling, wettability and adhesion of coating. For example, CAC, CYC, xylene and other thinners can dissolve the film formers and make proper viscosity to ensure the realization of performances like levelling, wetting, drying and curing of coating. There are organic solvent and inorganic solvent.
The functions of coating
1. Protection-to prevent metal rust, wood decay and cement weathering.
2. Decoration-furniture with coating has good-looking and refreshing.
3. Special functions-mildew proof, moisture proof, water proof, insulation, flame retardant, etc.
I. By functions: powder coating, anti-corrosion coating, fire retardant coating, waterproof coating, etc.
II. By chemical structure: nitro-lacquer, polyester paint, polyurethane paint, alkyd paint, emulsion paint, etc.
III. By application object: wood coating, marine coating, automotive coating, metallic paint, leather painting, etc.
IV. By application order: putty, primer sealer, primer, finish, etc.
V. By conventional classification: oil-based coating, water-based coating, emulsion paint, etc.
1. One-component paint: with only one component to adjust viscosity, like nitro-lacquer.
2. Multi-component paint: including three-components and two-component paint. Before use, each component must be mixed together according to the required ratio, for example, polyester paint and floor paint.
1. Gloss paint: After the coat dries, there is high gloss. (Glossiness within 90-105)
2. Highlight paint: After the coat dries, there is high but not dazzling gloss. (Glossiness within 65-75)
3. Semi-gloss paint: After the coat dries, there is medium gloss. (Glossiness within 45-55)
4. Matte paint: After the coat dries, there is low gloss. (Glossiness within 20-40)
5. Fully-matte paint: After the coat dries, there is very low gloss. (Glossiness around 10)
By application effect
1. Transparent varnish (also called water paint): After application, the color and pattern of the substrate can show
2. Colored varnish: there is dyestuff in the varnish. After application, the original texture of the substrate can show, but the original color has changed
3. Solid color paint (also called mixing water paint): After application, the color of the paint will show, covering the pattern, color or material of the substrate
4. Texture coating: stone-like coating, relievo paint, ceramic-like glaze, sand effect paint, powder coating, etc.
5. Artistic effect: cracking paint, hammer finish paint, leather-like paint, silver paint, orange-peel paint, etc.
6. By application position: interior wall paint, exterior wall paint, floor paint, traffic paint, etc.
Naming convention of coatings
From paint to coating
The word "paint" in China refers to Chinese wood oil and Chinese lacquer (raw lacquer) at the earliest. With production development, people gradually know that Chinese tallow tree seed oil, linseed oil and perilla seed oil can also be used as "paint" like "Chinese lacquer". With the appearance of many synthetic resins (phenolic resin, alkyd resin, epoxy resin, amino resin, polyurethane resin and Polyurethane) and their wide use in paint industry, the new organic products which are neither Chinese wood oil nor Chinese lacquer cannot be called "paint". So their name is changed to "organic coating", in short "coating" which is more scientific and reasonable. For simplicity, while naming coatings, all other coating varieties except powder coating are still called "paint" and are collectively called "coating".
Coating naming principle
Full name: name of pigment or color+main raw material name+basic name, for example: iron red phenolic anti-rust paint. If the pigment has significant effect on the film performance, the color name is replaced by pigment name. For product with professional use and special performance, explanation can be made if necessary to the film forming materials.