paint basic technology

8/7/2019 paint basic technology

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Basic Paint Technology

Coatings are mixtures of raw materials, each of which are manufactured to give certain properties. Basically,

the coating is made up of 4 types of raw materials.

The 4 Components of Surface Coatings

Pigment

Resin / Binder (also known as vehicle, medium, film former, polymer)

Additives

Solvent

The 4 Components of Surface Coatings

Of these, only the first three form the final dried coating film

Pigment

A fine powdered solid particle that is dispersed in the paint.

Function:

Optical Properties (colour, opacity, gloss reduction, reflectivity)

Durability & Protective Properties (UV resistance, corrosion inhibition, biocidal activity)

Pigments can be divided into 4 types:

Coloured Pigment

Insoluble and provide permanent colour


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Dyes

Soluble

Extender

Inorganic filler that imparts various properties to the coating. Properties include; flow, degree of gloss, anti-

settling properties, mechanical strength, hardness and thixotropy.

Examples: Barytes, China Clay, Mica, Talc.

Anti-corrosive Pigment

Prevent corrosion of metals by chemical and electrochemical means

Example: Zinc Phosphate, Red Lead, Zinc Chromate

Resin / Binder

A liquid or solid material that binds together the pigment particles, in order to form a continuous film, which

will contribute to the overall resistance of the coating.

Resins are predominant in determining the principle characteristics of the coating, both physically and

chemically. Coatings are generally named after their resins component, for example:

Polyurethane

Epoxy

Nitrocellulose

Alkyd

Acrylic

Acrylic Emulsions

Vinyl Emulsions


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Resins used in coatings manufacture, fall into 2 classes (convertible & non-convertible) depending on how

they form a film. This change of state is also known as drying.

Convertible Coatings

Form films that will not re-dissolve in their original solvent and are characterised by undergoing a chemical

change when drying.

Generic Types of resins in this category include:

Oil Modified Alkyd Resins dry by oxidation

2K Epoxy Resins dry by chemical cure

2K Polyurethane Resins - dry by chemical cure

Moisture Cured Polyurethane Resins dry by water absorption

Non-Convertible Coatings

Form films that will re-dissolve in their original solvent. Drying is simply effected by the evaporation of

solvent, with physical dry being achieved without any chemical change taking place.

Generic Types of resins in this category include:

Chlorinated Rubber Resins

Vinyl Resins

Cellulose Derivatives


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Additives

Term used to cover the minor addition of specialised raw materials that impart specific properties to the

coating.

Typical groups of additives include:

Aids to Manufacture

Dispersants

Aids to Shelf Life

Anti Skin

Preservatives

Aids to Application

Flow Promoters

Anti Static Agents

Aids to Film Formation

Anti Float Agents

Aids to Film Curing

Driers

Catalysts

Others

Optical Brighteners

Fire Retardants

Slip Additives

UV Absorbers


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Bactericides

Anti-Foul Additives

Solvent

A liquid that facilitates application, by carrying the other components onto the substrate to be coated.

The function of solvents is to dissolve the resin and reduce its viscosity to a suitable level for application.

Numerous solvent are used in the manufacture of coatings, each of which has different properties and

characteristics. Considerations on solvent choice include; toxicity, volatility, flammability, odour and

legislative impact.

Examples:

Aliphatic Hydrocarbons: White Spirit

Aromatic Hydrocarbons: Toluene, Xylene

Ketones: Acetone, Methyl Ethyl Ketone

Alcohol: Iso Propanol

Esters: Butyl Acetate

Solvents can be described in 3 ways:

True Solvents

A liquid that will infinitely dissolve or is completely compatible with a resin

Latent Solvent


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A liquid that is not a True Solvent. However, when mixed with a True Solvent, the mix will provide stronger

dissolving properties than the True Solvent alone.

Diluent Solvent

A liquid which is not a True Solvent. Normally the resin will only tolerate limited amounts of the diluent.

Normally used as a blend with True / Latent solvents to reduce the cost.

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