HMG Paints Ltd HMG Paints Ltd
One name that covers everything 		Guest User
Login / Register

HMG Coatings Knowledge

no pdf available
Follow HMG on Linkedin

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

  1. Pigment
  2. Resin / Binder (also known as vehicle, medium, film former, polymer)
  3. Additives
  4. Solvent

The 4 Components of Surface Coatings

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


  1. 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:
    1. Coloured Pigment

      2. Insoluble and provide permanent colour
    2. Dyes

      3. Soluble
    3. Extender

      4. 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.
    4. Anti-corrosive Pigment

      5. Prevent corrosion of metals by chemical and electrochemical means
      Example: Zinc Phosphate, Red Lead, Zinc Chromate

  2. Resin / Binder

    3. 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

    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.

    1. Convertible Coatings

      2. 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:
      1. Oil Modified Alkyd Resins – dry by oxidation

      2. 2K Epoxy Resins – dry by chemical cure

      3. 2K Polyurethane Resins - dry by chemical cure

      4. Moisture Cured Polyurethane Resins – dry by water absorption

    2. Non-Convertible Coatings

      3. 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:
      1. Chlorinated Rubber Resins

      2. Vinyl Resins

      3. Cellulose Derivatives

  3. Additives

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

    Typical groups of additives include:
    1. Aids to Manufacture
      • Dispersants
    1. Aids to Shelf Life
      • Anti Skin
      • Preservatives
    1. Aids to Application
      • Flow Promoters
      • Anti Static Agents
    1. Aids to Film Formation
      • Anti Float Agents
    1. Aids to Film Curing
      • Driers

      • Catalysts
    1. Others
      • Optical Brighteners

      • Fire Retardants
      • Slip Additives
      • UV Absorbers

      • Bactericides
      • Anti-Foul Additives
    2. Solvent

      3. 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:
      1. True Solvents

        2. A liquid that will infinitely dissolve or is completely compatible with a resin
      2. Latent Solvent

        3. 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.
      3. Diluent Solvent

        4. 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.