The Big 5 In Paint
The main ingredients of paint which could cover residential paints or industrial paint can be grouped as follows:
- Binder
- Pigment
- Extender
- Solvent
- Additives
The ingredients used and the relative amounts in the paint are of paramount importance for the final properties of the paint. To formulate a modern paint which satisfies technical,
health, safety, environmental and economical requirements is very complicated. Small variations in the relative amount of the paint ingredients may lead to great variations in the final properties of the paint.
Below is a visual representation of how paint is constructed using well known industrial paint brand Jotun.
Lets look at each main ingredient one by one as a deep dive into paint construction.
A – BINDER
Binders decide the properties of the paint and so are absolutely critical:
- Bind the pigment
- Give the coating adhesion to the substrate
- Promote chemical and atmospheric resistance
- Impart flexibility to the film
- Increase the abrasion resistance
The binder is the non-volatile portion of the paint. Resin is the binder that holds the pigment particles together and provides adhesion of the paint to the surface. Most paints or coatings are named by the generic type of resin (i.e. vinyl, epoxy, acrylic etc.). The resin, or binder, is responsible for most of a coating’s physical and chemical properties, chemical resistance, weather resistance, adhesion properties and also influence the hardness and abrasion resistance.
Different binders will have different curing mechanisms. In general the curing mechanism will determine how good protection a coating will offer. Oxidatively curing & physically drying coatings are usually single pack and offer poorer protection than their chemically curing, multi component counterparts.
If you haven’t used enough binder or any binder in your paint mix, you may find as a result that your metal paint won’t adhere to metal railings or that once dried it almost instantly cracks or wrinkles.
Often referred to as resins, binders can be classified as thermoplastic or thermoset. Thermoplastic resins can be repeatedly softened by heating and hardened by cooling. They can also be dissolved by the original solvent used in the coating; they are resoluble (i.e. vinyl, chlorinated rubber, acrylic etc.) They are usually one-pack products.
Thermosetting resins undergo a chemical reaction by the action of heat, catalysts, UV-light etc. They do not melt by heating or re-dissolve in solvent. Epoxy, polyurethane and silicates are such resins. They are usually two-pack products, but can also be one-pack coatings, cured by oxygen in the atmosphere, like alkyds.
The choice of the binder is determined by the purpose for which the paint is intended. For example epoxy for good chemical resistance and polyurethane for weather and gloss resistance. The binders can be modified to give certain properties. For example pure epoxy has very good chemical resistance but must be applied on a blast cleaned surface. Paints based on coal tar (now withdrawn in many countries) have very good water resistance and penetrating properties (surface tolerant), but are not very resistant to chemicals such as solvents. A combination of the binders give the paint fairly good chemical resistance as well as good resistance to water and good penetrating properties. boat detailing services