Resin - Convertible Binders

Resin - Convertible Binders

1. Oils and Oleoresinous Varnishes
The use of oils in paint formulation has already decline. Their use are limited in certain types of primer for steel and timber (refined linseed oil and linseed stand oil). Oils are often used for preparation of oleoresinous varnishes, specially for oil-modified alkyd resins.
Vegetable oils are classified as drying or nondrying oils.
Drying oils : linseed oil and tung oil will readily dry when exposed to oxygen. Soybean oil is called as semidrying oil, because of not drying quickly. The drying process is oxidative polimerization or auto-oxidation. The oxidation rate is slow but can be accelerated by the addition of driers such as cobalt or lead naphthenates.
Nondrying oils : castor oil and olive oil. The nondrying oil can not be oxidized readily. It can be converted to drying oil by heating (to 280 deg. C) for several hours to break down some of the constituent acids of the oil.

2. Alkyd resins
Alkyd resins are modified with some oils such as soya, linseed, dehydrated castor, and coconut oil.
Alkyds can be made directly from oil (triglyceride), a polyol, or an acid. The percentage of oil that contained in an alkyd will classifies the end use of the alkyd and affects properties such as speed of drying, flexibility, durability, etc.
The resin can be combined with such resins as acrylics, vinyl toluene, silicones, and amino-resins. They are fairly inexpensive and they have a variety of properties. These makes them popular for use in industrial coatings.

3. Polyester resins
Polyester resins are typically used in heat-cured coatings that need to be high in paint solids and low in solvent content. They have extremely good color retention that provides good over-bake protection and very good UV resistance.

4. Acrylic resins
Acrylic resins are very versatile and popular for industrial liquid coatings. It is happen because they provide toughness, good weathering ability, and has good resistance to abrasion and chemical attack.
The resins are the polymers and copolymers of the esters of methacrylic and acrylic acids.

5. Amino resins
They are usually used in baked coatings as cross-linking agents. They are used in proportions up to 50% of the total vehicle binder. They can be used with alkyds, polyesters, epoxies, thermosetting acrylics, phenolics, and other heat reactive resins.
Melamine and urea–formaldehyde are the most common examples of this resin.

6. Epoxy resins
Epoxy resins are have excellent corrosion and chemical resistance. But they tend to fade and chalk when exposed to sunlight (UV). They are used for interior applications or as primer for exterior applications. The epoxy resin is usually cross-linked with melamine or urea resin at high curing temperatures.

7. Urethane resins
Urethane resins are very good in chemical resistance, toughness and abrasion resistance, and exterior durability.
Urethanes are the reaction products of isocyanates with materials that have hydroxyl groups. The isocyanates are can be in many different forms, but the most widely used is Toluene Diisocyanate (TDI). The TDI has a noticeable vapor pressure and has an irritant effect on the mucous membranes and so requires special handling.