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Curing, drying and hardening of paint

Did you know that in the early twentieth century the paints used on cars manufacturers need the order of weeks to complete its cure?, Today thanks to the knowledge of the mechanisms involved in the curing process of the paintings we have paints that cure in few seconds.

Always we apply a paint we need to wait a time in which the paint passes from a liquid to a solid state, commonly known as drying time, the knowledge of the mechanisms of curing of the paint as well as the methods used to reduce this time, will allow select the materials and tools needed to do a quality work in a short space of time.

Many times we speak indistinctly of drying, curing and hardening of the paint, but it is important to clarify each of these concepts;

paint tip Drying - The paint drying process corresponds to the evaporation of all solvents and diluents added to the paint in order to make it liquid or reduce its viscosity.

paint tip Hardening - the hardening of paint corresponds to the process by which the main polymer of the paint it creates and hardens with all other pigments and additives which comprises the paint, creating a solid and adherent coating.

paint tip Curing - The paint curing process corresponds both drying and hardening process.

Curing = Drying + Hardening.

In response to the above definitions now we understand when a painting of two components do not add the hardener, we can observe over time the paint has dried (no smudges when touched) but has not hardened, allowing easy removal of the applied substrate, we say that the paint has dried (the solvent has evaporated), has not hardened (due hardener has not been added) and hence the paint has not cured.

One of the methods most used to classify the families of paint on the market is to identify by their curing mechanism, so we have:

Physical curing paints correspond to the set of paintings where the main resin is already formed, to cure the paint is only required to evaporate the solvent input into the painting itself.

Chemical curing paints correspond to the set of paints where the main resin (polymer) is created through chemical reactions (polyreactions) between various compounds, in this type of cure is necessary both drying and hardening process.

Nitrocellulose lacquers, acrylic lacquers, chlorinated rubber paints and vinyl paints are examples of paint which cured is physical, on the other hand polyurethane, epoxy, phenolic resins and polysiloxanes are examples of paint which cured is chemical.

All physical or chemical cured paints can accelerate or activate the curing process by applying one of the following techniques:

Hot air curing consist to apply certain temperature to the painted surface, such that the increase in temperature causes a faster evaporation of the solvents and accelerates the chemical reactions take place to create the main polymer or resin, ie the temperature acts as a catalyst which accelerates the drying and hardening process, thereby accelerating the curing process.

Painting booths with hot air recirculating used this method to accelerate the curing process, being the most used method due to the ease of curing of any workpiece regardless of its geometry, due to the ease of air penetration by any type of hole that has the workpiece.

Radiation cured used microwave or infrared technology for increasing the substrate temperature so that the heat it propagate along the paint accelerating the curing process, on the other hand ultraviolet radiation technology active the chemical reactions necessary to cause curing of the paint, the latest technologies used laser and plasma to accelerate the curing process.

The main advantage of the radiation curing is the short time need to solidify the paint, achieving curing times in order of seconds, as disadvantage this type of curing only can be applied in areas where radiation emitted can scope, therefore not used in complex workpieces with different shapes and hidden areas.

Electrical curing method convert electrical power into heat supplying it directly to the painted workpiece so that the heat generated accelerates the curing of the paint, on the other hand the use of electromagnetic fields heated at the molecular level the paints accelerating its curing process.

Now that you know the different methods to accelerate the curing of the paint, you always have to take into account the advice and guide that the paint manufacturer will provide, an increase in excess of temperature on the paint can cause defects such as pinholes and even destroying the paint film.

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