Curing by means of UV radiation stands out for its properties and results, but it is also a technique reserved for a very specific type of products and objectives. It is essential to know its possibilities to use it effectively.
By Alejandra García Vélez
Specialization is one of the main characteristics of UV curing, the products that use this type of process are very punctual and do so with the aim of achieving specific properties. The procedures to follow to make a successful application, as well as the cost and complexity of the equipment make this a technique of little diffusion, but with great results for those who apply it correctly.
As for its essence, ultraviolet curing operates under a process of polymerization of paints and varnishes susceptible to this light by means of high-pressure lamps. Normally, it is a closed chamber in which ultraviolet emitters are located at strategic points to direct this light to the treated product. "The orientation and targeting of these issuers is key to achieving a homogeneous result," explains José Manuel Fernández, spokesman for the Spanish company B.C.B S.L.
For his part, Federico Pérez Quiroz, account manager of finishing equipment at Graco Inc., complements by explaining that for this type of drying high-pressure tunnels are also used with mercury, iron or gallium lamps of 80 or 120 W / cm, as well as low pressure tunnels with lamps type TL03 or TL05, in addition to an elliptical deflector to spread radiation.
For this article, the opinion of Engineer Gregorio Garza, general manager of Thierica Mexico, was also consulted, who highlighted the importance of knowing that not all coatings can be cured in this type of furnaces "special coatings, known as photoreactive, are needed that react and harden with UV light," he said.
The Thierica official agreed with the other guests by highlighting the importance of the location of the different sets of lamps to attack the different angles of the piece to be treated, but added an additional element by highlighting that these cabins must have a cooling system by means of forced air so that the bulb does not overheat, as well as a high-efficiency filtration system for the air that is injected into them.
Beyond the technique
As for the main objective that is sought when using this type of furnaces, it should be noted its application in materials in which a high degree of hardness and abrasion resistance is needed, plastic cases and lenses are perfect examples of this type of materials.
It is also ideal for materials with high-brightness applications that are exposed to the sun's rays, such as car headlights, and that thanks to this technique have a greater resistance to the elements. Likewise, the wood, textile and printing industries are among the most benefited from its use.
In that sense, Federico Pérez affirms that, from his experience in Mexico, the furniture industry is the one that most uses this type of curing, especially in flat pieces or postformed products, with the aim of giving them more durability and greater resistance to the ambiennial elements.
In summary, this technique is ideal for those applications where the minimum curing time is an indispensable element, as it is much faster, or the use of this type of finishes is required, either for its visual result or for the physical properties it provides.
"There are applications in which you have no other option, such as those products that are constantly exposed to sunlight, and applications in which ultraviolet systems are used solely and exclusively to give it a better appearance," Garza said.
The good and the bad
As well as highlighting its usefulness and the benefits of its use, the experts consulted also explained the disadvantages that may exist and the care that is important to take into account when working with this type of cabins.
First of all, they point out that the coatings used for treatment in UV furnaces are very toxic and abrasive with the application equipment, in addition to reacting if subjected to high pressures.
"The advantages of UV curing processes can only be taken advantage of taking into account the appropriate precautions for use, to guarantee a safe, healthy and risk-free work", point out from B.C.B S.L.
In addition, they explain that UV radiation has a high erythemal effect (ability to redden and / or burn the skin), and that prolonged exposure can have a cumulative effect on cellular DNA, so it is mandatory to avoid looking directly at a lit ultraviolet lamp or any direct exposure, even for a short duration, to radiation.
Costs are generally a concern, as equipment is complex and requires a high investment, as are materials. Gregorio Garza points out in that sense that "in these equipment must have cooling systems, which forces the constant replacement of filter, as well as security systems (UV filters) so as not to damage the sight of people which increases its cost".
"UV coatings are regularly toxic, so they are normally applied with robot increasing the cost of the investment, on the other hand the cost of the coating itself is higher than a normal coating," added the Thermolic representative.
For his part, Fernández pointed to the importance of carrying out adequate maintenance of the system, which includes the cleaning and review of components on a regular basis. He also pointed out that it is essential to review the ventilation system to guarantee its useful life and avoid premature aging of the equipment.
Another important point to consider is the ecological, the paint booths in which these coatings are applied must have a high percentage of filtration so as not to pollute the environment.
Considerations for a better selection
Taking into account the factors mentioned in the previous paragraphs, if you are looking to work with a team of this type, the experts invited for this edition do not hesitate to make some general recommendations to get the most out of it.
"Ultraviolet systems are a very important technological advance, which give great added value to a product in terms of its cosmetic characteristics and physical and chemical properties," Garza said.
For his part, Fernández pointed out that when selecting the equipment, the curing energy and the necessary exposure times must be taken into account, because depending on these points a cabin of greater or lesser power will be needed. In addition, the work intervals and the space required must be taken into account, which will determine the need for light shutters, the type of shielding and reflectors.
To conclude, Fernández stressed that "it can be difficult to know the exact parameters that each treatment must meet. To succeed in the acquisition of the appropriate cabin it is highly advisable to consult the characteristics of the product to be treated to the manufacturer of inputs, and contrast these data with the manufacturer of the system that will be able to accurately calculate the necessary cabin ".
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