Tuesday, 5 April 2016

Surface Drying and Curing Coatings

Infrared (IR) Lighting Array

All infrared energy is part of the same electromagnetic spectrum that continually surrounds us. X-rays and ultraviolet energy waves are below the visible light spectrum, and infrared and short-wave radio waves are above the visible spectrum.

1.      Long-wave infrared isn’t very desirable for curing automotive coatings because it tends to heat the top of the paint film rather than penetrate through the paint to the substrate.
2.      Medium-wave infrared will penetrate through the paint film and heat the substrate. By warming the paint from the bottom up, the solvents are pushed out into the air. If you heat the top surface first, the solvents are trapped inside the paint film

3.      Short-wave infrared also heats the substrate, not the surface, but penetrates faster than medium-wave. Some short-wave units have a ramp-up setting that feeds the energy onto the surface gradually. Medium-wave units don’t need a ramp-up restriction since they take a few minutes to reach full heat

Drying / Curing

Drying and curing (cross-linking) are two very different processes:

·         Drying - use of infra-red lamps is highly recommended. IR drying in a moisture / dust free environment.
·         Curing – the product will be fully cured / hardened (subject to environmental conditions experience) in approx. thirty days

Because of the thickness and hardness of most coating products I would recommend you use a “wet application” method to ensure proper formation of a glass coat over the entire vehicle. Once this process is completed use Infrared Cure Lamps to cure the coating to the paint surface (curing at 155.0F for 15 - 25 minutes (dependent upon type of IR lamp used) further increasing its strength and durability. Moisture should be avoided for between 12-24 hours after drying

Shortwave Infrared Curing Lamp
Generally speaking, the higher the temperature, the shorter the wavelength produced. The different between the three types- long, medium and short, is in the depth of penetration through the paint film (in automotive applications) and excitement of the molecular structure. The advantage of using infrared is that only heats objects that are placed in its path, directly focusing energy where it's needed. Infrared equipment causes molecular excitement both in the paint and in the substrate which in turn causes heat to pass back through the coating via conduction. The use of shortwave infrared is in fact triggering a two-way conduction from the substrate and it is this effect that produces such good through curing.

Shortwave produces high temperature the dramatically accelerate the curing/drying process, unlike traditional method, the cured paint could not be skinned, trapping solvent that will produce solvent pop (a pinhole effect) to the finish. Another benefit is that infrared is much more efficient than convection, and it is this combination of fast, high quality curing with low running costs. 

.What temperature will an infrared heater reach?

There are a number of considerations that may affect the final product temperature. Standard portable automotive curing lamps are designed to accelerate the curing of any liquid coating that will eventually air-dry on its own. When used between 18″ and 36″ from the surface of the drying substrate, an infrared heater will generally reach target temperatures from 140° F to 200° F. These variances depend upon a range of factors, including actual heater model, size of the area to be dried, product mass relative to surface area, heater distance from the product, exposure time and ambient conditions.

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