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Polymerisation using pulsed light
Polymerisation is a chemical process causing a matrix or resin to solidify irreversibly.
The technology behind polymerisation using pulsed light, updated by Eurofeedback, finally brings an alternative solution to the usual technology based on mercury lamps.
There are many advantages to pulsed light:
 The low level of infrared light emitted minimises the heating of the base,
The instant start and stop of the lamp removes the need for the pre-heating stage,
Easy electro-control over the flash frequency in line with the speed at which the target moves,
Xenon lamps emit very little ozone and, as their energy output is better than that of mercury lamps, it is possible to reduce the number of ventilation units,
Xenon tubes do not contain mercury – the driers will therefore comply with future regulations,
The emission being under very high peak energy and in a very short space of time, the driers can polymerise significant thicknesses,
The spectrum is continually distributed between 200 nm and 900 nm – there is therefore a good interaction with the photo-initiators and, consequently, pigment influence is low.
Amongst the polymerisation applications, there feature the graphic arts (offset, silk-screen printing) as well as the polymerisation of glues and UV varnishes.
 A little bit of theory…
By definition, ultraviolet rays in the air are situated between 180 nm and 400 nm. This spectral band is broken down as follows:
- UV-C, between 180 nm and 280 nm,
- UV-B, between 280 nm and 315 nm,
- UV-A, between 315 nm and 400 nm.
A number of plasma sources can emit light within that spectral band, such as arc lamps, mercury lamps or xenon flash lamps.
The advantage of these is without doubt the light energy/electrical energy return, due to the low levels of infrared light emitted (only 5 to 10%).
For the sake of comparison, a mercury lamp needs heat for it to vaporise and, in that case, the energy lost in infrared light is between 50 and 60%.
There is a correlation between the temperature of the plasma and the energy distribution in the various bands of the spectrum. In this way, daylight corresponds to a dark body heated to a temperature of 5,500°K, as shown in the figure below.
It can be seen that, at such a temperature, emissions below 400 nm are especially low.
Any change in the energy distribution in the spectrum to increase the generation of UV rays will therefore require higher plasma temperatures. These will fall between 8,000 and 11,000°K.
Such an increase is "easily" obtained by changing some of the generator’s parameters, such as the duration of the flash pulse and the magnitude of the current in the lamp itself. For a given model of generator, these parameters can be adjusted electronically, which allows the easy search for the right parameters for the application and target to be treated.
Some of our generators are designed to deliver the majority of their energy in the visible light and UV-A bands and, in such cases, the applications targeted will be those of polymerisation.
Others are intended to deliver the majority of their energy in the 400 nm band, with a high proportion in the UVs and UV-Cs. These will be intended for use in decontamination or sterilisation.
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