fact, I was complaining that we had to choose between either a simple but inaccurate test or extremely expensive laboratory methods, such as real-time spectroscopy or the analysis of changes in the physical parameter. At that time it seemed as if anyone using a UV printing technology, whether screen or digital, had no simple and cheap tool, which would help us to achieve the relevant measurement.

Calorimetry is advantageous because it offers a direct measurement of the polymerisation rate, which is calculated on the basis that the amount of heat released is directly proportional to the number of monomer and oligomer units which are converted to polymers.

The thin film calorimeter, which was introduced at the beginning of the 80s and now perfected, (TFC) allows us to quickly measure the exothermic heat reaction from a polymerising sample through a highly sensitive sensor.

My old friend Stephen B. Siegel, from the well known American Company UVPS in Chicago, recently built the TFC-9000TM a CONTROL-CURE system to test UV inks and other UV coatings and evaluate their degree of polymerisation.

In principle, this device is a giant step forward. So far it is a “simulation” tool, which calculates the level of polymerisation reached by an ink under specific conditions and displays the result either via its own LCD display, or on a computer screen, when it is connected to the serial port.

Of course, it can be interesting to know how cured an ink is under these simulated conditions, which deliver an output from UV LEDs of 395 or 370 Nm for example. But you will find extremely big differences in the result, according to the LED output! You must also take into account that each UV curing unit in your plant will use one or two different makes of lamp, operating at different distances, different intensities and many other variables, all of which will give different results in terms of polymerisation level. And this is precisely why we need to useithis marvellous TFC-9000TM tool with our own equipment - we are unable to replicate the exact conditions of our equipment in a simulator.

Well aware of my desire for a specific tool, which is able to travel through “our” UV curing units at an affordable price, Stephen is now working on the second generation of his system and is preparing three different models:
1. a basic stripped down version at a very affordable price;
2. a good laboratory system, which has all of the basic functions, including storage for multiple tests within the unit, and which can also subtract the heat of the lamp itself from the test;
3. an upgraded model that will include additional functions.

The test station comprises an aluminium plate measuring 12.5 x 7.5 x 0.6 cm under a copper plate with a 3m wire, which is long enough to pass through any classical UV curing unit.

These enhanced tools will enable us to gain a precise curing measurement when used in conjunction with a specific ink passing through the curing unit at a certain speed and under a certain lamp output. Further, using our own knowledge and experience we will be able to judge if the level of curing is the good and proper one after taking into account secondary and postpolymerisation, two elements which were totally ignored in the above article, but that’s another story !

For further information contact info@uvps.com or visit www.uvps.com