UV/EB Chemistry Fundamentals Course from RadTech

Surface Treatment can play an important role in the success of UV LED applications. In many cases, without corona, plasma or flame surface treatment, curable inks will not wet out for proper adhesion.

Enercon is pleased to bring you access to a UV/EB Chemistry Fundamentals course developed by RadTech. We’re providing you with the first lesson below. You can sign-up for all the lessons which are conveniently delivered by e-mail from Radtech by registering here: RadTech.org. Future lesson topics include Chemistry, Materials, Photoinitiators, Equipment, Safety, Graphic and Industrial Applications.

Lesson #1: What is UV/EB Curing?

Like paint drying, conventional cure is a well-known method for developing the final properties of a coating. Commonly known as thermal cure, this process uses heat to remove the solvent from an applied coating or ink. Drying time is frequently on the order of minutes before the coating is dry to the touch. In UV curing, the heat or forced air is replaced by an UV lamp. This requires a change in the coating chemistry used. The time frame to get a cured coating is reduced significantly to fractions of a second. If no solvent is used in the UV curable formulation, the coating will retain the thickness of the wet coating unlike the thermally cured coating which loses its solvent.

UV Curing Process

Energy Curing is a common term used to describe UV, EB and visible light curing. This technology differs from well-known thermal or heat cure in that it uses UV energy, visible light or an Electron Beam to obtain the curing required. These three methods of supplying the energy differ in the type of energy used. Ultraviolet (or UV) energy is in the 200 to 400 nm range while visible light is usually in the 380 to 450 nm range. Electron Beam curing is a little different in that the curing is caused by a stream of high energy electrons. For most of this course, the emphasis will be on UV and EB Curing. Visible Light curing is similar to UV Curing in most aspects other than the choice of photoinitiators used and the equipment used to cure the formulation.

What is Energy Curing?

  • Using UV energy, visible light, or high energy electrons as opposed to thermal, evaporative, or oxidative (air-dry) cure to form a coating, film or ink.
  • Types of energy used for energy curing:
    • Ultra Violet (UV): 200-400 nm
    • Visible Light: typically 380-450 nm
    • Electron Beam: high energy electrons

There are several significant technical benefits from Energy Curing. In many cases, these benefits can allow the manufacture of a coated or printed part that would have been very difficult to achieve through traditional methods. Some of the properties that can be achieved using UV or EB curing are high gloss, high hardness, scratch and abrasion resistance and very fast cure. All of these properties can be adjusted if needed by modifying process conditions or through the use of additives in the formulation.

As Energy Curing depends on a line-of-sight from the UV lamp, this technology works best on flat substrates. Various work-arounds are required for curing coated 3D parts such as using mirrors to reflect the UV light or rotating the part or lamp.

There are many reasons why Energy Curing has become the technology of choice when a method of curing is selected. The most common reason for the strong interest in Energy Curing is productivity. Since the time to cure a coating or ink can take a fraction of a second with Energy Curing, this allows a dramatic increase in units coated and cured when compared to traditional methods. Another significant benefit partially related to the speed of cure is that the overall cost of a cured part could be reduced. While traditional UV or EB formulations may cost more per pound or kilo than the equivalent thermal cure chemistry, it is the combination of benefits such as line speed, reduced waste, recycled uncured formulation, etc. that reduced the cost per unit. As a benefit that is as important today as it was in the early years, significantly reduced VOC emissions from Energy Curing are able to help a manufacturing plant meet ever increasing environmental regulations.

The conversion from thermal curing to energy curing requires the use of lamps and EB units versus traditional oven systems. This has two benefits. First, the physical footprint of a lamp or EB unit can be and is usually much less than the cost of heating a long oven.

The Energy Curing Universe

Before we cover where Energy Curable materials are used in the world, it would be useful to briefly discuss the nature of who is involved with Energy Curable materials and how they interact with each other. This diagram shows an overview of the Energy Curable Universe. Most likely everyone who is viewing this lesson will fit in one of the boxes shown in the diagram.

Energy Curing Universe

The Raw Material Supplier is at the start of the chain. Their role is to develop and manufacture the materials that are used in Energy Curing. They will then pass the materials on to the Formulator who will combine the raw materials into a usable mixture much like a cook will combine ingredients for a cake.

The next step in the process will have the Formulator send the mixture (called a formulation) to a Convertor. The Convertor does exactly what their name implies, which is to convert the formulation they received into an end product. Their role is to both coat the final object and cure the material. The Equipment Supplier interacts closely with the Convertor to recommend the proper lights, coating, and test equipment that should be used.

Finally, the fully-coated and cured End Product (such as a printed label or coated floor tile) will end up in the hands of the final or End User.

Of course, in real life things are frequently more complicated than they may first appear. While this diagram demonstrates the basic relationship between the different participants in the Energy Curing Universe, frequently many of the parties involved will have some interaction with many of the other participants. Usually, this will take the form of discussing requirements with another party or informing someone of a new development. An example of this would be an Equipment Supplier giving a presentation on a new type of lamp to a Raw Material Supplier hoping that a new material would be developed to make use of the new lamp technology.

At times, even the distinction between the major participants gets blurred. One of the parties shown in the diagram may take on more than one role. An example of this would be a Raw Material Supplier that also will formulate a combined system and sell this directly to a Convertor. There are even companies that are vertically integrated and make their own raw materials, formulate these into the appropriate mixture and cure and coat them on the final product. This type of company is the exception rather than the rule.

To learn more about UV/EB Chemistry, click here and sign up for the free 10-minute lessons provided by RadTech.

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