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 A single technology UltraViolet Curing is used to improve the quality of finished products while boosting productivity through substantial
savings in energy,
time and labor.
In the UV curing
process, ultraviolet light interacts with specially
formulated chemistries to cure coatings faster and more economically
than traditional methods. UV curing was developed more than 30 years ago especially for the printing,
packaging, electronic and wood productsindustries. Today, the UV curing industry
is well positioned
to shape coatings, ink and polymer technologies as we enter the 21st century. Initially a commercial
success in the wood products and furniture indu-stries, UV curing is used today in a diverse number
of
industries. In the automotive industry, for example, these technologies are getting more and more common.
Finished product manufacturers find that UV curing offers at least three outstanding benefits: environmental
advantages, unique physical properties and production efficiencies. Environmental
Advantages
UV cured inks, coatings and adhesives
have always contained very low
levels of VOCs in the majority of cases zero VOC. These low-VOC-containing products become increasingly important,
offering manufacturers a way to meet or exceed current and pending environmental regulations to limit
emissions and control air quality. Unique Physical Properties
UV
curing is recognized as an “enhancement technology,” one that allows manufacturers to make their products
more attractive and durable. Finished products exhibit exceptional stain, abrasion and solvent resistance
coupled with superior toughness. Moreover, UV curing allows the printing and ink industries to achieve
the highest gloss attainable by any coating method. Production
Efficiencies
UV curing offers manufacturers new production opportunities for a
variety of specialty products, including optical fibers, photoimaging of printing plates and fast-curing
wood fillers. In addition, new and specialized UV lamp systems allow for three-dimensional curing which
opens markets for such new applications as bathroom vanities, molded plastic parts and furniture case
goods. Most important, the UV curing process reduces drying times, improves production efficiency and
provides pollution abatement. In addition, UV systems are typically easy to install on existing lines
and, because items coming off the line are fully dry, UV technology can often lead to reductions in
required factory space. UV Curing Process
The
UV curing process requires a
light source which directs UV or visible light onto the formulated product. Photoinitiators absorb the
UV energy from the light source, setting in motion a chemical reaction that quickly,
in
fractions of
a second, converts the liquid formulation into a solid, cured film. The bulk of the formulation is made
up of monomers and oligomers. Monomers are low molecular weight materials.
They
can be mono- or multifunctional
molecules, depending on the number of reactive groups (usually acrylate) they
possess. Functional monomers become part of the polymer matrix in the cured coating because their reactive
functional groups undergo polymerization during exposure to
UV light. Monomers also
function as diluents
in the formulations, used
to adjust system viscosity, and are sometimes referred to
as reactive diluents.
Oligomers, conversely, tend to be of higher molecular weight, viscous materials
where the molecular weight ranges from several hundred to several thousand grams/ molecule or even higher.
Usually, the type of oligomer backbone determines the final properties of the coating such
as
flexibility,
toughness, etc. These backbones can be epoxy, polyether, polyester, polyurethane or other types. The
functional groups that provide linkage between molecules are located at both ends of the oligomer molecules.
The functionality found to be most effective is the acrylate functional group. A
photoinitator can be categorized in different ways
According
to its mechanism According
to its product form According
to its absorption According
to its application According
to the depth of cure |
