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UV & EB TECHNOLOGY
MYTHS
While well established in many industries, some are still unfamiliar
with UV and EB processing, which may represent a different way
of thinking about curing inks, coatings and adhesives-- and may
also cause myths and misconceptions about the technology. Addressed
below are common misunderstandings about UV and EB. Misconception 1: UV/EB materials are dangerous
Overall,
UV/EB materials are much less toxic than solvent based and some
of the ingredients in water-based systems, they replace. UV/EB:
- has a very high or no flash point
- emit little to no volatile organic compounds or Hazardous
Air Pollutants
- has very low systemic toxicity
- as a class are not carcinogens (recent long-term skin painting
tests showed no carcinogenic effect, and the test materials
showed no systemic toxicity)
- are not fetal or reproductive toxins
- are not regulated as RCRA hazardous waste
- do not appear on any Community Right To Know list
Moreover, UV/EB curing materials are not absorbed through the
skin like solvents, and they have very low vapor pressures, making
inhalation less likely. Good industrial hygiene practices, knowledge
of safe handling procedures and worker training are essential
for safe handling of any chemical. When these principles are
followed, experience has shown that UV/EB curing technology is
safe.
Misconception 2: The UV light used in UV curing is
a significant hazard
The biological effects
of exposure to ultraviolet light resemble the typical symptoms
of sunburn. We are all familiar with sunburn, so anyone who
might be inadvertently exposed to excessive ultraviolet light
would be quickly aware of it. The American Council Of Government
And Industrial Hygienists (ACGIH) and National Institute for
Occupational Safety and Health (NIOSH) have established exposure
limits for UV light, that are easily met with shielding to minimize
escape of ultraviolet light into the workplace.
Misconception
3: Energy cure preparations are more expensive then conventional
coatings
A quick comparison
of the cost per gallon is usually the misleading reason that
energy cured 100% solids materials are considered higher
cost. A more realistic approach is to look at actual applied
cost per dry mil (or per item coated or adhered). The following
is an actual example:
- Assumption 1: Transfer efficiency is the
same for both coatings (rollcoat application).
- Assumption 2: The same coating thickness
will be applied.
- Constants used: Application of 1604 square
feet per gallon per mil.
- Paint A (thermoplastic rollcoat topcoat):
Total solids by volume 32.62 %.
- Paint A (thermoplastic rollcoat topcoat):
Cost per gallon of material of $13.67.
- Paint B (energy cured rollcoat topcoat):
Total solids by volume of 99.69 %.
- Paint B (energy cured rollcoat topcoat):
Cost per gallon of material $35.00
- Cost of Paint A (thermoplastic rollcoat
topcoat) in $/SQ. FT/Dry mil 0.0262.
- Cost of Paint B (energy cured rollcoat
topcoat) in $/SQ. FT/Dry mil 0.0219 or a savings of approximately
17%.
Misconception 4: UV finishes are prone to cracking
and yellowing
While this may have been true several years ago, the rapid
growth and advancement of the industry (with many chemical companies
offering new raw material products) and resulting advances in
UV/EB chemistry give the formulator a number of chemical classes
from which to choose. With this flexibility, the industry is
now able to easily meet customer requirements and develop products
that best fit customer applications--including requirements for
non-yellowing and resistance to cracking. In fact, on certain
poor weathering substrates like extruded vinyl, UV clear coats
are used to prevent premature yellowing as well as improve stain
and abrasion resistance. In another example, the headlights on
your car have a UV coating to prevent scratches, cracks, and
yellowing.
Misconception 5: UV/EB equipment is too expensive
Over
the last few years, the prices of capital equipment have come
down considerably. In addition, when considering capital equipment
costs, one must also look at:
- Space: A drying oven for a conventional thermal cure may
extend for 50 to 100 feet, a space consumption in the neighborhood
of 500 to 1000 square feet. At a floor space cost of only $0.50/ft2/month,
that costs $3000-6000 per year. The equivalent UV "dryer" would
require 50 to 100 square feet.
- Energy Consumption: One of the most significant cost factors
when comparing thermal cure to UV cure is the energy cost.
A large gas dryer ("oven") consumes 1.10 MBTU/Hr
(and requires large blowers) for the same production capacity
achieved with a UV dryer requiring only 82 kW total:
ENERGY CONSUMPTION
THERMAL - GAS:
1.50 MBTU/hr x $3.60/MBTU = $ 5.40/hr
Blowers:56 kW x $0.07/kW-hr = $ 3.92/hr
300 days/yr x 16/da x $9.32 = $44,736/yr
UV-ELECTRIC:
5.6kW/Lamp x 12 lamps
x $0.07 kW-hr = $ 4.70/hr
300 day/yr x 16 hr/da x $4.70 = $22,560.00/yr
- Productivity: UV/EB users enjoy an increase in up-time and
productivity due to the nature of the chemistry (doesn't skin
over in applicator, not clean up between shifts/weekends, faster
start-ups). Increased productivity means more profit dollars
which quickly pay for any initial capital equipment costs.
Other areas of cost savings come from reduced
parts in process and shorter processing time which directly relates
to lower inventories. Quicker cure allows for fewer particles to
contaminate the surface finish, which directly relates to rework
and scrap costs. In summary, there are both tangible and intangible
benefits to deciding to go to UV/EB curing. When factoring these
benefits into the selection criteria, UV/EB typically becomes the
most economical and environmentally safe solution! |
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