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:
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
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!