Ultra Violet (UV)/ Electron Beam (EB) Curing of Coatings: Operation – Applications – Market

Baskar Vairamohan

Project Manager

Industrial Center of Excellence Webcast

September 18, 2014

Ultra Violet (UV)/ Electron Beam (EB)

Curing of Coatings

Operation – Applications – Market

2© 2014 Electric Power Research Institute, Inc. All rights reserved.

Contents

• EPRI - Introduction

• UV/ EB Operation - Basics

• Applications

• Market Survey

• RadTech 2014 Conference – Round up

• Vendor Contacts

• Additional Resources


About EPRI

• Founded in 1972 as an independent,

non-profit center for public interest

energy and environmental research

EPRI’s Mission

Advancing safe, reliable, affordable

and environmentally responsible

electricity for society through global

collaboration, thought leadership and

science & technology innovation


Our Members…

• 450+ participants in more than 30

countries

• EPRI members generate

approximately 90% of the electricity

in the United States

• International funding of nearly 25%

of EPRI’s research, development

and demonstrations


Independent

Collaborative

Nonprofit

Three Key Aspects of EPRI

Independent

Objective, scientifically based

results address reliability,

efficiency, affordability, health,

safety and the environment

Nonprofit

Chartered to serve the public

benefit

Collaborative

Bring together scientists,

engineers, academic

researchers, industry experts

UV/ EB Curing Basics


Natural Source of UV Light

• Ultraviolet (UV) light has shorter

wavelengths than visible light.

• The Sun is a source of the full

spectrum of ultraviolet radiation,

which is commonly subdivided

into UV-A, UV-B, and UV-C.

• Some insects like bumble bee

can see this UV light


UV Basics

• Using UV energy (photons),

visible light to form a coating,

film or ink.

• Replaces thermal, evaporative,

or oxidative (air-dry) curing

• UV/ EB Types:

– Ultra Violet (UV): 100-400 nm

• UV-A: 315-400 nm (Long)

• UV-B: 280-315 nm (Medium)

• UV-C: 100-280 nm (Short)

– Electron beam: high energy

electrons


UV Basics (Contd…)

• UV radiation is emitted by, and

absorbed by, the valence electrons

of atoms.

• When an electron in an outer atomic

orbital encounters a photon with the

right level of energy, the electron will

absorb the photon and move from

its normal “relaxed” state to an

“excited” state.

• If the photon has enough energy,

the electron will leave the atom

entirely and become a free electron,

or free radical.

• Sources for UV:

– Most common is medium-

pressure (MP) mercury vapor

lamp.

– An electrode arc or

microwave energy is used to

excite the mercury, which

causes the UV emission.

– UV Light Emitting Diode (LED

is an emerging technology)


What is Curing?

• Curing is a set of chemical and physical processes that

coating materials must undergo after drying.

• The coating must attach itself to the substrate physically

(adhesion) or chemically (cohesion) and must cohere to

itself.

• It also need to undergo chemical reactions such as

“polymerization” (formation of plastic). These processes are

known collectively as curing.

• Depending upon the chemistry of the coating material,

curing can take place at room temperature, at elevated

temperatures, or by free radical reaction (UV/EB).


What is Curing? (Contd…)

• Non-UV Curing Process:

– Two Step Process:

• First Step – Solvent based paint is dried to remove

moisture

• Second Step – Thermal curing of the coating so the

coating adheres to the surface.

– Most of the industrial coatings used today are thermally

cured

– With thermally curable coatings, adding heat can

accelerate the curing process, but care has to be taken

not to overheat the coating.


Requirements of UV/EB Curing

Application

Energy Source (UV/EB)

Formulation

These 3 elements have to

work together to get

correct coating properties


Formulating a UV Curable System

PI*

Additives

Monomers

Oligomer

• Photoinitiator (Free-radical) : Any

chemical compound that

decomposes into free radicals when

exposed to UV

• Additives (Performance Tuning):

Chemical agents such as pigments,

fillers, wetting agents, etc. that add

various properties to the coating.

• Monomer (Viscosity and

Flexibility): A molecule that may

bind chemically to other molecules

to form a polymer.

• Oligomer (Basic Coating

Properties) : A polymer or polymer

intermediate or resin containing

relatively few structural units.

* PI stands for Photo Initiator


Role of Photo Initiators (PI)

• They absorb UV light or electrons to

form free-radical

• They initiate the polymerization process

by adding themselves to monomer/

oligomer

• Different PI’s absorb UV at different

wavelength

• The wavelength of PI should be

matched with wavelength of UV lamp

for optimal results

• They only react with UV to Visual light

in the electromagnetic spectrum

• They have long shelf life

Source: http://www.esf.edu/outreach/uvebwebinar/documents/Intro_Basic_UV_curing2012_MJI.pdf

Image Source: http://www.gallus-group.com/desktopdefault.aspx/tabid-

370/569_read-1681/

http://www.esf.edu/outreach/uvebwebinar/documents/Intro_Basic_UV_curing2012_MJI.pdf

http://www.gallus-group.com/desktopdefault.aspx/tabid-370/569_read-1681/


UV Curing Process

• UV curable coatings contain a

catalyst called a photo-initiator.

• Photo-initiators generally react to

wavelengths of between 200 and

400 nm.

• They absorb UV light and starts

a photochemical reaction that

employs the use of free

electrons, or free radicals, and

causes an almost instantaneous

cross-linking of the resins.

• UV curable coatings are

formulated with unsaturated

resins that are capable of free

radical reaction. Photo Source: Lumen Dynamics

http://www.ldgi.com/technology-learning-center/uv-bonding-curing/curing-process/

http://www.ldgi.com/technology-learning-center/uv-bonding-curing/curing-process/


UV Curing Process (Contd…)

• Unsaturated resins have fewer hydrogen atoms or

equivalent groups than saturated resins and will combine

directly with hydrogen, chlorine, oxygen, or various other

substances to form long chain polymers.

• Only the photo-initiator and exposure to ultraviolet light are

required to start and complete the reaction.

• Thermal processing is not necessary to cross-link the

resins used in liquid UV-curable coatings.

• Note: Some heat may be necessary with UV-curable

powder coatings in order to melt, flow, and level the

particles of powder before curing.


Electron Beam Curing

• Uses electrons to complete the polymerization process

– Electrons open double bonds initiating polymerization

– Note: no photoinitiator required

• EB systems can use UV formulations to get the required properties (opposite case is not true)

– Electrons decompose photoinitiator to form acid which then initiates polymerization

• EB systems formulations are less expensive than UV system formulations because of the absence of photoinitiators

Additives

Monomers

Oligomer

EB Formulation


Electron Beam Properties

• Ionizing radiation (low energy

electrons):

– Sufficient energy to break

bonds in coating to generate

free radicals

– Can penetrate into and

through a coating/ink and

through substrates

– Generate little or no heat

– Precision controlled

– Not affected by pigmentations

or transparency of coating or

substrate


Scratch Resistant Tests for UV/EB Coatings

• Steel Wool Tests

• Pencil Hardness Test

• Taber Wear Test

• Scratch measured in microns

Source: http://www.pcoatingsintl.com/wp-content/uploads/2014/04/A-Critical-Study-On-Scratch-Resistance-Tests-C-George-

Drazinakis.pdf

Rotary Steel Wool Tester

Pencil Hardness Tester

Taber Wear Tester (Haze Value)

http://www.pcoatingsintl.com/wp-content/uploads/2014/04/A-Critical-Study-On-Scratch-Resistance-Tests-C-George-Drazinakis.pdf

UV/ EB Applications


Additive Manufacturing – 3D Printing

Digital to Physical

3D CAD File Printing ResultPrint the model

Courtesy : Stratasys

Traditional Manufacturing – Subtractive

Digital Manufacturing – Additive (Building Layer by Layer)


Technology – PolyJet Process

Courtesy : Stratasys


New and Emerging Applications

• Bio-inspired Glue – Medical Field

• Shark Skin Aircraft Coatings

• Ultra-thin PV Application

• UV for rail road repair


Applications of UV/ EB Curable Coatings

• Industrial coatings and graphic arts market segments:

– Coatings for wood furniture and flooring

– Coatings for plastic, metal and paper

– Fiber optic coatings

– Coatings for electronic components

– Coatings used on automotive components

– Overprint varnishes

– Flexographic inks

– Screen Print inks

– Lithographic inks

– Laminating and pressure sensitive adhesives


Roll-to-Roll Coating Applications

• Other Applications;

– Display and Touch

Screens

– Solar, Battery and Fuel

Cell

– Flexible Electronics

– Medical

– Membranes

– Aerospace and

Automotive

– Lighting

– Many more….Source: Carestream Tollcoating


Advantages of UV Curing

1. Much faster than thermal processes - UV coatings cure in a matter of seconds, rather than minutes or hours.

2. Faster start-ups and shut-downs and lower energy consumption - UV lamps turn on and off almost instantaneously. There is virtually no energy or time lost waiting for the oven to come up to temperature in order to start or resume production, and stand-by modes are not necessary.

3. Improved productivity - Because UV coatings cure in a matter of seconds, higher line speeds are possible.

4. Less contamination – lower reject rates - No air movement to exhaust byproducts of combustion is necessary in UV curing systems. This reduces the chance of air-borne contamination of the coating.


Advantages of UV Curing (Contd…)

5. Reduces or eliminates VOC emissions and solid waste

disposal - Many UV coatings are 100% solids and contain

no solvents; thus VOC emissions can be eliminated.

6. Less space required - Due to the speed of cure, UV

systems require less floor space.

7. Superior finishes - UV curable coatings can offer improved

performance and visual properties.

8. Less thermal, noise, and air pollution - less thermal

pollution of the workplace and less noise pollution from

fans, burner regulators, etc. due to low heat requirement.

9. Can be used on temperature-sensitive substrates -

Substrates such as wood and plastic, and fully assembled

products that may contain gaskets and/or fluids, can be

safely coated with UV curable coatings.


Drawbacks of UV/EB

• Additional capital cost

– retrofitting can sometimes be difficult

– EB systems are expensive (capital cost), but is cost

competitive for many applications

• Inks and coatings are can be more expensive per pound

– but offset by improvements in productivity, superior

appearance

• Re-training of operators

– UV/EB inks/coatings perform differently compared to

conventional inks and coatings

UV/EB Curing - Market Survey


UV/ EB Formulated Average Annual Growth

Rate since 2011 (by Volume)

Source: RadTech 2014

27%

15%

15%

14%

14%

9%

8%

8%

8%

6%

0% 5% 10% 15% 20% 25% 30%

3D PRINTING/ ADDITIVE MANUFACTURING

MEDICAL APPARATUS

GRAHIC ARTS - INKJET INKS

DENTAL APPLICATIONS

OPTICAL ADHESIVES

METAL DECORATING

PRINTING PLATES

ELECTRONIC ADHASIVES

OPTICAL FIBER

FLOORING


2013 Worldwide Raw Materials Use for UV/EB

Curing (Total = 489,000 MT)

Oligomers39%

Monomers49%

Photoinitiators10%

Pigments/ Additives2%

Other12%

Note: MT – Metric Ton (= 1000kg = 2205 lb) Source: RadTech 2014


Worldwide & Europe UV/ EB Curing

Applications

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

World Europe


Worldwide Raw Materials = 489,000 MT

Europe Raw Materials = 150,000 MT


Sales of UV Lamp Technology – New Trend


$45

$269

$309

$507

2012 2023

UV LED Lamps Traditional UV LampsSales in millions of US Dollars


Markets for UV Applications

Source: EPRI


RadTech 2014 Conference

May 12-14, 2014

Chicago, IL


RadTech International (North America)

• RadTech is a non-profit trade association

• Over 700 Members

• Active for almost 30 years

• Our members are across the supply change

• Members support over 20 application areas for UV and EB

• Link: www.radtech.org

• Contact Information:

Gary M. Cohen | Executive Director

Phone: 240.497.1242 | Email: [email protected]

Mickey Fortune Phone: 240.643.0517 | Email: [email protected]

Address:

7720 Wisconsin Avenue, Suite 208Bethesda, MD 20814

http://www.radtech.org/

mailto:[email protected]



Vendor Contacts from RadTech 2014

EB VendorsUV Vendors


Phoseon Technology


Nordson Corporation


Toll Coating


Heraeus


Miltec UV


Energy Science Inc. (ESI) – UV and EB


Philips Lumileds

5x96 = 480 LED’s in this strip

– each with individual control


American Ultraviolet


Jelight Company, Inc.


PCT Engineering Systems – EB Curing


Bayer


Examples of UV/ EB Curing


Other Resources

1. UV Curable Coatings -- Marketing Kit – EPRI Product (1000138) – 2000 (Free-of-charge Download) http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000000001000138

2. UV & EB Curing of Coatings - Power of Light, Dr. Mike J. Idacavage (PL Industries A division of Esstech, Inc.), RadTech UV & EB 2014, May 12,13 2014

3. RadTech – Trade Association for all UV/EB curings- Formulations and Equipment – www.radtech.org

4. Proceedings from RadTech 2014 is available at http://radtech.org/2014proceedings/

5. CEATI – Electrotechnologies –Energy Efficiency Reference Guide: http://www.ceati.com/freepublications/7020_guide_web.pdf

http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000000001000138

http://www.radtech.org/

http://radtech.org/2014proceedings/

http://www.ceati.com/freepublications/7020_guide_web.pdf


Questions


Contact Information

Baskar Vairamohan C.E.M.

Project Manager | Electric Power Research Institute

942 Corridor Park Blvd | Knoxville | TN - 37932

Office 865-218-8189 | Cell 865-368-7197 | Fax 865-218-8085

Email: [email protected]


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