"Utilizing UV Curing in Decorating Plastic Substrates 101" presented by Steve Hatkevich, Director of R&D, American Trim LLC at RadTech UV & EB Technology Expo & Conference 2014. To learn more about UV & EB curing, visit http://www.radtech.org.

1. UTILIZING UV CURING IN
DECORATING PLASTIC
SUBSTRATES 101
By Steve Hatkevich, Director of R&D,
American Trim LLC

3. UV Curing at
• Organic Coatings Products (OCP), 20+ years of UV
formulating and manufacturing experience
• Material Deposition Center (MDC)
• Finish Development Center (FDC) at Amtrim’s Research
and Development Center, Lima, Ohio headquarters

4. Agenda
• Definitions
• Plastic substrate characteristics
• Role of surface energy of ink and substrates
• Types of UV curing
• Deposition methods for decoration
• Processes available to decorate both 2D and 3D surfaces
• How UV curing can benefit the process
• Conclusions

5. Definitions
• Plastics: Synthetic materials made from organic polymers that
can be molded into shape while liquid or soft and then set into
rigid or elastic forms. From the Greek “to mold”
• Ultraviolet (UV) Curing: Ultraviolet or UV curing is a process
that uses electromagnetic radiation in the UV spectral range
(wavelengths shorter than light but longer than X-rays; in the
range 0.4 × 10 --6 and 1 × 10 --8 meters) to initiate the
polymerization of monomers and/or oligomers typically through
the stimulation of photo initiators. UV curing provides virtually
instant drying/ polymerizing of inks, coatings or adhesives.
• Surface Energy: Measures the disruption of intermolecular
bonds at the surface of a material

6. Plastic Substrates – Fluid Relationship
• Adhesion is common problem in materials that possess
low surface energies. Examples can include High-Density
Polyethylene and Polypropylene
• High levels of surface energy on solid substrate and lower
surface tension in deposed liquid results in increased
molecular attraction & superior bond strength
• Lower substrate surface tension than that of the deposited
liquid, results in weakened attractive forces and repelling
of the liquid.
• Substrate surface energy should > 5mN/m (dyne/cm) of
deposited fluid material

7. Polymer Surface Tension & ContactAngle
Material CAS # Surface
Tension
mN/m @ 20oC
Contact
Angle
Polycarbonate (PC) 24936-68-3 43-45 82
Polyvinyl chloride (PVC) 9002-86-2 42 85.6
Polyvinyl fluoride (PVF) 24981-14-4 32.7 84.5
Acrylonitrile butadiene styrene (ABS) 9003-56-9 38.5 80.9
Polyethylene terephthalate (PET) 25038-59-9 39 72.5
Polyethylene (PE) 9002-88-4 33-37 96
Polypropylene (PP) 9003-07-0 29-30 102.1
Polyamide 6,6 (Nylon 6,6) 32131-17-2 47 68.3
Polystyrene 9003-53-6 39-41 87.4
Polymethyl Methacrylate (PMMA,
acrylic)
9011-14-7 37.5 70.5

8. Cautions
• “In the Industrial World, almost nothing we work with is
pure” &“You pay for purity”*
• Reported material surface tension figures will vary
depending on conditions of testing and material
manufacture
• The surface tension of a plastic will differ according to the
way it is made
• Extruded plastics will typically include surface waxes that
with reduce a plastic substrate’s surface tension
• Need to minimize infrared heat that can damage plastic
substrates & bloom plasticizers to plastic surfaces
inhibiting ink & coating adhesion
* Dene Taylor, PhD – Industry Consultant

9. Adhesion Promotion
• Surface roughening
• Solvent & co-solvent composition of fluid
• Primers & tie-coats
• Adhesion promoters:
• Covalent bonding
• Chemical similarity
• Other attractive forces, i.e. van der Waals,
electrostatic, hydrogen bonding
• Plasma, corona & flame treatment
• Plasma produces less heat eliminates need for
masking
Image sources: Dumore Corp., Plasmatreat, Enercon Industries

10. Determining Wetting for Adhesion
• Wetting Tests
• Water Break Test (dipping plastic substrate in water: film or bead)
• Dyne Pen Test (Sherman pen set with varying chemical dyne levels)
• Contact Angle Determination
• Gonimeter Methods (manual viewing of backlit drop on substrate)
• Automated Contact Angle Measurement (video camera & computer)
• Water Drop Contact Angle Measurements (TAPPI method T558)
• See also standard DIN 55660
• ASTM D5946 (Guide for treatment of low energy plastics)
• Marginal or no treatment >90° (under approximately 34 dynes/cm)
• Low treatment 85-90° (approximately 36-34 dynes/cm)
• Medium treatment 78-84° (approximately 39-36 dynes/cm)
• High treatment 71-77° (approximately 43-40 dynes/cm)
• Very high treatment <71° (above approximately 43 dynes/cm
•

11. Other Factors Matching UV Ink to Plastics
• Modulus: Stress behavior of ink/coating when dry should
be consistent with substrate
• Coefficient of Thermal Expansion & Chemical Structure:
Matching ink/coating to substrate considering the 3D
nature of both
• UV curable digital inks typically cure so rapidly that their
drops solidify before completely wetting out on the
substrate UV ink’s surfactant component has the highest
impact on the ink formulation’s surface tension
• Speed of the printing press & print head (higher drop
generation increases ink surface energy)

12. Types of UV Curing Exposure
• Near UV: 400-200 nm
• UV-A: 400-315 nm
• UV-B: 315-280 nm
• UV-C: 280-200 nm
• Far UV: 200-10 nm
• Deep UV: 31-1 nm
• Black light
• Arch lamp
• Mercury bulb
• LED
• Laser for Stereolithography
Image sources: Heraeus Noblelight, signindustry.com, printingtechnology.net
Microwave UV Mercury bulb
LED UV

13. Types of UV Curing Chemistry
• Free Radical: Over 90% of UV cure chemistry is the free radical type
using primarily acrylic (acrylate) components. A large variety of
monomers and oligomers are available providing a wide range of
properties. Polymerization halts with removal of UV source. Free
radical systems are vulnerable to oxygen inhibition where oxygen in
the air prevents the molecules at the surface from polymerizing.
• Cationic: Primarily contain epoxy and/or vinyl ether components.
Limited variety of currently available cationic monomers and
oligomers. Curing can continue after the light source is removed, but
it is minimal and often requires a thermal bump, or heating, to be
effective. Cationic photoinitiators can be toxic and their residues
corrosive. Cationic systems are high humidity vulnerable.

14. Deposition Methods for Decoration
• Screen Printing
• Inkjet
• Lithography
• Flexography
• Padprinting
• Spray for clear-coating
Image sources: Thieme, Durst
Industrial Screen Print: Thieme 3000 GS AM
Industrial Inkjet: Durst Rho 1012

15. Decorating 2D and 3D Surfaces
• Applications for UV cure decoration of plastics include
automotive headlamp lenses, control panels, plastic faucets,
television housings, eyeglass lenses, computer keyboards,
catheter tubes, toothpaste tubes, mobile phone cases, writing
pens and markers, drink bottles
• While UV cure chemistry accounts for just over 4% of industrial
decoration and coating. It is growing by about 10% per year
Image sources: Heraeus Noblelight Fusion UV Inc.

16. How UV Curing Benefit Plastic Decoration
• Virtually instant drying
• Compared with solvent inks:
• No VOC worker or environmental
exposure
• No loss of deposited film
thickness or volume
• Less waste & energy used
• Better adhesion & bond strength,
hardness or elasticity
• Resistance to "crazing,"
• Very high gloss possible
• Creates attractive look
• UV clear-coating provides
scratch, chemical & wear
resistance & lengthens image
life
• New free radical polymeric
chemistry is winning approval
for use in food packaging and
with medical devices
UV cure’s high gloss reflection

17. Additional References
• An Introduction to Light Curing Technology, Loctite Corp.,
Rocky Hill, CT.
• www.plasticsdecorating.com July/August 2013, Innovating
Inkjet Technologies for Plastic Products, by Scott R. Sabreen
and Dene Taylor, PhD
• Dynamic Surface Tension of Digital UV Curable Inks, by
Sudhakar Madhusoodhanan, Stephen Sung, Erik Delp, Devdatt
Nagvekar, Matthew Ellison, Daniel Wilson; Hexion Specialty
Chemicals
• Coating Plastics, Some Important Concepts from a Formulators
Perspective, by Lawrence C. Van Iseghem, Van Technologies,
Inc.

18. Conclusions
• UV cure printing of plastics presents a number of critical
challenges and choices
• Surface tension of the plastic substrate needs to be 5 to 8
dynes/cm higher than the ink or coating
• Substrate pretreatment is necessary for printing & coating most
plastics
• Inkjet UV cure offers both cost and adhesion challenges and
market opportunities
• UV cure decoration offers significant advantages for
performance and eliminating of VOC emissions over decorating
plastics with solvent-based inks

19. Thank You
Steve Hatkevich
Director of R&D
American Trim
shatkevich@amtrim.com