Current Status – Blisters

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Polyester Visual Blister Packaging
Stuff you gotta’ know!
AVPM Annual Meeting 2009
Pack Expo - Las Vegas
October 6, 2009
klöckner pentaplast of America
Polyester Blister Films:
Stuff You Gotta Know
– Environmental Marketing Claims
– Polyester (APET, UPET, RPET) properties & relative
costs
– Heating and Tooling Differences from vinyl
– How to measure and reduce Stress in formed
parts
Environmental Marketing Claims
– FTC – Beware of deceptive Sustainability or
Environmental Marketing claims
• Sears – had to throttle back biodegradable packaging claims
• Broad claims are considered misleading most of the time
• Be specific
– If you make a claim, be sure it is supported or
certified by an accredited independent 3rd party
• (Clue – if you have a horse in the race, you are not an independent 3rd
party)
APET, Utility PET and “RPET”
• Produced by Extrusion or Co-extrusion
– Prime
– Post industrial
– Recycled APET
» Buyback (“pre-consumer recycled content)
» Post Consumer (usually bottle flake)
• Closest rigid film alternative to PVC in price
• APET Films are slightly stiffer than PVC sometimes allowing slight
downguaging
• Utility and RPET can be brittle and vary in Performance and Cosmetics
due to recycled content heat history
• Can be more Difficult to Cut and Seal – but the industry is mid-stream
in this learning curve. Heating knife or die will help but do not let
sheet temp exceed 160F (the glass transition temp of PET)
Thermoforming grade Relative Material Costs
Polymer
Yielded Cost
Index
TH-PVC
100%
TH-Utility PVC
95%
(sometimes incl. buyback)
Prime APET
110%
Post industrial “UPET”
90%
RPET (PCR and preconsumer content)
95 - 105%
TH-G-PET-G
125%
Mold Design Considerations
• Very critical for success in thermoforming
• Minimum radius of 1/8” when possible
• Design undercuts/snap fits to capture, but return to zero
strain
• Remember to increase trim cuts for up-stackers to prevent
tearing into blisters (PET is not notch sensitive like PVC)
• Female molds with generous draft angles provide:
– more consistent flange thickness
– easier removal from mold
– fewer problems with bridging
• Vacuum holes clear and channels behind mold should be
large and direct to the vacuum hose.
Heating The Plastic Sheet
• Radiant heaters using ceramic elements or quartz
lamps are more efficient allowing better zone heating
vs. old cal rod style heaters
• Materials take heat differently
• Essential to maintain moderately high sheet
temperatures (but not so high that the sheet
crystallizes or turns white)
• Need to use temperature-sensing device to monitor
sheet temperature
Thermal Mechanical properties of
blister films
• Film Type
Polymer Film
Forming Temp. °C Rigid packaging films
Amorphous polyester
A-PET
(UPET/RPET)
140 – 165 °C
Polyvinylchloride
PVC
130 – 150 °C
Measure Actual Sheet Temperature
• Most critical variable when thermoforming
Polyester
• Measure actual sheet Temperature Versus
Oven Temperature
• Options:
– Temperature Indicating Tapes
– Mounted Infrared Eye
– Hand-Held IR Gun
Evaluating Birefringence to
Examine Residual Stress
• Definition: When a transparent material has internal stresses (molecular
level orientation) it has different refractive characteristics. The birefringence is
directly proportional to the stress level.
• Why Important?
–
–
–
–
Predict product performance
Impact resistance
Heat performance when reheating for heat sealed blisters
Susceptibility to environmental stress cracking
• Qualitative Evaluation
– Polarized Light
– Retardation / Fringe Order
How to prevent “High Internal Stress”
•
•
•
•
Internal stresses are caused from thermoforming at sheet temperatures
that are too cold.
Sheet temperatures must be as high as possible to have a low stressed
thermoformed part.
As oven temperatures are increased, the plastic sheet starts sagging too
much, and the material folds on itself on the mold or turns white
(crystallizing). To prevent overheating, consider reducing to 2 heat
indexes instead of 3 while continuing to monitor part stress.
When PET turns white, there is too much heat, unlike PVC, where white
blush is typical of cold forming.
Case Study of a High stress PET part
You can see here that the flange, or outer edge
of the package, has a lot of stress. This could
cause warping of the flange area during heat
sealing. The best way to count the fringes is to
look for an area with tight repeating rainbows.
Make sure you continue to count the repeating
rainbows in the same area of the package as
you add heat to the sheet. Decreasing the
amount of rainbows in that one area will
decrease the internal stresses in the entire
package. As you increase the sheet
temperature, you will see fewer repeating
rainbows.
In this picture, start counting from the bottom
right side of the blue box. The violet rings get
bigger and bigger as you move further away
from the origin of high stress. If you count
straight up, you can count 1, 2, 3, 4, 5, 6 rings.
Can you see it?
After adding heat: Medium stress
As heat is added to
the sheet, the
rainbows spread out
and decrease in
number. Counting
now, we see 1, 2, 3
and a little more.
Additional sheet temperature added for Lowest stress
In this photo, the stress
is completely gone.
Notice the stress is gone
in the flange as well.
Thank You
Questions?
Please contact:
Peter Gianniny
[email protected]
540-832-1422
Technical Review-Heat Seals
Components
• Blister types
• Adhesive Technologies
• Current Status
16
Technical Review-Heat Seals
Blister Type
• Traditional PVC – Vast Majority of Market
• PET & RPET Blisters -Expanding
17
Technical Review-Heat Seals
Blister Type – other impacts
• Blister Flange – need a minimal size to ensure
heatsealing operation adherence of the blister
to the ink/board stock
• Mold Release & denesting lubricants – need
minimal amounts to preclude disruption of
adhesion
18
Technical Review-Heat Seals
Visual Carded Packaging
Components & Assembly
Plastic Blister
Blister
Flange
Blister
Flange
Heat Seal Coating
Printing Ink
Clay Coating
Clay Coating
Chemical Sizing
BASE
SHEET
Paperboard
Chemical Sizing
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FINISHED
SHEET
Technical Review-Heat Seals
Adhesive Technology
• The adhesive itself is applied over wax-free inks
on the
blister board
• The heatsealing operation allows the molten
adhesive to wet out the blister and the
ink/board
20
Technical Review-Heat Seals
Adhesive Technology
• The adhesive does not “dive in” to the board
as originally thought. (Determined by AVPM technical
committee analysis)
• Thus – the blister itself is vital to a proper and secure
structure
• A proper seal is the result of the bond between blister
and ink/board, being strong enough so that the board
ruptures in the base sheet (not clay split!!)
21
Technical Review-Heat Seals
Adhesive Technology (Solvent Base)
• Applied off-line in second step on roll-coater over
dry inks (may require spray powder)
• Able to adhere to a wide variety and “quality” of
blisters – most forgiving technology – better wets
out the flange.
• EVA and Vinyl Technologies
• Solvent recovery or incineration required
22
Technical Review-Heat Seals
Adhesive Technology (Water – Base)
• Applied in-line over wet ink on a litho press
equipped with an in-line coating unit
• Lower cost than off-line coating - 1 step process
• PUR and Acrylic Technologies
23
Technical Review-Heat Seals
Current Status
• “Green” concerns drive the blister package to
more environmentally friendly components
• Board stock is repulpable (Beloit Study)
• Heatseal Adhesive – Currently water-base,
devoid of
organic solvents / and in-line which eliminates a
second operation which reduces energy and
cost
24
Technical Review-Heat Seals
Current Status – Blisters
• PVC Blisters – Issue with environment (Chlorine)
Being greatly reduced and eliminated in EU and
now in North America
• Recyclability provides for “better score” on
Walmart score card as well as with the
consumer/customer – Hence RPET!!!!
25
Technical Review-Heat Seals
Current Status – Blisters – RPET
• RPET Blisters vary in amount of “recycled”
components
• This may vary the surface energy and
corresponding effect on the ability of the
adhesive to wet the substrate and adhere the
blister to the ink/board
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Technical Review-Heat Seals
Current Status – Blisters – RPET
• Thus to overcome the variation – solvent base
systems
provide the safest solution (traditional system
with the ability to wet out the film when
sealed)
• Solvent base (EVA) in effect “covers the sins” of
the variation inherent in typical RPET blister
stock
27
Technical Review-Heat Seals
Current Status – Blisters – RPET
• Water base systems (PUR) - are being
developed to allow for their benefits (one-pass
/ no organic solvents)
• This will take the Blister Package to the
“greenest” option
• Best bet is to test the combination of board /ink
/ heatseal coating / blister in the laboratory
prior to approval
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Technical Review-Heat Seals
Current Status – Blisters - RPET
• When completed make sure to specify each
component!!!
• With the same board – ink – heatseal / and
specified RPET!!! This structure should provide
the optimal desired and properly sealed
package!!!
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Technical Review-Heat Seals
Questions??
Thank you!!!
Peter Garvin
Henkel
[email protected]
(513) 417 - 3980
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