avpm annual meeting 2009 pack expo - las vegas october 6, 2009 klöckner pentaplast of america...
TRANSCRIPT
AVPM Annual Meeting 2009
Pack Expo - Las Vegas
October 6, 2009klöckner pentaplast of America
Polyester Visual Blister Packaging Stuff you gotta’ know!
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 (sometimes incl. buyback)
95%
Prime APET 110%
Post industrial “UPET” 90%
RPET (PCR and pre-consumer 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 140 – 165 °C (UPET/RPET)
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 partYou 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.
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Technical Review-Heat Seals
Components
• Blister types
• Adhesive Technologies
• Current Status
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Technical Review-Heat Seals
Blister Type
• Traditional PVC – Vast Majority of Market
• PET & RPET Blisters -Expanding
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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
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Technical Review-Heat Seals
Heat Seal Coating
Printing Ink
Clay Coating
Clay Coating
Chemical Sizing
Chemical Sizing
Paperboard
Clay Coating
Plastic Blister
Blister Flange
Blister Flange
BASE SHEET
FINISHEDSHEET
Visual Carded PackagingComponents & Assembly
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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
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Technical Review-Heat Seals
Adhesive Technology• The adhesive does not “dive in” to the board
as originally thought. (Determined by AVPM technicalcommittee analysis)
• Thus – the blister itself is vital to a proper and secure structure
• A proper seal is the result of the bond between blisterand ink/board, being strong enough so that the board ruptures in the base sheet (not clay split!!)
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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 wetsout the flange.
• EVA and Vinyl Technologies• Solvent recovery or incineration required
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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
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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 oforganic solvents / and in-line which eliminates asecond operation which reduces energy and cost
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Technical Review-Heat Seals
Current Status – Blisters• PVC Blisters – Issue with environment
(Chlorine)Being greatly reduced and eliminated in EU andnow in North America
• Recyclability provides for “better score” on Walmart score card as well as with the consumer/customer – Hence RPET!!!!
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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
systemsprovide 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
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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 GarvinHenkel
[email protected](513) 417 - 3980