Toward a package durability predictive model

Transcription

1 Committee F02 on Flexible Barrier Packaging Toward a package durability predictive model Dr. Henk Blom Rollprint Packaging Products Addison, IL USA

2 Outline Review of packaging durability A predictive model? Preliminary data & test case What s next?

3 Package durability Relevant across industries Food packaging Medical device packaging Commercial packaging Inadequate packaging results in: Sterility breaches Food spoilage Over-concentration of medical solutions Shortens shelf-life

4 Common package defects Flex fatigue pinhole Puncture Abrasion pinhole Cut/puncture Abrasion pinhole Cut

5 Package durability testing Limitations Significant cost involved Pass/fail testing requires large sample sizes to be statistically meaningful Time consuming time spent on trucks and ships Not predictive Gelbo is not always a good predictor of actual package performance Process is usually iterative may require several cycles to identify best candidate

6 A predictive model? Is it possible to derive an empirical relationship between routine flexible material tests and package durability performance? P F = a E x + b I y + c T z +??? Would an equation (or family of equations) like this Be less expensive? Be faster? Enable easier screening of material candidates? Focus design efforts? Lead to innovative flexible package material designs?

7 Literature examples Zapp 1955 (Esso Labs) Abrasion of Butyl Rubber Studied abrasion properties of tires using Lambourn Abrader Abrasion loss = dynamic modulus x friction tensile strengt Verghese 1992 (Texas A&M) Correlation of Pinhole Development Due to Flexing to Mechanical Properties of Plastic Films Evaluated pinhole formation in 18 commercial flexible films using custom pinhole device # pinoles = f(modulus, impact strengt, impact strengt 2 ) Tan et al 2008 (Beijing University of Chemical Technology) Abrasion Resistance of Thermoplastic Polyurethane Materials Blended with Ethylene-Propylene-Diene Monomer Rubber Investigated abrasion resistance of TPU/EPDM blends by abrasion loss W = P 2Htg k P1.5 Dμ 2 H 0.5 K IC

8 Taber Abrasion Test Equipment Taber Model 5750 Linear Abraser Flexible Material Kit Stylus is dragged back and forth across a sample supported in a holder over a mandrel Test stops when electrical contact is made between stylus and mandrel - # cycles is recorded

9 Abrasion testing Inputs Material type Film thickness Applied load MD / TD Laminates Sealant / non-sealant Output Oriented PET Cast Nylon Ionomer Oriented Nylon Cast PP EVA/(L)LD Metallocenes (L)LDPE HDPE Cycles to failure Total tests: > 2300 Total cycles: ~1.2 million (~650 hours)

10 Abrasion variability Considerable sample to sample variability Source of variation? Technique Material surface??? Implication: larger sample sizes needed to determine statistical significance of results

11 Abrasion material ranking 2 mil films / 279 g Data spans 5 orders of magnitude Clear differences between types of materials TD is usually slightly better than MD

12 What would we expect?

13 Abrasion applied load

14 Abrasion applied load Various film thicknesses plotted at a range of applied loads Cycles to failure very sensitive to applied load Relationship linear on log-log plot Does this point to an underlying dependence on fundamental material properties?

15 Abrasion film thickness

16 Abrasion film thickness Materials shown were run at various applied loads Linear relationship of cycles to failure versus film thickness on a log-log plot Is slope related to modulus? Hardness? COF? Some combination? Construct mathematical model?

17 What about laminates? Laminate abrasion properties superior to raw material abrasion properties! Does the adhesive play a role? Is behavior related to overall thickness in some way? Does the interface in some way produce better abrasion resistance?

18 Conclusions - Abrasion Abrasion testing has significant variability Significant performance differences across material families Laminate performance not as expected; further investigation required Other areas of investigation: Extrusion coated structures; Surface treatment effects; Variability reduction; Effect of slip; Co-extruded films Mathematical modeling appears to have some promise relating abrasion resistance to basic material properties (for monolayer films)

19 Puncture properties Many different test methods within ASTM Spencer, dart drop, Instron slow puncture Various puncture speeds (very slow to very fast) Various tup diameters Do correlations exist between any two tests? Which is the most appropriate test? Do we need this many tests? Can current test methods be combined and further standardized?

20 opet puncture properties Film thickness appears to have no effect on the Spencer impact strength of PET Likely due to surface-initiated fracture properties Tup geometry not adequately accounted for in Spencer method Would other materials behave similarly?

21 Puncture - laminates No obvious correlation of raw film properties to laminate puncture performance Laminates perform far worse than raw films alone Related to energy transfer across interfaces?

22 Where do we go from here? Abrasion Significant work completed; additional work in progress Puncture Initial experiments performed; much more needs to be done in this area Flex pinholes Wide open for investigation Cut resistance Wide open for investigation

23 A journey of a thousand miles Generate interest across the industry to advance our understanding of package durability Create global collaborations across companies and industries to design and execute the next round of experiments to build and refine models Solicit input from other disciplines that might provide additional skill sets

24 Contact information Intrigued? Interested? Want to get involved? Contact Henk Blom

25 Acknowledgements Summer interns Jocelyn Blom Rachel Blom Chris Girgis Lab technician Amelia Gonzalez

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