FLEXIBLE PACKAGING DURABILITY STUDIES. Dr. Henk Blom Rollprint Packaging Products, Inc. Addison, IL USA

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1 FLEXIBLE PACKAGING DURABILITY STUDIES Dr. Henk Blom Rollprint Packaging Products, Inc. Addison, IL USA 456

2 O U T L I N E

3 Package durability Relevant across multiple industries Medical device packaging Food packaging Commercial packaging Inadequate packaging results in: Sterility breaches Over-concentration of medical solutions Food spoilage Shortened 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 usually not 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 Enable easier screening of material candidates? Focus design efforts? Lead to innovative flexible package material designs? Be less expensive? Be faster?

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 strength 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 # pinholes = f(modulus, impact strength, impact strength 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 EXPERIMENTAL DETAILS

9 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 Special thanks to the folks at Taber Instruments!!

10 Materials Monolayer Biaxially oriented nylon (BOPA) Cast nylon (cpa) mlldpe Blown, metallocene Oriented PET (opet) 6% EVA copolymer Cast PP (cpp) 5% EVA / 95% LLD blend HDPE - Blown Laminates 0.48 mil opet / adh / 2 mil 6% EVA 0.75 mil cpa / adh / 2 m il 6% EVA 0.60 mil BOPA / adh / 2 mil LDPE

11 Experimental details Variables Applied load Film thickness MD / TD Skin / Sealant (laminates) Constants Stroke length (1 in) Stroke speed (30 in/min) Pin 1.5 mm Ø Output Cycles to failure Side note: New ASTM test method under development by F02 committee

12 EXPERIMENTAL RESULTS Method variability Applied load & thickness Laminates

13 METHOD VARIABILITY

14 Cycles to failure (#) Overview Plot of cycles to failure (#) for oriented and cast polyamide Tested at two applied loads (206 and 279 g) MD and TD data N = 15 Load (g) Direction Material MD TD 1 mil BOPA MD TD 1 mil cpa Observations Some data sets have narrow distributions, others have rather wide distributions Data for a given material/load combination can span 2-3 orders of magnitude No apparent underlying cause for the observed differences

15 Cycles to failure (#) Overview Abrasion data for HDPE and LLDPE films Testing done in 2011 and g applied load N = Test date Direction Material MD TD 3 mil HDPE MD TD 5 mil mlldpe Observations From this subset of the available data, method appears to be relatively repeatable over time Materials with wide distribution in 2011 still broad; narrow distributions still narrow

16 Cycles to failure (#) Test date Direction Material MD mil BOPA 2012 TD MD mil cpp 2012 TD 2013 Overview Abrasion results for oriented nylon and cast propylene Testing done in 2011, 2012, and 2013 BOPA tested at 279 g; cpp tested at 206 g N = 15 Observations Data appears to be relatively repeatable over time in some cases, but not in others BOPA MD did we get better at our methods? cpp MD or TD 2011 vs or did we get worse?

17 Method variability Test data for flexible packaging somewhat variable Source of variability? Inherent in the material? Surface? COF? Thickness???? Test method? Sample loading? Contamination? Environment? Temperature? Humidity? Is it still a useful test? I think the following data will indicate that it is

18 APPLIED LOAD & THICKNESS

19 Overview Test data for cast PP films of varying thickness Semi-log plot against inverse applied load Both MD and TD are plotted Lines provided as aids to the eye Observations TD generally higher than MD likely an orientation effect Thicker films require more abrasion cycles to failure Inverse relationship with applied load increased load results in fewer cycles to failure Clearly not a linear relationship!

20 Observations Similar relationships as on previous slide Relationship to 1/applied load stronger for PET compared to cpp Overview Test data for oriented PET at various thicknesses. Semi-log plot against inverse applied load MD and TD data pooled N = 15 in most cases

21 Overview Abrasion data for various materials as a function of thickness Log-log plot cpa, 5% EVA, and 6% EVA tested at 206 g opet tested at 529 g cpp tested at 279 g N = 15 Observations As seen earlier, increased thickness leads to increased abrasion resistance Different materials have different sensitivities to thickness Low-modulus materials appear to be less sensitive to thickness than materials with a higher modulus

22 Overview Oriented PET at various applied loads Thickness range of 0.48 to 2.0 mil N = 15 in most cases (but not for data at 206 and 279 g) MD and TD data combined Observations Clear relationship of both applied load and thickness to abrasion resistance Remarkably linear behavior on a log-log plot Could there be some underlying relationship to fundamental material properties?

23 Abrasion coefficient Thus far we have cycles to failure (f) data for a number of materials as a function of thickness (t) and applied load (l) with data spanning several orders of magnitude How do we use a data set like this in modelling efforts? Can we reduce this data set to an abrasion coefficient (A) for a given material? Can we factor out thickness and applied load? A = log f x l t

24 Abrasion coefficient ranking Material Abrasion coefficient opet 39.3 opa 21.2 cpa 14.4 cpp 7.6 6% EVA 4.1 5% EVA/LLD 3.1

25 LAMINATES

26 Cycles to failure (#) 10,000 1, mil 2.0 mil BOPA / LDPE / 0.48 mil 2 mil 6% opet / 6% EVA 0.75 mil 2 mil 6% cpa / EVA / BOPA LDPE LDPE BOPA opet EVA 6% EVA / opet cpa EVA/LD EVA cpa Average

27 Conclusions Test method requires additional development to better understand source of variability Abrasion resistance of flexible packaging materials strongly related to applied load and material thickness Abrasion coefficient for monolayer materials provides a means to rank materials and begin modelling efforts Laminate behavior does not appear to be simply related to monolayer material abrasion performance

28 Recommendations ASTM test method needs to be finalized ILS conducted, P&B (precision and bias) determined Additional work required to understand and reduce test variability Surface effects Friction effects Others? Gather information on many more materials (especially laminates) Model development; collaborate with mathematical modelling experts Understand how this test relates to actual distribution

29 Acknowledgements Mr. Jason Obrecht Mr. Chris Girgis Mr. Nick Rohlfes Ms. Jocelyn Blom Ms. Rachel Blom

30 FlexPackCon 2013