ABRASION TESTING OF PACKAGING FILMS

Alan D. Jaenecke TABER® Industries, North Tonawanda, NY ABSTRACT When packaging sterilized medical devices or products, the integrity of the film is essential to ensure sterility of the device until usage. With competitive forces prompting the use of thinner gauge films, the risk of abrasion-induced failures increases dramatically. Until recently, there have been no effective means for packaging engineers to quantify which films would be most suitable for final applications. The Flexible Material Abrasion Kit allows engineers to perform a controlled laboratory test and analyze the variables that may influence the abrasion resistance of packaging films. This paper presents the concept behind the device and describes an actual case study. INTRODUCTION Packaging requirements for medical devices include protecting the product and maintaining the sterility of the packaged product until usage. Regulatory authorities recognize the importance of this and consider “packaging an accessory or a component of the medical device”. [1] It is the manufacturer’s responsibility to ensure the selected packaging option will withstand the typical events associated with product handling, distribution and storage. During distribution and handling, movement between a medical device and packaging film and any secondary packaging may occur. Shock, vibration or repetitive rubbing allows the device to abrade the cross-section of the film, thus increasing the potential for the sterile barrier to be compromised. Although standardized tests have been established to ensure packaging integrity is maintained, there currently is no widely accepted test method to compare the abrasion resistance of packaging films. Therefore, abrasion failures are usually caught after distribution testing or customer complaints.

Figure 1 – Typical Abrasion Failure The formats typically used for medical device packaging include blister packaging (forming films), premade pouches, premade breather bags, or preformed rigid trays. • Rigid packaging uses materials that are usually above 20 mils in thickness and not subjected to abrasion-

induced failures. While surface abrasion may be of concern, this packaging format is outside of the scope of this presentation.

• Forming films are sold to device companies in roll stock format. The films are then thermoformed with heat,

vacuum and pressure into a forming tool. The device is placed into the formed pocket and a non-formed web is sealed to the top of the package. Abrasion-induced failures are common with this type of packaging.

• Pre-made formats require a converter to heat seal a film to a mating web, such as another film or a porous

material (e.g. Tyvek® or paper). Although often mechanically weaker than films, porous materials are required for gas sterilized devices and require packaging engineers to minimize the product load being applied to the porous web. As a result, 95% of abrasion failures for these types of packaging are on the film side and not the porous side.

Manufactured from engineered thermoplastic films, these protective barriers usually range in thickness from 2 to 20 mils. Although the most common packaging films are between 3 to 6 mils, sustainability and cost containment are driving engineers to design packaging films with thinner gauges and lighter basis weights. In highly competitive markets like syringes and pipettes, engineers spend a considerable amount of time determining the thinnest (i.e. lowest cost) film that can be used without the product wearing through the film. With this trend toward thinner gauges, the concern for abrasion induced failures increases. A different problem exists for overly cautious companies. Not willing to risk failures, they specify an over-engineered packaging system. This approach drives up the hidden cost of materials, processing and shipment of products as well as yielding excessive waste and increasing disposal costs. [2] TEST DESIGN CONSIDERATIONS The primary elements involved in simulating a wear system include apparatus design, specimen preparation, test protocol, and measurement. Whether or not a particular type of abrasion test correlates with end-use performance depends not only on a similarity of abrading mechanisms, but also on the extent to which that mechanism is maintained during the course of the test. [3] The instrument selected to evaluate the abrasion resistance of flexible packaging film incorporates Taber Industries’ Linear Abraser model 5750. The tip of the stylus abrades the cross-section of a film specimen in a linear rubbing action under controlled conditions of pressure and abrasive action. When breakthrough occurs, the test is automatically stopped. Resistance to abrasion is then calculated based on the number of abrasion cycles required to wear through the film. Through experimentation, it was determined that a conical stylus led to poor results. Conical styli compress into the film samples, and have a tendency to rip the film as opposed to abrade it. Also differences in the stylus point, whether caused by tip wear or manufacturing variances, had an impact on time to failure. Because the mechanism of wear depends upon the topography of the counter face abradant, the decision to use an interchangeable, standardized needle stylus resolved much of these problems. Already employed to evaluate scratch resistance for paints and coatings, the stylus chosen has a 1 mm diameter hemispherical tip and is made from 1/16” tool steel heat treated to HRC 55 – 61 with an 8 RMS finish. To eliminate the possibility of wear debris build-up on the tip, the stylus was cleaned with a solvent prior to each test. Consistent specimen tensioning was also found to be essential for generating repeatable results. If the film sample was mounted too loose, the stylus would “slide” the film instead of abrading it. If too much tension was applied, there was the possibility of stretching the film and tearing it. Three prototypes were explored before deciding on the current solution. The first was a “linear tension” device (figure 2) that incorporated springs to provide a tensioning force. This concept was found to be too costly to manufacture and too cumbersome to mount specimens.

Figure 2 - Linear Tension Device The second concept was a “radial tension” fixture (figure 3) that affixed the sample between two rings. The rings were positioned over a solid base and weights placed on the rings to tension the sample. This idea was rejected because the specimens tended to “ripple” during testing.

Figure 3 - Radial Tension Fixture

The third idea was a “mandrel” apparatus (figures 4 & 5) that eliminated much of the variability with the previous two tensioning mechanisms. This apparatus, now referred to as the Flexible Material Abrasion Kit, consists of a base cradle into which a mandrel is placed. A specimen approximately 1 inch wide is positioned over the mandrel, and a top plate secures the sample and mandrel to the base cradle. Two foam strips on the top plate press down on the sides of the material, holding it in place. Alignment holes are incorporated into the base cradle to ensure proper positioning such that the stylus will travel on the centerline apex of the mandrel.

Figure 4 - Front view of the Mandrel Apparatus

Figure 5 - Mandrel Apparatus

With accelerated testing, the contact pressure (applied load) involved to push the abrading stylus against the specimen during the rubbing action usually exceeds what is seen in the field. This standard approach subjects the test specimen to harsher conditions which compresses the time of laboratory testing. Depending on the type and thickness of the film sample, test loads were selected between 100 and 500 grams force. The sliding velocity of the stylus was set at 30 cycles per minute. An automatic shut-off feature was incorporated to stop the test once the cross-section of the film was abraded through and the stylus tip made first contact with the mandrel. This provides a conclusive end-point for the test. INITIAL TEST VALIDATION To help ensure that packages hold up to the rigors of distribution and keep the contents sterile, some medical firms use packaging materials that include multiple thin layers of nylon. Compared to other film materials, nylon can prevent packaging failures by providing better resistance to abrasion, punctures and flex cracking. [4] For this initial study, two operators each tested twelve samples of fourteen different types of packaging films, including some with nylon:

Bag films: • Mono layer LLDPE film (3, 4, 5 mils) • 7-layer co-extrusions of LLDPE and Nylon (4, 5 mils) Premade (lamination) pouch materials: • OPET/PE film (48 ga.OPET / 0.5 mils LDPE / 1.5 mils LDPE) • BON lamination (100 ga. BON / adhesive / 3 mil EVA blend) Forming films • 3 layer co-extrusion of EVA and Surlyn® (4, 6, 10 mils) • 7 layer nylon based forming film (3, 4, 6, 8, 10 mils)

Based on previous experience, the supplier of the test specimens hypothesized how the materials would compare. For the bag films, it was predicted that testing on the mono layer LLDPE film would show an increasing level of abrasion resistance as the film’s thickness increases. The 7-layer co-extrusion film is highly loaded with slip additives which reduce the coefficient of friction. This should decrease the rate of abrasion, resulting in a more wear resistant film as compared to mono layer LLDPE film. Regarding the premade pouch materials, the

hypothesis was that the BON lamination film would show higher abrasion resistance as compared to the OPET/PE film. And for the forming films, the testing should quantify the difference between the respective thicknesses of the 3 layer co-extrusion film. Given the 30% nylon content of the 7 layer film, results should show higher overall abrasion resistance compared to the 3 layer co-extrusion. The results of the validation study corresponded to the hypothesized rankings and proved this approach can provide good characterization of abrasion resistance for films within the same test setup. But while both operators ranked material performance similarly, it was interesting to note the results for operator 2 were significantly more consistent than operator 1. This suggested there were additional sources of variation that had not been anticipated when establishing the test protocol.

Cycles to Failure by Material Type - Operator 2

0 50 100 150 200 250 300 350 400

4 mil EVA/Ionomer/EVA

3.0 mil LLDPE

4.0 mil LLDPE

2.5 mil OPET/PE

6 mil EVA/Ionomer/EVA

3 mil Nylon/PE

4.0 mil PE/Nylon/PE

5.0 mil LLDPE

4 mil Nylon/PE

10 mil EVA/Ionomer/EVA

5.0 mil PE/Nylon/PE

6 mil Nylon/PE

4 mil BON/PE

8 mil Nylon/PE

Cycles to Failure

Figure 6 – Test Results; Operator 2

REDUCING TEST VARIATION A comparison of testing notes revealed that procedural differences were likely responsible for the majority of the deviations, with a considerable source of the variation being attributed to sample orientation. Orientation is extremely important when evaluating laminated films of multiple layers, such as those used for premade pouch films. Because these laminations may not have symmetrical cross sections, abrasion resistance will likely be different depending on which side the stylus is placed against. While operator 2 abraded through the sealant side for all films with sealant (the preferred orientation), operator 1 did not. Testing the sealant side permitted a “groove” to be worn in the material which allowed the other stronger layers (Nylon, BOPA a.k.a. BON, OPET) to be abraded through more consistently. Because the opposite side tends to be made of a tougher material, the samples generally tore rather than being abraded. The second procedural difference involved testing with different loads. Operator 2 utilized his experience and modified the procedure by tailoring the test load to specific materials. For a few specimens, the load was lightened (increased), depending on whether the film was more or less abrasion resistant. Although this did not impact the overall rankings, it did influence the cycles to failure thus preventing data points from being compared between operators.

Localized movement of the test sample was a consistent problem through all initial validation tests. Although the sample appeared to be adequately secured in the holder, too often there was slight movement of the film in the area where the stylus abrades. Following this testing, it was found that adhering a double sided adhesive tape to the inside portion of the top plate significantly reduced any local material movement. All films will have some grain or bias direction and typically have less thickness variation in the machine directional (approximately ±5%) as compared to cross direction (approximately ±10%). For the purpose of this testing, specimens were only tested in the machine direction. In an attempt to minimize the influence thickness might have on test results, specimens were measured prior to testing such that the exact thickness was known. COMMISSIONED TEST STUDY In 2007, a film converter was contacted by a customer asking for assistance to select a film that would provide optimum abrasion resistance. The customer had experienced issues with abrasion related pinholes in bags and had been tasked to identify a replacement film that would eliminate these complaints. Based on the preliminary success of Taber’s initial validation study, the converter commissioned a study to evaluate the abrasion resistance properties of 6 different bag films to support their recommendation (18 tests performed on both sealant and non-sealant sides). All test parameters established during the validation phase remained the same, with the exception of test load (450 grams-force). By incorporating the experiences learned during validation, an updated test procedure was employed. As predicted, the test results provided a ranking of abrasion resistance matching the expected performance of the film samples. This study provided the quantitative data to support the converter’s recommendation for an optimal film. The benefit of such an approach allowed the customer to reduce their material selection process by weeks, and conduct ISTA distribution testing with the confidence that the replacement film would pass the testing requirements. From the converter’s perspective, the study validated their film performance. But more importantly, it confirmed the test approach as a viable means to develop new abrasion resistant films that offer cost savings and provide greater sustainability.

Figure 7 – Data Plot - Commissioned Test

CONCLUSIONS The process of wear involves a complex combination of interrelated influences, thus making it extremely difficult to replicate “field” wear in a laboratory setting. In spite of this, accelerated wear testing has the potential to provide considerable insight into the various factors that contribute to a material’s performance. Film companies spend considerable amounts of time and money optimizing complex film designs with the required durability properties. The development of a suitable abrasion test method for flexible packaging films allows packaging engineers to better understand and predict the variables that influence failures. The implied benefits are that abrasion-induced failures can be minimized if abrasion test data is considered during the packaging selection process. Unfortunately, no laboratory abrasion test can guarantee success in the field, but having this data will certainly improve the packaging selection process. At the time this presentation was written, a proposed draft method was reviewed and commented by ASTM subcommittee F02.20 on Flexible Barrier Packaging Physical Properties. A single lab repeatability study will be conducted followed by a inter-laboratory round robin study to determine precision and bias. Following approval of the procedure, it is anticipated that the test method will be presented to the AAMI subcommittee for medical devices packaging with the goal of incorporating into ISO 11607, Packaging for Terminally Sterilized Medical Devices. [5] References 1. P. Nolan, Common Mistakes in Validating Package Systems, p. 112, MD&DI May 2006

2. R. Troutman, Consider the Basics When Developing Packaging, p. 102 MD&DI January 2007

3. A. Jaenecke, Wear Damage on Decorated Plastics – Techniques to Understand and Improve Your Testing, p. 2, ANTEC 2008

4. W. Leventon, The Big Picture in Packaging, p. 74, MD&DI January 2007

5. ISO 11607, “Packaging for Terminally Sterilized Medical Devices” (Geneva: International Organization for Standardization 2003).

Definitions used in this article:

BON – Biaxial Oriented Nylon EVA – Ethylene Vinyl Acetate HDPE – High Denisty Polyethylene Surlyn® - Trade name for DuPonts’s ionomer product LLDPE – Linear Low Density Polyethylene LDPE – Low Density Polyethylene MAH – Maleic Anhydride OPET – Biaxial Oriented Polyester PE – Polyehylene PET – Polyethylene Terephthalate PP – Polypropylene PA – Polyamide ULDPE – Ultra High Low Density Polyethylene ETO – Ethylene Oxide

Latest Developments in On-Line Measurement and Control of Multilayer Blown Films

Full Spectrum InfraRed (FSIR) and Air Ring

Presented byName: Doug WrightTitle: Director – Marketing and Business DevelopmentCompany: Thermo Fisher Scientific

Agenda

Problem statement

Review the original paper

Latest developments

Future Investigations

Questions

2008 PLACE Conference September 14-17, 2008

Portsmouth, VA

New Blown Film Measurement and Control

Presented by: Name Marty Lauginiger Title Regional Sales Manager Company Thermo Fisher Scientific

4

Problem Statement

For Multilayer Barrier FilmsWith the oscillating frame, difficult to map the measurement data back to the individual die Understanding and compensating for the natural twist angle between the die and the “frost” lineDon’t know how much of each polymer is being usedDon’t understand the material distribution Total measurement on the bubble is too slow for effective controlOn the bubble solutions contact the bubbleGetting a line under process control takes too long, creating excessive scrap and reduces overall production time

5

Typical Blown Film Line

Diagram Courtesy of Alpha Marathn

6

System Configuration

7

Why This Solution Unique?

FSIR provides material discrimination of key layers

Scans the collapsed tube (double layflat) and distinguishes between top and bottom

• Splitting the tube is not necessary

APC uses PI (Proportional-Integral) control on an annular die• Actuator are Viscosity Heaters

Rotational speed of the collapsing frame is measured using a high resolution quadrature encoder

• Accuracy is maintained via a reference input every rotation, at the home position

8

The Solution - Sensor

Full Spectrum Infrared (FSIR)

• Simultaneous software based analysis of a complete near infrared spectral range

• Discriminate between multiple components• Report individual layer thickness as well as overall thickness

Non nuclear

Invented the technology

• >20 years of providing FSIR technology to our customers to better understand therefore control their process

9

The Physics Behind IR Measurement - General

Absorption is stronger at certain wavelengths compared to others

Each material has unique absorption pattern

EVOH

weaker

STRONGER

10

FSIR Material Spectra

Absorbance spectra increases with increased weight

PE Surlyn PE and Surlyn

11

The Solution - Controls

21Plus! Operating SystemData Mapping:

• Film measured as a collapsed tube

• Speed:• Bubble rotational speed measured at the collapsing frame• Haul Off Speed is measured at the winder or other convenient location

• Distance from the rotational point to the measurement point is entered

• Monitored by the digital tachometer

• Rotational data is saved along with corresponding measurement point position during each scan of the collapsed tube

Dynamic Twist Angle algorithm determines twist angle under the frost line for superior mapping and reduces start-up time

Photo Courtesy: Macro Engineering

Photo Courtesy: Gloucester Engineering

12

Data Mapping Technique

Start with the collapsed bubble in a “layflat” position with the first data setData set rotates, due to tower/top nip oscillation, creating the second data setThe process continues, creating a set of simultaneous equations from which to refine the die mapping therefore improving material controlStarts resolving within 1 minute or 4 scans of the web

A CB D E

J HI G F

J BA C D

I GH F E

1ST Iteration

2ST Iteration

V XW Y Z

V XW Y Z

=A+J =C+H=B+I =D+G =E+F

=J+I =B+G=A+H =C+F =D+E

Bubble

Collapsed Bubble in “Layflat” Condition

13

The Solution

14

Results

Case Study: Poorly Centered Die

Before: 12% After: 4.7%

** Results based on an Oakland offline lab profiler with resolution of 5000+ points across the web

15

Results – Auto Die

Before: 3.0% (2σ)

After 45 Min: 1.3% (2σ)

5 Mil (127 μm) Barrier Film

>50% reduction in CD spread in ~45 minutes

16

Results – Auto Die

After 35 Min: 2.7% (2σ)

After 65 Min: 0.9% (2σ)

Start: 3.7% (2σ)

17

Air Ring

Situation: Upgrade of an auto Air Ring on an existing manual annular die

End Product: 3 different, 5 layer medical flexible package films with annual resin consumption of ~2,000 tons

Applied the same mapping measurement and control algorithms as with the viscosity heaters in the annual die

18

Customer Results – Air Ring

>75% reduction in CD spread in ~25 minutes

19

Customer Results – Air Ring

20

The Value – Air Ring or Viscosity Heaters

50-70% reduction in CD variations

60% reduction in time for product change-overs and restarts

50% scrap reduction at winder• Additional scrap reduction in downstream operations

21

Summary

New revolutionary solution for high performance, multilayer blown film lines

Proprietary mapping algorithm controlling critical barrier layer films

• Includes dynamic twist angle compensation

Much faster measurement feedback and control as compared to conventional designs

• ~45 minutes for viscosity heater• ~25 minutes for air nozzle

Typical CD reduction of > 50%

Does not require splitting the bubble onto two winders• Measures and distinguishes top and bottom plies of layflat

Have systems running at both end user and OEM sites

Offers significant annual resin, scrap, and time savings

22

Future Investigations

Does this new technique provide better uniformity over the traditional total thickness measurement combined with gravimetric resin monitoring?

23

Acknowledge

Macro Engineering – Ontario, Canada

Amcor Flexibles Healthcare – Mundelein, IL

Latest Developments in On-Line Measurement and Control of Multilayer Blown Films Full Spectrum InfraRed (FSIR) and Air Ring

Please remember to turn in your evaluation sheet...

Any Questions??

PRESENTED BY

Doug WrightTitle: Director – Marketing and Business DevelopmentCompany: Thermo Fisher Scientificdouglas.wright@thermofisher.com