M e d i c a l D e v i ce & D i a g n o s t i c I n d u s t r y

A Canon Communications LLC Publication October 2006

R

Packaging

Choosing the Right

Sample Size for Integrity

Testing, p.80

International Regulation

Updates on Asia: CurrentRegulatory Practices, p. 106

Software

Making an MES Work forQuality and Productivity, p. 92

MD&MMINNEAPOLIS

Package Testing

Principles of Proper AgingMethods, p. 116

Coverage begins on p. 170

MD&MMINNEAPOLISMD&MMINNEAPOLIS

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Medical device manu-facturers invest agreat deal of time

and money to ensure thattheir products meet bothproduct performance needsand FDA guidelines. The se-lection of the appropriatepackaging materials andforms is among the criticaldecisions that need to bemade when bringing a prod-uct to market.

Manufacturers need pack-aging materials that providea microbial barrier and last-ing device protection over anextended period. Packagingwith these benefits delivers durabilityand safety from the manufacturerthrough storage and transport to theend-user.

Accelerated aging is a critical test fordocumenting the expiration dates formedical products.1 It is essential to un-

derstand how to properly test materials.Using copolyester as an example, thisarticle focuses on the conditions and re-quirements for proper accelerated aging.

The Need for Accelerated AgingConsideration of key variables at the

beginning of the packaging specifica-tion process is essential to guaranteeingmedical packaging integrity. Aging in-formation, including physical, thermal,and optical performance over time, isimperative for ensuring package in-tegrity. Obtaining this information also

helps to satisfy current FDA validationrequirements and provide evidence ofsterility and fitness-for-use over a prod-uct’s life cycle.

For example, when a product needs afive-year shelf life to allow time for dis-tribution, storage, and other constraints,the quality of the package-devicecombination should be monitored. Ob-serving the effects of time throughaccelerated-aging studies on a product-package combination can decrease thetime it takes to introduce a product inthe marketplace. Material exposure to P

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ACCELERATED AGING >>

The Need forSpecificity inAccelerated AgingTo maximize the benefits of copolyester plastics as packaging materials,manufacturers need to understand and use proper aging methods.

Glenn Petr ie

Glenn Petrie is field marketing devel-opment manager for medical packag-ing and tubing, SF&S specialty plas-tics, engineering, and specialty pro-grams at Eastman Chemical Co. (NewYork City).

Materials must provide a microbial barrier over an extended period.

an elevated temperature for a shortperiod of time ages a package-devicecombination to the same extent aswould be observed were it exposed toroom temperature for a longer period oftime (time-temperature superposition).

The American Society for Testing andMaterials (ASTM) has establishedguidelines to contribute to the reliabili-ty of materials, promote public health,

and improve quality of life. Accelerated-aging testing is done based on ASTMF1980-02 standard guidelines and in-corporates factors such as time at am-bient (room) temperature, accelerated-aging temperature, and ambienttemperature into a test equation.

Changes in relative humidity duringtesting away from standard laboratoryguidelines of 50% rh may affect theaging results. The ASTM guidelinessuggest that low- and high-humidityenvironments might need to be con-sidered in testing protocols. Industryconcern over relative humidity effectson physical aging has put the standardunder review. Because the effects arenot well known, most labs performtests at 50% rh.

An integral part of this testing on plas-

tics, including copoly-esters, is physical aging.As a plastic is held belowits glass transition (Tg)temperature, its physi-cal properties can im-prove or deteriorate overtime. It is essential thataccelerated-aging studiesbe performed properlysince each plastic materi-al ages differently. Fail-ing to perform or im-properly conductingaccelerated-aging testingon a medical deviceproduct–package combi-nation can lead to incor-

rect data and quality issues that canaffect the health and safety of end-users.

Accelerated Physical AgingPhysical aging is a process of molec-

ular relaxation that occurs in all amor-phous polymers held below their Tg

temperature. Aging has been observedin polyvinyl chloride (PVC), poly-styrene, styrene acrylonitrile (SAN),and polycarbonate, as well as incopolyester polymers. This discussionfocuses on the effects of aging oncopolyester polymers.

When a polymer is rapidly cooled tobelow its Tg level, which occurs in allcommercial melt-phase processingtechniques, it freezes into a nonequi-librium conformation with excess freevolume. In an attempt to attain equi-librium, the molecular chains rearrange

themselves into a denser structure, re-ducing the free volume of the system.Although this densification is difficultto detect, it directly affects other ther-modynamic and mechanical propertiesthat are easier to measure and can,therefore, be used to track the extent ofaging over time.

These properties increase in linearfashion with the log of aging time. Theaging process proceeds more quicklyat higher temperatures closer to thecopolyester’s Tg temperature. Thesetrends are consistent with other similarviscoelastic molecular relaxation pro-cesses, such as rheological behavior. Aswith other relaxation processes, timeand temperature can relate through theprinciple of time-temperature super-position. Molecular motions that occurover a given period of time at one tem-perature are equivalent to motions thatoccur over a longer time period atlower temperatures. Simply stated, anelevated temperature acts as a catalystfor the rate of motion.

Accelerated Aging of CopolyestersCopolyester plastics possess excel-

lent final application properties suchas long-term clarity and toughness.Using accelerated-aging testing oncopolyesters that are used in medicalpackaging helps manufacturers to cap-italize on these benefits. The ASTMguidelines suggest using an accelerat-ed aging (Q10) factor of 2.0 as a con-servative estimate for aging the pack-aging and device. The guidelines also

ACCELERATED AGING >>

Proper accelerated aging is necessary for ensuring productquality.

Accelerated aging is a critical test for documenting the expiration dates for medical products.

Table I. Accelerated physical aging data of copolyester Eastar 6763.

SIMULATED AGE/AGING ACCELERATED AGING TIME (HOURS)

TEMP. 165 17 20 12 7 3 2YEARS YEARS MONTHS MONTHS MONTHS WEEKS DAYS

23°C 1,400,000 150,000 15,000 8,800 5,100 500 48(74°F)

30°C 290,000 30,000 3,000 1,800 1,000 100 10(86°F)

40°C 30,000 3,100 300 180 110 10 1.0(104°F)

50°C 3,000 310 31 18 11 1.0 —(122°F)

60°C 310 32 3.1 1.9 1.1 — —(140°F)

65°C 99 10 1.0 0.6 — — —(150°F)

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