ASTM F2003-02(2022)
(Practice)Standard Practice for Accelerated Aging of Ultra-High Molecular Weight Polyethylene After Gamma Irradiation in Air
Standard Practice for Accelerated Aging of Ultra-High Molecular Weight Polyethylene After Gamma Irradiation in Air
SIGNIFICANCE AND USE
4.1 This practice summarizes a method that may be used to accelerate the oxidation of UHMWPE components using elevated temperature and elevated oxygen pressure. Under real-time conditions, such as shelf aging and implantation, oxidative changes to UHMWPE after sterilization using high-energy radiation may take months or years to produce changes that may result in deleterious mechanical performance. The method outlined in this practice permits the evaluation of oxidative stability in a relatively short period of time (for example, weeks).
4.2 This practice may also be used to oxidize UHMWPE test specimens and joint replacement components prior to characterization of their physical, chemical, and mechanical properties. In particular, this practice may be used for accelerated aging of UHMWPE components prior to evaluation in a hip or knee joint wear simulator as outlined in Guide F1714 (hip wear), Guide F1715 (knee wear), ISO 14242 (hip wear), or ISO 14243 (knee wear), or combination thereof.
SCOPE
1.1 It is the intent of this practice to permit an investigator to evaluate the oxidative stability of UHMWPE materials as a function of processing and sterilization method. This practice describes a laboratory procedure for accelerated aging of ultra-high molecular weight polyethylene (UHMWPE) specimens and components for total joint prostheses. The UHMWPE is aged at elevated temperature and at elevated oxygen pressure, to accelerate oxidation of the material and thereby allow for the evaluation of its long-term chemical and mechanical stability.
1.2 Although the accelerated aging method described by this practice will permit an investigator to compare the oxidative stability of different UHMWPE materials, it is recognized that this method may not precisely simulate the degradative mechanisms for an implant during real-time shelf aging and implantation.
1.3 The accelerated aging method specified herein has been validated based on oxidation levels exhibited by certain shelf-aged UHMWPE components packaged in air and sterilized with gamma radiation. The method has not been shown to be representative of shelf aging when the UHMWPE is packaged in an environment other than air. For example, this practice has not been directly correlated with the shelf life of components that have been sealed in a low-oxygen package, such as nitrogen. This practice is not intended to simulate any change that may occur in UHMWPE following implantation.
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are for information only and are not considered standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2003 − 02 (Reapproved 2022)
Standard Practice for
Accelerated Aging of Ultra-High Molecular Weight
Polyethylene After Gamma Irradiation in Air
This standard is issued under the fixed designation F2003; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 It is the intent of this practice to permit an investigator
1.6 This international standard was developed in accor-
to evaluate the oxidative stability of UHMWPE materials as a
dance with internationally recognized principles on standard-
function of processing and sterilization method. This practice
ization established in the Decision on Principles for the
describes a laboratory procedure for accelerated aging of
Development of International Standards, Guides and Recom-
ultra-high molecular weight polyethylene (UHMWPE) speci-
mendations issued by the World Trade Organization Technical
mens and components for total joint prostheses. The UHM-
Barriers to Trade (TBT) Committee.
WPE is aged at elevated temperature and at elevated oxygen
pressure, to accelerate oxidation of the material and thereby
2. Referenced Documents
allow for the evaluation of its long-term chemical and me-
2.1 ASTM Standards:
chanical stability.
D883 Terminology Relating to Plastics
1.2 Although the accelerated aging method described by
F648 Specification for Ultra-High-Molecular-Weight Poly-
this practice will permit an investigator to compare the
ethylene Powder and Fabricated Form for Surgical Im-
oxidative stability of different UHMWPE materials, it is
plants
recognized that this method may not precisely simulate the
F1714 Guide for GravimetricWearAssessment of Prosthetic
degradative mechanisms for an implant during real-time shelf
Hip Designs in Simulator Devices
aging and implantation.
F1715 Guide for Wear Assessment of Prosthetic Knee De-
1.3 The accelerated aging method specified herein has been
signs in Simulator Devices (Withdrawn 2006)
validated based on oxidation levels exhibited by certain shelf-
2.2 ISO Standards:
aged UHMWPE components packaged in air and sterilized
ISO 5834 Implants for surgery—Ultra-high molecular
with gamma radiation. The method has not been shown to be
weight polyethylene
representative of shelf aging when the UHMWPE is packaged
ISO 14242 Implants for surgery—Wear of total hip joint
in an environment other than air. For example, this practice has
prostheses
not been directly correlated with the shelf life of components
ISO 14243 Implants for surgery—Wear of total knee joint
that have been sealed in a low-oxygen package, such as
prostheses
nitrogen. This practice is not intended to simulate any change
that may occur in UHMWPE following implantation.
3. Terminology
1.4 The values stated in SI units are to be regarded as
3.1 Definitions—For definitions of terms in this practice
standard. The values given in parentheses are mathematical
relating to plastics, refer to Terminology D883. For definitions
conversions to inch-pound units that are for information only
of terms in this practice relating to UHMWPE, refer to
and are not considered standard.
Specification F648 and ISO 5834.
1.5 This standard does not purport to address all of the
3.2 Definitions of Terms Specific to This Standard:
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ThispracticeisunderthejurisdictionofASTMCommitteeF04onMedicaland Standards volume information, refer to the standard’s Document Summary page on
Surgical Materials and Devices and is the direct responsibility of Subcommittee the ASTM website.
F04.15 on Material Test Methods. The last approved version of this historical standard is referenced on
Current edition approved Nov. 15, 2022. Published November 2022. Originally www.astm.org.
approved in 2002. Last previous edition approved in 2015 as F2003 – 02 (2015). Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
DOI: 10.1520/F2003-02R22. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2003 − 02 (2022)
3.2.1 oxidation, n—theincorporationofoxygenintoanother ture within the thermal chamber shall be measured using
molecule (for example, UHMWPE) by means of a chemical thermocouplesandverifiedtobelessthan 61 °C.Notethatthe
reaction, resulting in the formation of a chemical covalent thermal chamber will need to be sufficiently large to accom-
bond. modate the pressure vessel described in 5.2.
3.2.2 oxygen bomb, n—a pressure vessel suitable for pre-
5.5 Temperature Controller—The combined apparatus or
conditioning of UHMWPE at an elevated temperature and
thermal chamber shall be equipped with a temperature control-
partial pressure of oxygen.
ler capable of controlling the heating rate with an accuracy of
0.1 °C⁄min.
4. Significance and Use
NOTE 2—Temperature stability and test interruption has been shown to
4.1 This practice summarizes a method that may be used to
significantly influence the outcome of accelerated aging studies.
accelerate the oxidation of UHMWPE components using
Consequently, the pressure vessel must maintain nearly constant tempera-
elevated temperature and elevated oxygen pressure. Under ture (that is, within 61 °C) throughout the duration of the testing period,
or the results may not be reproducible or may be unreliable.
real-time conditions, such as shelf aging and implantation,
oxidative changes to UHMWPE after sterilization using high-
6. Test Specimens
energy radiation may take months or years to produce changes
6.1 The test specimens shall be prepared in final form
that may result in deleterious mechanical performance. The
according to the requirements of any subsequent physical,
method outlined in this practice permits the evaluation of
chemical, or mechanical tests to be performed after accelerated
oxidative stability in a relatively short period of time (for
aging. For example, if the specimens will ultimately be
example, weeks).
subjected to hip joint simulation, they should be prepared in
4.2 This practice may also be used to oxidize UHMWPE
final form according to Guide F1714 and ISO 14242.
test specimens and joint replacement components prior to
6.2 Finished specimens shall not be machined after accel-
characterization of their physical, chemical, and mechanical
erated aging of (bulk) stock materials, because the accelerated
properties. In particular, this practice may be used for acceler-
oxidation procedure outlined in this practice will result in an
ated aging of UHMWPE components prior to evaluation in a
inhomogeneous distribution of chemical, physical, and hence
hip or knee joint wear simulator as outlined in Guide F1714
mechanical properties through the thickness of an aged part.
(hipwear),GuideF1715(kneewear),ISO 14242(hipwear),or
ISO 14243 (knee wear), or combination thereof.
6.3 Test specimens shall be removed from their packaging
prior to accelerated aging, because this practice is not intended
5. Apparatus
to reproduce the aging of UHMWPE that is stored in a
5.1 Combined Apparatus—An oxygen bomb (pressure ves-
low-oxygen environment.
sel) apparatus that is capable of maintaining the desired
7. Validation of Apparatus
temperature with an accuracy of 62 °C by itself may be used,
providing it incorporates the requirements of 5.2 – 5.4.
7.1 Thermal Chamber Validation—Using the calibrated
temperature sensor, validate the temperature of the accelerated
5.2 Pressure Vessel—If a combined apparatus is not used, it
will be necessary to enclose the specimens within a pressure aging apparatus to within 61 °C of the aging temperature.
7.1.1 Verify the calibration of the temperature sensor(s) that
vessel, also known as an “oxygen bomb,” capable of with-
standing a static pressure of 690 kPa (100 psi). The pressure will be used to validate the thermal conditions in the acceler-
ating aging apparatus. The temperature sensor shall be cali-
vessel shall be manufactured from stainless steel. The pressure
vessel shall be equipped with either a regulator or a safety brated as defined in the manufacturer’s instructions.
release valve to maintain the internal pressure to the desired
7.2 Pressure Vessel Validation—Verify the integrity of the
value,whenatequilibrium,toanaccuracyof 67kPa(61psi).
pressure vessel to within 67 kPa (61 psi) by conducting the
following 14 day (336 6 1 h) validation test:
5.3 Because oxygen-air mixtures will be maintained at
elevated temperatures for weeks at a time, it is recommended 7.2.1 Increase the pressure of pure oxygen inside the vessel
by 503 kPa (73 psi) at 70 6 1 °C.
that a laboratory that is performing aging at elevated pressure
take appropriate safety precautions. For this reason, the use of 7.2.2 Throughout the duration of the validation test, the
a commercially available and properly validated “oxygen gage pressure shall not vary by 67 kPa (61 psi).
bomb” is recommended. The pressure vessel must be of 7.2.3 Pressure vessels that are not capable of maintaining
suitable construction such that it does not leak, thereby leading the target gage pressure within the stated tolerance shall be
considered invalid for the purposes of accelerated aging until
to the reduction of pressure during the two-week aging period.
NOTE 1—Oxygen flow and test interruption have been shown to
the excessive leaking has been rectified.
significantly influence the outcome of accelerated aging studies.
7.3 The thermal chamber and pressure v
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