ASTM F2381-19

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Designation: F2381 − 10 F2381 − 19
Standard Test Method for
Evaluating Trans-Vinylene Yield in Irradiated Ultra-High
Molecular Weight Polyethylene Fabricated Forms Intended
for Surgical Implants by Infrared Spectroscopy
This standard is issued under the fixed designation F2381; 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
1.1 This test method describes the measurement of the number of trans-vinylene groups in ultra-high molecular weight
polyethylene (UHMWPE) intended for use in medical implants. The material is analyzed by infrared spectroscopy.
1.2 This test method is based on Guide F2102.
1.3 The applicability of the infrared method has been demonstrated in other literature reports. This particular method, using the
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intensity (area) of the C-H absorption centered at 1370 cm to normalize for the sample’s thickness, will be validated by an
Interlaboratory Study (ILS) conducted according to Practice E691.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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 safety, health, and healthenvironmental 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.
2. Referenced Documents
2.1 ASTM Standards:
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E1421 Practice for Describing and Measuring Performance of Fourier Transform Mid-Infrared (FT-MIR) Spectrometers: Level
Zero and Level One Tests
F2102 Guide for Evaluating the Extent of Oxidation in Polyethylene Fabricated Forms Intended for Surgical Implants
3. Terminology
3.1 Definitions:
3.1.1 trans-vinylene index (TVI)—a trans-vinylene index is defined as the ratio of the area of the absorption peak centered near
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965 cm to the area of the absorption peak centered near 1370 cm .
3.1.2 depth locator (DL)—a measurement of the distance from the articular surface, or surface of interest, that a spectrum was
collected and a corresponding TVI calculated.
3.1.3 trans-vinylene index profile—a trans-vinylene index profile is defined as the graphical representation of variation of the
sample’s trans-vinylene index with distance from its articular surface or the surface of interest. This is a plot of TVI versus DL.
Typically, the graph will show the profile through the entire thickness of the sample.
4. Significance and Use
4.1 Published literature shows that the yield of radiolytic reactions that occur during radiation treatment increases with radiation
dose level. Measurement of the products of these reactions can be used as an internal dosimeter.
This test method is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.15 on Material Test Methods.
Current edition approved June 1, 2010Oct. 1, 2019. Published July 2010November 2019. Originally approved 2004. Last previous edition approved in 20042010 as
F2381–04.–10. DOI: 10.1520/F2381-10.10.1520/F2381-19.
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 Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2381 − 19
4.2 Trans-vinylene unsaturations are formed during ionization treatment by abstraction of a hydrogen molecule, and to a lesser
extent by the recombination of two adjacent alkyl free radicals that reside on the same chain.
4.3 Previous work generated calibration curves of trans-vinylene absorption area as a function of absorbed radiation dose,
yielding a linear relationship for both gamma- and electron beam-irradiated polyethylene.
4.4 This data can be used to determine received dose as a function of position, assuming a calibration curve (TVI versus
radiation dose level) is known for the particular material and radiation conditions used, and can be used to determine uniformity
of dose level in irradiated polyethylene.
5. Apparatus
5.1 Infrared Spectrometer:
5.1.1 A calibrated infrared spectrometer capable of recording a transmission absorption spectrum over a minimum range of 900
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to about 2000 cm using about 200 μm-thick films at a resolution of 4 cm and an aperture of approximately 200 by 200 μm for
a rectangular aperture, or 200 μm diameter for a circular aperture.
5.1.1.1 Other modes of collection (that is, reflection, attenuated total reflection (ATR), and so forth) and aperture and sampling
step sizes may be used to generate the sample’s absorption spectrum provided they can be demonstrated to produce equivalent
results. Too large an aperture can result in a loss of profile accuracy.
5.1.1.2 When a Fourier Transform Infrared (FTIR) spectrometer is used, a minimum of 32 scans shall be collected per spectrum
as a default. A fewer number of scans may be performed if a user can verify that their FTIR spectrometer can reproducibly measure
the TVI with less than a 5 % difference in TVI compared with the default number of scans. In no case shall a TVI be reported
based on fewer than 8 scans per spectrum.
5.1.1.3 The FTIR instrument and sample compartment should be purged with a moisture- and carbon-dioxide-free inert gas (for
example, nitrogen, helium, or argon) to minimize spectral interference from these components.
5.2 Specimen Holder—Equipment, such as an x-y table, capable of accurately positioning the sample under the FTIR aperture
with a minimum resolution at the scale of the aperture dimensions.
5.3 Microtome—Equipment capable of producing films of thickness 200 μm or less of a sample perpendicular to the articular
surface or the surface of interest.
6. Sampling, Test Specimens, and Test Units
6.1 Using a microtome, or other appropriate device, prepare a thin slice of the sample about 200 μm thick. If the detected signal
from the FTIR is too weak with this thickness, a thicker sample may be used.
6.2 The slice shall typically be taken near the center of the sample’s articular surface or the surface of interest.
6.3 The orientation of the slice shall typically be perpendicular to the articular surface or the surface of interest.
6.4 Waviness in the infrared spectrum caused by Fourier rippling on the lower wavelengths can interfere with the trans-vinylene
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absorbance at 965 cm . This rippling is caused by internal reflection of the infrared beam, and can be avoided by lightly rubbing
the sample film against 400 grit sandpaper until the film becomes translucent. This roughening procedure should be done slowly
to avoid heating the film, and should be performed until the area under a single peak due to Fourier rippling is less than 10 % of
the area under the trans-vinylene peak.
7. Preparation of Apparatus
7.1 Prepare the infrared spectrometer for collection of a transmission absorption spectrum from a thin film of the UHMWPE
sample according to the manufacturer’s recommendations, Practice E1421, and the conditions described in 5.1.
8. Procedur
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