RM 8456 is medical grade UHMWPE, stearate-free. Mechanical properties
are given for RM 8456. They have been evaluated to serve as a guide
in assessing the uniformity of the material. The mechanical properties
evaluated at NIST are shown in Table 1 of properties and are given
with the expanded uncertainty of the measurements of tensile specimens
taken from bars supplied by the manufacturer. Reference values and
uncertainties for Young’s modulus, yield strength, ultimate strength,
and elongation are shown in Table 1. Reference values are noncertified
values that are the best estimate of the true value; however, the
values do not meet the NIST criteria for certification and are provided
with associated uncertainties that may not include all sources of
uncertainty. Other properties given are stated by the manufacturer
that supplied the materials as complying with ASTM Specification F648:
F648-00e1 Standard Specification for Ultra-High-Molecular-Weight
Polyethylene Powder and Fabricated Form for Surgical Implants
Property Summary:
For references to the source data and detailed discussions of the
properties, please go directly to the Certificate of Analysis for
RM 8456:
The Mechanical Properties were obtained with the following test
protocol:
• Specimen fixed in grips starting at a zero load.
• Crosshead speed set at 50 mm/min.
• Load cell and extensometer specifications as described in
ASTM D 638-96, calibrated every 10 tests electronically, both before
and after the testing session,
with dead weights.
• Data collection rate set at maximum for the instrument.
Data Status: Validated (V)
Except where noted otherwise:
a) The uncertainty ,u, given is, u = standard deviation (SD) of
measurements with a coverage factor of 2; i.e.;
u = 2 x SD, which approximates a 95 % confidence interval.
Structure: UHMWPE is a semi-crystalline polyolefin polymer. The
bars that constitute RM 8456 were formed by ram-extrusion of particles
of UHMWPE that the manufacturer states are less than # 16 sieve
size (ASTM-E11 )which allows particles less than 1.180 mm in diameter
to pass through (the particles themselves are formed by the polymerization
of ethylene and in a consolidated state, in the consolidated form
these particles are referred to as grains).
Tribology Characteristics:
The wear behavior of RM 8456 was not determined because UHMWPE
is used for medical joint applications after it has been exposed
to ionizing radiation, either to sterilize the material or to improve
its wear resistance (or to achieve both results). The amount and
kind of ionizing radiation treatments vary considerably among manufacturers
of orthopaedic joint prostheses. Published results may be found
at links that follow the disclaimers.
DISCLAIMERS:
A substantial effort has been made to select links from this database
on the basis of sound scientific judgment. However, the National
Institute of Standards and Technology (NIST) makes no warranties
regarding their uses, and NIST shall not be liable for any damage
that may result from errors or omissions in the database.
Certain trade names and other commercial designations are used
in this work for the purpose of clarity. In no case does such identification
imply endorsement by the National Institute of Standards and Technology,
nor does it imply that products or services so identified are necessarily
the best available for the purpose.
External Links at which you may find other data on medical grade
UHMWPE:
The values presented. Estimated
combined relative standard uncertainties of the property values are
listed in the second column. For example, a value of 6.0 with ur =
5 % is equivalent to 6.0 +/- 0.30. A question mark, (?), for ur means
the uncertainty could not be determined with the available data.
