ASTM F2183-02 Standard Test Method for Small Punch Testing of Ultra-High Molecular Weight Polyethylene Used in Surgical Implants

The standard “ASTM F2183-02 Standard test method for small punch testing of ultra-high molecular weight polyethylene used in surgical implants” developed by the American Society for Testing and Materials (ASTM) describes a test method for determining the mechanical behavior of ultra-high molecular weight polyethylene (UHMWPE) by small punch testing of miniature disk specimens (0,5 mm thick and 6,4 mm in diameter). This test method is designed to:

• Characterizing UHMWPE surgical materials after ram extrusion or compression molding
• To evaluate implants manufactured after radiation cross-linking and sterilization
• Testing implants that have been removed from the human body

The parameters of the small puncture test, i.e., peak load, ultimate displacement, ultimate load, and work to fracture, provide measurements of yield, ultimate strength, ductility, and toughness of UHMWPE under multiaxial loading conditions. Since the mechanical behavior of UHMWPE is different when loaded under uniaxial and multiaxial loading conditions, the small puncture test provides a complementary mechanical testing technique to the uniaxial tensile testing specified for medical grade UHMWPE by the standard “ASTM F648-21 Standard Specification for Ultra-High Molecular Weight Polyethylene Powder and Manufactured Form for Surgical Implants”.

In addition to being used as a research tool in implant take analysis, the small puncture test can be used as a laboratory screening test to evaluate new UHMWPE materials, such as those created by gamma or electron beam irradiation. This test method is also highly suitable for the characterization of UHMWPE before and after accelerated aging and, in this context, can provide a ranking of the mechanical degradation of different UHMWPE samples after oxidative degradation.

Small punch testing has been applied to other polymers, including polymethyl methacrylate (PMMA), bone cement, polyacetal, and high-density polyethylene (HDPE). However, small punch testing of polymers other than UHMWPE is outside the scope of this standard.

Microsample testing techniques are used to characterize the mechanical behavior of UHMWPE stock materials and surgical implants after manufacturing, sterilization, shelf life, radiation crosslinking, thermal processing, and implantation. Additionally, experimental UHMWPE materials can be evaluated after accelerated aging and hip or knee wear simulation.

As a result, small punch testing is used to determine relationships between abrasion performance and mechanical behavior of UHMWPE. This test method can also be used to rank the mechanical behavior of UHMWPE against a reference control material. Small punch test results may vary depending on sample preparation, test speed, and test environment. Therefore, if a precise comparison is required, these factors must be adjusted correctly.

The equipment used in these tests includes:

• The small punch tester consists of a hemispherical punch, die and punch guide. Each part is made of hardened steel. The guide is used to align the axis. The inner diameter of the guide hole is 2,57 mm, the depth of the concave part of the sample is 0,51 mm, and the diameter is 6,40 mm. The function of the die is to hold the sample during testing. The die hole inner diameter is 3,81 mm. The hemispherical head punch diameter is 2,50 mm.
• The testing machine is a suitable machine consisting of a drive mechanism and a load indicating device as described in the standard “ASTM D695-15 Standard test method for compressive properties of rigid plastics”. The load indicating device has a capacity of 250 N. The accuracy of the device shall be verified at least annually.
• The tests also use a compression meter to measure the length between the die and the punch during the test. If the displacement of the test device itself differs by less than 1 percent from the value measured by a properly calibrated compression meter, the displacement of the device may be used.
• The compression plate is connected to a compression plate or tool that transfers the load.
• The resolution of the micrometer used to measure the sample diameter and thickness is 0,0025 mm.
• A thermometer or thermocouple that measures the test temperature in the range of 20-24 degrees should be able to measure to 0,1 degrees.

Among the numerous testing, measurement, analysis and evaluation studies that our organization has provided for businesses in various sectors, our organization also provides testing services defined in the standard “ASTM F2183-02 Standard test method for small punch testing of ultra-high molecular weight polyethylene used in surgical implants” with its trained and expert staff and advanced technological equipment.