Carbon dioxide enhances artificial joints

22 April, 2010, 16:18

Special treatment of high-performance polyethylene turns it into a porous material, which can be used to make artificial joints rivaling the natural thing.

The rigid ultra-high molecular weight polyethylene (HMPE) has long been used in a number of applications, from sports equipment to body armor. It is also the material of choice for artificial joints and other medical implants, due to its high resistance to corrosion and low friction.

Now, researchers at the Institute of Organo-elemental Compounds in Russia have found a way to make the material even better, reports journal Nanozhurnal. They treated HMPE particles in a carbon dioxide environment with a high temperature and pressure. In the conditions, the CO2 turned into a so-called supercritical fluid, when it has some properties of both gas and liquid.

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In the polyethylene, the carbon dioxide caused small cavities varying in size between 5 and 15 nanometers to form. This “nanoporous” polyethylene is twice as slippery as its normal version, but retains its rigidity. An artificial joint made of this improved polyethylene will be as easy to bend as the natural one, scientists say.

Based on the new material, the researchers have also developed two composite versions – one with silver and gold nanoparticles, and another with acryl polymer. The technology could be available commercially in two years.