The increased analytical accuracy of modern equipment for polymer analysis has inevitably increased the scrutiny with which potential contaminants are detected and viewed. This is especially true in the medical device industry, where materials have intimate contact with the body such as implants, catheters and grafts. A number of polymers are used in medical applications, which can contain residual raw materials or by-products of production. In some cases, such as materials made of silicone or polyester-based polymers, these unwanted components can make up to several percent of the material, although this can be removed to some extent during manufacture. There are materials that can be used to remove impurities by dissolution and extraction. Hexane and methylene chloride are two such organic solvents, however they themselves often leave unwanted residues in the material and can alter its characteristics. Therefore, it is obvious that the use of scCO 2 will be extremely attractive in these applications and is already currently used in the production of a number of medical components.
The influence of scCO 2 swells the polymer molecules, this allows the fluid to penetrate deep into the component and dissolve any unwanted materials or solute trapped within it. The ability to dissolve materials increases with an increase of density, controllable through control of the system pressure and temperature. Of course when the pressure is reduced, all the carbon dioxide is also removed and unlike conventional liquid extraction, the residual solvent in the extracted material is...
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