Surface characterization techniques for polyurethane biomaterials

Lubrizol Advanced Materials Inc., Brecksville, OH, USA Corresponding author asterphoenix gmail.com 

Disclaimer Mention of trade names or commercial products in this chapter is solely for the purpose of providing specific information and does not imply endorsement by Lubrizol Corp. 

Using medical devices such as catheters, angioplasty balloons, pacemaker leads, and cardiovascular stents usually involves insertion of such devices into urinal tracts or blood vessels. During insertion, high surface lubricity of Ihe devices helps to facilitate the insertion process and reduce insertion-associated tissue damage, which benefits both the patient and the surgeon. Early approaches to decrease insertion friction involve using lubricants such as olive oil and silicon oil, or low friction materials like polyethylene. Due to the superior mechanical properties, polyurethane is extensively used in catheters/baUoons and it is desirable to improve the lubricity of polyurethane materials. 

In modem theory of friction, 90% of the total friction is believed to come from interatomic adhesion between two surfaces [8], If the interatomic adhesion is weakened, the friction force could be reduced. If water, the most abundant fluid in the body, easily wets the polymer surface and creates a thin layer between two surfaces to eliminate soUd/solid contact, the friction force could be significantly reduced. Therefore, a general approach of friction reduction is to increase the surface hydrophiUcity of polyurethane by coating or by surface chemical modification [9-22]. 

Gu et al. [23] used ozone to pretreat a Pellethane surface and later functionalized the surface with polyacrylic acid. The surface hydrophilicity of Pellethane thermoplastic polyurethane ( TPU ) is significantly improved by showing a much lower water contact angle (CA 25° vs 92° of pure Pellethane TPU, for CA test, please see Section 2.2) The COF of the modified surface was as low as 0.1. 

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