Medical Applications of Polyurethane

Polyurethanes have a wide variety of uses, but in terms of mass of material used, polyurethane represents only a small fraction of the synthetic polymer use in medical applications (Lamba et al., 1998); in fact it would seem that PVC is the most common medical polymer, largely due to its use in disposable devices, such as blood tubing and blood storage bags. Other major materials commonly used include polystyrene, polyethylene, and polypropylene. This however, underplays the importance of the polyurethanes; where complex mechanical and biocompatibility problems occur polyurethane is often the material of choice. Polyurethane has been used for example as a coating for cardiac pacemaker leads, as a coating for breast implants, in vascular devices, such as intra aortic balloons, and for gastric balloons. It is also often used for catheters and other general purpose tubing. However, in this respect, it should be noted that often the material requirements are rather stringent, particularly in terms of surface quality as shown in Fig. 3.1. Inflatable polyurethane implants can be used to aid sufferers of erectile dysfunction. The polymer is also used for wound dressings, such as Tegadermâ„¢ (manufactured by 3M), and for tissue adhesives (Gogolewski, 1989). It should also be noted that the ubiquitous nature of this material in clothing means that it is used in peripheral applications such as surgical drapes. Polyurethane is also used as an alternative to latex, to make disposable gloves and condoms (though strictly this is not a medical application; Bhattacharya et al., 1996).

Since polyurethane is generally more expensive than many bulk polymers, such as those mentioned in the previous paragraph, an obvious question is why use it? It is this question that this article is intended to address. In some cases the answer is simple. In the case of disposable gloves and condoms, this material provides an alternative to latex; latex allergy has become an increasing problem, to the extent that latex gloves, particularly the close fitting kind are being increasingly phased out of use. The use in foam dressings stems from the ability to produce hydrophilic foams which have an enhanced ability to soak up and

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