Polyurethane Based Materials with Applications in Medical Devices

Polyurethane materials have a huge role in everyday materials, for example, as foams they are used in car and household furnishings; the polymer is used in the construction industry, in the manufacture of footwear, and for coatings and adhesives, as well as in textiles. The demand for polyurethane materials is high (Biesman, 2002). Thus in a number of everyday guises and in specialist devices, polyurethanes play a vital role in medicine and are involved at all scales, from the construction materials used to build the wards through to bedding, surgical instruments, medical implants and ultimately microscale encapsulation devices. In this article, however, we shall focus largely on those structural devices which come into contact with the patient, for which the property of biocompatibility must be added to the other properties required such as flexibility, strength, and of course processibility. This places substantial additional demands on a material and a restricted range of synthetic organic polymers have been used in a wide variety of medical applications. Of these many materials, polyurethanes have attracted particular interest; firstly because the diisocyanate and diol monomers can be altered to provide materials with widely differing properties, such as melting or softening point andmechanical strength; secondly, other modifications such as the introduction of diamines to provide thermoplastic elastomers, or the combined use of multifunctional diols and foaming agents to produce rigid or flexible foams allow for the production of materials with the widest possible range of morphologies. In addition to the widely tunable physical properties, it has been found that thesematerials can also bemade to be substantially biocompatible, but where required can be made to biodegrade. Thus almost uniquely polyurethanes have the potential to be used both for permanent medical implants and to be used in systems where degradation is required such as scaffolds for tissue regeneration.