By Patrick Vermette
The authors of this booklet talk about polyurethanes utilized in various biomedical functions. Polyurethanes shape a wide family members of polymeric fabrics with a tremendous range of chemical compositions and homes the big variety of houses that may be completed with polyurethane chemistry has attracted the eye of builders of biomedical units who see promise within the mechanical flexibility of those fabrics mixed with their excessive tear power.
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Additional resources for Biomedical Applications of Polyurethanes (Tissue Engineering Intelligence Unit)
This is especially true near defects in a piece or in the vicinity of stress concentrators like holes, cuts or sharp angles. 87 Annealing relieves the residual stresses in a polymer by heating it to predetermined temperature, keeping it at this temperature for a preset period of time, and slowly cooling it down as a suitable rate. 88 Moreover, it is important to note that PUs absorb water. Moisture content must be kept as low as possible, particularly in melt processes. 89 In general, soft materials are processed at lower temperature than hard materials.
25 mm in thickness. They are made principally of rigid urethane and are used mainly for packaging or as surface modifier for water vapor permeability control. 80 Films are mainly produced by solution casting. The polymer must be completely dissolved to make a clear solution in order to obtain films that are clear and free of bubbles. When using a dipping process, the key to obtain a consistent thickness is to control the viscosity of the solution and the solids’ concentration. 5 Sterilization The ability of being sterilized while keeping its integrity is an essential requirement for all medical polymers.
Interest in isocyanates and polyurethanes grew gradually in the United States with the introduction of PU elastomers (1950) and flexible foams (1952) by Bayer. In their early years, polyurethanes were characterized by their good properties but high prices. The arrival of flexible polyurethane foams with high strength and low densities insured large-scale production of PU materials and their precursors. Between 1952-1954, Bayer developed a diisocyanate-polyester flexible foam suitable for the continuous commercial production of Moltopren.