Development of Polyurethane-Based Sheets by Phase inversion Method for Therapeutic Footwear Applications: Synthesis, Fabrication, and Characterization

It has been proved that polyurethane (PU) foam and viscoelastic PUs are offering better Cushioning and shock absorption properties than other materials such as foam rubbers, polyethylene, ethylene vinyl acetate, and polvvinyl chloride which are used currently as insole materials in therapeutic footwear for diabetic and orthopedic patients to "offload" or redistribute high pressure under the foot. The aim of this research work was to prepare viscoelastic materials based on PUs having the highest degree of phase separation that provides for the elastomeric nature of these polymers. Polymer structures with a high concentration of amide groups can be made with the addition of hydrazine or a diacid hydrazide to a diisocyanate. We had prepared various PUs by chain extending the isocyanate-terminated prepolymer with terepthalic dihydrazide, 5-hydroxy isothalic dihydrazide, and 1,4-butanediol. Polymers were developed into sheets by phase inversion method using dimethyl formamide as solvent and water as nonsolvent. To improve the mechanical properties of PU sheets the polymer solution was blended with polyester-based PU Desmopan 8078 (CPU) in 1 : 1 ratio and the solution mixture was developed into sheet by the same method. Further PU sheets based on only CPU were also developed with various concentrations of PU. The synthesized PU and their blends with CPU were characterized by infrared spectroscopy, differential scanning calorimetry, thermo gravimetric analysis, get permeation chromatography, and dynamic mechanical analysis. Morphological characteristic's of PU sheets were Studied by scanning electron microscopy. (c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 2387-2399, 2009