Abstract: A process for the preparation of polyurethane resins particularly suitable for electrostatic spinning which comprises forming a prepolymer of polyether glycol and a diisocyanate reacted in a molar ratio of about 1:2, and thereafter reacting the prepolymer with additional diisocyanate and a diol extender, the final molar ratio of the polyether, isocyanate and diol reactants being approximately 1:3.7:2.5. The reaction is conducted in an organic solvent at a temperature of about 45.degree. C. to obtain a polymer having an inherent viscosity of from about 2.0 to 2.4 in a solution of 25 to 30 percent solids. The solution is diluted to about 15 percent solids prior to spinning.

Abstract: A process for setting in a desired shape a product at least a portion of which comprises electrostatically spun fibres is disclosed. The process comprises maintaining the product in the desired shape at a temperature below the melding temperature of the electrostatically spun fibres. The desired shape may be the as-spun shape of the product or a shape obtained by deformation of the product, i.e. the product is reshaped. The fibres preferably comprise a polyurethane and reshaping is preferably effected on a former. The reshaped product may be employed as a vascular prosthesis.