Abstract: A process for producing a rigid orthopedic cast in which a bandage material is provided which is impregnated or coated in the form of webs or sheets with a solvent solution of a polyurethane prepolymer, a bifunctional chain-extender and a catalyst. The prepolymer urethane having two isocyanate end groups, being formed by the reaction of a bifunctional compound reactive with an isocyanate group with a molar excess of a diisocyanate, forms a final thermoplastic polymer in the presence of the chain-extender when the solvent is removed under evaporative conditions. The heated thermoplastic impregnated fabric can be wrapped in multiple layers under normal conditions around a broken body member, molded and cooled to form a strong, rigid supportive cast which is porous so as to prevent skin maceration or other medical ramifications related to a non-porous material.