Polyurethane composite sheet, a method of making such composite sheet, and use thereof in making a medical implant

A polyurethane composite sheet comprising:

• a fabric comprised of braided or woven strands of biocompatible, high-strength polymer fibers, the fabric having a thickness of 15-150 μm, a low areal density and an open structure;
• and
• a biocompatible and biostable polyurethane elastomer comprising polysiloxane segments, the polyurethane elastomer forming a continuous matrix of the composite sheet which fully covers and embeds the strands of the fabric sufficient to render the composite sheet non-porous;
• wherein
• the composite sheet comprises 10-90 mass % of the polyurethane elastomer, has a thickness of 25-250 μm and an areal density of 5-300 g/m2;
• and wherein
• the composite sheet has, in at least one direction, a non-linear uniaxial tensile behavior characterized by a 1%-secant modulus of 20-200 MPa, a hardening transition point at 10-45%, and a tensile strength of at least 25 MPa as measured in water at 37° C.