An exceptionally strong joint between two materials, which can be stronger than the materials being joined.  Bond strength can be more important than the polyurethane quality..e.g. it is no use having a tyre that will last for ever if it falls off the wheel.  Preparation and choice of the correct Bonding Agent are key to achieving excellent bonds.  Avoid small companies without their own grit blasting facilities, vapour degreasing facilities and where silicone release agents are applied by aerosol without scrupulous extraction and isolation.  One drop of silicone will spread for miles and contaminate any bond.  Once the Bonding Adhesive has been applied to a substrate, handling care is paramount.  No finger or thumb contamination must be allowed, no equipment contact and the filling process with moulds must be scrupulously monitored to ensure Mould Release Agent does not wash onto the Bonded surface.