Polyurethanes with two different types of –OH backbones castor oil (CO) and hydroxyl terminated polybutadiene (HTPB) were synthesized by using moderately reactive iso-phorone diiscocayante (IPDI) as curing agent. IR spectroscopy and mechanical property evaluations were carried out to elucidate the structure-property relationship of the polymer. It was found that the polymer, intersegment bonding had significant effects on the ultimate tensile properties. The CO based polymer exhibited far better mechanical properties than that of HTPB based polymer. However, a reverse behavior was observed in the composites. Composite fabricated with HTPB based polymer matrix showed four times the tensile strength of CO based composite. SEM comparison of the fractured composites revealed better wetting and adhesion properties with HTPB. Dynamic mechanical testing results indentified a relationship between the viscoelastic parameters and frequency of the applied load.