Dynamic mechanical spectroscopy continues to emerge as an effective laboratory instrument to analytically examine and characterize the molecular structure of polymers. Its value to the applications designer or engineer, however, has been rather limited. What it provides best, shear modulus, is not what they need or want which is flexural modulus. This paper compares dynamically determined shear modulus G with statically determined flexural modulus E and equates the two moduli through known theoretical equations. From the data generated, the value of Poisson's ratio was determined to be 0.28. The study is based on the evaluations of four distinct reaction injection molding (RIM) urethane systems.