Understand the basic properties that underlie the concept of relaxation when calculating the relaxation time for polymers. Relaxation occurs when a strain on the polymer is held constant, but the actual stress that it puts on the polymer decreases over the course of time. This generally occurs in a non-linear fashion. Relaxation differs somewhat from the polymer's tendency to creep, which is the deterioration that also occurs as a result of strain.
List the basic elements required to solve the equation used to calculate polymer relaxation time. The basic equation, known as the Volterra equation, calculates relaxation based on both stress and strain. The factors considered when calculating relaxation time include stress and strain, the overall time being considered and the relaxation function. The calculation for creep time is nearly identical, but requires that you replace the relaxation function with the creep function.
Plug in the known quantities and solve for the relaxation time. The Volterra equation indicates that the relaxation time is calculated by subtracting the relaxation function from the stress. This equation only works when the relaxation and creep functions of viscoelastic materials can be separated. When they are not separable, you are unable to calculate the relaxation separately. Instead, you will need to use more complicated models that require additional and more complex calculus.