1. The principal mechanical properties of polymer materials can be elucidated in tests associated with small deformation not exceeding, for example, an extension of 1%. 2. These are deformation properties and not strength properties, since the strength is defined basically on the basis of tests associated with large deformation. 3. In the determination of formulas which approximate the experimental curves it is expedient to determine the values of two parameters (γ), a and b, corresponding respectively to the initial deformation and the rate of growth of the delayed deformations. 4. Having the values of a and b one can, applying the formula of the strength of materials for polymers, taking into account the duration of application of the load, obtain the values of the elastic number, and the deformation moduli of the first and second kind, and their initial values. 5. Determining the values of a and b at different temperatures, one can obtain the brittle point temperature Tbr, the glass transition temperature Tgl, the temperature of free relaxation T1, and the temperature of transition to the viscofluid state T2. Tgl must be determined as a function of the stress intensity. 6. A constant Poisson coefficient for a given material does not exist for polymer materials. However, performing strain tests with determination of longitudinal and transverse deformations and obtaining $$\Delta l = a + bt^{{\raise0.5ex\hbox{$\scriptstyle 1$}\kern-0.1em/\kern-0.15em\lower0.25ex\hbox{$\scriptstyle 4$}}} ,\left| {\Delta d} \right| = a_1 + b_1 t^{{\raise0.5ex\hbox{$\scriptstyle 1$}\kern-0.1em/\kern-0.15em\lower0.25ex\hbox{$\scriptstyle 4$}}} ,$$ one can calculate the instantaneous values: $$\mu t = \frac{{l\left( {a_1 + b_1 t^{{\raise0.5ex\hbox{$\scriptstyle 1$}\kern-0.1em/\kern-0.15em\lower0.25ex\hbox{$\scriptstyle 4$}}} } \right)}}{{d\left( {a + bt^{{\raise0.5ex\hbox{$\scriptstyle 1$}\kern-0.1em/\kern-0.15em\lower0.25ex\hbox{$\scriptstyle 4$}}} } \right)}}.$$ 7. The above discussion makes possible a comparative estimate of polymer materials among themselves and with ordinary materials and can be an example for standardization after appropriate discussion and approval.