Polymers and polymer-based materials are used in many applications
in medicine and industry. These applications frequently have a very high
performance demand, which makes their long-term aging characteristics of
paramount importance. At the same time they are subjected to degradation
due to environmental factors, including light, temperature, stress, and others.
During the aging the degradation of polymers lead to changes in the physical and mechanical properties. As a result of degradation the material may
become less deformable and brittle. These eects are studied in long-term
tests of specimens made of polyurethane in tension, compression, cyclic loading, climatic and strain aging, as well as in experiments carried out on the
rubber samples in tension and climatic aging at room temperature. In all
experiments a signicant eect of hardening and embrittlement of materials
during long-term aging is observed. The obtained results allow us to formulate
the interconnected kinetic equations for the creep rate and damage parameter. These equations are written in the scale of real and eective time. The
analytical relations for creep, damage parameter and the criteria of long-term
strength are obtained. Corresponding theoretical curves are constructed and
their qualitative agreement with the experimental curves is shown.