Features of viscoelastic behavior of materials based on heat-resistant polymers

In the example of polybenzoxazole, the relationships of viscoelastic behavior have been investigated for monolithic heat-resistant polymers over a wide range of temperatures (from 22° to 230°C) and initial deformations (from 0.5 to 2.5%). The experimental data on stress relaxation, covering the regions of linear and nonlinear viscoelasticity, are approximated by the basic equation of the primary cubic theory of Il'yushin, using the singular kernel of Rzhanitsyn. For the first time, the region of stable mechanical capability of monolithic heat-resistant polymers has been defined with due regard for relaxation characteristics.