2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/16223Constitutive equations are derived for enthalpy recovery in polymeric glasses after thermal jumps. The model is based on the theory of cooperative relaxation in a version of the trapping concept. It is demonstrated that some critical temperature and some critical degree of crystallinity exist above which the energy landscape becomes homogeneous and structural relaxation ceases.13 pages, 5 figures, LATEXSoft Condensed Mattertext