The enthalpy and volume consolidation measurement of polymers during cooling and physical ageing makes possible to determine the effect of thermodynamic inner stress on their mechanical properties. Since the inner stress is not supported by viscous nuclei, its concentration in the polymeric elastic network is much larger as the over-all stress. Thus the possible network fractures may change the mechanical properties of polymeric materials. The inner stress evolution will be monitored from enthalpy and volume consolidation. The thermodynamic description of ageing and the inner stress will be proposed on basis of the thermodynamics of irreversble processes. The polymers will be tested after the cooling step and during the creep. The stability of their properties in terms of the bulk modulus and the coefficient of expansion will be evaluated. The originality of investigation will consist of the relation of mentioned polymer properties to the inner stress during the long-term ageing. |
