- Identification: IAA2060401 - Grant Agency of the Academy of Sciences of the Czech Republic
- Duration: 2004 - 2007
- Principal investigator: Ing. Pavel Říha CSc.
Subject of research
The enthalpy and volume consolidation mesurement of polymers during cooling and physical ageing makes possible to determine the effect of thermodynamic inner stress on their mechanical properties. Science the inner stress is not supported by viscous nuclei, its concentrations on 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 irreversible processes. The polymers will be tested after the cooling step and during the creep. The stability of their properties in therms 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.
Research Goal
The bulk modulus and free energy were found as decisive for the effect of inner pressure on the physical aging of polymers. The measured data for a set of polymers (PMMA, PC, PS, PVC, PET) support this finding both in time and temperature dependences.
