Molecular aspects of rubberlike elasticity :: a comparison of two different network systems/

The glass transition temperature, the equilibrium modulus, the relaxation behavior in the glass transition region, and the swelling behavior in mixed solvents of two structurally different model network systems, the PPG-DRF system and the PIP-HDI system, were studied. These materials are important since they mimic the behavior of the theoretically described perfect networks closely. A range in material properties was induced by introducing stoichiometric imbalances and different molecular weights of the network components in the system. Several theories for each aspect of the properties of these two systems were tested against the experiment. It can be concluded that the PPG-DRF system behaves as a copolymer, following from the glass transition temperature and relaxation, and the swelling behavior. The end group contribution was important for the glass transition temperature. The PIP-HDI system does not behave as a copolymer. The Constrained Chain model was applicable to the equilibrium modulus data for both systems. The trapped entanglement contribution was not explicitly relevant. The swelling in mixed solvents could only be explained when azeotropic behavior of the solvent mixture is assumed