Effect of diluent on the gel point and mechanical properties of polyurethane networks

Abstract

Gel point conversions and equilibrium tensile moduli of polyester-based polyurethane networks were determined for different dilutions during network formation. Also, the limiting dilution beyond which the network was not formed at full conversion of functional groups was determined. It ranged between 92 and 94% of diluent. The scaling dependences against the reference states - the ring-free case and the limiting dilution case - showed that the excluded volume effects were operative and structural changes associated with cyclization affected the rates of both the intramolecular and the intermolecular reactions. © Springer-Verlag 2007.