CORRELATION OF LINEAR VISCOELASTIC BEHAVIOR AND MOLECULAR-WEIGHT EVOLUTION IN THE BULK URETHANE POLYMERIZATION

Bulk polymerization of urethane made from diphenylmethane 4, 4' diisoc yanate (MDI) and polyether macro diol was performed from size exclusio n chromatography and viscoelastic studies. Coupling the viscoelastic c haracterization and the kinetic law showed that the viscoelastic behav ior of the urethane system is only dependent of the degree of polymeri zation. The theological study proved that low physical interactions ca n be found between the polyurethane chains. Furthermore, the critical molecular weight corresponding to a theological maximum effect of thes e interactions was observed close to the value Me = 2Me, characterizin g the onset of the topological entanglement coupling. A qualitative ex planation of this singular behavior was attempted from a hydrogen bond ing point of view. On the other hand, the linear viscoelastic properti es of polyurethane samples of different molecular weights were studied . The main viscoelastic parameters, eta(0), J(e)(0) and G(N)(0) were d etermined. (C) 1997 John Wiley & Sons, Inc.