CROSS-LINKED POLYCARBONATE POLYURETHANES - PREPARATION AND PHYSICAL-PROPERTIES

Polyurethanes (PUs) were prepared by using diols containing polar grou ps such as carbonic groups -O-COO-, carbonic and ester -COO- groups, c arbonic and ether -O- groups. Synthesis and film preparation condition s are given. The physical properties of the PUs such as density, glass transition temperature, T(g), melting point, T(m), are all presented. A correlation between T(g) and the rotational energy barriers of the polydiol single units is discussed. The PUs were characterized by mech anical tests on dry samples. The crosslink density of the PU network w as evaluated by mechanical equilibrium relaxation tests on samples swo llen in toluene. The results are discussed according to the more recen t Flory's theory of rubber elasticity. PUs containing a CO3 group pres ent an affine-like behaviour while PUs containing both CO3 and ether o r ester groups show a behaviour in between affine and phantom models.