Novel dynamic viscoelastic measurements of polyurethane copolymer melts and their implication to tack results

A series of polyurethane multiblock copolymers with different proportions of hard segments (urethane) to soft segments (polyadipate of hexane-1,6-diol), are investigated. Dynamic viscoelastic functions of homogeneous melts in the terminal zone are determined. For the first time, entanglement modulus values of such copolymers are reported, which allows estimation of the packing length. These parameters do not vary with changing the hard-to-soft segment ratio, a result that is explained by u compensating effect of the chain architecture. For samples of similar molecular weight, the relaxation time of the terminal zone increases as the hard-to-soft segment ratio augments. The adhesives obtained from PUR solutions show a correlation between the elastic modulus and the debonding stress-strain curves in tack experiments.