POLYURETHANE UREAS WITH VARIOUS UREA STRUCTURES - SOLUTION BEHAVIOR AND MORPHOLOGY

Both the effect of the diamine chain extender on solution properties a nd the effect of added LiCl destroying the urea hydrogen bonds of the PUU's (polyurethane ureas) in DMF have been investigated. PUU solution s with an even number of CH2 units in the chain extender have higher v iscosities than the corresponding solutions with an odd number of CH2 units. While the viscosity of solutions with odd-numbered methylene gr oups is independent of time, the even-numbered ones show a drastic inc rease in dependence on time and gelation may even occur. Due to dimini shed associates, time-independent solution systems of low viscosity ha ve also been obtained by adding a small amount of LiCl to solutions wi th even-numbered methylene groups. In films cast from the solutions th e effect of LiCl has been proved in the solid state.