A CRITERION FOR MICROPHASE SEPARATION IN SEGMENTED POLYURETHANE AND POLYURETHANE UREAS

A criterion for microphase separation in segmented polyurethanes and p oly(urethane urea)s is proposed. The existence of correlation between the ratios chi(hs)/(chi(hs)cr and the degree of segregation (alpha(seg )) was established, where chi(hs) is the thermodynamic interaction par ameter between soft and hard blocks, calculated from the solubility pa rameters, and (chi(hs))cr is its critical value, calculated using the Scott equation. Correlation between the ratio chi(hs)/(chi(hs)cr, the degree of segregation alpha(seg) and the flexibility parameter sigma w as also found.