Studies of the Structure of Polyurethane Elastomers. I. The Number-average MW Determination of the Hard-segment in the Poly(Ether)Urethane Elastomer by Means of Perchloric Acid Depolymerization

Abstract

Urea segment which is called a hard-segment in the poly(ether)urethane elastomer (PEUE) consisting of a polyether segment,urethane segment,and urea segment was isolated by means of perchloric acid depolymerization. The number-average molecular weight (MW) of the urea segment obtained by the above method was determined by elemental analysis and by volumetric analysis. By comparing the analytical results with the results calculated for a random polymerization, the number-average MW of the hard-segment was found to deviate from that expected from the equal reactivity of the two isocyanate groups in 4,4′-diphenyl methane diisocyanate (MDI). Therefore, an apparent reactivity ratio of two isocyanate groups in MDI (A) can be calculated from the number-average MW of the hard-segment isolated by means of perchloric acid depolymerization.