A three parameter kinetic model of formation of linear polyurethane from 2,4-toluenediisocyanate and butane-1,4-diol

A model of linear isothermal polymerization of two bi-functional monomers, one of which has alike functional groups of different reactivities, is pres ented. The model has been applied to the polymerization of 2,4-toluenediiso cyanate (TDI)(a) and butane-1,4-diol carried out in solution at 86 or 101 d egrees C. The rate constant K of the reaction between an isocyanate group i n position 3 of TDI and a hydroxy group, the ratio K of reactivities of gro ups in position 3 relative to that in position 2, and the ratio k(phi) of r eactivities of an isocyanate group in the monomer relative to that at the e nd of an oligomer chain, have been evaluated from experimental data to be 6 .51 . 10(-4) dm(3) . mol(-1) . s(-1), 1.47, and 1.55 at 86 degrees C, and 1 7.2 . 10(-4) dm(3) . mol(-1) . s(-1), 1.55, and 1.62 at 101 degrees C, resp ectively.