Linear segmented polyurethanes. II. A mathematical model for the prepolymerization stage

Abstract

In the first part of this sequel, an experimental investigation on the synthesis of linear segmented polyurethanes was presented,that included estimation of the kinetic constants at 60C for the prepolymerization and finishing stages. This work presents two comprehensivemathematical models that simulate the mentioned prepolymerizations, in reactions between two poly(tetramethylene oxide) PTMOmacrodiols and an excess of methylene diphenyl diisocyanate. The models require to input the molar mass distribution (MMD) of the initialmacrodiol. The single-phase (or homogeneous) model calculates a final MMD of approximately 40,000 different molecular species, andsomewhat underestimates the observed molar mass dispersities. The double-phases (or heterogeneous) model produces a better fit of theobserved MMDs by simulating two independent polymerizations carried out in parallel. The double-phases model contains three adjustableparameters: the reaction imbalances into both phases, and an ?effective? rate constant. In part III of this sequel, the presented models willbe extended to simulate the finishing stages.