SYNTHESIS OF A LINEAR POLYURETHANE. II. MATHEMATICAL MODEL

POLO, MARA L.; PESOA, JUAN; NICOLAU, V.; SPONTON, MARISA; ESTENOZ, D. A.; MEIRA, G. R.

Los Cocos

Simposio; XII SIMPOSIO ARGENTINO DE POLÍMEROS; 2017

UNC

In the first part of this sequel [1], the synthesis of linear segmented thermoplastic polyurethanes (STPUs) by reaction between methylene diphenyl diisocyanate (MDI), poly(tetramethylene oxide) (PTMO) macrodiol, and 1,4-butanediol (BD) as chain extender, was experimentally investigated. In this work, a novel polymerization model is presented that estimates the detailed molecular structure of the evolving reaction mixture. Standard hypotheses for linear step polymerizations [2] were adopted, i.e.: a) reactivities of functional groups independent of chain length; and b) absence of intramolecular or secondary reactions. The mathematical model predicts the evolution of the molar mass distribution (MMD) along both the Prepolymerization and Finishing stages. The model requires to input the chain length distribution (CLD) of the initial PTMO. At the Prepolymerization end, MMD involved 34400 different molecular species. Due to the very large number of species generated in the Finishing stage (around 56,000,000), a simplified model was developed which considers initial PTMO as monodisperse. Then, the complete distribution was recuperated through convolution operations. Size exclusion chromatography (SEC) enabled to readjust the kinetic constants estimated in the first part of this sequel.