Linear Segmented Polyurethanes. I. A Kinetics Study

M. POLO; M. SPONTÓN; F. JARAMILLO; D. ESTENOZ; G. MEIRA

JOURNAL OF APPLIED POLYMER SCIENCE

JOHN WILEY & SONS INC

Lugar: New York; Año: 2018

0021-8995

This work investigates the 2-steps polymerization between methylene diphenyl diisocyanate (MDI), two different poly(tetramethylene oxide) (PTMO) macrodiols, and 1,4-butanediol (BD) as chain extender. At the end of the Prepolymerization, the reaction mixture contains MDI in excess and a prepolymer withisocyanate end groups. Then, BD and a solvent (THF) were added to start the Finishing stage under nominalstoichiometric equilibrium. The reaction was analyzed by FTIR, 1H-NMR, and size exclusionchromatography (SEC). 1H-NMR was employed to follow global concentrations of unreacted isocyanateend groups and urethane internal groups. This information enabled to estimate effective rate constants, thatresulted: k1 = 1.07×10-3 Lmol-1s-1 for the Prepolymerization; and k2 = 1.94×10-4 Lmol-1s-1 for the Finishingstage. In addition, 1H-NMR measurements enabled to estimate the evolution (with extent of reaction) of thenumber-average number of structural units along the Prepolymerization and Finishing stages; and suchestimates adequately verify Flory?s classical expressions. In the second part of this sequel, the SECmeasurements of molar mass distributions (MMDs) and averages are compared to predictions from a newcomprehensive polymerization model.