Gel permeation chromatographic analysis of polyurethane prepolymer synthesis kinetics II. The effects of stoichiometry and type of diisocyanate

Abstract

The kinetics of formation of polyurethane prepolymers is studied by an analytical technique which involves reactive quenching of the isocyanate, separation of the oligomeric species by GPC, and measurement by UV absorbance of the quenched moieties. The precision of the kinetic parameters and the ratios of the oligomers are determined. The effect of changes in reactant stoichiometry on the ratio of oligomers is measured and compared to the value predicted by an equation from Flory. Toluene diisocyanate is shown to give fewer high oligomers than predicted, while methylene diphenylene diisocyanate gives nearly the predicted values. Tetramethylxylene diisocyanate gives more high oligomers than predicted, an unexpected but possibly important result. Catalyst is shown to increase the reaction rate of the last by more than 200 times. © 1994 John Wiley & Sons, Inc.

Structural investigations of toluene diisocyanate (TDI) and trimethylolpropane (TMP)-based polyurethane prepolymer

“…These reactions affect the molar mass distribution and final product properties such as curing dynamics and mechanical properties of segmented polyurethane in various ways [17,18]. The chemical structure of polyurethane prepolymer has been extensively studied by several techniques such as gel permeation chromatography (GPC) [19][20][21][22][23], nuclear magnetic resonance (NMR) spectroscopy [14,24,25] and mass spectrometry (MS) [26][27][28]. It is essential to thoroughly investigate the mechanism of urethane reactions and other side reactions to control the properties of the resulting polyurethane products, and most importantly, to obtain polyurethane prepolymer which could be purified through the thin film evaporator.…”

New segmented polyurethane ureas based on 4,4?-dicyclohexylmethane diisocyanate and on various soft segments

“…Anomalous behaviors have already been encountered in the synthesis of PPO-based diisocyanate prepolymers when using meta-␣,␣,␣Ј,␣Ј-tetramethyl xylylene diisocyanate (m-TMXDI) with a ferric catalyst. 8 The catalyzed reaction kinetics at 80°C was thus investigated more precisely by SEC. Figure 3 depicts the evolution of the concentrations of various species with time.…”

“…7,8 Surivet et al 9 used SEC measurements to investigate the kinetics of the reaction between H 12 MDI and benzyl alcohol (BZA) in bulk. Mixtures containing 1 mol H 12 MDI and 1 mol BZA (that is NCO : OH ϭ 2) were studied according to a simple scheme (Scheme 1).…”

Poliuretanos como materiais de revestimento de superfície

“…Pela reação do poliol com o di-ou poliisocianato é formado um pré-polímero constituído de cadeias de baixo peso molecular com grupamentos terminais reativos [15] . Esses grupamentos podem ser isocianato (NCO) ou hidroxila (OH), dependendo da razão entre o número de equivalentes-grama dos monômeros.…”