Kinetic study of the urethane and urea reactions of isophorone diisocyanate

Abstract

Kinetic studies of the catalyzed urethane reactions between isophorone diisocyanate (IPDI) and alcohols and of the urea reactions between an isocyanate-terminated prepolymer [IPDI-PPG2000-IPDI, where PPG2000 is poly(propylene glycol) with a number-average molecular weight of 2000 g/mol] and water in the bulk state were performed with Fourier transform infrared (FTIR) spectroscopy. Dibutyltin dilaurate was used as the catalyst for the urethane reaction, and various tertiary amines were used as catalysts for the urea reactions. The reactions were followed through the monitoring of the change in the intensity of the absorbance band for NCO stretching at 2270 cm 21 in the FTIR spectra; the activation parameters were determined through the evaluation of the kinetic data obtained at various temperatures (within the range of 30-608C). The kinetic data indicated that the catalyzed isocyanate/alcohol and isocyanate/water reactions both followed second-order kinetics during their initial stages but later followed third-order kinetics resulting from the autocatalytic effects of hydrogen bonding between the hydroxyl groups and the newly formed urethane and urea groups. Furthermore, activation energies of 64.88 and about 80 kJ/mol for the isocyanate/alcohol and isocyanate/water reactions, respectively, indicated that the ureaforming reactions were more sensitive to the reaction temperature than the urethane-forming reactions.

Monitoring of polyurethane dispersions after the synthesis

“…This fitting accuracy permits us to assume the first-order or at least the pseudo-first-order kinetics behavior. This is not in agreement with the reported second order at the beginning and the third order at higher conversions when the ratio of NCO to water OH was 1 : 1 21 . Again, the continuous water environment in PUDs governs the residual NCO group-reaction kinetics.…”

“…Nevertheless, the chemical changes can be monitored with FT-IR. [4][5][6][7][8][9][10][11][12][13][14]21,26,27 Table 3 consists of the formulation and properties of the PU prepolymer before being dispersed. There is no doubt that PUD colloidal features depend upon the PU prepolymer.…”

“…Therefore, those data were obtained by means of FT-IR spectroscopy, which represents a powerful tool to monitor NCO groups in an aqueous environment. 4,5,9,10,20 A conversion of the NCO groups was obtained through integrated absorbance-peak areas: [21][22][23][24] A v dv bc a v dv bcA…”

Kinetics of urethane formation from isophorone diisocyanate: The alcohol nature effect

“…The kinetics of urethane for mation involving IPDI has been reported in many papers [4][5][6][7][8][9][10]. At the same time, the kinetics of reac tions involving the cycloaliphatic and aliphatic NCO groups of IPDI was considered in detail only in few works and selectivity data differ significantly in a quantitative sense and provide no clear insight into the comparative reactivities of these groups.…”

Estudio de Nanocompuestos de Espumas de Poliuretano Reforzadas con Nanocargas en Base Carbono

“…In this study, the reaction of both sets of FPU nanocomposite foams follows a third-order kinetics resulting from the autocatalytic effect of hydrogen bonding between the hydroxyl groups and the formed urethane and urea groups. [202][203][204] The Where λ is the wavelength of the X-ray beam source and θ is the radial scattering angle. It can be observed, in all cases, that at the early stages of the reaction there is a homogeneous liquid present.…”