Polyurethane reactions, adiabatic

Typical adiabatic temperature rise of epoxy and polyurethane reactions. 

The system of Eqs. 13.3-17 and 13.3-18 can be solved for the adiabatic, isothermal, or constant wall flux cases using the Crank-Nicolson method. The thermomechanical and reaction data for such systems were evaluated by Lifsitz, Macosko, and Mussatti (99) at 45°C for a polyester triol and a chain extended 1,6-hexamethylene diisocyanate (HDI) with dibutyltin as a catalyst. Figure 13.46 gives the temperature profiles for the isothermal-wall case. Because of the high heat of polyurethane formation and the low conductivity of... 

Fig. 13.46 Temperature distribution in a reacting polyurethane slab isothermal-wall simulations. Dotted line denotes the adiabatic temperature rise and x s indicate gel points, k = 1, n — 1, AT — 0.423, and B = 18.7, 4>gel = 0.707. [Reprinted by permission from E. Broyer and C. W. Macosko, Heat Transfer and Curing in Polymer Reaction Molding, AICHE J. 22, 268 (1976).]...

Adiabatic Reaction. The experiments were conducted In an adiabatic reactor constructed at the laboratory of the Polymer Institute consisting of a 250 mis polyester container well insulated with a thick wall of a polyurethane foam poured in situ. 

Most studies of the kinetics of the isocyanate-hydroxyl reacfion have been done in systems composed of monofunctional reactants in various solvents (2 ). Even in these ideal systems, which have little resemblance to the more complicated polyurethane formulations, the reaction mechanism and kinetics are not well understood especially for the catalyzed reaction. This coupled with the added complexities encountered in polyurethane systems requires empirical determination of kinetic data if conversion during polymerization is to be predicted. A few kinetic studies on simple polyurethane systems have been reported (3, 4 ). Infrared spectroscopy was used to measure reaction rates in low catalyst formulations (3) while adiabatic temperature rise methods have been used to study fast systems (3 4, 5 ). 

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