Reactive extrusion of poly(urethane-isocyanurate)

Reactive extrusion of poly(urethane-isocyanurate) (PUIR) was studied in an intermeshing corotating twin-screw extruder. Toluene diisocyanate (TDI) and polypropylene glycol (PPG) were used as initial materials with dibutyltin dilaurate (DBTDL) as catalyst. The reaction was first examined in a batch reactor as well as in an internal mixer in order to obtain the kinetics and temperature/torque evolution trends during the formation of PUIR, respectively. For the specified screw speed and temperature profile of the extruder, a working domain can be recommended for the reactive extrusion, in terms of NCO/OH ratio (r) and catalyst concentration (C), to reach a sufficient extent of reaction. The effects of screw speed and temperature profile on the residence time parameters of the reaction mixture were investigated. It is found that the axial mixing and the RTD behavior of the reaction mixture in the extruder can be well represented by the axial dispersion model. For the reaction condition of r = 3, C = 2%, and barrel temperature profiles of 75-150(degree)C or 90-165(degree)C, the optimum screw rotation speed for complete NCO conversion is 20 rpm. The structures, thermal stabilities, morphologies, and physical and dynamic mechanical properties of reactively extruded PUIRs were investigated.