Temperature issues in the preparation of water-based polyurethanes

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This post was last edited by QXZ-1966 on 2009-10-25 09:38. I would like to ask about the temperature issues in the synthesis process of water-based polyurethanes; this is the temperature I use. When the actual IPDI reacts with N210 for 2 hours without a catalyst, the temperature is 90 degrees; then it drops to 70 degrees where DMPA is added for chain extension, with the reaction temperature remaining at 85 degrees over a period of 4 hours. I would like to ask whether such temperatures are appropriate. Also, when extending the reaction time by another two hours, silicone-containing polyethers are added – should the reaction temperature still be around 85 degrees, or might it be too high? I’m not sure whether these silicone-modified polyethers should be added during the prepolymerization stage or during chain extension. Additionally, it’s unclear whether it’s better if the viscosity of the prepolymer formed during the previous reaction is high or low; my senior colleague said that a certain viscosity needs to be achieved, but once that viscosity is reached, further increase is not possible, and a lot of loss occurs during emulsification.