Synthesis of high-hardness polyurethane

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Experimental procedure: Material A: TMN-400, N210, J403 (three types of alcohols). Material B: H12MDI, trimethylolpropane A and B in a mass ratio of 1:1. Material A is added to a three-necked flask equipped with mechanical stirring and a thermometer; the temperature is raised to 100–120°C, and vacuum dehydration is carried out for 1–2 hours. Cool it down to 50–60 °C, add a small amount of amorphous molecular sieve and MOCA, and mix well. After 30 minutes, add Material B to Material A and stir thoroughly; then place the mixture in an oven at 120 °C. (Observation: No rapid reaction occurs to form solid polyurethane after mixing; it remains in liquid form, and trimethylolpropane also does not dissolve.) Question: 1. The trimethylolpropane purchased is in solid form and is insoluble in H12MDI – when is the appropriate time to add it? Should it be mixed with Material B? If so, how should it be dissolved? What else should we do if not? 2. Is it because no catalyst was added that no rapid reaction occurred to form solid polyurethane after mixing? Is it still because trimethylolpropane was not used correctly? 3. Does H12MDI need to be stored under nitrogen protection? Does it deteriorate quickly in the air?