Hello friends.

I have an isocyanate prepolymer that is white in color and heterogeneous (containing solid particles) with high viscosity (gel-like). This prepolymer is stable in a closed container and dries when exposed to air. I performed a series of chemical analyses like FT-IR, GPC, and thermal analysis on this polymer and its soluble and insoluble components in THF. In the GPC chromatogram, I had three distinct peaks with molecular weights of 170, 479, and 6826, and in the TGA-DSC chart of the original sample, there were two weight loss steps (52% in the temperature range of 300 to 320 and 36% from 350 to 500 degrees). The FT-IR analysis shows that the original sample and the extracted components are MDI with different molecular weights, and of course, based on searches with FT-IR databases, the original sample was also suggested as part 1 of a two-component polyurethane.

What method do you suggest for determining the exact formulation of this substance? It should be noted that when this substance is mixed with PPG, it creates an elastomeric adhesive, and another point is that through elemental analysis and ash percentage determination, I realized that it has no mineral filler. If this substance is MDI, what causes it to polymerize when exposed to air?