Complex sentence: Methylene diphenyl 4,4'-diisocyanate, most often abbreviated as 4,4'-MDI and also known as Pure MDI, is an aromatic diisocyanate manufactured for reaction with a polyol in the manufacture of polyurethane.
Split into simpler sentences: Methylene diphenyl 4,4'-diisocyanate, most often abbreviated as 4,4'-MDI and also known as Pure MDI, is an aromatic diisocyanate. It is reacted with a polyol in the manufacture of polyurethane.