Soybean oil based polyisocyanurate cast resins

Two series of polyisocyanurates were prepared from polymeric 4,4′‐diphenylmethane diisocyanate (MDI) and soy‐based or polypropylene oxide polyols by varying isocyanate indexes from 105 to 350. Increasing isocyanate index gave polyisocyanurates with increased thermal stability, flame resistance, tensile strength, modulus, and glass transition. Impact was lower. Soy‐based polyisocyanurates displayed better thermal stability, higher rigidity (modulus), and higher strength than those based on the propylene oxide polyols of the same molecular weight and functionality. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3333–3337, 2003