Pure MDI and novel uretonimine-modified isocyanates based high performance polyurethane elastomers

Currently, the use of uretonimine modified MDI is a well consolidated fact in polyurethane applications. Known industrial products are prepared by means of high and medium temperature processes, both employing phosphorous catalysts. EniChem, has experimented with a novel concept - the use of the phosphorus catalysts which are removable from the products and reusable for the production. Advantages include the absence of phosphorus residues in the final product, lighter color and smoother production cycle. Further refinement also focused on reactivity and low temperature stability. In this case, EniChem has defined uretonimine MDI derivatives suitable for: ○ Applications requiring high reactivity; ○ Applications where the reactivity control can play an important role. This paper also presents the results of an evaluation of the effects of: ○ Polyol molecular weight ○ Polyol reactivity ○ NCO content of prepolymers. on polyurethane elastomers mechanical properties. The base was made up by a range ofpolyols differing by their chemical structure, molecular weight, reactivity and by pure MDI or uretonimine-modified liquid MDI; combining them on real two-component systems, quasi-prepolymers and prepolymers. Mechanical characteristics such as hardness, tensile strength, elongation at break, abrasion and chemical resistance were checked. Furthermore, process related aspects, such as component temperature before mixing and during polymerization were also verified.