An overview of advances in methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI) based polyurethanes: Chemistry, properties, and applications

Methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI) remain the dominant aromatic diisocyanates used to produce polyurethanes (PUs), a class of polymers with unparalleled versatility spanning foams, elastomers, coatings, adhesives, and specialty materials. This review synthesizes the literature (with emphasis on the last ~۷ years) to present: (۱) the core chemistry of MDI- and TDI-based polyurethane formation and modern synthetic/processing variants (prepolymers, blocked isocyanates, latent systems); (۲) structure–property relationships arising from hard/soft segment microphase separation, crosslink density, and formulation additives; (۳) major advances in high-performance formulations including thermoplastic polyurethanes (TPUs), nanocomposites, and dynamic/dissociative networks (vitrimers) that enable reprocessing and self-healing; and (۴) sustainability trends - bio-based polyols, non-phosgene and greener isocyanate routes, and chemical recycling strategies. This review highlights key enabling chemistries (transcarbamoylation, urethane exchange, glycolysis-derived feedstocks), summarizes representative performance gains from nanofillers and modified formulations, and discusses technological challenges for scaling sustainable and recyclable PU systems. Finally, recommendations are offered for research directions that are likely to accelerate the adoption of circular, lower-toxicity MDI/TDI-based PUs across major application sectors.

کلیدواژه ها:

Polyurethanes ، Methylene diphenyl diisocyanate (MDI) ، Toluene diisocyanate (TDI) ، Aromatic diisocyanates ، Structure&ndash ، property relationships ، Nanocomposites