Segmented thermoplastic polyurethanes (TPU), which are composed of alternating hard and soft segments covalently linked together display unique combination of morphological, thermal and mechanical properties depending on the type and nature of the hard and soft segments and their compositions. One of the most critical factors that influence the chemical structure, topology, microphase morphology and properties of TPUs is the synthetic procedure followed and the reaction conditions employed. Unfortunately, this point is generally overlooked, most probably since the majority of the fundamental kinetic studies on polyurethane formation reactions performed in 1960s. This study focuses on the kinetic analysis of polyurethane formation reactions, where the effect of the type and structure of the diisocyanate, solvent, reactant concentrations, reaction temperature and catalysts were investigated. Special emphasis was given to the investigation of reactions between aromatic diisocyanate MDI and poly(tetramethylene oxide)glycol (PTMO-1000). It was demonstrated that when used as a reaction solvent or co-solvent, dimethylformamide (DMF) dramatically increases the reaction rates of both the urethane formation (alcohol-isocyanate reactions), but also the side reactions which lead to allophanate and biuret formation . Optimum reaction conditions were determined to minimize the side reactions, when DMF is used as a solvent in MDI based urethane formation reactions.

Polyurethane synthesis revisited: Effect of solvent and reaction conditions on prepolymer formation and polymer properties

248th National Meeting (2014)

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