Synthesis of polyisocyanurate prepolymer and the resulting flexible elastomers with tunable mechanical properties

Abstract

Polyurethane (PU) is used in a wide range of applications due to its diverse chemical and physical properties. To meet the increasing demands on thermal and mechanical properties of PU...

Fabrication of High-Performance Polyisocyanurate Aerogels through Cocyclotrimerization of 4,4′-Methylene Diphenyl Diisocyanate and Its Mono-Urethane Derivatives

“…To prepare the isocyanate mixture, MDI was reacted with either 2-ethyl-1-hexanol (C6,2) or 1-octanol (C8) in molar ratios of 1 to 0.1 or 1 to 0.25 via solvent-free synthesis (Scheme ). Statistically, the reaction between diisocyanate and primary alcohol also could yield diurethane structures, which would remain unreactive during the gelation process . The reaction was, therefore, performed by dropwise slow-addition of the alcohol into the isocyanate at a relatively low temperature (50 °C) to increase the selectivity of isocyanate groups and to mitigate the formation of diurethane.…”

“…The molar ratio of alcohols and MDI was also set to be lower than 0.25 to ensure that the subsequent reaction mixture only contains mono-and difunctional isocyanates. 33 The mono-and difunctional isocyanate mixtures were further cocyclotrimerized at room temperature using potassium 2-ethylhexanoate (KEH) as a trimerization catalyst to obtain a PIR network. To study the mechanism behind the trimerization, the reaction of p-tolyl isocyanate and one equivalent of 2-ethylhexyl p-tolylcarbamate in the presence of 2 mol % KEH was carried out in an NMR tube at room temperature (Scheme 2a).…”

“…To counter this issue, researchers have explored cocyclotrimerization of mono- and difunctional isocyanate mixtures, resulting in a PIR-rich network with reduced cross-link density and brittleness. , Materials derived from this mixture exhibited notable flexibility and possessed a high decomposition temperature ( T d5% > 400 °C). In another work, this approach was adopted to fabricate flexible PIR materials using mono- and difunctional isocyanate mixtures prepared from 2-ethyl-1-hexanol and 4,4′-methylene diphenyl diisocyanate (MDI). , To take the development one step further, in this work we present a synthetic protocol to fabricate superinsulating, thermally stable, hydrophobic PIR aerogels with excellent mechanical performance. Initially, mixtures of mono- and difunctional isocyanates were synthesized through the reaction between MDI and primary monofunctional alcohols such as 2-ethyl-1-hexanol (C6,2) or 1-octanol (C8) in varying molar ratios.…”

“…In another work, this approach was adopted to fabricate flexible PIR materials using mono- and difunctional isocyanate mixtures prepared from 2-ethyl-1-hexanol and 4,4′-methylene diphenyl diisocyanate (MDI). 33 , 34 To take the development one step further, in this work we present a synthetic protocol to fabricate superinsulating, thermally stable, hydrophobic PIR aerogels with excellent mechanical performance. Initially, mixtures of mono- and difunctional isocyanates were synthesized through the reaction between MDI and primary monofunctional alcohols such as 2-ethyl-1-hexanol (C6,2) or 1-octanol (C8) in varying molar ratios.…”

Phosphorus-Containing Polyisocyanurate Elastomers for Flame Retardant Application

“…A promising way to develop a flexible network with a high concentration of PIR structures is to synthesize a PIR-containing isocyanate prepolymer via co-trimerization of mono- and difunctional isocyanates (Scheme c). − In this way, the cross-link density of the PIR prepolymer is more controllable and the flexibility of the network is tunable. In addition, the liquid PIR prepolymer can be prepared via this synthetic way and it provides the possibility to prepare PIR elastomers in both solvent and solvent-free conditions.…”