The co‐catalytic effect of carbamate groups in cyclotrimerization of isocyanates

Synthesis, Mechanisms and Kinetics of Formation of Bi-Component Polyurethanes

“…Depending on synthesis conditions [4][5][6][7][8][9] (solvent or molten state), a large number of reactions can occur in parallel to the reaction yielding urethane groups 1,2,5,10,11 . These reactions may be secondary 6,[10][11][12][13][14][15] or principal 16 according to the properties required for the polyurethanes synthesised. The presence of water and excess isocyanate in the reaction medium may generate side products such as urea 1,5,11,12 or biuret 1,5,6,11,12 .…”

“…Similarly, in certain operating conditions and under the effect of temperature, allo phanate 1,5,6,11,12,16 may form in the presence of excess isocyanate 1,.2,15,16 . When the temperature increases, isocyanate homopolymerisation reactions may also occur and form a dimer 1,5,11,12 (uretidine dione) or a trimer 1,6,[11][12][13] (isocyanurate) with a heterocycle containing four or six members, respectively, thereby conferring specifi c properties on the polymers.…”

Reaction Injection Molding

“…160,175 Processing conditions are similar to those of polyurethane RIM except that the mold temperature needs to be around 100°C. If the mold temperature is too low, isocyanurate reaction may be incomplete near the wall, which results in a sticky surface.…”

Novel Heat-Resistant Isocyanate- Based Polymers

“…The introduction of heat resistant, heterocyclic groups in polyurethanes such as isocyanurates, oxazolidones, and cycloimides has gained considerable commercial importance ( Figure 1). The thermal stability of these linkages, as measured on model compounds and model polymers, has been reported by a number of different investigators [1][2][3][4][5][6][7] The isocyanurate ring is generally produced by isocyanate trimerization using selective catalysts and is hydrolytically and thermally very stable. However, polyisocyanurates are inherently brittle due to their high crosslink density.…”