Identification of Oligomers in the Reaction of Polyols with Isocyanates by¹³C-NMR and GPC

Reactivity of isocyanates with urethanes: Conditions for allophanate formation

“…In the C=O region of the 13 C-NMR spectra for non-neutralized samples, isocyanurate functions were identified by their resonances at 149.03 ppm. According to literature [13,27], the other four peaks have been attributed to the C=O groups from urethane (153.67 ppm), allophanate (154.88 ppm and 151.06 ppm), and aryl-aryl urea ( 152.57 ppm) functions (see Figure 6-b).…”

“…After the reaction of OMO with tIPDI, at T = [170-200°C] and [NCO]/[urethane] = [0.5-1] for 60min, the 13 C NMR spectrum (Fig.10) reveals the presence of five main signals in the carbonyl region : according to literature [13,24,30,33] Depending on the nature of the isocyanate that reacts with the urethane, two different allophanates can be expected (Fig.11). Each allophanate function contains two carbonyl groups, one coming from the initial urethane function, and the other coming from the isocyanate function.…”

“…Okuta [11] dissolved the formed polyurethane networks in dimethylsulfoxide, DMSO and dimethylacetamide, DMAc, by degrading the allophanate and biuret linkages with aliphatic primary amine followed by NMR analysis of the degradation products to yield quantitative information about crosslinks. Spirkova et al [12] and Schwetlick et al [3] used HPLC to identify the reaction products with model compounds, in the same way as Sebenik [13] with SEC and 13 C NMR.…”

“…At 130°C, and with a NCO/OH ratio of 4, Sebenik et al [13] found that the kinetic rate constant for the formation of allophanates from isocyanates and polyols lied in the range 4-7.10 -5 L.mol -1 .s -1 . Kogon [8] found that at 100-140°C, the rate constant of ethyl-α,γ-diaryl allophanates increased from 1.0.10 -6 to 6.0.10 -6 L.mol -1 .s -1 .…”

Preparation and chemical reactions of rigid cross‐linked poly(vinyl chloride) foams modified by epoxy compounds

“…However, the signals of 154.91 and 151.06 ppm appeared clearly in the spectrum of the mixture of TDI and EOH (T/EOH-b), which corresponded to the two C@O carbons from allophanate (Scheme 2b), according to the literature. [33][34][35] The peak at 72.11 ppm was attributed to the tertiary carbon connected with oxygen in allophanate. Enlargement of the NAH regions in the 1 H-NMR spectra for T/EOH-b is shown in Figure 7(a).…”