The reaction between urea and ethylene carbonate occur with partial release of CO2 and partial incorporation of carbonate groups into products. The carbonate groups were found to be attached both to nitrogen of urea and to oxyethylene chain. The most effective catalyst of the synthesis was potassium carbonate. The hydroxyethyl and hydroxyethoxy groups of urea derivatives undergo partial dimerization to form carbamate groups in the products. The products of reaction between urea and ethylene carbonate have good thermal stability, they start to decompose at 200°C. The obtained products can be used as polyol components for polyurethane foams. Polyurethane foams obtained from hydroxyethoxy derivatives of urea (EC8) are rigid products of low water uptake, good stability of dimensions, low mass loss on 30 days heating at 150°C, enhanced thermal stability and good compressive strength.
ABSTRACT:The work aimed at synthesis of hydroxypropoxy compounds containing oxalamidoester group from oxamic acid (OA) and propylene carbonate (PC) substrates. The thermal stability of obtained products was tested to estimate their usefulness for formation of polyurethane foams. The influence of initial molar ratio of reagents, amount of catalyst and temperature of reaction between OA and PC on structure of product was studied. The Matrix-Assisted Laser Desorption Ionization Time of Flight (MALDI ToF) analysis of products evidenced that in the conditions used the formation of hydroxypropoxy derivatives of OA was accompanied by homocondensation of OA, which became minor process in presence of excess of PC. The physicochemical and thermal properties of products were studied.
Reactions of parabanic acid with propylene carbonate in the presence of 1,4-diazabicyclo[2.2.2]octane as catalyst were studied. During the reactions parabanic acid rings undergo opening and linear oligomeric products are formed. They are built from oxyisopropylene units formed in normal way of propylene carbonate ring opening. The oligomers discussed are characterized with higher thermal stability than parabanic acid and they can be used to produce thermally stable polyurethane foams. The chemical structures of the products obtained were characterized using IR, 1 H NMR and MALDI TOF methods. On the basis of these analytical results the mechanisms of the processes leading to the products' formation were interpreted in detail.
The hydroxyalkylation of urea and N,N 0 -bis(2-hydroxypropyl)urea (BHPU) with propylene carbonate (PC) was studied by spectral analysis of oligomeric products using 1 H-NMR, IR and MALDI ToF methods. During the hydroxypropylation the carbonate groups in a product are partially preserved. Additionally, the hydroxypropyl groups of urea derivatives undergo partially dimerization to give carbamate groups. The obtained derivatives posses enhanced thermal stability.
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