Abstract
A new material non-isocyanate polyurethane (NIPU), a poly(acyl-urethane) (PUAcyl), was obtained using castor oil (Ricinus communis L.), urea, and BF3⋅OEt2 as a promoter under a solvent-free methodology. The structure of the PUAcyl was confirmed by Fourier-transform infrared spectroscopy (FTIR), showing the carbamate carbonyl stretching vibration and 1H and 13C nuclear magnetic resonance (NMR), which also presented characteristic carbamate chemical shifts. In addition, the appearance of a carbamate peak in the 13C NMR spectrum, in the solid state, corroborates the structure of the PUAcyl. The confirmation that PUAcyl is a polymer was carried out by gel permeation chromatography (GPC) and a reaction mechanism for its formation has been proposed. The PUAcyl showed a satisfactory thermal stability measured by thermogravimetry (TG), furthermore the differential scanning calorimetry (DSC) and dynamic mechanical analyses (DMA) suggest that the material has polymeric chains with varying sizes and exhibit good damping properties in a temperature range compatible with daily applications. Therefore, this work provides an effective way to prepare isocyanate-free PUAcyl with promising applications such as acoustic coating.
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