Polyurethanes

New segmented polyurethane ureas based on 4,4?-dicyclohexylmethane diisocyanate and on various soft segments

“…However, because of the presence of some monofunctional species resulting from the synthesis, 3 its hydroxyl functionality is also lower than 2.0. The analysis of its microstructure by 1 H and 13 C nuclear magnetic resonance (NMR) 4 revealed that the inversion rate was very low (only 1.3 to 2.5% primary hydroxyl groups), whereas 0.22 nonreactive extremities (allyl or methyl vinyl) could be found for every 100 propylene oxide units, that is, a number average functionality of 1.92.…”

“…1 By adjusting the chemical nature and respective amounts of the reagents, it is thus possible to obtain a wide range of materials with tailored properties. Thermodynamic immiscibility between hard and soft segments often induces phase separation, which generates a two-phase morphology and confers an elastomeric character to these thermoplastic materials.…”

A new homologous series of linear aliphatic unsaturated hydroxypolyesters a polyol soft segments for polyurethanes: Synthesis and characterization

“…To achieve a desired OH-terminated polymer, in addition to selection of a proper diol/diacid (or diester) ratio and duration of the first stage, the magnitude of vacuum and its duration (in the second stage) are critical, because the eliminated diol is removed and M V n increases rapidly under the vacuum and higher temperatures. As another viewpoint, these facts are based on the 3 In this work, all of poly(cis-2-butenylene car-The le Chatelier principle will determine the equiboxylate)s were successfully prepared as OH-terlibrium status: removing xOH causes the reaction minated polymers with low polydispersity ( M V w / progress. Fortunately, the boiling point of cis-2-M V n Å 1.3-2.7).…”

Poliuretanas: caracterização, avaliação estrutural e efeito induzido pela radiação gama

“…PURA banda amida Ili, em torno de 1295 cm-1 é ativa somente no Raman, enquanto que a banda amida li, em torno de 1560 cm•1 , é ativa somente no dos dados das sínteses de Yeon et al23 e Chen et al24 Tabela 5.7 Análise elementar de C, H e N da PUR e desvio aparente*.…”

“…Isto indica que além da degradação dos segmentos originários do PTMO e BD, este primeiro responsável pela cristalinidade observada na PUR por DSC , também há uma certa degradação do grupo uretânico. Cabe ressaltar a observação do surgimento de um ombro da banda em 3300 cm-1 , na região de 3400-3500 cm-1 , proveniente da oxidação do polímero e formação de grupos OH . Isto está de acordo com as observações feitas por Ravat et al8 Para a PUR sulfonada, as observações foram semelhantes, devendo incluir ainda a diminuição na intensidade da banda em 1037 cm-1 , atribuída ao estiramento simétrico dos grupos sulfonato, em todas as doses.Para a Tecoflex, verifica-se o mesmo efeito da PUR, embora seja observada ainda a diminuição nas bandas de estiramento simétrico e antisimétrico dos grupos CH 2 nos espectros IR.…”