In this study, three different microcellular polyurethane elastomers (MPUE) based on 4,4'-diphenylmethane diisocyanate with different rigid segment contents are prepared (Formulations 1, 2, and 3 with 32, 35, and 42% of rigid segment content, respectively). The MPUE are obtained through a two-step method using a prepolymer system. The samples are analyzed to determine their thermal, morphological, and chemical properties. The thermogravimetric analysis indicates the presence of two degradation stages, referring to the rigid and flexible phases, respectively. The differential scanning calorimetry tests indicate that for the MPUE there was an increase in the glass transition temperature of the flexible phase with an increase in the percent of the rigid phase. An increase in the quantity of the rigid phase present in the MPUE results in greater values for the crosslink density, which in turn results in an increase in the rigidity of the material. The scanning electron microscopy micrographs indicated a large number of closed cells and that a higher rigid segment content give a better cell homogeneity of the samples.
Resumo: Neste trabalho, foram preparados três diferentes elastômeros microcelulares de poliuretano (EMPU) baseados em 4,4'-diisocianato de difenilmetano (MDI), com diferentes concentrações de fase rígida (Formulações 1, 2 e 3, com 32, 35 e 42% de fase rígida, respectivamente). As amostras foram preparadas através do método de duas etapas, pelo sistema de pré-polímero. As amostras dos EMPU foram caracterizadas através de ensaios físico-mecânicos, químicos e morfológicos. Os resultados dos ensaios mecânicos mostraram que o aumento no percentual da fase rígida levou a um aumento na resistência à tração e na resistência ao rasgo. O alongamento na ruptura não apresentou variação significativa com a modificação do percentual da fase rígida. O ensaio de resistência química demonstrou que os EMPU formulados apresentaram baixos índices de inchamento para solventes industriais comumente utilizados. Entretanto, em acetona, um elevado índice de inchamento foi observado. As análises morfológicas indicaram que o aumento no percentual da fase rígida promoveu a formação de células menores distribuídas de forma mais homogênea no EMPU. Palavras-chave: Elastômero microcelular de poliuretano, propriedades mecânicas, microscopia eletrônica de varredura. Effect of rigid Segment content on the Physical, Mechanical, Chemical and Morphological Properties of Microcellular Polyurethane ElastomersAbstract: In this study, three different microcellular polyurethane elastomers (MPUE) based on 4,4'-diphenylmethane diisocyanate (MDI) with different rigid segment contents were prepared (Formulations 1, 2 and 3 with 32, 35 and 42% of rigid segment content, respectively). The MPUE were obtained through a two-step method using the prepolymer system. The samples were analyzed to determine their physical, mechanical, morphological and chemical properties. The results showed that a greater rigid segment content gave higher tensile, compressive and tear strength values. The deformation at break did not show significant changes with a variation in the rigid segment content. The MPUE had a low swelling index in common industrial solvents. However, in acetone a high swelling index was observed. The SEM micrographs indicated a large number of closed cells, and that a higher rigid segment content gave a better cell homogeneity of the samples. Keywords: Microcellular polyurethane elastomers, mechanical properties, scanning electron microscopy. IntroduçãoOs poliuretanos (PUs) são considerados como copolímeros em bloco segmentados, formados pela reação de poliadição entre diisocianatos, polióis e extensores de cadeia [1][2][3] . Os mesmos são constituídos por segmentos rígidos e flexíveis [4,5] . A reação entre diisocianato e extensores de cadeia forma o segmento rígido, enquanto que o poliol é responsável pelo segmento flexível [2,4,5] .Os elastômeros microcelulares de poliuretano (EMPU) são materiais que resistem a condições severas encontradas em diversas aplicações, como em automóveis e máquinas industriais [7,8] . Os mesmos apresentam uma densidade apare...
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