Nanocompósitos de poliuretano termoplástico com estruturas de carbono: estudo das propriedades elétricas e do efeito de memória de forma

• Ano de defesa: 2021
• Autor(a) principal: Valim, Fernanda Cabrera Flores
• Orientador(a): Andrade, Ricardo Jorge Espanhol
• Banca de defesa: Castro e Silva, Cecilia de Carvalho , Scuracchio, Carlos Henrique, Maia, João Manuel Luis Lopes, Carastan, Danilo Justino
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Presbiteriana Mackenzie
• Programa de Pós-Graduação: Engenharia de Materiais e Nanotecnologia
• Departamento: Escola de Engenharia Mackenzie (EE)
• País: Brasil
• Palavras-chave em Português: poliuretano termoplástico; polímeros com memória de forma; grafeno; nanotubos de carbono; compósitos com memória de forma eletroativos
• Área do conhecimento CNPq: CNPQ::ENGENHARIAS
• Link de acesso: https://dspace.mackenzie.br/handle/10899/28438

In the present work, carbon-based nanostructures were incorporated in thermoplastic polyurethane (TPU) to obtain nanocomposites with better electrical properties (regarding electrical conductivity and permittivity) and shape memory effect (SME), aiming at the development of electroactive shape memory composites (SMPCs). TPUs are versatile polymers widely studied by their promising SMEs. These are multiblock copolymers whose morphology is highly dependent on thermodynamic parameters. Therefore, in order to understand the morphology of the TPU used, a firstly a study of the influence of annealing at 110 ºC for 0, 8, 16 and 24 hours was developed. The results showed that the phase separation between the hard and the soft segments of TPU increased the shape recovery ratio (Rr) values, due the formation of new hard domains; on the other hand, the shape fixity ratio (Rf) decreased as the material underwent longer annealing times, regarding to the increase in material stiffness. In order to enhance the electrical properties of TPU and SMEs, nanocomposites containing 0.1 wt.% of graphite (Gr), graphene nanoplatelets (GNP) and multilayers graphene oxide (mGO) were developed by casting method. From the obtained materials, the SMPCs presented enhancement on the SME, regarding to the maximum strain (εload) and Rr, especially after 24 hours of annealing at 110 ºC; and the variation between Rf values before and after annealing decrease in comparison with the neat polymer. On the electrical properties, an increase on electrical conductivity (σAC) for graphene nanoplatelets (TPU+GNP) and graphite (TPU+Gr) nanocomposites was observed, while all materials presented an improvement on σAC after 24 hours of annealing. Finally, nanocomposites with higher contents (up to 1.5 wt.%) of GNP, carbon nanotubes (CNT) and their hybrids were developed in order to achieve the electrical percolation of the material. The electrical percolation threshold was verified for nanocomposites containing 0.25 wt.% of carbon nanotubes; and the partial return of the shape under an electrical stimulus was observed for the hybrid nanocomposite containing 0.5 wt.% of CNT and 1.0 wt.% of GNP, with a total concentration lower from the reported literature.