Thermomechanical characterization of shape-memory polymeric composites

• Autor(a) principal: Fonseca, Beatriz Condesso Macedo Lobo da
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/21209
• topic: Materiais compósitos - Propriedades termomecânicas; Efeito de memória de forma; Poliuretanos; Nanotubos de carbono; Grafeno; Ensaios mecânicos

The shape-memory materials are nowadays an important subject in the scienti c community due to their huge technological potential. These materials have the capability of being triggered by an external stimulus and, consequently, change their shape. Considering the recent development of the biomedical industry, this dissertation aims to develop the applicability of shape-memory materials into biomedical devices, enabling a more e cient operability. Therefore, the shape-memory polyurethane was chosen to this end due to their high biocompatibility and proximity between the thermal transition temperature of the material and the human body temperature. However, the thermoplastic polyurethane (TPU), and the shape-memory polymers in general, possesses major drawbacks related to the inferiority of its mechanical performance as compared with shape-memory alloys (SMAs) and its large shape recovery time. In order to pursue the mechanical reinforcement and improvement of the polyurethane properties, it was conducted an experimental study in which polyurethane nanocomposites containing carbon based nanoparticles were produced. It was used carbon nanotubes (CNTs), treated and non-treated, and graphene, as these materials exhibit excellent thermo-mechanical properties reported in the literature. The nanocomposites were produced through mechanical melt mixing and injection moulding and they were incorporated with 0.5 vol.%, 1.0 vol.% and 1.5 vol.% of non-treated CNTs, treated CNTs and non-treated graphene. It was performed the morphological, thermal and mechanical characterization of the nanocomposites. Thermo-mechanical properties, such as glass transition temperature (Tg), melting temperature (Tm), speci c heat capacity (cp), thermal di usivity ( ), elastic modulus (E), tensile strength at break ( b) and elongation at break ("b) were evaluated. In the present dissertation it could be analysed the in uence of the di erent types of nanoparticles and di erent concentrations on the thermo-mechanical properties of the produced nanocomposites. Through this, the best relation regarding the materials and parameters used in this work was determined. It was also possible to draw some conclusions regarding the shape-memory performance of the nanocomposites.