Nanocompósitos a base de polietileno de baixa densidade utilizando óxido de grafeno e grafeno como cargas

• Autor(a) principal: Medeiros, Gabriela Santos
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações do Mackenzie
• Texto Completo: http://dspace.mackenzie.br/handle/10899/26436
• topic: PEBD; grafeno; óxido de grafeno; nanocompósitos; embalagens; propriedades de barreira; CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA

The main objective of this scientific project was to obtain and characterize polymeric nanocomposites based on low-density polyethylene-LDPE and two-dimensional fillers (graphene oxide and graphene) in order to improve the barrier properties in which there are significant losses in mechanical properties and transparency. Initially, synthesized by the Hummers method, graphite oxide (Gr-O) was characterized by Raman spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Graphene oxide (GO) obtained after liquid exfoliation in Gr-O water was characterized by atomic force microscopy (AFM). The results confirmed the graphite oxidation process to obtain GrO, as well as a GO with up to 10 stacked layers. Similarly, graphene from the 2DM company was analyzed, and Raman spectroscopy showed graphene with a few layers (higher concentration in 5 layers). Nanocomposites were obtained by melt blending using a twin screw extruder with load contents of 0.05, 0.1 and 0.3 mass%. These materials were injected and specimens were obtained for thermal (DSC), rheological and mechanical tests. For the first two characterizations no change in materials due to the low amount of load is noticed, however, better mechanical performances are observed for LDPE / GO (0.05%) and LDPE / G (0.05%) compositions. After the first extrusion, the material was again processed in a single-screw extruder to produce the films, which were analyzed by different techniques. The results indicated that the fillers allowed an increase of the crystallinity, as well as smaller concentrations presented better distribution of particles. Simultaneously with the influence of the orientation of the particles, better performances for the films analyzed mechanically in the longitudinal direction were observed. The surface properties (contact angle) of the films corroborate the performance of the materials for barrier properties to water vapor and oxygen gas, with the intervention of functional groups (GO), crystallinity and particle distribution being the most important factors to increase these properties. A new nanocomposite was prepared, 1.0% graphene in LDPE, and the results indicated few modifications observed for surface, morphological, thermal and mechanical properties. However, it is clear that more significant improvements in barrier properties require a higher load content which causes loss of film translucency.