Síntese de composto de magnésio por rota verde para uso em vulcanização de elastômeros

• Autor(a) principal: Silva, Arianne Aparecida da
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/16397
• topic: Óxido de magnésio; Extrato de chá verde; Camellia sinensis; Ativador; Borracha Nitrílica; Vulcanização; Magnesium Oxide; Green tea extract; Activator; Nitrile Rubber; Vulcanization; Magnésio; ENGENHARIAS::ENGENHARIA QUIMICA::TECNOLOGIA QUIMICA

This work aims to study the technical feasibility of using nanometric MgO obtained by the green route, as an activator in NBR rubber compositions, replacing industrially used ZnO. Green MgO (MgO-V) was synthesized from the aqueous extract of green tea (Camellia sinensis) and characterized by X-ray diffraction (XRD), Infrared Spectroscopy with Fourier Transform (FT-IR) , thermogravimetric analysis (TG and DTG), dispersive energy spectroscopy (EDS), high resolution scanning electron microscopy (SEM-FEG) and determination of the particle size distribution by dynamic light scattering (DSL). Characteristic MgO bands were observed in the FT-IR spectrum, Mg and O in the composition of the materials by EDS, average diameter of the crystallite in the range of 15 – 23 nm in the DRX and analysis by DLS confirmed a fraction of nanometric particles. A study was carried out to understand how MgO behaves in the vulcanization of NBR, where it was evaluated the effect of commercial MgO (MgO-C) and stearic acid (AE) in the rheometric, kinetic parameters, cross-link density (DLC) and thermal properties, compared to the composition containing ZnO as activator of vulcanization. It was observed that MgO started the vulcanization process earlier, presenting a faster reaction kinetics, but it needs more time to achieve high conversions. Furthermore, it did not show significant changes in DLC and presented better thermal stability in relation to ZnO, justifying its use as an activator in NBR. The MgO content had an effect on the kinetic and rheometric properties. To study the technical feasibility of using green MgO as an activator, it was compared with commercial MgO and ZnO. The 3: 1 MgO-V / AE composition was chosen for comparison to 3: 1 and 7: 1 MgO-C / AE compositions and 3: 1 ZnO / AE composition. Comparisons were made with respect to rheometric parameters, DLC, vulcanization kinetics, rheological behavior, mechanical properties and thermal stability. The synthesized MgO-V showed higher cross-link densities and better thermal stability than ZnO and MgO-C, although the mechanical properties were similar, MgO-V showed higher torque retention and higher activating capacity when compared to MgO -C, since its results with 3 phr (parts per hundred of rubber) were similar to the results with 7 phr of MgO-C, making possible the use of MgO synthesized by green route as a promising vulcanization activator.