Obtenção de nanocompósitos a partir da co-coagulação da borracha nitrílica e hidrotalcita

• Ano de defesa: 2014
• Autor(a) principal: Braga, Fernanda Cristina Fernandes
• Orientador(a): Furtado, Cristina Russi Guimarães
• Banca de defesa: Sousa, Ana Maria Furtado de , Sirqueira, Alex da Silva , Silva, Luciana Portal da , Nunes, Regina Celia Reis
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade do Estado do Rio de Janeiro
• Programa de Pós-Graduação: Programa de Pós-Graduação em Química
• Departamento: Centro de Tecnologia e Ciências::Instituto de Química
• País: BR
• Palavras-chave em Português: Nanocompósito; co-coagulação; látex; borracha nitrílica; hidrotalcita; vulcanização
• Palavras-chave em Inglês: Nanocomposite; co-coagulation; latex; nitrilic rubber; hydrotalcite; vulcanization
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ORGANICA::POLIMEROS E COLOIDES
• Link de acesso: http://www.bdtd.uerj.br/handle/1/15632

Nanostructured particles have been widely used as a reinforcing filler in rubber matrices and effective substitutes for, already established conventional fillers such as carbon black, mica and silica. In particular, clays have shown great potential when it comes better dispersed in the polymeric matrix due to its high aspect ratio. Within the vast universe of clay minerals, anionic clays, also known as layered double hydroxide (LDH), have the advantage of being able to be structurally designed for many different purposes, by modifying the anions or cations, or even combine them into lamellar structure. Among the existing methods to prepare elastomer-clay composites, the latex co-coagulation is an effective and economically viable, since method the rubber obtained after the coagulation process already contains the incorporated filler. This work was dedicated to evaluate the co-coagulation of NBR latex and LDH, aiming to obtain nanocomposites. This way, LDH with Mg/Al-CO3 composition was modified with anions dodecyl sulphate, dodecyl-benzene-sulphonate and stearate aqueous suspensions were prepared using ultraturrax as dispersion tools and the ultrasound probe. The process variables were evaluated in type and content of LDH, mixing time latex / aqueous suspension of LDH, quantity of coagulant and mixins speed. Finally, the clots obtained were formulated to verify the effect of LDH on the kinetics of vulcanization, and also for conventional determination of mechanical properties. The results obtained proved that the methodology of dispersion of the hydrotalcite in nitrile latex prior to the coagulation process is a viable alternative for obtaining nanocomposite. The use of ultrasound probe as a tool in the aqueous dispersion of LDH contributed to higher stability of the suspension and the adjusting the parameters of the coagulation system, led to obtainment of uniform clots of macroscopic and microscopic point of view. The micrographs of the clots obtained by SEM-FEG confirmed the information collected from the X-ray diffraction that showed the formation of a partially exfoliated system, due to the absence of the characteristic peaks of hydrotalcite, and indicated the coexistence of particles dimensions micrometric the nanometric within the same structure. The chemical composition of LDH in the presence of atoms of magnesium and aluminum combined with hydroxyl groups favored the reduction of both the induction time as pre-curing. The mechanical properties were more sensitive to the degree of dispersion of the charge were hardness, compression set, and tensile modulus at 300% strain (E300), particularly for composites containing 10% w/m for natural LDH and LDH modified with stearate. The flame resistance of nanocomposites NBR-LDH vulcanizates increased slightly compared to pure NBR, since this is a characteristic of hydrotalcite, due to its chemical composition