Desenvolvimento de revestimentos híbridos anticorrosivos PMMA-CeO2 com propriedade self-healing
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Data
2019-12-09
Autores
Rodrigues, Mariana Selvaggio
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Híbridos orgânico-inorgânicos constituem uma nova classe de materiais considerados como alternativa ambientalmente compatível para substituir revestimentos anticorrosivos à base de cromatos, atualmente banidos pela alta toxicidade do crômio hexavalente. Neste contexto, nanocompósitos híbridos à base de poli(metacrilato de metila) (PMMA) e nanopartículas de CeO2, sintetizados pelo processo sol-gel, foram desenvolvidos a fim de obter revestimentos anticorrosivos de alta performance, com elevada estabilidade térmica e habilidade de inibição ativa da corrosão pela propriedade de autorregeneração (self-healing). Inicialmente foi realizada a síntese das nanopartículas de CeO2 pela reação de LiOH com Ce(NO3)3·6H2O, variando-se a proporção molar entre estes reagentes, e em seguida foi realizada a polimerização radicalar do monômero metacrilato de metila (MMA) com o agente acoplador 2-hidroxietil metacrilato (HEMA), para obtenção de híbridos PMMA-CeO2. Os materiais sintetizados foram depositados por dip-coating sobre substratos de aço carbono A1020 e liga de alumínio AA7075, e formaram filmes homogêneos e sem presença de poros ou trincas. A técnica de espalhamento de luz dinâmico (DLS) foi utilizada para o estudo da formação das nanopartículas de óxido de cério, enquanto que os revestimentos PMMA-CeO2 foram caracterizados por medidas de espessura, microscopia óptica, microscopia de força atômica (AFM), análise termogravimétrica (TGA) e espectroscopia de impedância eletroquímica (EIS). Os resultados mostraram que a utilização de menor quantidade de LiOH leva a formação de menores nanopartículas de CeO2 (~5 nm), melhor estabilidade térmica (219 °C) e excelente desempenho anticorrosivo, com módulo de impedância de 10 GΩ cm2 e 100 GΩ cm2 para os revestimentos depositados em alumínio e aço, respectivamente.
Organic-inorganic hybrids are a new class of materials considered as an environmentally compatible alternative to replace chromate-based anticorrosive coatings, currently banned by the high toxicity of hexavalent chromium. In this context, hybrid nanocomposites based on poly(methyl methacrylate) (PMMA) and CeO2 nanoparticles, synthesized by the sol-gel process, were developed in order to obtain high performance anti-corrosion coatings with high thermal stability and ability to actively inhibit corrosion by the self-healing property. Initially, the synthesis of the CeO2 nanoparticles was performed by the reaction between LiOH and Ce(NO3)3.6H2O, varying the molar ratio of these reagents, and then the radical polymerization of methyl methacrylate (MMA) monomer and the coupling agent 2-hydroxyethyl methacrylate (HEMA) was performed to obtain PMMA-CeO2 hybrids. The synthesized materials were deposited by dip-coating on A1020 carbon steel and AA7075 aluminum alloy substrates, and yielded homogeneous films without pores or cracks. Dynamic light scattering (DLS) was used to study the formation of cerium oxide nanoparticles, while the PMMA-CeO2 coatings were characterized by thickness measurements, optical microscopy, atomic force microscopy (AFM), thermogravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). The results showed that lower amount of LiOH leads to the formation of smaller CeO2 nanoparticles (~5nm), improved thermal stability (219 °C) and excellent anticorrosive performance, with 10 GΩ cm2 and 100 GΩ cm2 impedance modulus for aluminum and steel deposited coatings, respectively.
Organic-inorganic hybrids are a new class of materials considered as an environmentally compatible alternative to replace chromate-based anticorrosive coatings, currently banned by the high toxicity of hexavalent chromium. In this context, hybrid nanocomposites based on poly(methyl methacrylate) (PMMA) and CeO2 nanoparticles, synthesized by the sol-gel process, were developed in order to obtain high performance anti-corrosion coatings with high thermal stability and ability to actively inhibit corrosion by the self-healing property. Initially, the synthesis of the CeO2 nanoparticles was performed by the reaction between LiOH and Ce(NO3)3.6H2O, varying the molar ratio of these reagents, and then the radical polymerization of methyl methacrylate (MMA) monomer and the coupling agent 2-hydroxyethyl methacrylate (HEMA) was performed to obtain PMMA-CeO2 hybrids. The synthesized materials were deposited by dip-coating on A1020 carbon steel and AA7075 aluminum alloy substrates, and yielded homogeneous films without pores or cracks. Dynamic light scattering (DLS) was used to study the formation of cerium oxide nanoparticles, while the PMMA-CeO2 coatings were characterized by thickness measurements, optical microscopy, atomic force microscopy (AFM), thermogravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). The results showed that lower amount of LiOH leads to the formation of smaller CeO2 nanoparticles (~5nm), improved thermal stability (219 °C) and excellent anticorrosive performance, with 10 GΩ cm2 and 100 GΩ cm2 impedance modulus for aluminum and steel deposited coatings, respectively.
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Palavras-chave
Self-healing, Revestimento anticorrosivo, Híbrido orgânico-inorgânico, Processo sol-gel