Desenvolvimento de híbridos orgânico-inorgânicos com propriedade self-healing para aplicações anticorrosivas
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Data
2022-05-23
Autores
Souza, Thiago Augusto Carneiro de
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Universidade Estadual Paulista (Unesp)
Resumo
A motivação que levou à execução desse trabalho consistiu em juntar a experiência do grupo e combinar formulações de híbridos contendo inibidores inorgânicos e orgânicos de sucesso como polimetacrilato de metila (PMMA-sílica + Li2CO3 e PMMA-sílica + (NH4)2Ce(NO3)6 (CAN) / PMMA-CeO2 + Li2CO3), buscando novos materiais (PMMA-sílica + tiadiazola 5-(benziltio)-1,3,4-tiadiazol-2-tiol – (BTT) e/ou 2-Mercaptobenzotiazol (MBT) / PMMA-CeO2 + BTT e/ou MBT) e avaliando a influência dos solventes no material substituindo tetraidrofurano (THF) por solventes mais verdes, como isopropanol ou etanol. Foram desenvolvidos uma série de híbridos orgânico-inorgânicos à base de PMMA e aditivos distintos, sintetizados por meio do processo sol-gel (PSG) e polimerização radicalar de MMA, com o objetivo de se testar formulações e combinações de reagentes que resultassem em revestimentos anticorrosivos de alta performance, elevada resistência mecânica, estabilidade térmica e que apresentassem a capacidade de se auto-regenerar (self-healing). Inicialmente, realizou-se a síntese utilizando precursores inorgânicos à base de nanopartículas de cério (inibidor inorgânico) e de sílica modificados com os inibidores inorgânicos à base de cério (Ce(NO3)3.6H2O) e CAN, e de lítio, como carbonato de lítio (Li2CO3), e modificados com inibidores orgânicos como MBT e BTT pelo PSG. Em seguida, realizou-se a polimerização dos monômeros com os agentes acopladores, utilizando iniciador térmico peróxido de benzoíla (BPO). A solução coloidal resultante foi utilizada para a deposição de filmes híbridos sobre substratos de aço carbono A1020 e Alumínio AA7075 por dip-coating. Foram aplicadas técnicas variadas de caracterização estando, entre elas, espectroscopia de fotoelétrons induzidos por raios-X (XPS), espectroscopia Raman, microscopia de força atômica (AFM), microscopia eletrônica de varredura (MEV) e análise termogravimétrica (TGA) para caracterização estrutural e térmica. Além disso, como complemento, foram realizados testes de adesão e medidas de espessura. Para análise da eficiência anticorrosiva, utilizou-se espectroscopia de impedância eletroquímica (EIS), com exposição das amostras em meio salino (3,5% NaCl) em função do tempo de imersão. Análises estruturais por XPS confirmaram a distribuição uniforme das nanopartículas inorgânicas na matriz de PMMA e o teor nominal dos inibidores. Os revestimentos sintetizados apresentaram resultados semelhantes àqueles já obtidos nos trabalhos anteriores do grupo, alguns com módulos de impedância em torno de 1 GΩ cm2 e vida útil acima de 1 ano. As propriedades dos filmes também se assemelharam a algumas já vistas como: superfícies homogêneas de baixas rugosidades (0,33-2,75 nm), espessuras (entre 1,40-13,53 μm) e adesão (até 11 MPa) dentro dos intervalos mais frequentes, estabilidade térmica maior que 200 °C.
The motivation that led to the execution of this work consisted of joining the group's experience and combining successful formulations (PMMA-silica + Li2CO3 and PMMA-silica + (NH4)2Ce(NO3)6 CAN / PMMA-CeO2 + Li2CO3), looking for new materials (PMMA-silica + tiadiazola 5-(benzylthio)-1,3,4-thiadiazole-2-thiol – (BTT) and /or 2-Mercaptobenzothiazole (MBT) / PMMA-CeO2 + BTT and/or MBT) and evaluating the influence of solvents on the material trying to replace THF by green solvents as isopropanol or ethanol. A series of organic-inorganic hybrids based on polymethyl methacrylate (PMMA) and different additives were developed, synthesized through the sol-gel process (PSG) and radical polymerization, with the objective of testing formulations and combinations of reagents that resulted in high performance anti-corrosion coatings, high mechanical resistance, thermal stability and which have the ability to self-healing. Initially, the synthesis was carried out using inorganic precursors based on cerium nanoparticles (inorganic inhibitor) and silica modified with inorganic inhibitors based on cerium (Ce(NO3)3.6H2O) and CAN, and lithium, as lithium carbonate (Li2CO3), and modified with organic inhibitors such as 2-Mercaptobenzothiazole (MBT) and thiadiazole (5-(benzylthio)-1,3,4-thiadiazole-2-thiol - BTT) by PSG. Then, the polymerization of the monomers was carried out with the coupling agents, using the thermal initiator of benzoyl peroxide (BPO). The resulting colloidal solution was used for the deposition of hybrid films on A1020 carbon steel and AA7075 aluminum substrates by dip-coating. Various techniques were applied, including X-ray induced photoelectron spectroscopy (XPS), Raman spectroscopy, atomic force microscopy (AFM) and thermogravimetric analysis (TGA) for structural and thermal characterization. In addition, as a complement, adhesion tests and thickness measurements were performed. And, in order to analyze the anticorrosive efficiency, electrochemical impedance spectroscopy (EIS) was used, with immersion of the samples in saline medium (3.5% NaCl), taking into account the immersion time. The samples were also observed in scanning electron microscopy (SEM). The synthesized hybrids presented similar results to those already obtained in the group's previous works, some with impedance modules around 1 GΩ cm2 and a useful life of over 1 year. The structural properties also resembled some previously seen, such as low roughness values between 0.33 and 2.75 nm (smooth and homogeneous surfaces), thickness (between 1.40 - 13.53 μm) and adhesion (up to 11 MPa) within the most frequent ranges, thermal stability higher than 200°C.
The motivation that led to the execution of this work consisted of joining the group's experience and combining successful formulations (PMMA-silica + Li2CO3 and PMMA-silica + (NH4)2Ce(NO3)6 CAN / PMMA-CeO2 + Li2CO3), looking for new materials (PMMA-silica + tiadiazola 5-(benzylthio)-1,3,4-thiadiazole-2-thiol – (BTT) and /or 2-Mercaptobenzothiazole (MBT) / PMMA-CeO2 + BTT and/or MBT) and evaluating the influence of solvents on the material trying to replace THF by green solvents as isopropanol or ethanol. A series of organic-inorganic hybrids based on polymethyl methacrylate (PMMA) and different additives were developed, synthesized through the sol-gel process (PSG) and radical polymerization, with the objective of testing formulations and combinations of reagents that resulted in high performance anti-corrosion coatings, high mechanical resistance, thermal stability and which have the ability to self-healing. Initially, the synthesis was carried out using inorganic precursors based on cerium nanoparticles (inorganic inhibitor) and silica modified with inorganic inhibitors based on cerium (Ce(NO3)3.6H2O) and CAN, and lithium, as lithium carbonate (Li2CO3), and modified with organic inhibitors such as 2-Mercaptobenzothiazole (MBT) and thiadiazole (5-(benzylthio)-1,3,4-thiadiazole-2-thiol - BTT) by PSG. Then, the polymerization of the monomers was carried out with the coupling agents, using the thermal initiator of benzoyl peroxide (BPO). The resulting colloidal solution was used for the deposition of hybrid films on A1020 carbon steel and AA7075 aluminum substrates by dip-coating. Various techniques were applied, including X-ray induced photoelectron spectroscopy (XPS), Raman spectroscopy, atomic force microscopy (AFM) and thermogravimetric analysis (TGA) for structural and thermal characterization. In addition, as a complement, adhesion tests and thickness measurements were performed. And, in order to analyze the anticorrosive efficiency, electrochemical impedance spectroscopy (EIS) was used, with immersion of the samples in saline medium (3.5% NaCl), taking into account the immersion time. The samples were also observed in scanning electron microscopy (SEM). The synthesized hybrids presented similar results to those already obtained in the group's previous works, some with impedance modules around 1 GΩ cm2 and a useful life of over 1 year. The structural properties also resembled some previously seen, such as low roughness values between 0.33 and 2.75 nm (smooth and homogeneous surfaces), thickness (between 1.40 - 13.53 μm) and adhesion (up to 11 MPa) within the most frequent ranges, thermal stability higher than 200°C.
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Palavras-chave
Materiais compostos, Processo sol-gel, Revestimentos, Corrosão e anticorrosivos, Eletroquímica