Publication: Lacado de aluminio con conversiones base silano: influencia del pretratamiento con antorcha de plasma atmosférico
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2012-01
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2012-01-25
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Abstract
En esta Tesis Doctoral se ha estudiado y caracterizado el proceso de pretratamiento con silano de la aleación de aluminio AA 6063 para su posterior lacado. El tratamiento de silanización se caracteriza por una baja temperatura de procesado, procedimientos de preparación simples y la posibilidad de ser usado en un amplio rango de técnicas de recubrimiento como inmersión o rociado. Se toman dos silanos: un bisilano (bis-1,2-(trietoxisilil)etano, BTSE), que favorecerá el entrecruzamiento de la capa y su unión con el sustrato, y un monosilano (γ- metacriloxipropiltrimetoxisilano, MPS), que además de permitir la unión con el sustrato favorecerá la reacción con el recubrimiento polimérico. Se estudian, por tanto, dos procedimientos de silanización: en un paso, empleando únicamente la disolución del monosilano, y en dos pasos, combinando el uso del bisilano con el del monosilano. En primer lugar se optimiza el tiempo de hidrólisis y el contenido de disolventes en ambas disoluciones para conseguir un alto grado de especies hidrolizadas, controlando la formación de especies condensadas. En segundo lugar se optimizan las condiciones de silanización y, tras analizar la influencia del tratamiento de limpieza del sustrato metálico sobre la distribución del silano, se introduce el pretratamiento por antorcha de plasma atmosférico. Este, además de limpiar el sustrato metálico, disminuye la energía superficial de la aleación de aluminio mejorando la distribución del silano y por tanto su adherencia. Una vez caracterizadas las capas de silano formadas y definidos los procedimientos óptimos de silanización se procede al pintado de los sustratos y a su evaluación. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
This PhD is focused on the study and characterization of AA 6063 aluminum alloy pretreatment process with silanes and lacquering of pretreated alloy. Silanization treatment is characterized by low processing temperature and simple preparation procedures. Also, silanization can be carried out using a wide range of layer application techniques, such as dipping or spraying. Two silanes (a monosilane and a bisilane) are studied. The bisilane (bis-1,2- (triethoxysilyl)ethane, BTSE) will promote the crosslinking within silane layer and the bonding of silane itself to the substrate. The monosilane (γ-methacryloxypropyltrimethoxysilane, MPS) will also promote the bonding with the polymeric coating (laquer). Therefore, two silanization methods are evaluated. A “one-step process”, considering only the use of the monosilane solution, and a “two-step process”, combining the monosilane and the bisilane solutions. Process optimization has been achieved reaching the following items. Firstly, hydrolysis time and solvent content of the two solutions are optimized to achieve a high degree of hydrolyzed species controlling the formation of condensed species. Secondly, silanization conditions are optimized. After analyzing the influence of metal substrate cleaning treatment on silane distribution, atmospheric plasma torch treatment is introduced. This treatment provides metal surface cleaning and surface energy decreasing, hence improving silane distribution and its adhesion. Finally, once silane coating layers are characterized and adequate silanization procedures are found, the silanized substrates are painted and evaluated.
This PhD is focused on the study and characterization of AA 6063 aluminum alloy pretreatment process with silanes and lacquering of pretreated alloy. Silanization treatment is characterized by low processing temperature and simple preparation procedures. Also, silanization can be carried out using a wide range of layer application techniques, such as dipping or spraying. Two silanes (a monosilane and a bisilane) are studied. The bisilane (bis-1,2- (triethoxysilyl)ethane, BTSE) will promote the crosslinking within silane layer and the bonding of silane itself to the substrate. The monosilane (γ-methacryloxypropyltrimethoxysilane, MPS) will also promote the bonding with the polymeric coating (laquer). Therefore, two silanization methods are evaluated. A “one-step process”, considering only the use of the monosilane solution, and a “two-step process”, combining the monosilane and the bisilane solutions. Process optimization has been achieved reaching the following items. Firstly, hydrolysis time and solvent content of the two solutions are optimized to achieve a high degree of hydrolyzed species controlling the formation of condensed species. Secondly, silanization conditions are optimized. After analyzing the influence of metal substrate cleaning treatment on silane distribution, atmospheric plasma torch treatment is introduced. This treatment provides metal surface cleaning and surface energy decreasing, hence improving silane distribution and its adhesion. Finally, once silane coating layers are characterized and adequate silanization procedures are found, the silanized substrates are painted and evaluated.
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Aleaciones de aluminio, Silanización