Publication: Materiales nanocumpuestos basados en LDPE relleno con nanotubos de carbono con potenciales propiedades bactericidas
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2015-10
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2015-10-06
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Abstract
En este trabajo, se ha seleccionado como material de estudio polietileno de baja densidad, LDPE, ya que es un polímero con múltiples aplicaciones en diversos campos.
Se busca como objetivo principal, preparar y caracterizar nuevos materiales basados en LDPE con potenciales propiedades antibacterianas. Para ello, se van a estudiar dos posibles maneras de conseguirlo: La primera de ellas, consiste en realizar un procesado mecánico sobre el polietileno, concretamente, una molienda del alta energía con bolas de acero y en condiciones criogénicas. La segunda que se plantea, es preparar un material nanocompuesto, insertando nanotubos de carbono, CNT, en una matriz de polietileno de baja densidad, LDPE. De esta manera se prepararon tres materiales basados en polietileno, el primero consistió en el polímero solamente triturado, el segundo es el polímero triturado y molido bajo condiciones criogénicas y el tercero es el polímero triturado, molido y con un 1% en peso de CNT.
Los materiales finales se prepararon en forma de películas (films) por prensado en caliente, utilizando una prensa de platos calientes.
Antes de realizar el estudio de la capacidad antibacteriana de cada uno de los materiales preparados, se caracterizaron mediante distintas técnicas y métodos. En particular se estudiaron y compararon las propiedades térmicas, mecánicas y estructurales del polietileno tradicional, el polietileno molido y material nanocompuesto, entre otras razones, para saber si las propiedades se mantienen en el LDPE, a pesar de los cambios introducidos. Esta caracterización se realizó mediante diferentes técnicas como son: ensayo de tracción, que proporciona información sobre las propiedades mecánicas, calorimetría diferencial de barrido (DSC) y análisis termogravimétrico (TGA) que aportan información sobre las propiedades térmicas, medidas de ángulo de contacto (análisis de mojabilidad), a través del cual, se obtiene la energía superficial del material y por último, espectrometría infrarroja (FTIR) que muestra información relativa a la estructura interna del material.
Después se procedió a estudiar el efecto antibacteriano en relación a la bacteria Echerichia Coli de los nuevos materiales frente al polímero base mediante técnicas de análisis de imagen por microscopía electrónica de barrido (SEM) y un ensayo de cultivo convencional sobre placa Petri.Se observaron pequeños cambios poco significativos en las propiedades de los materiales ensayados, indicativo de que no disminuyen la calidad ni reducen el campo de aplicación de los mismos.
También se pudo ver que con los dos métodos de preparación propuestos, se reduce el número de bacterias sobre la superficie de los materiales, siendo más marcado el efecto antibacteriano, cuando se insertan nanotubos de carbono. Estos resultados son altamente novedosos pues es la primera vez que se describe el efecto antibacteriano de nanotubos de carbono en el interior de LDPE.
The present paper analyzes the Low-density polyethylene (LDPE), a polymer known by its multiple applications to various fields. The main goal is to prepare and characterize new materials based on LDPE with antibacterial properties. For this purpose, two different options were explored: The first one is based on a mechanical process applied to the polyethylene, in particular, a high-energy milling with steel balls and under cryogenic conditions. The second way consists in preparing a nanocomposite through the insertion of carbon nanotubes (CNTs) in a LDPE matrix. Three different materials were made following these procedures. The first one was the polymer just grinded, the second one grinded under cryogenic conditions and the third one grinded and with CNT added in a 1% its weight. The materials were finally prepared as a pressed flat film using a hot-plate press. Before the antibacterial properties of these materials were to be tested, different technologies were used to characterize them. In order to know whether the properties changed in the modified LDPE, the thermal, mechanic and structural properties of the three handled polyethylenes were analyzed and compared. This characterization was conducted through the following technologies: the tensile test provides information about mechanical properties; both Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) about thermal properties; wetting performance analysis shows the material surface energy; and Fourier transform infrared spectroscopy (FTIR), giving information related to the material´s internal structure. A further study determined afterwards the antibacterial effect of the Echerichia Coli bacteria upon the new materials in relation to the base polymer. That was carried out using scanning electron microscope (SEM) techniques and a conventional growing trial on a Petri dish. Small and not significant changes in the material properties were observed, which means neither their quality, nor their application field diminishes. Moreover, the bacteria over the material surfaces decreased in the two new proposed procedures. This antibacterial effect was more noticeable in the material with carbon nanotubes. It is worth stressing the innovative side of this approach, since it is the first time that the antibacterial effect of carbon nanotubes in LDPE is proved.
The present paper analyzes the Low-density polyethylene (LDPE), a polymer known by its multiple applications to various fields. The main goal is to prepare and characterize new materials based on LDPE with antibacterial properties. For this purpose, two different options were explored: The first one is based on a mechanical process applied to the polyethylene, in particular, a high-energy milling with steel balls and under cryogenic conditions. The second way consists in preparing a nanocomposite through the insertion of carbon nanotubes (CNTs) in a LDPE matrix. Three different materials were made following these procedures. The first one was the polymer just grinded, the second one grinded under cryogenic conditions and the third one grinded and with CNT added in a 1% its weight. The materials were finally prepared as a pressed flat film using a hot-plate press. Before the antibacterial properties of these materials were to be tested, different technologies were used to characterize them. In order to know whether the properties changed in the modified LDPE, the thermal, mechanic and structural properties of the three handled polyethylenes were analyzed and compared. This characterization was conducted through the following technologies: the tensile test provides information about mechanical properties; both Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) about thermal properties; wetting performance analysis shows the material surface energy; and Fourier transform infrared spectroscopy (FTIR), giving information related to the material´s internal structure. A further study determined afterwards the antibacterial effect of the Echerichia Coli bacteria upon the new materials in relation to the base polymer. That was carried out using scanning electron microscope (SEM) techniques and a conventional growing trial on a Petri dish. Small and not significant changes in the material properties were observed, which means neither their quality, nor their application field diminishes. Moreover, the bacteria over the material surfaces decreased in the two new proposed procedures. This antibacterial effect was more noticeable in the material with carbon nanotubes. It is worth stressing the innovative side of this approach, since it is the first time that the antibacterial effect of carbon nanotubes in LDPE is proved.
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Keywords
Nanocumpuestos, Polietileno de baja densidad (LDPE), Microbiología, Propiedades bactericidas, Nanotubos de carbono (CNT)