Publication: Durabilidad y biodeterioro de materiales compuestos de matriz polimérica reforzados con fibras naturales: efecto de tratamientos de plasma
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2018-05
Defense date
2018-07-12
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Abstract
En la presente Tesis Doctoral se han utilizado dos procesos de plasma frio, plasma de baja presión (LPP) y plasma atmosférico por antorcha (APPT), con el fin de resolver los problemas fundamentales de los de materiales compuestos de matriz polimérica reforzados con fibras naturales: la débil interfase entre refuerzo y matriz producida por la mala adhesión entre fibras naturales y matrices poliméricas y el biodeterioro causado por la acción de microorganismos inherentes a las fibras naturales.
Para ello, se seleccionaron diferentes tipos de fibras naturales y diferentes matrices termoplásticas, entre las que se incluyen polímeros convencionales y biopolímeros, y se optimizaron, en primer lugar, los parámetros de cada tratamiento de plasma. Posteriormente, se evaluó el efecto de los mismos sobre las siguientes propiedades:
- Adhesión entre fibra y matriz, mediante microscopía electrónica de barrido, ensayos de pelado y ensayos de pull-out.
- Propiedades mecánicas de los materiales compuestos finales, a partir de ensayos de tracción y de flexión en tres puntos.
- Durabilidad, realizando medidas de absorción de agua y analizando la evolución de propiedades térmicas y mecánicas.
- Procesos de descomposición de los materiales, calculando la energía del proceso a partir de análisis termogravimétricos y estimando el tiempo de vida.
- Biodegradación de los materiales, mediante el ensayo “soil burial”.
- Biodeterioro causado por la presencia de microorganismos, analizando el carácter biocida de los tratamientos de plasma.
Los resultados obtenidos demuestran que la elección del tratamiento es adecuada ya que se observa una mejora en la adhesión entre fibra y matriz que, a su vez, repercute en un incremento de las propiedades mecánicas, una menor absorción de agua por parte de los materiales compuestos y una reducción considerable de los microorganismos pre-existentes en las fibras naturales.
In the present PhD Thesis it have been used two cold plasma treatments, low pressure plasma (LPP) and atmospheric pressure plasma torch (APPT), with the aim of resolving the main problems of natural fibers reinforced polymeric composites (NFRP): the weak interface between reinforcement and matrix, due to the poor adhesion between natural fibres and polymeric matrices, and the bio-deterioration caused by the action of the microorganism innate to the natural fibers. Different types of natural fibers and thermoplastic matrices were selected such as conventional polymers and biopolymers. First of all, parameters of each plasma treatment were optimized. Afterwards, their effect was evaluated over the following properties: - Fibre-matrix adhesion, through scanning electron microscopy, peel-out tests and pull-out tests. - Mechanic properties of the final composites, by tensile and three point bending tests. - Durability, by water absorption measurements and analyzing the evolution of both thermal and mechanical properties. - Decomposition processes of all materials by calculating the process energy through thermogravimetric analysis and estimating time to failure. - Biodegradation of the materials by soil burial test. - Biodeterioration caused by the presence of microorganism, by analyzing the biocide character of plasma treatments. The obtained results show that the treatment selection is suitable due to a better adhesion between fiber and matrix, which involves mechanical properties improvement, less water absorption and a reduction on the microorganism innate to the natural fibres.
In the present PhD Thesis it have been used two cold plasma treatments, low pressure plasma (LPP) and atmospheric pressure plasma torch (APPT), with the aim of resolving the main problems of natural fibers reinforced polymeric composites (NFRP): the weak interface between reinforcement and matrix, due to the poor adhesion between natural fibres and polymeric matrices, and the bio-deterioration caused by the action of the microorganism innate to the natural fibers. Different types of natural fibers and thermoplastic matrices were selected such as conventional polymers and biopolymers. First of all, parameters of each plasma treatment were optimized. Afterwards, their effect was evaluated over the following properties: - Fibre-matrix adhesion, through scanning electron microscopy, peel-out tests and pull-out tests. - Mechanic properties of the final composites, by tensile and three point bending tests. - Durability, by water absorption measurements and analyzing the evolution of both thermal and mechanical properties. - Decomposition processes of all materials by calculating the process energy through thermogravimetric analysis and estimating time to failure. - Biodegradation of the materials by soil burial test. - Biodeterioration caused by the presence of microorganism, by analyzing the biocide character of plasma treatments. The obtained results show that the treatment selection is suitable due to a better adhesion between fiber and matrix, which involves mechanical properties improvement, less water absorption and a reduction on the microorganism innate to the natural fibres.
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Biodegradación, Biodeterioro, Materiales compuestos de matriz polimérica, Biopolímeros, Plasma de baja presión, Plasma atmosférico, Propiedades mecánicas