Obtaining improved latex formulations for the increase of electrical resistance in medium voltage insulating gloves
- Autores: Neudys del Valle González Gómez
- Directores de la Tesis: Elaine Armelin (dir. tes.), Jordi-Roger Riba Ruiz (codir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2017
- Idioma: inglés
- Tribunal Calificador de la Tesis: Carlos Alemán Llansó (presid.), María Dolores Fernández Fernández (secret.), Maria Àngels Serra Albet (voc.)
- Programa de doctorado: Programa de Doctorado en Polímeros y Biopolímeros por la Universidad Politécnica de Catalunya
- Calificación: Sobresaliente Cum Laude
- Materias:
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- Resumen
Natural rubber (NR) from Hevea brasiliensis is a material of great commercial interest because of its natural origin and low cost, being one of the most valuable elastomers obtained from renewable resources. In the electrical industry, insulating gloves made of NR are commonly used as protection against electric shock in low, medium and high voltage applications. Unfortunately, the physical and chemical behavior of these materials at a microscopic level and especially under conditions of high electrical stress is still quite unknown. Innovative and extensive studies on this are required to improve their performance. Another important aspect is the strong emergence of direct current (dc) applications in the low and medium voltage fields. This represents an added challenge to the application of these materials, since in some cases, the international standards impose even more restrictive test voltages than in the case of alternating current (ac). In this sense, this thesis proposes a strategy for latex compounding and particle size filler reduction, to investigate the physical-chemical properties of the final material, with special emphasis on the electrical properties. This thesis also aims at optimizing the behavior of the latex films under the application of ac and dc voltages, to maximize their dielectric breakdown voltage and reduce the leakage current, as also approached. Thus, in the first part of the thesis, the size reduction of filler particles, such as titanium dioxide (TiO2), zinc oxide (ZnO) and silicates is proposed by means of a sonication process. The objective was to reduce the leakage current in the NR polymer matrix because of tendency of the particles to form agglomerates. Usually, the ceramic additives, when agglomerated, act as charge dopants, increasing the electron conduction and dielectric loss. New formulations were also proposed, including non-functionalized and functionalized perovskite nanoparticles to manufacture insulating gloves with enhanced their properties at higher electric stress. Barium titanate (BaTiO3) was chosen as filler in nanosized dimensions (~100 nm), due to its high dielectric constant, low loss tangent (~10-2) and high breakdown strength. Non-fuctionalized BaTiO3 nanoparticles were added in different proportions to the NR formulation: 0.1 wt.%, 0.25 wt.%, 0.4 wt.% and 0.5 wt.%. In general, it was observed that by increasing the perovskite content in NR, the electric strength and capacitance of the samples were also increased. The electrical properties were evaluated using electrochemical impedance spectroscopy (EIS), volumetric and surface resistivity analysis and dielectric breakdown measurements under the application of ac voltages. In order to reduce the size of the agglomerates and improve the dispersion of the BaTiO3 nanoparticles in the NR matrix, it was proposed to functionalize BaTiO3 with hydrogen peroxide (H2O2). In this third stage, BaTiO3 nanoparticles previously functionalized with H2O2, were added to the NR polymer matrix in different concentrations: 0.25 wt.%, 0.5 wt.%, 1 wt. %, 5 wt.% and 10 wt.%; and in nanosized dimensions. Dielectric breakdown tests were performed under the application of dc voltages for both positive and negative polarity. The results obtained in the dc dielectric tests, showed that as the content of functionalized BaTiO3 increased in the NR matrix, the leakage current of the composite was reduced, compared to the NR pristine polymer.
