Fenómenos de relajación interfacial en compuestos epoxi/aluminio

Abstract

RESUMENEn este trabajo se estudiaron los fenómenos de relajación de materiales compuestos polímero/metal en función de la cantidad de partículas de metálicas incorporadas (aluminio). El concepto de módulo eléctrico fue empleado para analizar los procesos de relajación tipo Debye y Maxwell-Wagner-Sillar, debido a que presenta varias ventajas con respecto al análisis clásico de la parte real ( ´) e imaginaria ( ´´) de la permitividad. El material compuesto se obtuvo por colada y posterior curado a 100ºC por 2 horas, previa mezcla en un mezclador ultrasónico de ambos componentes. La densidad de las muestras se determinó por el método de Arquímedes, mientras que las fracciones en volumen se establecieron mediante termogravimetría. Las mediciones de propiedades dieléctricas se realizaron en el rango de frecuencias de 25Hz a 1Mhz y temperatura de 30 a 120ºC. Por último, la microestructura fue observada mediante Microscopía Electrónica de Barrido. Las micrografías revelaron que la incorporación del metal no incrementó en forma significativa la cantidad de defectos o la porosidad. Los resultados del análisis dieléctrico mostraron que los materiales poseen muy buenas propiedades dieléctricas a bajas temperaturas, y que los fenómenos de relajación son propios de la resina y modificados por la influencia de las cargas metálicas debido a fenómenos de relajación interfacial tipo MWS.Palabras Clave: Materiales compuestos, aluminio, epoxi, dieléctricos. Interfacial relaxation phenomena in epoxy /aluminum composites ABSTRACTInterfacial dielectric relaxation has been studying in composite materials made with epoxy resin and aluminum. Electric modulus, which has been proposed for the description of systems with relaxation process, presents advantages in comparison to the classic approach of the real and imaginary part of dielectric permittivity. In composite polymer materials, relaxation phenomena at the low frequency region are attributed to the heterogeneity of the system. Epoxy was diluted using tetrahydrofuran as solvent in order to reduce matrix viscosity and to facilitate the mixing step. The fillers were mixed with the resin using an ultrasonic mixer during 4 minutes. The composites were prepared pouring them into suitable moulds and cured at 100ºC for 2 hours. Density was measured by the Arquimedes method and real volume fraction of each composite was found by termogravimetric analysis. Dielectric measurements were performed from 25 Hz to 1 MHz and 20 ºC to 120 ºC. It was found that the epoxy -aluminum composites had higher permittivity and a strong dependence with filler concentration. Relaxation processes were influenced by the epoxy resin near their T g , while metal content modified the real permittivity values. Interfacial polarisation processes known as Maxwell-Wagner-Sillar were generated by particles. This process is attributed to the accumulation of charges on the interface that helped to displace peaks to higher frequencies.

Influence of two carbon plies on adhesion of unidirectional flax‐fibers reinforced epoxy composites

“…This electric modulus has recently been adapted for the investigation of dielectric processes occurring in composite polymeric systems and also proposed for the description of systems with ionic conductivity . The electric modulus, M * , is defined by the following equation : …”

Synthesis, characterization and dielectric investigation of ZnO-doped polyaniline nanocomposites

“…It was found that the values of the real part of the electric modulus (M ) started increasing above the 20 KHz frequency for all the samples. In the low region, a frequency-independent plateau was observed, followed by a high-frequency-dispersed region in all the composites due to the disordered media [34]. Among all the samples, the heavily loaded ZnO-doped PANI composites were found to possess higher values at higher frequencies, which is attributed to the formation of interfacial polarization.…”