Fenómenos de relajación interfacial en compuestos epoxi/aluminio
AUTOR(ES)
Ramajo, L., Castro, M.S., Reboredo, M.M.
FONTE
Matéria (Rio de Janeiro)
DATA DE PUBLICAÇÃO
2008-06
RESUMO
Interfacial 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 Tg, 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.
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