Study On Dielectric Properties Of MMT/SiO₂/EP Micro-nano Composites

Epoxy(EP)is widely used in electrical equipment insulation,but in more areas of application of epoxy resin put forward higher requirements.Due to the special properties of micro and nano particles,many properties of the matrix can be changed after being combined with the epoxy resin,which is beneficial to the wider application of the epoxy resin in the engineering field.In the past,the research work of composite materials mainly focused on the modification of nano-or micro-fillers.In recent years,the research on the properties of micronano composites co-doped with two kinds of scale fillers has become a research focus.In this paper,montmorillonite(MMT)is treated by intercalation agent and pre-dispersed by ultrasonic vibration.Hydrophobic Si O2 with particle size of 10?m was selected as the micro-filler.Epoxy resin-based micro-,nano-and micro-nano composites were prepared by melt blending and ultrasonic dispersion.Transmission electron microscopy(TEM)was used to observe the topography of the filler and its dispersion in the matrix.The effect of filler on the glass transition temperature of epoxy resin matrix was investigated by differential scanning calorimeter(DSC).The high-resistance meter,industrial frequency AC breakdown test platform,high-voltage schering bridge with high and low temperature test chamber and broadband dielectric spectrometer were used to test the material's conductance,breakdown,relative permittivity and loss parameters.The differences of dielectric properties between pure epoxy resin,nanocomposites,microcomposites and micro-nano composites were compared.The experimental results show that the filler dispersed evenly in the EP matrix without obvious agglomeration.The composite has an increase in glass transition temperature compared to EP.The conductivity increases slowly at low temperature.With the increase of temperature,the conductivity begins to increase rapidly.In the low temperature region,the conductivity of the composite material is greater than that of the EP and the high temperature region on the contrary.The introduction of micro-filler at room temperature will reduce the breakdown strength of the composites,but with the increase of temperature,the breakdown field strength of EP is more obvious than the composite material.The breakdown strength of nanocomposites at each temperature is the highest.The relative permittivity and loss tangent of composites are higher than that of EP.The relative dielectric constant of M5 increases to a maximum of about 16.70% at 140?.The relative permittivity of M4N1 is lower than that of EP at low temperature,and the loss tangent of M5 is 108% higher than that of EP at 140?.The relative dielectric constant of M4N1,M1N4 increased by 70% over EP.While N5 is slightly lower than EP at 140?.At room temperature,the results of wideband dielectric spectroscopy show that the relative dielectric constants of all the samples are almost constant at low frequencies and decrease with increasing frequency.The relative permittivity of composites is higher than that of EP.Loss tangent at low frequency composite material is greater than the EP,the opposite when high frequency.