Experimental Study On Key Factors-Surface Treatment Affecting Dielectric Properties Of Nano-MgO /LDPE Composite

The dielectric properties of polyethylene nano-composite are effected by nano-filler concentration, nano-filler size, and surface treatment. In this article, nano MgO is treated by different surface treatment. Nano MgO with different concentrations(0.1wt%、0.5wt%、1wt% and 2wt%) is filled into LDPE. Microscopic characteristics are studied by infrared spectrum, transmission electron microscopy and differential scanning calorimetry experiments. Different dielectric properties of nano MgO/LDPE composite are studied by broadband dielectric spectrum experiment, space charge and dc breakdown experiments.Micro experiments show that: 1) Infrared spectrum experiment shows that after different surface treatment, the light transmittance of nano MgO declines. Besides,new characteristic peaks are also introduced. 2) Transmission electron microscopy experiments show that after surface treatment, the dispersion of nano MgO in LDPE is better, when compared to untreated nano MgO/LDPE. 3) Differential scanning calorimetric experimental results show that the crystallinity of treated nano MgO/LDPE increases. The highest of untreated nano MgO/LDPE increases by 1.66% when compared to pure LDPE. The highest of treated nano MgO/LDPE increases by 12.61% when compared to pure LDPE.Broadband dielectric spectrum experiments show that:(1)The dielectric constant of pure LDPE is about 2.2. The dielectric constant of untreated nano MgO/LDPE is 2.2~2.7. The dielectric constant of treated nano MgO/LDPE is 2.2~2.4.(2) The dielectric loss of pure LDPE is below 0.003. The dielectric loss of nano MgO/LDPE is 0.010~0.0194. The dielectric loss of nano MgO/LDPE treated by titanate coupling agent is higher.(3) The conductivity of pure LDPE and nano MgO/LDPE increases with the increase of frequency.Space charge experiments show that: 1) When the concentrations are 0.1wt% 、 1wt% and 2wt%, the accumulation of space charge in nano MgO/LDPE treated by aluminum acid ester coupling agent is less. When the concentrations are 0.5wt%, the accumulation of space charge in nano MgO/LDPE treated by silane coupling agent is less. 2) When the concentrations are 0.1wt%, the attenuation rate of mean charge density in nano MgO/LDPE treated by aluminum acid ester coupling agent is less. When the concentrations are 0.5wt%、1wt% and 2wt%, the attenuation rate of mean charge density in nano MgO/LDPE treated by silane coupling agent is less.Dc breakdown experiments show that:1) Adding nano MgO treated by different surface treatment can improve the breakdown voltage, when compared to pure LDPE. The growth rate of positive polarity dc breakdown field strength is about 22% ~ 53%. The growth rate of negative polarity dc breakdown field strength is about 8% ~ 30%; 2) The growth rate of positive polarity dc breakdown field strength is about 36% ~ 54%, when compared to untreated nano Mg O/LDPE. The growth rate of negative polarity dc breakdown field strength under the concentration of 0.1wt%、0.5wt% and 2wt% is about 5% ~ 36%. The negative polarity dc breakdown field strength under the concentration of 1wt% is smaller than that of untreated nano Mg O/LDPE.