Dielectric Study Based On PEI Nanocomposites And Their Surface Effects

Polyetherimide,often known as PEI,is a high-performance polymer with stable dielectric properties,outstanding mechanical capabilities,and thermal stability.However,because of its low dielectric constant,its applications are restricted in the electrical and electronic domains.This thesis will begin with two ways to overcome the challenges that have been outlined above:Initially,we doped the polymer matrix with inorganic nanoparticles that had a low dielectric constant to improve the dielectric constant of polymer nanocomposites without significantly sacrificing the breakdown strength.Subsequently,while analyzing polymer nanocomposite films,we discovered that the film thickness also affects the dielectric properties.Consequently,we tested the change in the dielectric properties of pure polymer films with varying thicknesses.As a result,the effects of varying the thickness of pure polymer films were evaluated for their effects on the dielectric characteristics of the films,and the mechanisms behind the effects were investigated in greater detail.The following is an outline of the primary findings and conclusions from the experiment:(1)MgO/PEI polymer nanocomposites were prepared and tested for changes in their dielectric and energy storage properties.When the content of MgO nanoparticles is 0.3 vol%,the dielectric constant is enhanced to 4.5,which is about 1.4 times that of PEI films,due to the enhancement of the dielectric response by the interfacial polarization effect;while the dielectric constant of the composites is 6.5 when the content of MgO nanoparticles reaches 20 vol%,which is about 100%higher compared to PEI films,where the main factor is that the introduction of high volume fraction of MgO nanoparticles would provide more free volume,favoring the dielectric response of some of the dipoles,when the polymer film thickness also increases significantly,which raises speculations about surface effects.(2)In this study,thin film samples of two common polymers,poly(vinylidene fluoride-trifluoroethylene)[P(VDF-TrFE)]and poly(ethylene imide),were made with varying thicknesses so that the surface effects of each polymer could be studied.The dielectric constants of PEI polymer films grew from 3.4 to 5.8 as the thickness of the films increased from 10 μm to 50 μm,representing an increase of almost 71%.On the other hand,the ferroelectric polymer P(VDF-TrFE)has an enhanced dielectric constant and a greatly increased piezoelectric coefficient.The piezoelectric coefficient of the P(VDF-TrFE)polymer film was 28.5 pC/N when its thickness reached 50 μm,approximately 44%greater than that of the 10 μm film.Testing and characterizing polymer film samples of varying thicknesses allowed for the investigation of the effect of thickness on dielectric characteristics,hysteresis lines,and the piezoelectric effect.Moreover,the surface effect was verified during this process.