Abstract
Polymeric materials have many applications in multiple industries. In this paper, silicon nitride nanoparticles (Si3N4) were incorporated into a polyimide (PI) matrix to obtain composite films via the in situ polymerization method. The Si3N4 nanoparticles were consistently scattered in the composites, and the thickness of PI/Si3N4 films was around 50 µm. The effects of nanoparticle content on the dielectric constant, loss tangent and breakdown strength were simultaneously studied. A 3 wt.% doped PI/Si3N4 film revealled excellent dielectric properties, a dielectric constant (ε) of 3.62, a dielectric loss tangent (tanδ) of 0.038, and a breakdown strength of 237.42 MV/m. The addition of Si3N4 formed an interface layer inside PI, resulting in a large amount of space charge polarization in the electric field. The space charge of materials from the microscopic point of view was analyzed. The results show that there are trapenergy levels in the composites, which can be used as a composite carrier center and transport channel, effectively improving the performance of a small amount of nanoparticles film.
Highlights
Polyimide (PI) has been broadly used in the fields of electronic packing, the automotive and chemical industries, aerospace and precision machinery, etc. [1,2,3] due to its low dielectric constants, outstanding mechanical properties, high resistance to various temperatures (400 ◦ C), excellent solvent resistance and good biocompatibility [4]
The results show that the thermal stability of the composites is improved, which is due to the high thermal conductivity of silicon nitride
The relationship between the breakdown strength and the space charge is based on the electronic transport in the nanoscale system, gap and small doping amount
Summary
Polyimide (PI) has been broadly used in the fields of electronic packing, the automotive and chemical industries, aerospace and precision machinery, etc. [1,2,3] due to its low dielectric constants, outstanding mechanical properties, high resistance to various temperatures (400 ◦ C), excellent solvent resistance and good biocompatibility [4]. Recent downsizing of current and cost reduction demands a reduction in its thickness. This means that the polyimide film is required to show a good performance as an insulating material under a high electric field and to keep the dielectric constant in some level. In order to achieve this goal, there have been great efforts to use high dielectric constant fillers, such as linear, flaky carbon materials or metal materials. Carbon and metal materials have high electrical conductivity, which seriously affects the insulating properties of the polymer, resulting in a dilemma that the dielectric strength and dielectric constant can only be improved
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