Preparation And Properties Of Composite Polymer-based Dielectric Thin Film

Solution casting method has been employed to prepare dielectric-film materials, including PVDF, PVDF/CN-PVA and PES/CN-PVA. Its dielectric constant dielectric loss and breakdown voltages have already been tested. Its surface morphology, crystalline, thermal stability and thermal-decomposition temperature have been evaluated.It noticed that the dielectric constant of PVDF could be as high of 9.8 with the measurement frequency was 1KHz, its breakdown voltage got reach of 53V/μm, while its dielectric loss no large than 0.035. New material, CN-PVA, has been used to improve the dielectric properties of PVDF/CN-PVA. It found its dielectric constant could as large as 16 with its breakdown voltage being 71V/μm and dielectric loss lower than 0.05 at the same time. Similarly, the dielectric constant of the composite dielectric material PES/CN-PVA was 9.5 at its best. When the mass ratio of PES and CN-PVA was 10:1, PES/CN-PVA got the most high dielectric constant, which as much as 9.5, was three times large as PES. When the measurement frequency was as high as 5MHz, the dielectric loss of PES/CN-PVA still kept lower than 0.03. What’s more, it found that the absorb of new material of CN-PVA has decreased the breakdown voltage of PES/CN-PVA, but its breakdown voltage still maintained in the level of 80 V/μm.According to the research, it found that the permittivity of the film would increase while the film became thinner when the thickness of the film was less than 10μm, which was called “thin-bed effect”.The surface morphology of PVDF indicate that there were α-phase crystalline and β-phase crystalline present in the film of PVDF. While there were tuft grid crystalline in CN-PVA, and the molecules of PES keep short-range regular arrangement, and the crystalline of PES/CN-PVA presence as starfishes.The diffraction curves and the infrared spectrograms showed that there are α-phase crystalline and β-phase crystalline present in the film of PVDF, and there are crystalline appeared in the interface of PES/CN-PVA, while the PES was amorphous.According to the DSC curves, it found that the crystallinity of α-phase crystalline of PVDF was 66.13%. The crystallinity of α-phase of PVDF/CN-PVA was 58.85% and the crystallinity of β-phase crystalline was 6.43%.What’s more, the TGA curves of PVDF, PVDF/CN-PVA and PES/CN-PVA have been evaluated. The thermal decomposition temperature of PVDF was 461.4℃, while the thermal decomposition temperature of PVDF/CN-PVA was about 293℃. The TGA curves of PVDF/CN-PVA has two inflection points. And the thermal decomposition temperature of PES/CN-PVA was 250.2℃.