Papers by Keyword: Polyimide Film

Abstract: Polyimide films treated with an alkali and ion exchange undergo surface-confined hydrolysis to produce polyimide composites. On the other hand, it is unclear what impact this method has on the mechanical properties of PI films. This paper reports the effects of the mechanical properties of PI films exposed to an alkali (KOH) solution with different treatment time. The mechanical properties of the re-cycloimidization PI films were improved when the proper initial KOH treatment time was used. The reason might be that PI could effectively reduce the formation of the shear zone to cracks due to the increase in ductility after the proper KOH treatment and more ductile PI chains led to re-orientation at the drawing process. Therefore, the strength and elongation of the re-cycloimidization PI films were better than those of the pristine PI films. This study focused on the effects of the KOH treatment on the mechanical properties of the PI film for the first time and proposed a mechanism to explain the reason that the appropriate time of KOH treatment can enhance the mechanical properties. The results presented here can provide guidelines for preparing composite PI films via ion-exchange by the proper KOH treatment time in future studies.

Abstract: Polyimide (PI) has good mechanical properties, heat resistance and low temperature performance, and thus shares a wide range of applications. Atmospheric pressure plasma jet was designed for polyimide films surface modification in this paper. The impacts of exposure time and gas ratio on the film surface morphology and property were studied. Scanning Electron Microscope (SEM) results prove that the treated film surface becomes rough and the contact angle decreases rapidly with exposing to plasma. The contact angle did not decrease anymore after extending plasma exposing time to 20 seconds Moreover the intensity of C=O absorption band increases as shown in the Fourier transform infrared spectroscopy (FTIR).

Abstract: This study explores the dynamic mechanical properties (e.g., storage shear modulus, loss tangent and shear viscosity) and formability of a polyimide film by visco-elasticity measurement and hot-embossing tests. The variations of storage shear modulus, tangent delta and the shear viscosity were measured as a function of the temperature for two frequencies. As a polyimide goes through its glass transition, it exhibits dramatic decreases in shear modulus and viscosity as well as the peak of tangent delta, and continues to show strong dependence on frequency and temperature. Moreover, the filling characteristics (e.g., surface appearance, replicated depth and surface roughness) of polyimide were investigated by hot-embossing tests at different temperatures using a mold with an aspect ratio of 2.5:1.

Abstract: Surface modification of polyimide(PI) films was treated with oxygen RIE by varying ion doses from 1x1016 to 1x1018 ions/cm2 at an ion beam energy of 250 eV. Following the modification of PI surface, metal films consisting of NiCr/Cu and Cu were deposited on modified PI films by D.C. magnetron sputtering and electroplating, respectively. The surface modified PI film was characterized by XPS, AFM, SEM and contact angle measurement, respectively. The water contact angle of PI film decreased significantly from 64° to 4.4° with an increase of ion dose, indicating that the surface energy of PI film increased. The XPS spectrum showed that functional group, particularly C-O bonding, on modified PI surface was significantly increased by interaction between scissored unstable chains and reactive ions. The modified PI film surfaces by oxygen RIE showed significant improvement in adhesion to a overcoated metal film of NiCr/Cu.

Abstract: In this work, the effects of atmospheric-pressure plasma treatment of polyimide films on surface and dielectric characteristics were studied by using X-ray photoelectron spectroscopy (XPS), surface free energies, and dielectric spectrometer. The total surface free energies and dielectric constants of plasma treated polyimide film were deareased with increasing the treatment time, which was mainly due to a lower London-dispersive component, while the specific component was increased. This could be attributed to an increase of the polar fluorine groups of polyimide per unit surface area. And the fluorine content of the polyimide film was increased with increasing the amount of the treatment time, resulting in decreasing dielectric constant of the film. It was found that the replacement of fluorine led to the decrease of the local electronic polarizability of polyimide, or to the increase of the free volume, which could be attributed to the relatively large volume of fluorine.

Abstract: Constraction and characteristics of sorption polymeric relative humidity sensors, sorption SiOx microhumidity sensors, and condensation type (dew point) sensors are compared. The characteristics of the sensors are examined in dew point range from -80 to +20oC. An integrated multifunctional humidity sensor, for measurements in wide humidity range at different conditions is developed. The sensors are intended for use in various branches of industry, and in scientific researches.