No abstract

AbstractDuring the fabrication of black polyimide composite films, it is common to introduce carbon black (CB) into this composite system. The introduction of CB significantly decreases the resistivity of the films and consequently has a great effect on the inherent insulation property of polyimide. Here, the exploration of the conductive mechanism of CB/polyimide composite films is aimed to explain the change on resistivity fundamentally. In this study, two kinds of representative CBs were chosen to prepare CB/polyimide composite films. The rudiment of the conductive mechanism was built up based on the resistivity curves, and scanning electron microscopy (SEM), tensile, thermal gravimetric analysis, Fourier transform infrared (FT-IR) spectroscopy, UV, Raman and X-ray diffraction (XRD) were conducted to confirm it. The experimental results further verified the mechanism and gave us a chance to propose an integrated conductive mechanism including three sections (tunneling effect mechanism, conductive network mechanism and doping mechanism) for CB/polyimide composite films. As the conductive mechanism has been understood, it paves the way for optimization of the fabrication of conductive black polyimide films and insulating black polyimide films, even other colorful polyimide composite films.

No abstract

Two kinds of thermoplastic polyimides (PIs) were synthesized via a two-step method with 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 4,4′-oxydianiline (ODA) diamine, and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), and their thermal degradation kinetics was studied by thermogravimetric analysis at different heating rates under nitrogen. Derivative thermogravimetric analysis curves indicated a simple, single-stage degradation process in PI BTDA-BAPP and a two-stage degradation process in PI BTDA-ODA-BAPP. The activation energies ( Eas) of the thermal degradation reaction were determined by the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods without a knowledge of the kinetic reaction mechanism. By comparing the values of Ea and weight loss temperatures, it was demonstrated that the thermal stability of PI BTDA-ODA-BAPP was superior to that of PI BTDA-BAPP.

Polyimide (PI)/mica hybrid films were successfully prepared by in situ condensation polymerization method, in which the mica particles were modified by coupling agent γ-aminopropyltriethoxy silane (APTS) to strengthen the interaction between the mica particles and PI matrix. The morphology, structure, thermal and mechanical properties as well as dielectric properties of PI films were systematically studied via Scanning electron microscope (SEM), Fourier transform infrared spectrometer (FT-IR spectrometer), Thermal gravimetric analysis (TGA), tensile experiments, Thermal mechanical analyzer (TMA), impedance analyzer, etc. The results indicated that the mica particles were dispersed homogeneously in PI matrix, leading to an improvement of the mechanical property, thermal stability and hydrophobicity. It was novel to notice that hybrid films exhibited low coefficient of thermal expansion (CTE) and low dielectric constant simultaneously. The CTE and dielectric constant of hybrid film dropped to 25.36 ppm/k and 2.42 respectively, in the presence of 10 wt% mica into polyimide matrix.