In situ preparation and characterization of polyimide/silica composite hemispheres by inverse aqueous emulsion technique and sol-gel method

Abstract

In this paper, micron-scale polyimide/nano-silica (PI/nano-SiO 2 ) composite hemispheres were fabricated by employing inverse aqueous emulsion technique and sol-gel method. Homogeneous inverse emulsion was obtained through using the precursor solution as dispersed phase which contained poly(amic acid) ammonium salt (PAAS), tetraethyl orthosilicate (TEOS) and deionized water, liquid paraffin (LP) as continuous phase, and Span80 as surfactant. The PI/SiO 2 hybrid hemispheres could be got by adding excess dehydrating agent into the emulsion. The Fourier transform infrared (FT-IR) results demonstrated that PAAS had been converted to polyimide (PI) after adding the dehydrating agent into the emulsion and that the success of the reaction between TEOS molecules. The research showed that the morphologies of PI/SiO 2 hybrid hemispheres, compared with the pure PI hemispheres, were still hemispherical and did not change with the varied silica contents. The surfaces of these samples were without clear interface between the SiO 2 particles and the polymer matrix. And, the SEM images of the hybrid hemispheres after hydrofluoric acid (HF) etching or high temperature calcination showed that the SiO 2 particles were well dispersed in the organic component, and the diameter of silica particles was nano-scale. The EDX results of the spheres which were after etching in hydrofluoric acid solution or after calcination showed that some 99.98 % of the silica particles were removed and the success of the removal of the organic component, respectively. Furthermore, thermal gravimetric analysis (TGA) results showed that the thermal stability of PI hemispheres could be improved by incorporating the inorganic component.

Synergistic improvement of mechanical and thermal properties in epoxy composites via polyimide microspheres

“…PI microspheres were prepared by nonaqueous inverse emulsion polymerization as reported in the previous literature 36,37 . Initially, as shown in Figure 1, the compound surfactants Span‐85 and Tween‐80 were added to the continuous phase liquid paraffin in a certain proportion and stirred at room temperature for 2 h. Then 10 mmol of ODA was dissolved in 18 ml DMF and mixed with above system at 40°C for 2 h under ultrasonic to form a stable Span85 + Tween80‐DMF‐LP nonaqueous emulsion.…”

Phosphine oxide based polyimides: structure–property relationships

“…11 The main approaches to achieve these results include the incorporation of thermally stable and exible or asymmetrical linkages, introduction of large polar or non-polar pendant substituents and/or interruption of the chain symmetry and of molecular iteration by copolymerization reactions. 9,[12][13][14] One approach which is worth to investigate is the incorporation of phosphorus based moieties in the polyimide backbone not only to improve the physical properties and its processability but also to simultaneously enhance its ame resistance. Moreover, chemically incorporated reactive phosphoruscontaining monomers into the polymer backbone can avoid several problems, such as leaching over time.…”

Preparation and Prospect of Polymer Nanocomposites Used in High Voltage Equipment

“…Kuan et al [25] prepared PMMA/VTES-g-EG composites by this method and studied its thermal stability. Ma et al [26] investigated the preparation of PI/SiO2, the SEM images of PI/SiO2 composite particles by this method are shown in Fig. 8.…”

“…Fig.8 (a, b) SEM images of PI/SiO2 composite particles. [26] Prospect At present, the main ways for preparing polymer nanocomposites include the above mentioned four methods. There are different characteristics and application range for each method respectively.…”