Synthesis And Performance Evaluation Of A Polyimide Microsphere

In recent years, microscale materials have aroused people’s wide concern. They are going to be applied in a diverse area of application, including the fields of aerospace, opto-electronics and medical apparatus and instruments. Because polyimide microspheres not only have microspheres’characteristics, like large specific surface area, strong adsorption and agglutination, but also show polyimide’s excellent heat resistance, high mechanical strength and eminent dielectric properties, they will have a broader application prospect.To prepared polyimide microspheres which had excellent heat resistance and good water-dispersion stability, flexible diamine and dianhydride monomer,1,3-bis (3-aminophenoxy) benzene (m-APB) and 3,3’,4,4’-diphenyl ether dianhydride (ODPA), were used to synthesize polyamide acid by two-step method, and phthalic anhydride (PA) was used as the blocking agents. Then soluble polyimide solution was obtained by chemical imidization. Finally, polyimide microspheres were prepared successfully by re-precipitation method.The influences of synthesize polyamide acid solution and chemical imidization process were tested by rotational viscometer. In addition, the appropriate storage conditions were determined by testing the viscosity of polyamide acid solution. The results showed that the viscosity of polyamide acid was larger at room temperature (25℃) after reaction of 9h. The larger storage solid content was or the lower storage temperature was, the greater the viscosity of polyamide acid solution was. But the polyamide acid should be performed as soon as possible for subsequent experiments, in order to ensure the stability of the polyamide acid solution. The viscosity of polyimide was larger at room temperature (25℃) after reaction of 12h. And the product was confirmed to be the polyimide which was partly imidized through infrared spectrum analysis and the conductivity of polyimide acid solution.Polyimide microspheres particle size was tested under different conditions by particle size analyzer test and the effects on polyimide microspheres particle size were also analyzed. It was found that the size of microspheres could be changed by varying precipitant, mixing speed, the solid content of polyimide solution and polyimide solution/cyclohexane volume ratio, respectively. With the extension of incubation time, the particle size of polyimide microspheres increased, but the size had little change after reaching a certain time. Because of the rigidity of the polyimide segment increased, the segmental motion was poor, and the particle size of microspheres would also increase.The result of scanning electron microscopy test showed that the morphology of polyimide microspheres was good. Through DSC and TG experiments, the glass transition temperature of polyimide microspheres was discovered, namely 208℃. This indicated that weight loss temperature was higher, which illustrated that the polyimide microspheres had excellent heat resistance. The polyimide microspheres were dispersed in water. With the extension of standing time, the solution had no obvious settlement. It concluded that the polyimide microspheres which including some polyamide acid could formed emulsion with good water-dispersion stability.The application of polyimide microspheres in the process of profile control and water shutoff was tested by multi-function core displacement device. According to the result, polyimide microspheres had characteristics of "able to inject, able to block, able to move". So polyimide microspheres could be used for profile control and water shutoff, and effectively enhance oil recovery.