| Summary: | 碩士 === 國立臺灣大學 === 化學工程學研究所 === 90 === For the potential of applying supercritical fluid technology on polymer chemistry, this study investigated the interaction of supercritical carbon dioxide (SCCO2) — polycarbonate(PC) system. By the Isco high pressure equipments and Fickian diffusion model, the sorption and diffusivity of carbon dioxide in the PC substrate have been measured. Based on such results, this research also applied the SCCO2 on synthesizing conducting polypyrrole (PPy) polymer composites. The substrate, PC or polystyrene (PS), is firstly impregnated with pyrrole monomer in the SCCO2 atmosphere. The impregnated substrate is then soaking in the iron(III) chloride aqueous solution to generate a conducting polymer composite. By varying the impregnation time of each substrate, the morphology, conductivity, composition of the composite have been investigated and discussed.
The CO2 — PC system is found to be well fitted to the Fickian diffusion model. The solubility of CO2 in PC raises from 7.6 wt.% at high temperature and low pressure to 14.7 wt.% at low temperature and high pressure. The crossover of solubility isotherm has been found when the SCCO2 density is about 680 kg/m3, which indicates a change of sorption phenomena. Contrary to previous author, the CO2 desorption diffusivities (Dd) is larger than the sorption diffusivities (Ds) at low temperature range in this study. The CO2 plasticizing effect on polymer substrate can be used to explain the antithetic result. And the CO2 plasticizing effect on PC has been verified by tensile testing.
In this study, the synthesizing conducting polymer composites with and without SCCO2 are compared. The surface morphology of composites become more delicate with SCCO2 impregnating process and result in raising of conductivities. Furthermore, the different CO2 sorption amount and desorption rate of PC and PS polymer substrate lead to the difference of PPy content inside the polymer substrate. The conductivity of PPy/PS composite reaches 5 10-2S/cm. The scanning electron microscope images and element analysis results indicate that PS can be a better substrate than PC.
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