| Summary: | 碩士 === 中國文化大學 === 材料科學與製造研究所 === 92 === The sorption and diffusion of supercritical carbon dioxide (SCCO2) into polyetherimide (PEI) was investigated in this study. PEI were treated with CO2 at a temperature ranged from 40oC to 60oC and pressure ranged from 20MPa to 40MPa and soaking times between 0.25 and 52 h. The solubility of carbon dioxide in polymer was measured by a gravimetric method under various conditions.
The CO2 — PEI system was found to be well fitted to the Fickian diffusion model, which was applied to calculate the sorption amount and the diffusivity. The change of weight-loss phenomenon, and physical properties (e.g. the modulus of elasticity) were followed systematically. The equilibrium sorption amount (Ms) of CO2 in PEI was from 9.0wt % (at 60oC and 20MPa) to 12.8 wt % (at 40oC and 40MPa). The sorption amount increased with pressure and decreased with temperature of SCCO2. According to the crossover of solubility isotherm versus SCCO2 density, it was indicated that a change of sorption phenomena in PEI at SCCO2 density about 893kg/m3. The interaction of carbon dioxide with polymers at various desoption time was also been demonstrated by fourier transform IR spectroscopy. The evidence of the interaction was the observation of the CO2 antisymmetric stretching mode ( ) near 2340 cm-1, this indicated that CO2 had specific interaction with imides group in PEI, carbonyl group in PC and sulfonyl group in PSF. Comparison of DMA measurement of pure and CO2 treated polymer, which showed a shift in glass transition temperature after CO2 treatment, this implied that PEI, PC, and PSF had plasticized by CO2. The CO2 sorption amount in PC was greater than that of others because the carbonyl group in PC had stronger interaction with CO2 and could absorb more CO2. This implied that the greater degree of plasticization on PC by CO2. For this reason DMA measurement showed that PC had a greater shift in glass transition temperature after CO2 treatment than that of PEI and PSF.
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