Preparation of carbon membranes from poly ( urethane imide ) and poly-imide copolymers
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摘要: 利用傅立叶变换红外光谱(FTIR)跟踪不同温度下聚氨酯酰亚胺(Poly-urethane-imide,PUI)聚酰亚胺(polyimide ,PI)共聚物(PUI-PI)的热解反应过程,扫描电镜(SEM)表征所制炭膜的结构形貌, N2吸附仪测定计算微孔炭膜的表面积和微孔体积,结合不同PIPUI体系的炭化收缩率、微孔炭膜水通量的分析,研究了由PI-PUI制备微孔炭膜时不同嵌段的热稳定性及其梯度炭化成孔特性。结果显示:氨基甲酸酯基团在200℃~300℃温间分解,酰亚胺基团在500℃~700℃温间热解,分别为炭膜贡献了大孔和微孔;PUI前驱体的加入能有效降低炭膜的收缩率;外加炭黑对减少炭膜的收缩也有一定的作用,并能显著提高炭膜的微孔体积和总孔体积。Abstract: Pyrolysis of poly ( urethane imide ), polyimide and their copolymer was investigated by FTIR spectroscopy and the resultant carbon membrane was characterized by SEM, nitrogen adsorption and a water flux test. Results indicate that the urethane group is decomposed at 200-300℃ while the imide group is decomposed at 500-700℃. The macropores and micropores are formed during the pyrolysis in the thermally labile urethane component and the thermally stable imide component, respectively. The shrinkage of the polymers during pyrolysis decreases with increasing number of urethane groups or decreasing number of imide groups. The pore size of the carbon membrane can be controlled over a wide range by changing the ratio of imide and urethane components. The addition of carbon black can effectively reduce the shrinkage and apparently increase specific surface area and micropore volume.
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