不同製備條件酚醛樹脂氣凝膠及碳氣凝膠之孔隙特性

The Pore Characteristics of Phenol-formaldehyde Aerogels and Carbon Aerogels Prepared under Different Conditions

林睿晨(Ruei-Chen Lin) ； 李文昭(Wen-Jau Lee)

《林產工業》 37卷2期 (2018/06) Pp. 111-120

https://doi.org/10.6561/FPI.201806_37(2).0005

摘要

碳氣凝膠（Carbon aerogel）為一種特殊的輕質多孔性碳材料，本研究以酚和福馬林為原料，碳酸鈉為催化劑，在不同甲醛／酚（F／P）、碳酸鈉／酚（C／P）莫耳比、反應物濃度、反應溫度條件下製作酚醛樹脂（Phenol-formaldehyde；PF）水凝膠（Hydrogels），將水凝膠經-20℃凍結後，利用冷凍乾燥脫水使形成氣凝膠（Aerogels），再以700℃加熱形成碳氣凝膠。由試驗結果得知，較高反應物濃度及較大F／P、C／P莫耳比混合液所需膠化時間較短。SEM圖顯示經冷凍乾燥脫水之氣凝膠為相互連結之顆粒狀粒子所構成，其孔隙結構以中孔為主，氮氣等溫吸脫附曲線屬於IUPAC分類Type IV（a）型。氣凝膠經700℃加熱後之碳化收率48.1～58.6%，所得碳氣凝膠同時具備微孔及中孔結構。與氣凝膠比較，碳氣凝膠之比表面積大幅增加，平均孔隙直徑明顯減小。其中以F／P莫耳比2／1，C／P莫耳比3／1之碳氣凝膠有較發達的孔隙結構，其比表面積達598 m^2／g。

關鍵字

氣凝膠 ； 碳氣凝膠 ； 冷凍乾燥 ； 水凝膠 ； 酚醛樹脂

並列摘要

Carbon aerogel is a special lightweight porous carbon material. In this study, phenol and formalin were used as raw materials, sodium carbonate was used as a catalyst. Phenol-formaldehyde resin (PF) hydrogels having different formaldehyde/phenol (F/P) and sodium carbonate/phenol (C/P) molar ratios were prepared at different reactant concentrations and reaction temperatures. After the hydrogel was frozen at -20℃, it was dehydrated by freeze-drying to form an aerogel, followed by heating at 700℃ to form an carbon aerogel. The experimental results showed that the mixture with a higher reactant concentration and a larger F/P and C/P molar ratio had a shorter gelation time. The SEM image showed that the aerogel which was dehydrated by freeze-drying was composed of mutually connected granular particles. The pore structure of aerogel is dominated by mesoporous type. The nitrogen isotherm adsorption-desorption curve of the aerogel belongs to the type of IV(a) as defined by the IUPAC classification. The carbonization yield of the aerogel after heating at 700°C was between 48.1% and 58.6%, and the obtained carbon aerogel had both microporous and mesoporous structures. Compared with aerogels, the specific surface area of carbon aerogels was greatly increased, and the average pore diameter was significantly reduced. Among them, the carbon aerogel with the F/P molar ratio of 2/1 and C/P molar ratio of 3/1 had a more developed pore structure which had a specific surface area of 598 m^2/g.

並列關鍵字

Aerogels ； Carbon aerogels ； Freeze-drying ； Hydrogels ； Phenol-formaldehyde resin