含生質物酚醛樹脂製作氣凝膠及碳氣凝膠之性質

Properties of aerogels and carbon aerogels prepared with biomasscontaining phenol-formaldehyde resin

本研究以酚/甲醛/碳酸鈉/水之混合液製作酚醛樹脂（Phenol-formaldehyde resin| PF）水凝膠（Hydrogels），設定甲醛/酚莫耳比3/1，碳酸鈉/酚莫耳比1/3，反應物濃度20%，並利用木材鉋花（Wood shavings| WS）、椰子殼纖維（Coconut shell fiber| CSF）、影印廢紙（Copying paper| CP）及廢紙纖維（Waste paper fiber| WPF）為添加物。隨後將經-20°C凍結之水凝膠利用冷凍乾燥脫水形成氣凝膠（Aerogels），再以800°C加熱形成碳氣凝膠（Carbon aerogels），探討添加不同種類生質物對所製作氣凝膠及碳氣凝膠孔隙性質之影響。由試驗結果得知，生質物的容積密度受其外觀型態所影響，酚/甲醛/碳酸鈉水溶液在密封環境下經90°C加熱可形成水凝膠，添加生質物可降低PF樹脂水凝膠脫水時之收縮應力，並維持其完整形態。生質物添加可提高PF樹脂氣凝膠之吸附能力，氣凝膠經過高溫處理形成碳氣凝膠時可增加其比表面積及總孔隙體積，並降低平均孔隙直徑，其中微孔體積增加比率大於中孔體積增加比率。WPF-PF、WS-PF及CP-PF三種碳氣凝膠之吸脫附曲線屬於International Union of Pure and Applied Chemistry（IUPAC）分類之TypeⅣ（a）型，其中並以WPF-PF碳氣凝膠有最大的吸附能力，WS-PF碳氣凝膠次之。

In this study, a phenol/formaldehyde/sodium carbonate/water mixture was used to make phenol-formaldehyde resin (PF) hydrogels. The molar ratio of formaldehyde/phenol and sodium carbonate/ phenol were set to 3/1 and 1/3, respectively| and the reactant concentration was set to 20%. In addition, wood shavings (WS), coconut shell fiber (CSF), copying paper (CP) and defibrated waste paper fiber (WPF) were used as additives. After the hydrogel was froze at -20°C, it was dehydrated by freeze-drying to form an aerogel, followed by heating at 800°C to form a carbon aerogel. The effects of adding different kinds of biomass on the pore properties of aerogels and carbon aerogels were investigated. The results showed that the bulk density of biomass was affected by its appearance. A phenol/formaldehyde/sodium carbonate aqueous solution could form a hydrogel by heating at 90°C in a sealed environment. The addition of biomass reduced the shrinkage stress of the PF hydrogel during dehydration and maintain its shape. The adsorption capacity of PF aerogel was improved by adding biomass. When the aerogel was converted into a carbon aerogel by high temperature treatment, its specific surface area and total pore volume was increased, and the average pore diameter was reduced. The ratio of the increased micropore volume was greater than that of the mesopore volume. The nitrogen isothermal adsorption-desorption curve of the carbon aerogel of WPF-PF, WS-PF and CP-PF belonged to Type IV(a) of the IUPAC (International Union of Pure and Applied Chemistry) classification. Among them, carbon aerogel of WPF-PF had the largest adsorption capacity, followed by the carbon aerogel of WS-PF.