Preparation and characterization of carbon materials from phenol formaldehyde resin with pore forming substance

This paper describes the carbonization behavior of phenol-formaldehyde resin (PF) blended in the presence of simple organic substances of m-phthalic acid (PA), trimesic acid (TMA) and phloroglucinol (PG). The weight loss and heat flow were monitored in order to study their carbonization behavior by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), respectively. These organic additives showed some interactions with PF during heat treatment up to 1273 K in a flowing argon. The temperature range, at which interactions occurred, depended upon the type of pore formers. Examination of TGA and DSC results indicates that effectiveness of interaction between pore former and PF at their interface is as follows: PG>TMA>PA. It is suggested that phenolic group in pore formers interacted strongly with PF than carboxylic group does, thus changing the carbonization behavior during heating process of PF resin. 1.Introduction Blending method has been studied as a possible method to prepare porous carbon materials without further activation. This method includes a manner, which pore former is blended in carbon precursor. The pore former decomposes during heat treatment, leaving pores in carbon matrix. Hatori et al. [1, 2] and Takeichi et al. [3, 4] applied blending method to prepare carbon films, which possess mesopores and macropores. They used polyimide membranes as a carbon precursor. Oya et al. [5,6] prepared mesoporous carbon fiber from phenol formaldehyde resin as carbon precursor, suggesting that the blending method leads to the possibility of modifying pore surface. Horie et al. [7, 8] loaded metals onto pore surface by carbonizing phenol-formaldehyde resin that was blended with pore former containing Pt(II)-acetylacetonate. On the other hand, Horikawa et al. [9] reported that there was an interaction between phenol formaldehyde resin and pore former, resulting in the decomposition of pore former and the formation of pores. In our preliminary experiments, we found carbon precursor derived from phenol formaldehyde resin blended with benzoic acid yielded higher carbon residue than the expected yield calculated from the ratio of PF and benzoic acid [10]. It was because their carbonization behavior was affected by interactions between phenol formaldehyde resin and benzoic acid. Our final goal is to control pore surface structure by using these interactions at interface between carbon precursors and pore formers. Therefore, it is important to investigate their carbonization behavior. In this paper, we use phenol formaldehyde resin (PF) as a carbon precursor and simple organic substances as a pore former, and studies interactions between PF and organic substance by using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). 2.Experimental 2-1. Materials Phenol formaldehyde resin (Gun-ei chemical Ind. Co: PF) was used as the carbon precursor. Pore formers, which have several functional groups of phenolic and carboxylic groups. The pore formers used in this study were as follows; m-phthalic acid (Wako chemical Co. Ltd., designated as PA), trimesic acid (Wako chemical Co. Ltd., TMA) and phloroglucinol (Wako chemical Co. Ltd., PG). Table 1 is a summery of pore formers studied in the present work. Table 1 Summery of pore former studied in this work Abbreviation Melting point* [K] Empirical formula Molecular structure Substance COOH