Cellulose/Expandable Graphite Composite Aerogels with Good Flame- Retardant and Filtration Performance

Abstract

Cellulose has been widely used in filtration owing to its abundance, low density, and high specific surface area. However, the use of cellulose-based scaffolds for filtration under high temperatures or with sparks is difficult to realize because cellulose is highly flammable. To develop an advanced cellulose-based filtration material with excellent flame-retardant and filtration performance, in this study, an ice template is employed to prepare a cellulose/expandable graphite (EG) aerogel with a direction porous structure for filtration. The effect of the EG concentration in the aerogel on the aerogel’s physical properties, as well as its flame-retardance and filtration performance is investigated. Experimental data indicates that a compound aerogel with a 30 wt% EG concentration is extinguished immediately after leaving the fire source and has a self-extinguishing time as short as 0.155 s. The formation of a direction porous structure in cellulose/EG aerogels provides a pathway for air movement during the filtration process. The use of EG could improve the filtration performance of cellulose aerogels by increasing the specific surface area. When the EG concentration in the aerogel is 30 wt%, the blocking efficiency of particle sizes less than 0.3 and 0.5 µm reaches 98 % and 99 %, respectively, and the blocking efficiency of particle sizes less than 1.0 µm is 96 %. As-prepared cellulose/EG aerogels have good mechanical properties and thermal stability, which implies that they can be used for filtration under high temperatures and sparks. Moreover, the filtration performance of cellulose/EG aerogels prepared using ice templates with direction porous structure and excellent flame-retardance can potentially be used for filtration-based applications under high temperature and electrical spark conditions. The use of EG and direction porous structures in cellulose aerogels provides a novel idea for the functionalization of cellulose scaffolds.