Abstract

Preparation of modified expandable graphite with boric acid as assistant intercalator

Author(s): Xiuyan Pang, Shuxia Ren, XuezhiYang

With KMnO4 as oxidant, H2SO4 as intercalator and boric acid (H3BO3) as assistant intercalator, modified expandable graphite (written as EGB) was successfully prepared in oxidizing and intercalating reaction of natural graphite. When themass ratio of C:KMnO4:H2SO4(98%):H3BO3 was controlled as 1.0:0.4:5.0:0.6 (g·g-1), H2SO4 diluted to amass concentration of 78 wt%before intercalation reaction, and the reaction lasted 40 min at 40°C, the expanded volume and initial expansion temperature of the prepared EGB reached 570mL·g-1 (at 800!) and 141°C, respectively. XRD pattern testified its intercalation and layer structure and FTIR spectroscopy illuminated the main functional groups of intercalating composite. Flame retardancy of EGB for linear lowdensity polyethylene (LLDPE) was also investigated.Addition of 30 wt % the EGB to the polymer improved the limiting oxygen index (LOI) from17.6 to 30.2%, and theUL-94 reachedV-0 level.Whereas, the LOI of the same amount normal expandable graphite (EG)was only 25.1%, and theUL- 94 only reached V-1 level.