Graphitization of lignin-modified phenolic resins: role of lignin pretreatments

Abstract

Aiming at the generation of graphitic carbon from low-cost phenolic resins, this study investigated the role of lignin pretreatments on the amount of crystalline carbon generated from lignin-phenol-formaldehyde resins containing boron oxide, boric acid and ferrocene as graphitizing additives. Kraft lignin used to synthesize the resins was initially subjected to thermal and thermomechanical treatments to improve processability and promote greater mobility for ease of graphitization during carbonization. The results showed that the characteristics of lignin used to prepare the thermosetting resins affect the quantity of graphitic carbon that was generated during pyrolysis. The lignin-modified resin prepared using Kraft lignin, which has the lowest molecular weight and polydispersivity values produced the highest amount of graphitic carbon. This formulation containing 10 wt.% boric acid presents a graphitization level value of 73%. In addition, limited amounts of crystalline carbon were generated when boron oxide and ferrocene were used as graphitizing additives.