Preparation and characterization of functional cellulose nanofibrils via formic acid hydrolysis pretreatment and the followed high-pressure homogenization

Abstract

This article described a sustainable route, which combined relatively mild formic acid (FA) hydrolysis pretreatment of bleached softwood pulp with high-pressure homogenization, to prepare cellulose nanofibrils (F-CNFs). Results showed that the prepared F-CNFs had high thermal stability (e.g. the onset decomposition temperature was over 290°C). Also, it was found that the prepared F-CNFs were more homogeneous and the length of the F-CNFs became shorter with the increase of hydrolysis time in FA hydrolysis, and a maximum crystallinity index of about 52.9% could be achieved when the hydrolysis time was 6h. Compared to H-CNFs (prepared by HCl pretreatment), F-CNFs showed better dispersibility in DMSO, DMF and DMAC respectively because of the introduction of ester groups on the surface of F-CNFs. This high compatibility leads to that the F-CNFs may have great potential in reinforcing polymeric matrix materials. In addition, FA could be easily recovered. Thus, FA hydrolysis pretreatment plus high-pressure homogenization could be a sustainable and economically feasible process for the production of CNFs.