Abstract
In this study, pulped cellulose fibres were pre-treated with aqueous morpholine prior to mechanical disruption in the production of cellulose nanofibrils (CNF). The properties of the morpholine pre-treated CNF (MCNF) were closely compared with CNF obtained from carboxymethylation (CMCNF) and TEMPO-oxidation (TCNF) pre-treatment methods. An investigation of the swelling behaviours of cellulose in varying concentrations of morpholine revealed that there is a synergistic behaviour between morpholine and water in its ability to swell cellulose. As a result, cellulose pulp dispersed in 1:1 mole ratio of morpholine to water was well swollen and readily fibrillated by mechanical shear. Surface chemistry analyses indicated that the surface of the MCNF remained unmodified, compared to the CMCNF and TCNF which were modified with anionic groups. This resulted in only a slight decrease in crystallinity index and a minimal effect on the thermal stability of MCNF, compared to CMCNF and TCNF which showed marked decreases in crystallinity indices and thermal stabilities. The average widths of MCNF, CMCNF and TCNF, as measured from electron microscopic images, were broadly similar. The higher polydispersity of MCNF widths however led to a differential sedimentation and subsequent lower aspect ratio in comparison with CMCNF and TCNF as estimated using the sedimentation approach. Also, the presence of electrostatic repulsive forces, physical interactions/entanglements and lower rigidity threshold of the CMCNF and TCNF resulted in higher storage moduli compared to the MCNF, whose elasticity is controlled by physical interactions and entanglements. Aqueous morpholine pre-treatment can potentially be regarded as an ecologically sustainable process for unmodified CNF production, since the chemical reagent is not consumed and can be recovered and reused.
Highlights
Cellulose nanofibrils (CNF), alongside cellulose nanocrystals and bacterial nanocellulose, are the three types of nanocellulose that have been identified in literature (Abdul Khalil et al 2014; Bharimalla et al.2015; Jonoobi et al 2015; Klemm et al 2011; Lavoine et al 2012; Nechyporchuk et al 2016a; Siroand Plackett 2010)
The properties of CNF materials obtained from morpholine pre-treatment have been investigated and compared with the properties of CNFs made from carboxymethylation and TEMPO-oxidation pre-treatments, under the same mechanical processing conditions
Initial swelling of cellulose in various concentrations of morpholine revealed that there is a synergism between morpholine and water, which enhanced the swelling of cellulose
Summary
Cellulose nanofibrils (CNF), alongside cellulose nanocrystals and bacterial nanocellulose, are the three types of nanocellulose that have been identified in literature (Abdul Khalil et al 2014; Bharimalla et al.2015; Jonoobi et al 2015; Klemm et al 2011; Lavoine et al 2012; Nechyporchuk et al 2016a; Siroand Plackett 2010). Keywords Cellulose nanofibrils (CNF) Á Morpholine pre-treatment Á Carboxymethylation Á TEMPO-oxidation Á Surface modification Á Mechanical fibrillation Á Sedimentation Eyholzer et al (2010) showed a 31% decrease in crystallinity index of CNF after carboxymethylation pre-treatment followed by mechanical processing.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
