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Nanofibrillated cellulose/nanographite composite films
Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
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2016 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 4, 2487-2500 p.Article in journal (Refereed) Published
Abstract [en]

Though research into nanofibrillated cellulose (NFC) has recently increased, few studies have considered co-utilising NFC and nanographite(NG) in composite films, and, it has, however been a challenge to use high-yield pulp fibres (mechanical pulps) to produce this nanofibrillar material. It is worth noting that there is a significant difference between chemical pulp fibres and high-yield pulp fibres, as the former is composed mainly of cellulose and has a yield of approximately 50 % while the latter is consist of cellulose, hemicellulose and lignin, and has a yield of approximately 90 %. NFC was produced by combining TEMPO (2,2,6,6-tetramethypiperidine-1-oxyl)-mediated oxidation with the mechanical shearing of chemi-thermomechanical pulp (CTMP) and sulphite pulp (SP); the NG was produced by mechanically exfoliating graphite. The different NaClO dosages in the TEMPO system differently oxidised the fibres, altering their fibrillation efficiency. NFC-NG films were produced by casting in a Petri dish. We examine the effect of NG on the sheet-resistance and mechanical properties of NFC films. Addition of 10 wt% NG to 90 wt% NFC of sample CC2 (5 mmol NaClO CTMP-NFC homogenised for 60 min) improved the sheet resistance, i.e. from that of an insulating pure NFC film to 180 Omega/sq. Further addition of 20 (CC3) and 25 wt% (CC4) of NG to 80 and 75 wt% respectively, lowered the sheet resistance to 17 and 9 Omega/sq, respectively. For the mechanical properties, we found that adding 10 wt% NG to 90 wt% NFC of sample HH2(5 mmol NaClO SP-NFC homogenised for 60 min) improved the tensile index by 28 %, tensile stiffness index by 20 %, and peak load by 28 %. The film's surface morphology was visualised using scanning electron microscopy, revealing the fibrillated structure of NFC and NG. This methodology yields NFC-NG films that are mechanically stable, bendable, and flexible.

Place, publisher, year, edition, pages
2016. Vol. 23, no 4, 2487-2500 p.
Keyword [en]
Nanofibrillated cellulose, Nanographite, Nanocomposites, TEMPO, High-speed homogenisation
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:miun:diva-28778DOI: 10.1007/s10570-016-0990-2ISI: 000380089300017Scopus ID: 2-s2.0-84975467623OAI: oai:DiVA.org:miun-28778DiVA: diva2:970709
Available from: 2016-09-14 Created: 2016-09-14 Last updated: 2016-12-19Bibliographically approved
In thesis
1. Mechanical Pulp-Based Nanocellulose: Processing and applications relating to paper and paperboard, composite films, and foams
Open this publication in new window or tab >>Mechanical Pulp-Based Nanocellulose: Processing and applications relating to paper and paperboard, composite films, and foams
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with processing of nanocellulose originating from pulps, with focus on mechanical pulp fibres and fines fractions. The nanocellulose materials produced within this research project were tested for different purposes ranging from strength additives in paper and paperboard products, via composite films to foam materials. TAPPI (Technical Association of Pulp & Paper Industry) has recently suggested a standard terminology and nomenclature for nanocellulose materials (see paper I). In spite of that we have decided to use the terms nano-ligno-cellulose (NLC), microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC) and nanocellulose (NC) in this thesis . It is well-known that mainly chemical pulps are used as starting material in nanocellulose production. However, chemical pulps as bleached sulphite and bleached kraft are quite expensive. One more cost-effective alternative can be to use fibres or fines fractions from thermo-mechanical pulp (TMP) and chemi-thermomechanical pulp (CTMP).

 

In paper II-IV, fractionation has been used to obtain fines fractions that can easily be mechanically treated using homogenisation. The idea with this study was to investigate the possibility to use fractions of low quality materials from fines fractions for the production of nanocellulose. The integration of a nanocellulose unit process in a high-yield pulping production line has a potential to become a future way to improve the quality level of traditional products such as paper and paperboard grades.

 

Paper III describes how to utilise the crill measurement technique as a tool for qualitative estimation of the amount of micro- and nano-material produced in a certain process. The crill values of TMP- and CTMP-based nanocelluloses were measured as a function of the homogenisation time. Results showed that the crill values of both TMP-NLC and CTMP-NLC correlated with the homogenisation time. In Paper V pretreating methods, hydrogen peroxide and TEMPO are evaluated. Crill measurement showed that hydrogen peroxide pretreatment (1% and 4%) and mechanical treatment time did not improve fibrillation efficiency as much as expected. However, for TEMPO-oxidised nanocelluloses, the crill value significantly increased with both the TEMPO chemical treatment and mechanical treatment time. In paper V-VII TEMPO-mediated oxidation systems (TEMPO/NaBr/NaClO) are applied to these fibres (CTMP and Sulphite pulp) in order to swell them so that it becomes easy to disrupt the fibres into nanofibres with mechanical treatment.

 

The demand for paperboard and other packaging materials are steadily increasing. Paper strength properties are crucial when the paperboard is to withstand high load. A solution that are investigated in papers IV and VI, is to use MFC as an alternative paper strength additive in papermaking. However, if one wish to target extremely higher strength improvement results, particularly for packaging paperboards, then it would be fair to use MFC or cationic starch (CS). In paper VI CS or TEMPO-based MFC was used to improve the strength properties of CTMP-based paperboard products. Results here indicate significant strength improvement with the use of different levels of CS (i.e., 20 and 10 kg t–1) and 5% MFC. The strengthening impact of 5% MFC was approximately equal to that of 10 kg t–1 of CS.

 

In paper VII, NFC and nanographite (NG) was used when producing composite films with enhanced sheet-resistance and mechanical properties. The films produced being quite stable, flexible, and bendable. Realising this concept of NFC-NG composite film would create new possibilities for technological advancement in the area of high-yield pulp technology.  Finally, in paper VIII, a new processing method for nanocellulose is introduced  where an organic acid (i.e., formic acid) is used. This eco-friendly approach has shown to be successful, a nanocellulose with a uniform size distribution has been produced.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2016. 93 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 245
Keyword
mechanical pulp, thermo-mechanical pulp, chemi-thermomechanical pulp, fractionation, fines, homogenisation, nanocellulose, nano-ligno-cellulose, microfibrillated cellulose, nanofibrillated cellulose, paper, strength properties, crill, TEMPO, nanographite (NG), composite films
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-29076 (URN)978-91-88025-64-7 (ISBN)
Public defence
2016-04-22, O102, Holmgatan 10, SE-851 70, Sundsvall, 10:56 (English)
Opponent
Supervisors
Note

Vid tidpunkten för disputationen var följande delarbeten opublicerade: delarbete 5 och 7 inskickade, delarbete 6 och 8 manuskript.

At the time of the doctoral defence the following papers were unpublished: paper 5 and 7 submitted, paper 6 and 8 manuscripts.

Available from: 2016-10-11 Created: 2016-10-10 Last updated: 2017-02-28Bibliographically approved

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