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Polycaprolactone  Nanocomposites Reinforced  with   Cellulose Nanocrystals  Surface - modified  via  Covalent  Grafting  or  Physical Adsorption - a Comparative study
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. 831220-7585. (Coating Technology)ORCID iD: 0000-0002-3755-722X
(English)Manuscript (preprint) (Other academic)
Keyword [en]
cellulose nanocrystals, covalent grafting, physical adsorption, reversible-deactivation radical polymerization (RDRP), polycaprolactone (PCL), nanocomposites.
National Category
Polymer Technologies
Identifiers
URN: urn:nbn:se:kth:diva-184107OAI: oai:DiVA.org:kth-184107DiVA: diva2:914548
Note

QS 2016

Available from: 2016-03-24 Created: 2016-03-24 Last updated: 2016-03-24Bibliographically approved
In thesis
1. Surface Modification of Nanocellulose towards Composite Applications
Open this publication in new window or tab >>Surface Modification of Nanocellulose towards Composite Applications
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanocelluloses have attracted great interest during recent decades owing to their renewability, abundancy and remarkable physical and mechanical properties. The aim of this work was to investigate new strategies for surface modification and functionalization of nanocelluloses and their subsequent incorporation in polymer-host matrices.

Nanocomposites of cellulose nanofibrils (CNF) and polycaprolactone (PCL) were produced by employing CNF nanopaper (NP) as a template and surface-initiated ring-opening polymerization (SI-ROP) of ε-caprolactone (ε-CL). SI-ROP of ε-CL from filter paper (FP) was also carried out for comparison. A larger amount of PCL was grafted from NP than from FP. The grafted NP had stronger mechanical properties than neat PCL.

Cellulose nanocrystal (CNC)-reinforced polyvinyl acetate (PVAc) nanocomposites were also investigated. CNC were modified via “SI-reversible addition-fragmentation chain transfer and macromolecular design via the interchange of xanthate” (SI-RAFT/MADIX) polymerization of vinyl acetate (VAc). The resulting nanocomposites exhibited improved mechanical performance than the unmodified CNC.

It is generally agreed that covalent grafting is superior to physical adsorption for the modification of a reinforcing agent. However, this hypothesis has never been thoroughly investigated. CNC was modified either through covalent grafting or through physical adsorption of poly(butyl methacrylate) (PBMA). Both methods resulted in improved mechanical performance than that of pure PCL or PCL containing unmodified CNC. However, covalent grafting gave the best mechanical performance even at high relative humidity.

Functionalized CNC (F-CNC) were obtained through a versatile methodology employing organic acids bearing a functional group were employed for the simultaneous acid hydrolysis and esterification of cellulose fibers. This provided a facile route for the preparation of F-CNC.

Abstract [sv]

Intresset för nanocellulosa har ökat markant under de senaste decennierna eftersom de är förnyelsebara, finns att tillgå i stor mängd, och har mycket bra fysikaliska och mekaniska egenskaper. Syftet med detta arbete var att undersöka nya strategier för ytmodifiering och funktionalisering av nanocellulosa och dess inkorporering i polymera matriser.

Nanokompositer av cellulosa nanofibriller (CNF) och polykaprolakton (PCL) framställdes genom att CNF nanopapper (NP) användes som ett startmaterial från vilken ε-kaprolakton (ε‑CL) polymeriserades med ringöppningspolymerisation (SI-ROP). Som jämförelse ympades även ε-CL från filterpapper (FP) med SI-ROP. Resultatet var att större mängd av polykaprolakton (PCL) ympades från NP jämfört med FP. Det ytmodiferade NP hade bättre mekaniska egenskaper jämfört med ren PCL.

Nanokompositer av cellulosananokristaller (CNC) och polyvinylacetat (PVAc) undersöktes också. CNC modifierades via “SI-reversible addition-fragmentation chain transfer and macromolecular design via the interchange of xanthate” (SI-RAFT/MADIX) polymerisation av vinylacetat (VAc). Nanokompositerna uppvisade bättre mekaniska egenskaper jämfört med omodifierade CNC.

Man har antagit att kovalent ympning är en överlägsen metod för modifiering av ett förstärkande element jämfört med fysikalisk adsorption, men denna hypotes har aldrig undersökts ordentligt. CNC har modifierats endera genom kovalent ympning eller fysikalisk adsorption av poly(butylmetakrylat) (PBMA). Båda metoderna gav förbättrad mekanisk prestanda jämfört med ren PCL och PCL innehållande omodifierad CNC, men kovalent ympning gav bäst prestanda även vid hög relativ fuktighet.

Funktionell CNC (F-CNC) framställdes genom en användbar metod som baseras på organiska syror med en funktionell grupp. F-CNC erhålls genom att hydrolysen av cellulosafibrer utförs genom att använda en kombination av sur hydrolys och förestring. Detta är en enkel och mycket användbar metod för att framställa F-CNC.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 1, 78 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:12
Keyword
Nanocellulose, surface modification, functionalization, composites
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-184091 (URN)978-91-7595-888-0 (ISBN)
Public defence
2016-04-22, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160324

Available from: 2016-03-24 Created: 2016-03-23 Last updated: 2016-04-01Bibliographically approved

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