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Nanocomposites from Clay, Cellulose Nanofibrils, and Epoxy with Improved Moisture Stability for Coatings and Semi-Structural Applications
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.ORCID iD: 0000-0001-8547-9046
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.ORCID iD: 0000-0001-7870-6327
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2019 (English)In: ACS Applied Nano Materials, E-ISSN 2574-0970Article in journal (Refereed) Published
Abstract [en]

A new type of high reinforcement content clay-cellulose-thermoset nanocomposite was proposed, where epoxy precursors diffused into a wet porous clay-nanocellulose mat, followed by curing. The processing concept was scaled to > 200 µm thickness composites, the mechanical properties were high for nanocomposites and the materials showed better tensile properties at 90% RH compared with typical nanocellulose materials. The nanostructure and phase distributions were studied using transmission electron microscopy; Young’s modulus, yield strength, ultimate strength and ductility were determined as well as moisture sorption, fire retardancy and oxygen barrier properties. Clay and cellulose contents were varied, as well as the epoxy content. Epoxy had favorable effects on moisture stability, and also improved reinforcement effects at low reinforcement content. More homogeneous nano- and mesoscale epoxy distribution is still required for further property improvements. The materials constitute a new type of three-phase nanocomposites, of interest as coatings, films and as laminated composites for semi-structural applications.

Place, publisher, year, edition, pages
2019.
Keywords [en]
biocomposite, nanocellulose, mechanical, montmorillonite, fire
National Category
Composite Science and Engineering Paper, Pulp and Fiber Technology Nano Technology Materials Chemistry
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-249724DOI: 10.1021/acsanm.9b00459OAI: oai:DiVA.org:kth-249724DiVA, id: diva2:1305863
Funder
Swedish Foundation for Strategic Research , RMA11-0065Knut and Alice Wallenberg Foundation
Note

QC 20190520

Available from: 2019-04-18 Created: 2019-04-18 Last updated: 2019-05-20Bibliographically approved
In thesis
1. High Clay Content Cellulose Nanocomposites for Mechanical Performance and Fire Retardancy
Open this publication in new window or tab >>High Clay Content Cellulose Nanocomposites for Mechanical Performance and Fire Retardancy
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Materials based on wood can offer sustainable alternatives to fossil-based plastics and composites, and show interesting mechanical properties. However, the issue of their flammability is generally unresolved. In this thesis, eco-friendly, fire retardant clay-cellulose nanofibril materials are investigated. The work focuses particularly on structure-property relationships and physical properties of these materials. The thesis is structured in two parts. The first part is concerned with paper-like materials, designated as “films”. The second part discusses materials of high-porosity, so-called “foams”.

In the first part, films of clay and cellulose nanofibrils are prepared by filtration from water. The composition is systematically varied (from 0 to 100% clay) and effects on the nanostructure are investigated by synchrotron X-ray scattering, helium pycnometry and microscopy techniques. The mechanical properties of the films are determined by tensile testing, optical properties are measured by transmittance/haze tests, and strong effects of nanostructure are observed. A film with 50 wt% clay is demonstrated as a fire retardant coating on wood, by cone calorimetry testing. These films are also pre-impregnated with epoxy precursors and cured, to form ternary composites of clay, cellulose nanofibrils, and epoxy. These ternary nanocomposites show remarkably well-preserved mechanical and gas barrier properties in moist environment.

In the second part, foams of high porosity are prepared by freeze-drying a suspension based on poly(vinyl alcohol), cellulose nanofibrils, and clay. The cellular structure is investigated by scanning electron microscopy, and effects from composition and cross-linking are analyzed. The compressive properties of the foams are determined and related to their structure. Addition of poly(vinyl alcohol) influences the unique degradation and charring behavior of cellulose nanofibrils in the presence of clay so that fire retardancy is decreased.

Abstract [sv]

Material baserade på trä kan erbjuda hållbara alternativ till fossilbaserade plaster och kompositer, men deras brandegenskaper är inte särskilt goda. I denna avhandling undersöks miljövänliga, brandskyddade nanokompositer från cellulosa/nanolera. Arbetet fokuserar särskilt på struktur-egenskapsrelationer och fysikaliska egenskaper hos dessa material. Avhandlingen är uppbyggd i två delar. Den första delen handlar om pappersliknande material, betecknade som "filmer". Den andra delen diskuterar material med hög porositet, så kallade "skum".

I den första delen framställs filmer av lera (montmorillonit) och nanofibriller från cellulosa genom filtrering från vattensuspension. Kompositionen varieras systematiskt (från 0 till 100% lera) och effekter på nanostrukturen undersöks med hjälp av synkrotronröntgen, heliumpyknometri och mikroskopi. Mekaniska egenskaper hos filmerna mäts genom dragprovning, och optisk transmittans / haze där det visar sig att nanostrukturen är betydelsefull. En film med 50 viktprocent lera används som en brandskyddande ytskikt på trä, med konkalorimetri-experiment för att mäta brandegenskaper. Dessa filmer impregneras med epoxi och härdas, och bildar ternära kompositer av nanocellulosa, lera och epoxi. Dessa ternära nanokompositer visar goda mekaniska och gasbarriär-egenskaper i fuktig miljö.

I den andra delen framställs skum med hög porositet genom frystorkning av en suspension baserad på polyvinylalkohol, cellulosa nanofibriller och lera. Cellstrukturen analyseras med elektronmikroskopi, och effekter från sammansättning och tvärbindning analyseras. Skummens tryckegenskaper mäts och relateras till struktur. Polyvinylalkohol påverkar termisk nedbrytning hos nanocellulosa i närvaro av katalyserande lera så att brandhämmande egenskaper försämras.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 62
Series
TRITA-CBH-FOU ; 2019:26
Keywords
nanocellulose, nanofibril, nanofiber, CNF, nanoplatelet, nanostructure, tactoid, montmorillonite, MTM, foam, aerogel, porosity, PVA, poly(vinyl alcohol), epoxy, moisture, biocomposite, biomaterial, biobased, flame, cone calorimetry, gas barrier, coating, film.
National Category
Composite Science and Engineering Nano Technology Paper, Pulp and Fiber Technology Materials Chemistry
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-249955 (URN)978-91-7873-174-9 (ISBN)
Public defence
2019-05-22, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research , RMA11-0065
Note

QC 20190425

Available from: 2019-04-25 Created: 2019-04-23 Last updated: 2019-04-25Bibliographically approved

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Publisher's full texthttps://doi.org/10.1021/acsanm.9b00459

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Medina, LilianAnsari, FarhanCarosio, FedericoSalajkova, MichaelaBerglund, Lars

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