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High Clay Content Cellulose Nanocomposites for Mechanical Performance and Fire Retardancy
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites.ORCID iD: 0000-0001-8547-9046
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 [en]
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: urn:nbn:se:kth:diva-249955ISBN: 978-91-7873-174-9 (print)OAI: oai:DiVA.org:kth-249955DiVA, id: diva2:1306479
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
List of papers
1. Nanostructure and Properties of Nacre-Inspired Clay/Cellulose Nanocomposites—Synchrotron X-ray Scattering Analysis
Open this publication in new window or tab >>Nanostructure and Properties of Nacre-Inspired Clay/Cellulose Nanocomposites—Synchrotron X-ray Scattering Analysis
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2019 (English)In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 52, no 8, p. 3131-3140Article in journal (Refereed) Published
Abstract [en]

Nacre-inspired clay nanocomposites have excellent mechanical properties, combined with optical transmittance, gas barrier properties, and fire retardancy, but the mechanical properties are still below predictions from composite micromechanics. The properties of montmorillonite clay/nanocellulose nanocomposite hybrids are investigated as a function of clay content and show a maximum Young’s modulus as high as 28 GPa. Ultimate strength, however, decreases from 280 to 125 MPa between 0 and 80 wt % clay. Small-angle and wide-angle X-ray scattering data from synchrotron radiation are analyzed to suggest nanostructural and phase interaction factors responsible for these observations. Parameters discussed include effective platelet modulus, platelet out-of-plane orientation distribution, nanoporosity, and platelet agglomeration state.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
National Category
Composite Science and Engineering Paper, Pulp and Fiber Technology Nano Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-249608 (URN)10.1021/acs.macromol.9b00333 (DOI)
Funder
Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research , RMA11-0065
Note

QC 20190521

Available from: 2019-04-12 Created: 2019-04-12 Last updated: 2019-05-21Bibliographically approved
2. Clay nanopaper as multifunctional brick and mortar fire protection coating: Wood case study
Open this publication in new window or tab >>Clay nanopaper as multifunctional brick and mortar fire protection coating: Wood case study
2016 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 93, p. 357-363Article in journal (Refereed) Published
Abstract [en]

Abstract Wood is one of the most sustainable, esthetically pleasing and environmentally benign engineering materials, and is often used in structures found in buildings. Unfortunately, the fire hazards related to wood are limiting its application. The use of transparent cellulose nanofiber (CNF)/clay nanocomposites, with unique brick-and-mortar structure, is proposed as a sustainable and efficient fire protection coating for wood. Fire performance was assessed by cone calorimetry. When exposed to the typical 35 kW/m2 heat flux of developing fires, the time to ignition of coated wood samples increased up to about 4 1/2 min, while the maximum average rate of heat emission (MARHE) was decreased by 46% thus significantly reducing the potential fire threat from wood structures.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Nanocomposite, Cellulose, Nanofiber, Fire retardant, Cone calorimetry
National Category
Materials Chemistry
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-180362 (URN)10.1016/j.matdes.2015.12.140 (DOI)000369587500040 ()2-s2.0-84957812821 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , RMA11-0065
Note

QC 20160208. QC 20160304

Available from: 2016-01-12 Created: 2016-01-12 Last updated: 2019-04-23Bibliographically approved
3. Nanocomposites from Clay, Cellulose Nanofibrils, and Epoxy with Improved Moisture Stability for Coatings and Semi-Structural Applications
Open this publication in new window or tab >>Nanocomposites from Clay, Cellulose Nanofibrils, and Epoxy with Improved Moisture Stability for Coatings and Semi-Structural Applications
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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.

Keywords
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:nbn:se:kth:diva-249724 (URN)10.1021/acsanm.9b00459 (DOI)
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
4. High-Strength Nanocomposite Aerogels of Ternary Composition: Poly(vinyl alcohol), Clay, and Cellulose Nanofibrils
Open this publication in new window or tab >>High-Strength Nanocomposite Aerogels of Ternary Composition: Poly(vinyl alcohol), Clay, and Cellulose Nanofibrils
2017 (English)In: ACS Applied Materials & Interfaces, ISSN 1944-8244, Vol. 9, no 7, p. 6453-6461Article in journal (Refereed) Published
Abstract [en]

Clay aerogels are foam-like materials with potential to combine high mechanical performance with fire retardancy. However, the compression strength of these aerogels is much lower than theoretically predicted values. High-strength aerogels with more than 95% porosity were prepared from a ternary material system based on PVA, MTM clay platelets and cellulose nanofibrils (CNF). A hydrocolloidal suspension of the three components, was subjected to freezedrying so that a low-density aerogel foam was formed. Cell structure was studied by FE-SEM microscopy. Interactions at the molecular scale were observed by XRD and FT-IR. Crosslinking was carried out using glutaraldehyde or borax, and moisture stability was investigated. These biobased ternary aerogels showed much better compression strength than previously studied materials, and show higher strength than high-performance sandwich foam cores such as crosslinked PVC foams.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
Keywords
montmorillonite, nanocellulose, PVA, foam, mechanical properties, moisture
National Category
Materials Chemistry
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-200931 (URN)10.1021/acsami.6b15561 (DOI)000394829800086 ()2-s2.0-85013782831 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research
Note

QC 20170314

Available from: 2017-03-03 Created: 2017-03-03 Last updated: 2019-06-19Bibliographically approved
5. Recyclable Nanocomposite Foams of Poly(vinyl alcohol), Clay and Cellulose Nanofibrils - Mechanical Properties and Flame Retardancy
Open this publication in new window or tab >>Recyclable Nanocomposite Foams of Poly(vinyl alcohol), Clay and Cellulose Nanofibrils - Mechanical Properties and Flame Retardancy
(English)Manuscript (preprint) (Other academic)
National Category
Composite Science and Engineering Paper, Pulp and Fiber Technology Nano Technology Materials Chemistry
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-249952 (URN)
Funder
Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research , RMA11-0065
Note

QC 20190521

Available from: 2019-04-23 Created: 2019-04-23 Last updated: 2019-05-21Bibliographically approved

Open Access in DiVA

The full text will be freely available from 2020-04-22 20:25
Available from 2020-04-22 20:25

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Medina, Lilian

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Output format
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