Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Flame-Retardant Cellulose Fibre/Fibril Based Materials via Layer-by-Layer Technique
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology. (Fibre Technology)ORCID iD: 0000-0001-9856-6536
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

According to an analysis conducted by the Swedish Chemicals Inspectorate in 2006, the approximate numbers of fire injuries per year in Sweden are 100 deaths, 700 major and 700 minor injuries.1 Observations also show that there has been an increase in the number of house fires during recent years. One possible explanation can be the increased use of plastics in the building industry and in furniture. The advantages of easy processing, light weight and low cost make plastic materials most prevalent in the market.  However, plastics behave significantly differently from natural materials in the case of fire. Polymeric materials, including rigid polyurethane foams (PU) which are widely used in the building industry due to their insulating properties, are highly flammable and they release heat at a very high rate. In addition, polymeric materials release more harmful smoke, toxic gases and combustion products than natural materials. A house fire typically starts with the ignition of a combustible material. Flames then spread to nearby materials and shortly thereafter the heat radiation generated reaches a point where the contents of the room suddenly and simultaneously ignite. This stage is called a flash over. After this stage, the fire is fully developed and it continues until everything is consumed. The higher rate of heat and smoke production from plastic materials reduces the time to flash over and hence the time to escape from a fire. The traditional flame-retardant treatments are based mainly on halogenated compounds which are classified as gas phase flame-retardants. The halogenated flame-retardants are under severe investigation due to their adverse effect on health and on the environment since they release toxic gases during combustion and they may leach out and accumulate in the food chain.2-3 The restrictions due to growing environmental concerns have been a driving force to develop alternative flame-retardants by using natural and renewable resources. In recent years, the layer-by-layer (LbL) technique has been used as a simple and versatile surface engineering technique to construct functional nanocoatings through the sequential adsorption of polyelectrolytes and charged nanoparticles in an effort to impart flame-retardant characteristics by inhibiting the combustion cycle.4-5 This thesis presents the physical modification of cellulose fibre/fibril based materials as a means of improving flame-retardant properties.

In the first part of work described in this thesis, the adsorption of polyelectrolyte multilayers onto pulp fibres was investigated as a way to impart flame-retardant characteristics to paper-based materials. It was found that intumescent nanocoatings consisting of nitrogen and phosphorus containing polyelectrolytes such as chitosan (CH) and poly(vinylphosphonic acid) (PVPA) were able to significantly improve the thermal stability and flame-retardant properties of sheets made of LbL-treated fibres, and were able to self-extinguish the flame in the horizontal flame test (HFT). High magnification images revealed that this improvement in flame-retardancy was due to the formation of a coherent char layer on the fibres (Paper I).6 In addition to imparting flame-retardancy by the LbL-coating of polyethylenimine (PEI) and sodium hexametaphosphate (SHMP), it was also possible to improve the mechanical properties of the paper material with this treatment (Paper III).7

In the second part of the work, wet-stable porous cellulose fibril-based aerogels were developed by freeze-drying and used as a template for the build-up of intumescent nano-brick wall assemblies. The formation of multilayers of CH, PVPA and montmorillonite clay (MMT) was investigated as a function of solution concentration, and it was found that five quadlayers (QL) of CH/PVPA/CH/MMT treated aerogels using 5 g/L solutions of the respective components were able to self-extinguish the flame in HFT and that they showed no ignition under the heat flux of 35 kW/m2 used in cone calorimetry (Paper II).8 In a different application, a novel low density, porous, wet-stable cellulose fibre network was developed using chemically modified cellulose fibres by solvent exchange from water to acetone followed by drying at room temperature. The fibre networks (FN) were modified using the LbL technique to construct a flame-retardant nanocoating consisting of CH, SHMP, and inorganic particles (i.e., MMT, sepiolite (SEP), and colloidal silica (SNP)). The influence of the shape of the nanoparticles on flame-retardancy was investigated and it was found that plate-like and rod-like clays with a high aspect ratio showed self-extinguishing behaviour in HFT. A 5 QL of CH/SHMP/CH/SEP reduced the peak heat release rate and total smoke release by 47% and 43%, respectively, with an addition of only ~8 wt% to FN (Paper IV).

Finally, non-crystalline cellulose gel beads were used as a substrate for the LbL assembly of CH and SHMP in model studies aimed at identifying the molecular mechanisms responsible for the fire-retardant properties of the LbL structures. The beads were formed by precipitating the dissolved cellulose-rich fibres according to an earlier described procedure,9 and it was shown that these smooth cellulose beads can be utilized as a model substrate to study the influence of LbL chemistry and nanostructure on flame-retardancy. These new types of model systems thus constitute a new important tool for clarifying the mechanism behind flame-retardant nanocoating systems (Paper V).  

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. , p. 81
Series
TRITA-CBH-FOU ; 2018:8
Series
ISSN, ISSN 1654-1081
Keyword [en]
Flame-retardant, cellulose fibre, cellulose nanfibril, layer-by-layer technique
National Category
Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-225861ISBN: 978-91-7729-728-4 (print)OAI: oai:DiVA.org:kth-225861DiVA, id: diva2:1196659
Public defence
2018-05-04, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20180411

Available from: 2018-04-11 Created: 2018-04-10 Last updated: 2018-05-15Bibliographically approved
List of papers
1. Flame-Retardant Paper from Wood Fibers Functionalized via Layer-by-Layer Assembly
Open this publication in new window or tab >>Flame-Retardant Paper from Wood Fibers Functionalized via Layer-by-Layer Assembly
2015 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 42, p. 23750-23759Article in journal (Refereed) Published
Abstract [en]

The highly flammable character of cellulose-rich fibers from wood limits their use in some advanced materials. To suppress the flammability and introduce flame-retardant properties to individual pulp fibers, we deposited nanometer thin films consisting of cationic chitosan (CH) and anionic poly(vinylphosphonic acid) (PVPA) on fibers using the layer-by-layer (LbL) technique. The buildup of the rnultilayer film was investigated in the presence and absence of salt (NaCl) using model cellulose surfaces and a quartz crystal microbalance technique. Fibers were then treated with the same strategy, and the treated fibers were used to prepare paper sheets. A horizontal flame test (HFT) and cone calorimetry were conducted to evaluate the combustion behavior of paper sheets as a function of the number of bilayers deposited on fibers. In HFT, paper made of fibers coated with 20 CH/PVPA bilayers (BL), self-extinguished the flame, while uncoated fibers were completely consumed. Scanning electron microscopy of charred paper after HFT revealed that a thin shell of the charred polymeric multilayer remained after the cellulose fibers had been completely oxidized. Cone calorimetry demonstrated that the phosphorus-containing thin films (20 BL is similar to 25 nm) reduced the peak heat release rate by 49%. This study identifies a unique and highly effective way to impart flame-retardant characteristic to pulp fibers and the papers made from these fibers.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2015
Keyword
layer-by-layer assembly, flame-retardant, thermal stability, wood fibers, chitosan, poly(vinylphosphonic acid)
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-177953 (URN)10.1021/acsami.5b08105 (DOI)000363994700047 ()26457504 (PubMedID)2-s2.0-84945892481 (Scopus ID)
Note

QC 20151203

Available from: 2015-12-03 Created: 2015-11-30 Last updated: 2018-04-10Bibliographically approved
2. Superior Flame-Resistant Cellulose Nanofibril Aerogels Modified with Hybrid Layer-by-Layer Coatings
Open this publication in new window or tab >>Superior Flame-Resistant Cellulose Nanofibril Aerogels Modified with Hybrid Layer-by-Layer Coatings
2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 34, p. 29082-29092Article in journal (Refereed) Published
Abstract [en]

Nanometer thin films consisting of cationic chitosan (Ch), anionic poly(vinylphosphonic acid) (PVPA), and anionic montmorillonite clay (MMT) are deposited on highly porous, wet-stabilized cellulose nanofibril (CNF) aerogels via the layer-by-layer (LbL) technique. Model experiments with silicon oxide surfaces are used to study the details of LbL formation and the multilayer structure. Formation of layers on the aerogels is also investigated as a function of solution concentration by use of polyelectrolyte titration. Thermogravimetric analysis indicates that the LbL coating significantly improves thermal stability of the CNF aerogel. Horizontal flame test shows that aerogels coated with five quadlayers of Ch/PVPA/Ch/MMT, using solutions/dispersion of high concentration, are able to self-extinguish immediately after removal of flame, and LbL-coated aerogels do not ignite under heat flux (35 kW/m(2)) in cone calorimetry. The LbL-coated aerogel can prevent flame penetration from a torch focused on the surface, achieving temperature drops up to 650 degrees C across the 10 mm thick specimen for several minutes. LbL treatment is hence a rapid and highly effective way to specifically tailor the surface properties of CNF aerogels in order to confer unprecedented flame-retardant characteristics.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
Keyword
layer-by-layer assembly, flame-retardant, thermal stability, cellulose nanofibril, aerogel
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-215391 (URN)10.1021/acsami.7b08018 (DOI)000409395500103 ()28767227 (PubMedID)2-s2.0-85028701297 (Scopus ID)
Funder
Swedish Foundation for Strategic Research
Note

QC 20171009

Available from: 2017-10-09 Created: 2017-10-09 Last updated: 2018-04-10Bibliographically approved
3. Tailoring flame-retardancy and strength of papers via layer-by-layer treatment of cellulose fibers
Open this publication in new window or tab >>Tailoring flame-retardancy and strength of papers via layer-by-layer treatment of cellulose fibers
2018 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 4, p. 2691-2709Article in journal (Refereed) Published
Abstract [en]

The layer-by-layer (LbL) technology was used to adsorb polyelectrolyte multilayers consisting of cationic polyethylenimine (PEI) and anionic sodium hexametaphosphate (SHMP) onto cellulose fibers in order to enhance the flame-retardancy and tensile strength of paper sheets made from these fibers. The fundamental effect of PEI molecular mass on the build-up of the multilayer film was investigated using model cellulose surfaces and a quartz crystal microbalance technique. The adsorption of a low (LMw) and a high molecular weight (HMw) PEI onto cellulose fibers and carboxymethylated (CM) cellulose fibers was investigated using polyelectrolyte titration. The fibers were consecutively treated with PEI and SHMP to deposit 3.5 bilayers (BL) on the fiber surfaces, and the treated fibers were then used to prepare sheets. In addition, a wet-strength paper sheet was prepared and treated with the same LbL coatings. Thermal gravimetric analysis of LbL-treated fibers showed that the onset temperature for cellulose degradation was lowered and that the amount of residue at 800 °C increased. A horizontal flame test and a vertical flame test were used to evaluate the combustion behavior of the paper sheets. Papers prepared from both cellulose fibers and CM-cellulose fibers treated with HMw-PEI/SHMP LbL-combination self-extinguished in a horizontal configuration despite the rather low amounts of adsorbed polymer which form very thin films (wet thickness of ca. 17 nm). The tensile properties of handsheets showed that 3.5 BL of HMw-PEI and SHMP increased the stress at break by 100% compared to sheets prepared from untreated cellulose fibers.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Chemical Sciences
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-225422 (URN)10.1007/s10570-018-1749-8 (DOI)000428925300039 ()2-s2.0-85044097243 (Scopus ID)
Note

QC 20180411

Available from: 2018-04-04 Created: 2018-04-04 Last updated: 2018-04-19Bibliographically approved
4. Development of hybrid coatings to reduce flammability of low density cellulose fiber networks via layer-by-layer assembly
Open this publication in new window or tab >>Development of hybrid coatings to reduce flammability of low density cellulose fiber networks via layer-by-layer assembly
(English)Manuscript (preprint) (Other academic)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-225947 (URN)
Note

QC 20180411

Available from: 2018-04-11 Created: 2018-04-11 Last updated: 2018-04-11Bibliographically approved
5. A study of layer-by-layer nanocoatings on model cellulose gel beads to clarify their flame-retardant characteristics
Open this publication in new window or tab >>A study of layer-by-layer nanocoatings on model cellulose gel beads to clarify their flame-retardant characteristics
(English)Manuscript (preprint) (Other academic)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-225948 (URN)
Note

QC 20180416

Available from: 2018-04-11 Created: 2018-04-11 Last updated: 2018-04-16Bibliographically approved

Open Access in DiVA

The full text will be freely available from 2020-12-31 10:00
Available from 2020-12-31 10:00

Authority records BETA

Koklukaya, Oruc

Search in DiVA

By author/editor
Koklukaya, Oruc
By organisation
Fibre Technology
Paper, Pulp and Fiber Technology

Search outside of DiVA

GoogleGoogle Scholar

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 89 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf