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Cellulosic Thermal Insulation with Improved Water Resistance and Fire Retardancy
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.ORCID iD: 0000-0002-2272-5067
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sweden is one of the largest countries by area in Europe, and almost 70% of it is covered by forest. These abundant forest resources benefit the Swedish bioeconomy, but the pulp and paper industry is facing the challenge of a decrease in the demand for printing paper due to a significant shift to electronic media; therefore, it is a priority to use pulp to produce alternative value-added products, such as thermal insulating materials in buildings. Cellulosic thermal insulation can reduce the heating energy consumption of buildings, and decrease the emission of CO2, thus contributing to a sustainable society.

However, cellulosic thermal insulation needs to overcome its poor water resistance, to lower the risk of fungi and ensure a good interior air quality. In the work described in this thesis, cellulosic insulation materials have been produced from pulp fibers, water, and foaming agent by a foam-forming technique. Hydrophobic extractives isolated from birch outer bark were used to functionalize the insulating materials. These materials showed an improved water resistance due to the intrinsic non-polarity of the extractives, promising thermal insulation properties and fungal resistance.

Fire retardancy is another challenge for cellulosic thermal insulation, and cellulosic insulation materials were here prepared from formulations containing pulp and commercial fire retardants. Fire test results showed that the materials containing 20% expandable graphite or 25% synergetic fire retardant had a significantly improved fire retardancy, being able to resist a small flame attack for a short period without substantial flame spreading. A study of the mechanism of fire retardancy confirmed that the fire retardants can catalyze the dehydration of pulp and promote the generation of a protective char layer that prevents the materials from further decomposition.

Bio-based fire-retardant coatings such as sulfonated kraft lignin and nanoclay can provide a more efficient fire-retardant protection on the cellulosic insulation than a fire retardant incorporated in the materials. A nanoclay coating performed the best because of its very good thermal stability. The effective bio-based fire-retardant coating is promising for future use in cellulosic thermal insulation materials.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. , p. 59
Series
TRITA-CBH-FOU ; 2018:29
Keywords [en]
Bio-based, Cellulosic, Fire retardant, Thermal insulation
National Category
Paper, Pulp and Fiber Technology Wood Science
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-233516ISBN: 978-91-7729-864-9 (print)OAI: oai:DiVA.org:kth-233516DiVA, id: diva2:1240461
Public defence
2018-09-14, K1, Teknikringen 56, KTH Campus, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
Energy-efficient cellulosic insulation products/panels for green building solutions
Funder
Swedish Research Council Formas
Note

QC 20180821

Available from: 2018-08-21 Created: 2018-08-21 Last updated: 2018-08-21Bibliographically approved
List of papers
1. Cellulose fiber based fungal and water resistant insulation materials
Open this publication in new window or tab >>Cellulose fiber based fungal and water resistant insulation materials
2017 (English)In: International Journal of the Biology, Chemistry, Physics, and Technology of Wood, E-ISSN 1437-434X, Vol. 71, no 7-8, p. 633-639Article in journal (Refereed) Epub ahead of print
Abstract [en]

The development of thermal insulation materials from sustainable, natural fibrous materials is desirable.In the present study, cellulose fiber based insulation foams made of bleached chemi thermo mechanical pulp(CTMP) have been investigated. To improve water resistance, the foams were impregnated with hydrophobic extractives from the outer bark of birch (Betula verrucosa)and dried. The surface morphology of the foams and the distribution of the deposited particles from the extractives were observed by scanning electron microscopy (SEM).The modified foams showed improved water resistance, as they did not disintegrate after immersion in water for7 days, whereas the unmodified foam did. Compared to the unmodified foam, the modified foams absorbed 50%less moisture within 24 h. The modification had no negative effects on the thermal insulation properties, fungal resistance or compressive strength of the foams. The proposed approach is simple and can be easily integrated into plants working based on the biorefinery concept.

Place, publisher, year, edition, pages
Berlin, Germany: Walter de Gruyter, 2017
Keywords
biorefinery; birch bark; cellulose; fungal resistance; insulation; water resistance
National Category
Wood Science Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-205367 (URN)10.1515/hf-2016-0162 (DOI)000404721500013 ()2-s2.0-85023159213 (Scopus ID)
Projects
Energy-efficient cellulosic insulation products/panels for green building solutions
Funder
Swedish Research Council Formas
Note

QC 20170424

Available from: 2017-04-14 Created: 2017-04-14 Last updated: 2019-05-29Bibliographically approved
2. Cellulose-fiber-based insulation materials with improved reaction-to-fire properties
Open this publication in new window or tab >>Cellulose-fiber-based insulation materials with improved reaction-to-fire properties
2017 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, no 3, p. 466-472Article in journal (Refereed) Published
Abstract [en]

The poor reaction-to-fire properties of cellulosic thermal insulation need to be improved to meet the safety regulations for building materials. In this study, cellulose-fiber-based insulation foams were prepared from formulations containing mechanical pulp and commercial fire retardants. Results of single-flame source tests showed that foams developed from the formulations with 20% expandable graphite (EG) or 25% synergetic (SY) fire retardants had substantially improved reaction-to-fire properties, and passed fire class E according to EN 13501-1. The results indicated that the foams could resist a small flame attack without serious flame spreading over a short period of time. Compared with the reference foam that contained no fire retardant, the peak heat release rate of the 20% EG and 25% SY foams decreased by 62% and 39% respectively when the samples were subjected to a radiance heat flux of 25 kW m-2 in a cone calorimeter, which suggested enhanced reaction-to-fire properties of these foams.

Place, publisher, year, edition, pages
AB Svensk Papperstidning, 2017
Keywords
cellulose, reaction-to-fire properties, thermal insulation
National Category
Wood Science Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-205581 (URN)10.3183/NPPRJ-2017-32-03-p466-472 (DOI)000418120600005 ()2-s2.0-85050678604 (Scopus ID)
Projects
Energy-efficient cellulosic insulation products/panels for green building solutions
Funder
Swedish Research Council Formas
Note

QC 20190918

Available from: 2017-04-19 Created: 2017-04-19 Last updated: 2019-09-18Bibliographically approved
3. Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants
Open this publication in new window or tab >>Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants
2019 (English)In: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926, Vol. 135, no 6, p. 3015-3027Article in journal (Refereed) Published
Abstract [en]

The mechanism and kinetics of thermal degradation of materials developed from cellulose fiber and synergetic fire retardant or expandable graphite have been investigated using thermogravimetric analysis. The model-free methods such as Kissinger–Akahira–Sunose (KAS), Friedman, and Flynn–Wall–Ozawa (FWO) were applied to measure apparent activation energy (Ea).The increased Ea indicated a greater thermal stability because of the formation of a thermally stable char, and the decreased Ea after the increasing region related to the catalytic reaction of the fire retardants, which revealed that the pyrolysis of fire retardant-containing cellulosic materials through more complex and multi-step kinetics. The Friedman method can be considered as the best method to evaluate the Ea of fire-retarded cellulose thermal insulation compared with the KAS and two methods. A master-plots method such as the Criado method was used to determine the possible degradation mechanisms. The degradation of cellulose thermal insulation without a fire retardant is governed by a D3 diffusion process when the conversion value is below 0.6, but the materials containing synergetic fire retardant and expandable graphite fire retardant may have a complicated reaction mechanism that fits several proposed theoretical models in different conversion ranges. Gases released during the thermal degradation were identified by pyrolysis–gas chromatography/mass spectrometry. Fire retardants could catalyze the dehydration of cellulosic thermal insulating materials at a lower temperature and facilitate the generation of furfural and levoglucosenone, thus promoting the formation of char. These results provide useful information to understand the pyrolysis and fire retardancy mechanism of fire-retarded cellulose thermal insulation.

Place, publisher, year, edition, pages
Springer Netherlands, 2019
Keywords
Thermal degradation, Thermal kinetics, Fire retardant, Cellulose fiber, Thermal insulating
National Category
Paper, Pulp and Fiber Technology Wood Science
Identifiers
urn:nbn:se:kth:diva-233485 (URN)10.1007/s10973-018-7564-5 (DOI)000462553400011 ()2-s2.0-85050669625 (Scopus ID)
Funder
Swedish Research Council Formas
Note

QC 20180821

Available from: 2018-08-20 Created: 2018-08-20 Last updated: 2019-08-27Bibliographically approved
4. Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardants
Open this publication in new window or tab >>Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardants
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Sustainable thermal insulating materials produced from cellulosic fibers provide a viable alternative to plastic insulation foams. Industrially available, abundant, and inexpensive mechanical pulp fiber and recycled textile fiber provide potential raw materials to produce thermal insulating materials. To improve the fire retardancy of low-density thermal insulating materials produced from recycled cotton denim and mechanical pulp fibers, bio-based fire retardants, such as sulfonated kraft lignin, kraft lignin, and nanoclays, were coated onto sustainable insulating material surfaces to enhance their fire retardancy. Microfibrillated cellulose was used as a bio-based binder in the coating formula to disperse and bond the fire-retardant particles to the underlying thermal insulating materials. The flammability of the coated thermal insulating materials was tested using a single-flame source test and cone calorimetry. The results showed that sulfonated kraft lignin-coated cellulosic thermal insulating materials had a better fire retardancy compared with that for kraft lignin with a coating weight of 0.8 kg/m2. Nanoclay-coated samples had the best fire retardancy and did not ignite under a heat flux of 25 kW/m2, as shown by cone calorimetry and single- flame source tests, respectively. These cost-efficient and bio-based fire retardants have broad applications as sustainable thermal insulating materials for improved fire retardancy.

Keywords
bio-based; cellulose; coating; fire retardant; thermal insulating material
National Category
Paper, Pulp and Fiber Technology Wood Science
Identifiers
urn:nbn:se:kth:diva-233487 (URN)10.1515/npprj-2018-0031 (DOI)000460119600011 ()2-s2.0-85061101260 (Scopus ID)
Funder
Swedish Research Council Formas
Note

QC 20180822

Available from: 2018-08-20 Created: 2018-08-20 Last updated: 2020-03-09Bibliographically approved

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