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Biography [eng]

My research area involves in developing cellulosic fiber-based thermal insulation materials based on forest resources, and the effect of treatment conditions on the properties of final products is also discussed as well. Besides, the investigation of eco-friendly multi-functional fire retardant based on the chemicals isolated from forest resources has been underway, and the possibility of flame retardant consisted of the non-toxic compound and the flammability of insulation materials while the various compositions of fire retardants were added to the cellulosic insulation products are being evaluated.

Publications (4 of 4) Show all publications
Zheng, C., Li, D. & Ek, M. (2019). Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardants. Nordic Pulp & Paper Research Journal, 34(1), 96-106
Open this publication in new window or tab >>Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardants
2019 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 34, no 1, p. 96-106Article in journal (Refereed) Published
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/m(2). Nanoclay-coated samples had the best fire retardancy and did not ignite under a heat flux of 25 kW/m(2), as shown by cone calorimetry and single-flame source tests, respectively. These cost-efficient and bio-based fire retardants have broad applications for improving fire retardancy of sustainable thermal insulating materials.

Place, publisher, year, edition, pages
AB SVENSK PAPPERSTIDNING, 2019
Keywords
bio-based, cellulose, coating, fire retardant, thermal insulating material
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-246233 (URN)10.1515/npprj-2018-0031 (DOI)000460119600011 ()2-s2.0-85061101260 (Scopus ID)
Note

QC 20190403

Available from: 2019-04-03 Created: 2019-04-03 Last updated: 2019-04-03Bibliographically approved
Zheng, C., Li, D. & Ek, M. (2019). Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants. Journal of thermal analysis and calorimetry (Print), 135(6), 3015-3027
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
Zheng, C., Li, D. & Ek, M. (2018). Bio-based fire retardant and its application in cellulose-based thermal insulation materials. Paper presented at 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, LA. Abstract of Papers of the American Chemical Society, 255
Open this publication in new window or tab >>Bio-based fire retardant and its application in cellulose-based thermal insulation materials
2018 (English)In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-240174 (URN)000435537703081 ()
Conference
255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, MAR 18-22, 2018, New Orleans, LA
Note

QC 20190111

Available from: 2019-01-11 Created: 2019-01-11 Last updated: 2019-01-11Bibliographically approved
Zheng, C. (2018). Cellulosic Thermal Insulation with Improved Water Resistance and Fire Retardancy. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Cellulosic Thermal Insulation with Improved Water Resistance and Fire Retardancy
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
Bio-based, Cellulosic, Fire retardant, Thermal insulation
National Category
Paper, Pulp and Fiber Technology Wood Science
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-233516 (URN)978-91-7729-864-9 (ISBN)
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
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2272-5067

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