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Highly porous flame-retardant and sustainable biofoams based on wheat gluten and in situ polymerized silica
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-7674-0262
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-0236-5420
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2014 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, no 48, 20996-21009 p.Article in journal (Refereed) Published
Abstract [en]

This article presents a novel type of flame-retardant biohybrid foam with good insulation properties based on wheat gluten and silica, the latter polymerized in situ from hydrolysed tetraethyl orthosilicate (TEOS). This led to the formation of intimately mixed wheat gluten and silica phases, where, according to protein solubility measurements and infrared spectroscopy, the presence of silica had prohibited full aggregation of the proteins. The foams with "built-in" flame-retardant properties had thermal insulation properties similar to those of common petroleum- and mineral-based insulation materials. The foams, with a porosity of 87 to 91%, were obtained by freeze-drying the liquid mixture. Their internal structure consisted of mainly open cells between 2 and 144 mu m in diameter depending on the foam formulation, as revealed by mercury intrusion porosimetry and scanning electron microscopy. The foams prepared with >= 30% TEOS showed excellent fire-retardant properties and fulfilled the criteria of the best class according to UL94 fire testing standard. With increasing silica content, the foams became more brittle, which was prevented by cross-linking the materials (using gluteraldehyde) in combination with a vacuum treatment to remove the largest air bubbles. X-ray photoelectron and infrared spectroscopy showed that silicon was present mainly as SiO2 .

Place, publisher, year, edition, pages
2014. Vol. 2, no 48, 20996-21009 p.
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-158350DOI: 10.1039/c4ta04787gISI: 000345531200073Scopus ID: 2-s2.0-84911479268OAI: oai:DiVA.org:kth-158350DiVA: diva2:782481
Note

QC 20150121

Available from: 2015-01-21 Created: 2015-01-07 Last updated: 2017-05-29Bibliographically approved
In thesis
1. Biofoams and Biocomposites based on Wheat Gluten Proteins
Open this publication in new window or tab >>Biofoams and Biocomposites based on Wheat Gluten Proteins
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Novel uses of wheat gluten (WG) proteins, obtained e.g. as a coproduct from bio-ethanol production, are presented in this thesis. A flame-retardant foam was prepared via in-situ polymerization of hydrolyzed tetraethyl orthosilicate (TEOS) in a denatured WG matrix (Paper I). The TEOS formed a well-dispersed silica phase in the walls of the foam. With silica contents ≥ 6.7 wt%, the foams showed excellent fire resistance. An aspect of the bio-based foams was their high sensitivity to fungi and bacterial growth. This was addressed in Paper II using a natural antimicrobial agent Lanasol. In the same paper, a swelling of 32 times its initial weight in water was observed for the pristine WG foam and both capillary effects and cell wall absorption contributed to the high uptake. In Paper III, conductive and flexible foams were obtained using carbon-based nanofillers and plasticizer. It was found that the electrical resistance of the carbon nanotubes and carbon black filled foams were strain-independent, which makes them suitable for applications in electromagnetic shielding (EMI) and electrostatic discharge protection (ESD). Paper IV describes a ‘water-welding’ method where larger pieces of WG foams were made by wetting the sides of the smaller cubes before being assembled together. The flexural strength of welded foams was ca. 7 times higher than that of the same size WG foam prepared in one piece. The technique provides a strategy for using freeze-dried WG foams in applications where larger foams are required.

Despite the versatile functionalities of the WG-based materials, the mechanical properties are often limited due to the brittleness of the dry solid WG. WG/flax composites were developed for improved mechanical properties of WG (Paper V). The results revealed that WG, reinforced with 19 wt% flax fibres, had a strength that was ca. 8 times higher than that of the pure WG matrix. Furthermore, the crack-resistance was also significantly improved in the presence of the flax.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. 98 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2017:30
Keyword
Wheat gluten, biofoam, biocomposite, freeze-drying, flame-retardant, silica, antimicrobial, bimodal, conductive biofoam, flax fiber, crack-resistance
National Category
Polymer Technologies
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-207778 (URN)978-91-7729-453-5 (ISBN)
Public defence
2017-08-25, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council Formas, 243-2011-1436
Note

QC 20170524

Available from: 2017-07-14 Created: 2017-05-23 Last updated: 2017-07-14Bibliographically approved

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Wu, QiongAndersson, Richard L.

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