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Biofoams and Biocomposites based on Wheat Gluten Proteins
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. (Polymeric Materials)ORCID iD: 0000-0002-7674-0262
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 [en]
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: urn:nbn:se:kth:diva-207778ISBN: 978-91-7729-453-5 (print)OAI: oai:DiVA.org:kth-207778DiVA: diva2:1098277
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
List of papers
1. Highly porous flame-retardant and sustainable biofoams based on wheat gluten and in situ polymerized silica
Open this publication in new window or tab >>Highly porous flame-retardant and sustainable biofoams based on wheat gluten and in situ polymerized silica
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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 .

National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-158350 (URN)10.1039/c4ta04787g (DOI)000345531200073 ()2-s2.0-84911479268 (Scopus ID)
Note

QC 20150121

Available from: 2015-01-21 Created: 2015-01-07 Last updated: 2017-05-29Bibliographically approved
2. Highly Absorbing Antimicrobial Biofoams Based on Wheat Gluten and Its Biohybrids
Open this publication in new window or tab >>Highly Absorbing Antimicrobial Biofoams Based on Wheat Gluten and Its Biohybrids
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2016 (English)In: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 4, no 4, 2395-2404 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents the absorption, mechanical, and antimicrobial properties of novel types of biofoams based on wheat-gluten (WG) and its biohybrids with silica. The hybrid WG foams were in situ polymerized with silica using two different silanes. When immersed in water, the 90-95% porous WG and silica-modified hybrid WG foams showed a maximum water uptake between 32 and 11 times the original sample weight. The maximum uptake was only between 4.3 and 6.7 times the initial weight in limonene (a nonpolar liquid) but showed reversible absorption/desorption and that the foams could be dried into their original shape. The different foams had a cell size of 2-400 mu m, a density of 60-163 kg/m(3), and a compression modulus of 1-9 MPa. The integrity of the foams during swelling in water was improved by cross-linking with glutaraldehyde (GA) or by a thermal treatment at 130 degrees C, which polymerized the proteins. In the never-dried state, the foam acted as a sponge, and it was possible to squeeze out water and soak it repeatedly. If the foam was dried to its glassy state, then the cells collapsed and did not open again even if the solid foam was reimmersed in water, saving as a sensor mechanism that can be used to reveal unintended exposure to polar liquids such as water under a product's service life. Small-angle X-ray scattering revealed that the gliadin-correlated structure expanded and then disappeared in the presence of water. The foam was made antimicrobial by impregnation with a Lanasol solution (a bromophenol existing in algae). It was also shown that the foam can act as a transfer/storage medium for liquids such as natural oils (rapeseed oil) and as a slow-release matrix for surfactant chemicals.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
Keyword
Protein, Freeze-drying, Swelling, Sponge, Lanasol
National Category
Chemical Sciences Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-185985 (URN)10.1021/acssuschemeng.6b00099 (DOI)000373554600061 ()2-s2.0-84964378085 (Scopus ID)
Note

QC 20160504

Available from: 2016-05-04 Created: 2016-04-29 Last updated: 2017-05-29Bibliographically approved
3. Conductive biofoams of wheat gluten containing carbon nanotubes, carbon black or reduced graphene oxide
Open this publication in new window or tab >>Conductive biofoams of wheat gluten containing carbon nanotubes, carbon black or reduced graphene oxide
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2017 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, no 30, 18260-18269 p.Article in journal (Refereed) Published
Abstract [en]

Conductive biofoams made from glycerol-plasticized wheat gluten (WGG) are presented as a potential substitute in electrical applications for conductive polymer foams from crude oil. The soft plasticised foams were prepared by conventional freeze-drying of wheat gluten suspensions with carbon nanotubes (CNTs), carbon black (CB) or reduced graphene oxide (rGO) as the conductive filler phase. The change in conductivity upon compression was documented and the results show not only that the CNT-filled foams show a conductivity two orders of magnitude higher than foams filled with the CB particles, but also that there is a significantly lower percolation threshold with percolation occurring already at 0.18 vol%. The rGO-filled foams gave a conductivity inferior to that obtained with the CNTs or CB particles, which is explained as being related to the sheet-like morphology of the rGO flakes. An increasing amount of conductive filler resulted in smaller pore sizes for both CNTs and CB particles due to their interference with the ice crystal formation before the lyophilization process. The conductive WGG foams with CNTs were fully elastic with up to 10% compressive strain, but with increasing compression up to 50% strain the recovery gradually decreased. The data show that the conductivity strongly depends on the type as well as the concentration of the conductive filler, and the conductivity data with different compressions applied to these biofoams are presented for the first time.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
Keyword
Carbon black, Carbon nanotubes, Compaction, Crude oil, Fillers, Graphene, Nanotubes, Pore size, Solvents, Yarn, Compressive strain, Conductive fillers, Conductive Polymer, Electrical applications, Orders of magnitude, Percolation thresholds, Reduced graphene oxides, Reduced graphene oxides (RGO), Foams
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-207441 (URN)10.1039/c7ra01082f (DOI)000399005500011 ()2-s2.0-85016468994 (Scopus ID)
Note

Funding details: EIT, European Institute of Innovation and Technology; Funding details: 243-2011-1436, Svenska Forskningsrådet Formas; Funding text: This work was financed by the Swedish Research Council Formas (No. 243-2011-1436). R. L. Andersson acknowledges the support from: European Institute of Innovation and Technology (EIT)-KIC InnoEnergy, Swedish Centre for Smart Grids and Energy Storage (SweGRIDS) and ABB AB.

QC 20170523

Available from: 2017-05-23 Created: 2017-05-23 Last updated: 2017-11-29Bibliographically approved
4. Freeze-dried wheat gluten biofoams; scaling up with water welding
Open this publication in new window or tab >>Freeze-dried wheat gluten biofoams; scaling up with water welding
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2017 (English)In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 97, 184-190 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a simple and rapid wet welding technique that enables the scaling up of freeze-dried protein (wheat gluten (WG)) biofoams for e.g. thermal insulation applications. The welding occurred by first wetting faces of foam cubes in water and then pressing them together for a limited time period. The water plasticized thin cell-walls of the two foams formed a dense weld when the plasticized cells collapsed under the drying step. The welds were always stronger and stiffer than the surrounding cellular structure. Based on three-point bending, it was shown that welded specimens (four-cube samples) were 7 times stronger than specimens produced directly as one piece with similar total size. This illustrated the problem of freeze-drying larger products; by instead assembling smaller foams into a large object the overall foam structure became more homogeneous. In addition, the dense welds become “walls” that limit gas convection in the mainly open cell structure, beneficial for thermal insulation. This is the first report on combined freeze-drying and water welding. It shows the sustainable potential of the technique for foam production, since only water is used as a foaming/welding agent.

Place, publisher, year, edition, pages
Elsevier, 2017
Keyword
Assembling, Biofoam, Mechanical properties, Welding, Wheat gluten
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-200886 (URN)10.1016/j.indcrop.2016.12.010 (DOI)000394064600021 ()2-s2.0-85006846901 (Scopus ID)
Note

QC 20170206

Available from: 2017-02-06 Created: 2017-02-03 Last updated: 2017-05-29Bibliographically approved
5. Flexible strength-improved and crack-resistant biocomposites based on plasticised wheat gluten reinforced with a flax-fibre-weave
Open this publication in new window or tab >>Flexible strength-improved and crack-resistant biocomposites based on plasticised wheat gluten reinforced with a flax-fibre-weave
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2017 (English)In: Composites Part A: Applied Science and Manufacturing, ISSN 1359-835X, Vol. 94, 61-69 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents strength-improved and crack-resistant wheat gluten biocomposites, using flax-fibre-weaves as reinforcement. The composites were produced by dip-coating of the weave into a wheat gluten/glycerol (WGG) solution, or by compression moulding. The most extensive coverage and wetting of the flax yarns occurred during the compression moulding, and the adhesion between the fibres and the matrix increased with increasing glycerol content. The compression-moulded sheets were, at a comparable flax content, stiffer than those produced by dipping, whereas their strength was similar and their extensibility slightly lower. Tensile tests on notched samples showed that the flax yarn improved the crack-resistant properties significantly; the maximum stress increased from 2 to 29 MPa using a content of 19 wt.% flax fibres. A clear advantage of this novel mechanically flexible biocomposite is that it can be shaped plastically under ambient conditions, while at the same time providing in-plane stiffness, strength and crack-resistance.

Place, publisher, year, edition, pages
Elsevier, 2017
Keyword
A. Biocomposites, A. Fibres, B. Fracture toughness, B. Mechanical properties
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-200890 (URN)10.1016/j.compositesa.2016.12.016 (DOI)000394193300007 ()2-s2.0-85007227713 (Scopus ID)
Note

QC 20170203

Available from: 2017-02-03 Created: 2017-02-03 Last updated: 2017-05-29Bibliographically approved

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