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Wheat Gluten Fractions as Wood Adhesives-Glutenins Versus Gliadins
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
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2012 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 123, no 3, 1530-1538 p.Article in journal (Refereed) Published
Abstract [en]

Plant proteins, such as wheat gluten, constitute attractive raw materials for sustainable wood adhesives. In this study, alkaline water dispersions of the protein classes of wheat gluten, glutenin, and gliadin were used as adhesives to bond together wood substrates of beech. The aim of the study is to measure the tensile shear strength of the wood substrates to compare the adhesive performance of glutenin and gliadin and to investigate the influence of application method and penetration of the dispersions into the wood material. A sodium hydroxide solution (0.1M) was used as dispersing and denaturing agent. Dispersions with different protein concentrations and viscosities were used, employing wheat gluten dispersions as references. Two different application methods, a press temperature of 110 degrees C and a press time of 15 min, were employed. The tensile shear strength and water resistance of the wood substrates were compared, using a slightly modified version of the European Standard EN 204. The bond lines of the substrates were examined by optical microscopy to study the penetration and bond-line thickness. The results reveal that the adhesive properties of gliadin are inferior to that of both glutenin and wheat gluten, especially in terms of water resistance. However, the tensile shear strength and the water resistance of gliadin are significantly improved when over-penetration of the protein into the wood material is avoided, rendering the adhesive performance of gliadin equal to that of glutenin and wheat gluten.

Place, publisher, year, edition, pages
2012. Vol. 123, no 3, 1530-1538 p.
Keyword [en]
adhesives, mechanical properties, proteins, renewable resources, biopolymers
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-51267DOI: 10.1002/app.34312ISI: 000296862700027Scopus ID: 2-s2.0-80255126228OAI: oai:DiVA.org:kth-51267DiVA: diva2:464081
Note
QC 20111212Available from: 2011-12-12 Created: 2011-12-12 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Exploring the Wood Adhesive Performance of Wheat Gluten
Open this publication in new window or tab >>Exploring the Wood Adhesive Performance of Wheat Gluten
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The increasing environmental concern has reawakened an interest in materials based on renewable resources as replacement for petroleum-based materials. The main objective of this thesis was to explore plant proteins, more specifically wheat gluten, as a binder in wood adhesives intended for typical solid wood applications such as furniture and flooring.

Alkaline and acidic dispersions of wheat gluten were used as wood adhesives to bond together beech wood substrates. Soy protein isolate was used as a reference. The tensile shear strengths of the substrates were measured for comparison of bond strength and resistance to cold water. AFM in colloidal probe mode was used to investigate nanoscale adhesion between cellulose and protein films. Wheat gluten was divided into the two protein classes; glutenins and gliadins, and their adhesive performance was compared with that of wheat gluten. Heat treatment and mild hydrolysis were investigated as means for improving bonding performance of wheat gluten. The treated wheat gluten samples were analysed by SE-HPLC and 13C-NMR to correlate molecular size distribution and structural changes with bonding performance.

Soy protein isolate is superior to wheat gluten, especially in regards to water resistance. However, the bond strength of wheat gluten is improved when starved bond lines are avoided. The AFM analysis reveals higher interfacial adhesion between soy protein isolate and cellulose than between wheat gluten and cellulose. These results partly explain some of the differences in bonding performance between the plant proteins. Soy protein isolate contains more polar amino acid residues than wheat gluten and possibly interacts more strongly with cellulose. Furthermore, the bond performances of wheat gluten and glutenin are similar, while that of gliadin is inferior to the others, especially regarding water resistance. The extent of penetration of the dispersions into the wood material has a large impact on the results. The bonding performance of gliadin is similar to the others when over-penetration of the dispersion into the wood material is avoided. Moreover, the bond strength of the wheat gluten samples heated at 90°C was in general improved compared to that of wheat gluten. A small improvement was also obtained for some of the hydrolyzed wheat gluten samples (degree of hydrolysis: 0-0.6 %). The improvements in bonding performance for the heat treated samples are due to polymerization, while the improvements for the hydrolyzed samples are due to denaturation. The 13C-NMR analysis of the treated samples confirms some degree of denaturation.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 74 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:23
Keyword
plant protein, wood adhesive, mechanical properties, wheat gluten, soy protein isolate, gliadin, glutenin, adhesion, hydrolysis, heat treatment, AFM
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-94883 (URN)978-91-7501-348-0 (ISBN)
Public defence
2012-06-01, Sal K2, Teknikringen 28, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20120514Available from: 2012-05-14 Created: 2012-05-11 Last updated: 2012-05-14Bibliographically approved
2. Protein-Based Adhesives for Particleboards
Open this publication in new window or tab >>Protein-Based Adhesives for Particleboards
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main objective of this study was to elucidate the possibilities to use wheat gluten (WG) as a binder for particleboards, as well as soy protein isolate (SPI). The focus was on the effect of the adhesive formulation and the processing conditions, while the press parameters were kept constant. Some aspects of the dispersion and the preparation of the dispersions that were investigated are: the dispersing agent (sodium hydroxide 0.1 M or citric acid 0.05 M), the time (1, 3 or 5h) to prepare the dispersion, the temperature (room temperature, 50 or 80°C) during the preparation of the dispersions and the effect of storing (1, 2.5 or 4 days) the dispersions before application. Additionally, utilization of cross-linker polyamidoamine-epichlorohydrin (PAAE) and trimethylolpropane triacetoacetate (AATMP) were evaluated. Furthermore, the utilization of green particles versus dried particles was examined. The concentration (12, 16, 20 or 24%) of WG dispersion and the process for applying it to the particles were studied. Two application methods were evaluated, in application method 1 (appl. 1) all the dispersion was added to the particles in one step before the particles were dried. When application method 2 (appl. 2) was employed the dispersion was added in two steps, some of the dispersion was added before the drying and some after the drying. The considered board properties were internal bond (IB), thickness swelling (TS) and water absorption (ABS). The wetting, penetration and film formation of the WG dispersions on the wood was investigated employing different microscopy techniques. For the WG dispersions it looks as if a lower temperature is preferable for the preparation of the dispersion and that the time to prepare the dispersion is of no importance. Furthermore, storing the dispersions for more than one day before it was used as an adhesive for particleboards (PB) resulted in poorer boards. Using the right cross-linker, such as PAAE enhances the binding abilities of WG. According to this study it is beneficial to use dried particles instead of green particles. Additionally, the results show that the interaction between the concentration of WG dispersion and how it is applied is a significant factor, considering the IB value. However, in general the two step process (appl. 2) is preferable. The microscopy study reveals that this can be explained by the balance between wetting, penetration, and flow of the dispersion on the wood. The two step application results in less over-penetration when the viscosity of the dispersion is low.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 64 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:2
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-178939 (URN)978-91-7595-792-0 (ISBN)
Public defence
2016-01-15, K1, Teknikringen 56, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20151209

Available from: 2015-12-09 Created: 2015-12-09 Last updated: 2015-12-09Bibliographically approved

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