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D'Amico S.,Competence Center for Wood Composites and Wood Chemistry Wood K plus | Hrabalova M.,Institute for Natural Materials Technology | Muller U.,Competence Center for Wood Composites and Wood Chemistry Wood K plus | Muller U.,University of Natural Resources and Life Sciences, Vienna | Berghofer E.,University of Natural Resources and Life Sciences, Vienna
Industrial Crops and Products | Year: 2010

The main objective of this research was to study the potential of renewable polymers based on wheat corn for wood-to-wood bonding and wood composites. Commercial wheat flour containing mainly starch and proteins was used as biobased glue. To evaluate the strength on wood joints under different curing temperatures tensile shear strength of spruce wood specimen was tested according EN 302-1. Thermal properties of the wheat flour glue were studied by means of differential scanning calorimetry (DSC). Pasting profiles of the wheat flour slurry were investigated by using a Micro Visco-Amylograph (MVA). With rising pressing temperature an increase of bond strength was observed up to a temperature of 105 °C. Under these conditions excellent bonding strength was reached and mainly wood failure was detected. At higher temperature a slight reduction of bond strength was observed, which can be related to beginning thermal modification of wood, especially changes in character of the wood surface. Best adhesive performance was not reached until the granular order was disrupted and thus starch molecules were separated. Changes in the molecular structure of starch during heating are described by means of analytical methods helping to explain the effects on the bond strength. © 2009 Elsevier B.V. All rights reserved. Source


Schwanninger M.,University of Natural Resources and Life Sciences, Vienna | Stefke B.,Competence Center for Wood Composites and Wood Chemistry Wood K plus | Hinterstoisser B.,Competence Center for Wood Composites and Wood Chemistry Wood K plus | Hinterstoisser B.,University of Natural Resources and Life Sciences, Vienna
Journal of Near Infrared Spectroscopy | Year: 2011

The weight percentage gain and the acetyl group content of wood due to acetylation with acetic anhydride have been analysed by means of Fourier transform infrared spectroscopy (FT-IR) and Fourier transform near infrared spectroscopy (FT-NIR). Spruce wood of various sample shapes, chemically modified by applying acetic anhydride with and without catalysts and, as close as possible to industrial applications were selected from the sample sets used previously for calibration/quantification. In the previous paper, band assignments were provided to an extent to understand the functional groups upon which the calibrations were based. In the present work the qualitative results are extensively discussed with respect to the literature including old and new band assignments. Therefore, this article features some characteristics of a review. It has been proved that, using either FT-IR or FT-NIR, it is possible to follow chemical changes in wood due to acetylation. Fourier self-deconvolution and second derivatives of the mid-infrared spectra provided identical additional information. The disappearance of functional groups, such as hydroxyl groups, as well as the appearance of carbonyl groups and methyl groups in the acetyl ester groups, allowed us to confirm results from other studies including the accessibility and reactivity of the hydroxyl groups. A new, definitive band assignment of the second overtone of the C=O stretching vibration from acetyl groups at 5242 cm -1 was possible. Furthermore, it is shown that, with increasing weight percentage gain, aromatic esters are formed which can be distinguished from the alkyl esters in FT-IR. However, certain questions concerning the accessibility and reactivity of the hydroxyl groups and band assignment still remain. © IM Publications LLP 2011. Source


D'Amico S.,Competence Center for Wood Composites and Wood Chemistry Wood K plus | D'Amico S.,Competence Center for Wood Composites and Wood Chemistry Wood K plus | D'Amico S.,University of Natural Resources and Life Sciences, Vienna | Hrabalova M.,University of Natural Resources and Life Sciences, Vienna | And 2 more authors.
European Journal of Wood and Wood Products | Year: 2012

Earlier research into native wheat flour for wood to wood bonding showed excellent bonding properties comparable to synthetic adhesives, but no data about ageing behaviour is available. Short and long term effects on mechanical properties were analysed by lap joint testing and modified DCB-specimens. Results showed no significant reduction in bonding properties, but a trend to lower adhesive strength after 12 months of storage was noticeable. Changes in wheat polymers were observed by means of DSC and FTIR-ATR. Soluble degradation products of starch were analysed by GC-FID after methanolysis and derivatisation. FTIR measurements indicated changes in the structure of starch, but no appreciable alteration of proteins. Investigations by DSC showed increasing crystallinity during 3 months of storage. After 6 months more degradation products were detected. Results indicated that hydrolysis of starch is responsible for a moderate decrease of bonding performance; wheat proteins seem to be less affected. © Springer-Verlag 2012. Source

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