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Sundsvall, Sweden

Nordqvist P.,KTH Royal Institute of Technology | Khabbaz F.,Casco Adhesives AB | Malmstrom E.,KTH Royal Institute of Technology
International Journal of Adhesion and Adhesives

The tensile strength of beech substrates bonded with dispersions of alkali-denatured soy protein isolate (SPI) and wheat gluten (WG) was measured for comparison of bond strength and resistance to cold water. The proteins were denatured with 0.1 M NaOH (pH 13). Dispersions with different protein concentration and viscosity were investigated. The adhesive properties were studied at different press temperatures (90, 110, and 130 °C) and press times (5, 15, and 25 min). Two types of application methods were used in order to overcome the problem with different viscosity of the dispersions. In addition, SPI was denatured at two different pH levels (approximately 10 and 13) and with two different concentrations of salt (158 μM and 0.1 M), in order to compensate for the different isoelectric points of the proteins. The adhesive properties of WG powder with different particle sizes were also compared. The tensile strengths of the wood substrates were measured according to somewhat simplified versions of the European Standards EN 204 and EN 205. The bond lines were studied with light microscopy. The results indicate that the adhesive properties of SPI are superior, particularly with regard to water resistance. However, the water resistance of WG was to some extent improved when starved adhesive joints could be avoided. Similar tensile strength values were obtained for the dispersions of alkali-denatured SPI regardless of pH or salt concentration. No apparent difference in adhesive strength was observed for the WG dispersions from powder with different particle sizes. © 2009 Elsevier Ltd. All rights reserved. Source

Johnsson B.,Casco Adhesives AB | Roffael E.,University of Gottingen | Behn C.,University of Gottingen
International Wood Products Journal

Addition of urea to a melamine modified urea formaldehyde resin in the surface and core layer reduces significantly the formaldehyde release of the particleboards bonded therewith. Under the used boundary conditions (long press time) urea addition seems to have no noticeable negative impact on the physical-mechanical properties of the boards. The reduction of formaldehyde release due to urea addition as a scavenger can be followed by measuring the emission in the chamber according to EN 717-1, the perforator method according to EN 120 and the flask method as described in EN 717-3. The results reveal that under the used conditions a good correlation exists between the emission in the chamber and the corrected perforator values (R2=0·865), as well as between the chamber value and the formaldehyde emission measured by the 3h-flask method (R2=0·792) according to EN 717-3, a slightly better correlation was found between the measured flask values after 24 h and the emission in the chamber (R2=0·869). The correlations seem to hold in the emission range between 0·06 and 0·016 ppm. ©2014 IWSc, the Wood Technology Society of the Institute of Materials, Minerals and Mining Received 14 March 2013. Source

Khosravi S.,KTH Royal Institute of Technology | Khosravi S.,Casco Adhesives AB | Khabbaz F.,Casco Adhesives AB Analyscentrum | Nordqvist P.,KTH Royal Institute of Technology | Johansson M.,KTH Royal Institute of Technology
Industrial Crops and Products

The aim of this study was to elucidate the possibilities of using soy protein isolate (SPI) and wheat gluten (WG) as binders for particleboards. One-layer particleboards were produced in laboratory scale. Parameters regarding the formulation of the adhesive and the gluing process were investigated, while the press parameters were kept constant. The considered factors were: the use of protein as a dispersion and/or as a dry protein powder, the temperature during the preparation of the dispersion, the time for preparing the dispersion, the storage time of dispersion prior to gluing, and the use of dried core particles or green particles. The board properties evaluated were: internal bond (IB), thickness swelling (TS) and water absorption (ABS). The results were statistically evaluated and SIMCA-P+ software was employed as a multivariate analyzing tool. The results show that protein adhesives can work as adhesive for particleboard. The results also reveal that it is preferable to use the dispersion as a binder rather than the dry protein. Furthermore, in the case of the SPI, the time for preparing the dispersion is a significant parameter; it appears that longer dispersion time results in enhanced board properties. According to the results, the temperature during the preparation does not seem to have any impact on the gluing properties of the SPI dispersions. On the other hand, in the case of WG dispersions, the temperature has an impact on the properties of the adhesive, favouring lower temperature, while the time is insignificant. Additionally, if the dispersion has been stored for more than 1 day before it is used, it results in boards with poorer mechanical and water resistance properties. The utilization of the green chips, instead of the dried core particles, is clearly a disadvantage, especially regarding the water resistance of the particleboards. It appears that SPI is superior to WG when it comes to the water resistance as well as the mechanical properties of the boards. However, it is not possible to compare these two proteins explicitly, since SPI contains a higher percentage of protein. Additionally, WG contains more starch, which is known to give poorer water resistance properties. © 2010 Elsevier B.V. Source

Johnsson B.,Casco Adhesives AB | Engstrom B.,Casco Adhesives AB | Roffael E.,University of Gottingen
Wood Science and Technology

The correction factor developed by Jann and Deppe (1990) to adjust the measured perforator values of particleboards and fibreboards measured at different moisture contents in the range of 3% ≤ u ≤ 9% to the level at 6.5% moisture content has two main deficiencies. It takes no account of the influence of the molar ratio of the resins used, which seems to remarkably impact the relationship between the moisture content and the measured perforator values. Moreover, research work revealed that the correction factor to be applied also depends on the moisture content, at which the perforator value was measured, according to an inversely proportional correlation. Besides, the correction factor according to Jann-Deppe leaves this fact unconsidered. © 2011 The Author(s). Source

Roffael E.,University of Gottingen | Johnsson B.,Casco Adhesives AB | Engstrom B.,Casco Adhesives AB
Wood Science and Technology

In Europe, the perforator method (EN 120) is the mostly used laboratory method of the wood-based panel industry. Usually, the measured perforator value depends on the moisture content of the boards. According to DIBt-100, the measured perforator values are corrected to a common moisture content (MC) of 6.5% using an established equation proposed by Jann and Deppe (1990). The correction factor of Jann and Deppe (1990) is based on the assumption that particle- and fibreboards change their perforator values to the same extent regardless whether increasing or decreasing the moisture content in the range of 3 ≤ u ≤ 9%. Application of this correction factor to particle- and fibreboards of higher moisture content than 6.5% can lead to biased corrected results in favour of low emission. The corrected values can also lead to paradoxical relation between the perforator values and emission in the low-emission region. © 2010 The Author(s) 5. References:. Source

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