Purbond AG

Sempach, Switzerland

Purbond AG

Sempach, Switzerland
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Klausler O.,ETH Zurich | Hass P.,ETH Zurich | Amen C.,Purbond AG | Schlegel S.,University of Cooperative Education | Niemz P.,ETH Zurich
European Journal of Wood and Wood Products | Year: 2014

Tensile shear tests according to EN 302-1 for load-bearing timber structures were performed on European beech wood (Fagus sylvatica L.) and Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] bonded by means of a one-component polyurethane adhesive (1C PUR). Results reveal a substantial loss of tensile shear strength (TSS) and wood failure percentage (WFP) at the wet stage compared to the dry stage. As can be seen from microscopic images, this is accompanied by a loss of adhesion at the boundary layer. Therefore, the aim of this work was to find a priming fluid that improves the load transmission between adhesive and adherend at the wet stage without introducing formaldehyde into the gluing process. A substantial improvement of TSS and WFP was achieved by means of the hygroscopic organic solvent N,N-dimethylformamide (DMF). In addition, contact angle measurements were carried out, revealing that DMF heavily enhances the wettability of the joining surface. Furthermore, it was attempted to integrate the outcomes into the swelling strain model stated by Frihart in 2009. By way of comparison a hydroxymethylated resorcinol coupling agent, a mixture of diphenylmethane-4,4-diisocyanate isomers and water were also tested as priming fluids. The data confirm that TSS and WFP of 1C PUR bonded wooden joints do not correlate, whilst WFP is mostly not normally (at wet stage often bimodally) distributed. © 2014 Springer-Verlag Berlin Heidelberg.


Clau S.,ETH Zurich | Dijkstra D.J.,Bayer Material Science | Gabriel J.,Purbond AG | Klausler O.,ETH Zurich | And 3 more authors.
International Journal of Adhesion and Adhesives | Year: 2011

The thermal stability of adhesives for load-bearing construction has been one of their key parameters since engineered wood products were introduced in timber construction. In the case of one-component moisture-curing polyurethane (1C PUR) adhesives, knowledge about relationships between their chemical structure and the resulting bonding properties is limited, especially under high-temperature conditions. In this study the structureproperty relationships of 1C PUR prepolymers were analyzed in the temperature range from 20 to 200 °C by means of mechanical and rheological tests. NCO-terminated urethane prepolymers were prepared from systematically varied MDI and polyether mixtures. The structural parameters investigated were the urea and urethane group content, cross-link density, ethylene oxide content and the adjustment of functionality via NCO or polyether component. Bonded wood joints were tested for their tensile shear strength and polymer films were analyzed by means of DMA and DSC. The results revealed a significant influence of hard segment content and cross-link density on the thermal stability of the prepolymers. Not all parameters that affect the film properties significantly influence bonding. © 2011 Elsevier Ltd. All rights reserved.


Clauss S.,ETH Zurich | Gabriel J.,Purbond AG | Karbach A.,Currenta GmbH | Matner M.,Bayer AG | Niemz P.,ETH Zurich
Holzforschung | Year: 2011

Only small amounts of additives are needed to formulate one-component polyurethane (1C PUR) adhesives for various applications. The current study illuminates the effects of the formulation on the mechanical properties of pure adhesives, on the one hand, and their performance in bonded wood joints on the other. Tensile shear tests on bonded wood joints, tensile tests on adhesive films, and nanoindentation measurements in the interphase region of the bond were performed. Analyses by means of infrared, atomic force, and electron microscopy provided the explanatory basis for the results obtained. Additionally to laboratory made 1C PUR, unmodified commercial 1C PUR, melamine-urea- formaldehyde (MUF), and phenol-resorcinol-formaldehyde (PRF) were tested for comparison. The results obtained confirm that the mechanical properties of 1C PUR adhesives are significantly affected by their prepolymer composition. The adhesive formulation by means of additives, on the other hand, does not affect the mechanical properties but is to a large extent responsible for the bonding performance. © 2011 by Walter de Gruyter Berlin Boston.


Clauss S.,ETH Zurich | Dijkstra D.J.,Bayer AG | Gabriel J.,Purbond AG | Karbach A.,Currenta GmbH | And 3 more authors.
Journal of Applied Polymer Science | Year: 2012

Filler materials are part and parcel for the adjustment of adhesives, in particular, their rheological and mechanical properties. Furthermore, the thermal stability of adhesives can be positively influenced by the addition of an expedient filler, with inorganic types common practice in most cases. In this study, one-component moisture-curing polyurethane adhesives for engineered wood products based on isocyanate prepolymers with different polymer-filled polyether polyols were investigated with regard to the filler's potential to increase the thermal stability of bonded wood joints. The property changes due to the addition of fillers were determined by means of mechanical tests on bonded wood joints and on pure adhesive films at different temperatures up to 200°C. Additional analyses by atomic force and environmental scanning electron microscopy advanced the understanding of the effects of the filler. The tested organic fillers, styrene acrylonitrile, a polyurea dispersion, and polyamide, caused increases in the cohesive strength and stiffness over the whole temperature range. However, the selected filler type was hardly important with regard to the tensile shear strength of the bonded wood joints at high temperatures, although the tensile strength and Young's modulus of the adhesive films differed over a wide range. Prepolymers with a lower initial strength and stiffness resulted in worse cohesion, in particular, at high temperatures. This disadvantage, however, could be compensated by means of the filler material. Ultimately, the addition of filler material resulted in optimized adhesive properties only in a well-balanced combination with the prepolymer used. © 2011 Wiley Periodicals, Inc.


Luedtke J.,Thuenen Institute of Wood Research | Amen C.,Purbond AG | van Ofen A.,University of Hamburg | Lehringer C.,Purbond AG
European Journal of Wood and Wood Products | Year: 2015

European hardwood species such as beech, oak and ash present a potential alternative to commonly used softwoods in glued engineered wood products. To date, mainly amino- and phenoplast adhesives are used for bonding these hardwoods, but some one-component polyurethane (1C-PUR) adhesives prove to offer an alternative when combined with a primer pretreatment. Therefore, a study was conducted to examine the influences of primer treatment and other parameters, such as surface machining and press time on the bondability of ash, beech, oak and—as a reference—Norway spruce. Delamination and block shear tests were conducted according to current European standards. Furthermore, information about bonding quality was gathered by means of microscopic glue line thickness measurements. The results suggest that the primer treatment is able to significantly enhance the bonding quality of hardwoods. The choice of the surfacing method causes some significant changes in the primer effectiveness. However, not all species were equally affected. The influence of the primer treatment on shear tests in a dry state was rather low throughout the series and only little significance was found. similar results were found after variations of the press time. © 2015, Springer-Verlag Berlin Heidelberg.


Amen-Chen C.,Purbond AG | Gabriel J.,Purbond AG
European Journal of Wood and Wood Products | Year: 2015

Southern yellow pine and Douglas fir were glued with two different 1C PUR adhesives and evaluated by means of the vacuum-pressure and delamination tests according to the Canadian Standard CSA O112.9 and the European Standard EN 391, method B, respectively. By using a water-based primer before application of the adhesive, wet wood failure percentage and delamination resistance of the polyurethane adhesives dramatically increased compared to matched samples glued under the same conditions without primer. Standard requirements were achieved when primer was used. © 2015, Springer-Verlag Berlin Heidelberg.


Lehringer C.,Purbond AG | Gabriel J.,Purbond AG
RILEM Bookseries | Year: 2014

Manufacture of engineered wood products requires safe adhesive systems. Since their introduction in the mid-1980s, one component polyurethane (1C-PUR) adhesives have proven to provide a reliable alternative to commonly water based aminoplast (UF, MF, MUF) and phenoplast (PR, PRF) adhesive systems. No formaldehyde, no mixing and fast curing at room temperature are some of the reasons, why 1C-PUR adhesives have continuously experienced increasing acceptance in the field of structural timber gluing. Driven by the intention to establish a highest possible level of adhesive performance and security, this successful development was accompanied by extensive scientific and industrial research activities. The present article aims at providing an understandable overview of the most relevant results from those research activities during the past years. Major aspects such as chemical and physical bondline integrity, adhesive behaviour at elevated temperature and fire, and gluing of alternative wood species will be addressed in order to present an insight into 1C-PUR adhesive-technology and an outlook to its future development. © RILEM 2014.


An adhesive system for preparing lignocellulosic composites comprising: a) a primer composition; and, b) a polyurethane adhesive composition, wherein said primer composition comprises: 1 to 100% by weight of the composition of at least one compound having a hydroxyl number of less than or equal to 30 mg KOH/g and being selected from the group consisting of polyalkylene glycols, polyalkylene glycol monoethers or polyalkylene glycol di-ethers; 0 to 99% by weight of the composition of solvent; and, 0 to 5% by weight of the composition of surfactant selected from the group consisting of water soluble surfactants, water emulsifiable surfactants and mixtures thereof. The adhesive system has particular applicability to wooden substrates characterized by high levels of water soluble extractives and, in particular, arabinogalactan.


Patent
Henkel AG and Purbond AG | Date: 2014-08-04

An adhesive system for preparing lignocellulosic composites comprising a) an aqueous primer composition and, b) a polyurethane adhesive composition, wherein said aqueous primer composition comprises: from 0 to 25 wt. %, by weight of the composition, of polyol selected from the group consisting of water soluble polyols, water dispersible polyols, water emulsifiable polyols and mixtures thereof, wherein said polyols have a molecular weight less than 5000 daltons; and, up to 10 wt. %, by weight of the composition, of surfactant selected from the group consisting of water soluble surfactants, water emulsifiable surfactants and mixtures thereof, with the proviso that the aqueous primer composition must comprise at least one of said polyol or a surfactant having hydroxyl functionality and a molecular weight of less than 5000 daltons.

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