lnu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Finger jointing of green Scots pine
Linnaeus University, Faculty of Science and Engineering, School of Engineering. (Byggteknik)
2005 (English)In: Green gluing of wood- process – products – market : International conference / workshop, Borås, April 7-8, 2005 / [ed] Björn Källander, Borås, 2005, p. 55-65Conference paper, Published paper (Refereed)
Abstract [en]

Finger jointing of green timber enables the wood industry to produce value-added products by using a new efficient process. Green finger jointing has gradually accelerated in New Zealand, USAand Canada, but is still relatively unknown in Europe. This study evaluates three green adhesive systems used with green Scots Pine timber: 1) a modified Phenol Resorcinol Formaldehyde (PRF) known as Greenweld®, 2) a one-component polyurethane adhesive and 3) a soy protein and PRF (soy/PRF) adhesive. Green adhesives have been compared with a conventional exterior PRF-Reference adhesive used with kiln-dried timber. The evaluation of mechanical performance was carried out with 4-point bending, according to EN 408. The warp of dried finger-jointed timber was measured in the form of bow, spring and twist and microscopy studies of glue lines were performed. The moisture durability of the adhesives was tested according to ASTM-D 4688-95. The tensile strength, WFP (Wood Failure Percentage) and failure modes were determined. Results showed that bending strength did not differ either between green adhesive systems and PRF-Reference dry system, or among green adhesives themselves. The warp of dried timber was on the same level for green glued finger joints and for conventional finger joints. The durability test showed that the PUR adhesive used in the green process had highest dry tensile strength compared to the other tested adhesives. The wet tensile strength after accelerated aging of all four adhesives did not differ significantly. The dry WFP without any treatment was high for all three adhesives used for green gluing and did not differ from the PRF-Reference. However, the wet WFP after cyclic boiling treatment of the green adhesive systems turned out to be lower than the wet WFP of the PRF-Reference adhesive. The results of the failure mode also illustrate that the green adhesives glue line of the wet specimens failed more often in the interface between wood and the adhesive than those with the PRF-Reference adhesive. Additionally, microscopy studies of the glue lines revealed that the penetration of polyurethane adhesive was deepest, Greenweld’s penetration was similar to PRF-Reference and sapwood glue lines of green adhesives had more cavities than heartwood glue lines.

Place, publisher, year, edition, pages
Borås, 2005. p. 55-65
Keywords [en]
finger jointing, green gluing, durability
National Category
Engineering and Technology
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
URN: urn:nbn:se:lnu:diva-18593ISBN: 91-85533-31-9 (print)OAI: oai:DiVA.org:lnu-18593DiVA, id: diva2:525516
Conference
International conference / workshop Green gluing of wood- process – products – market. Borås, April 7-8 2005COST Action E34 Bonding of Wood in cooperation with SP Swedish National Testing and Research Institute
Available from: 2012-05-08 Created: 2012-05-08 Last updated: 2012-09-14Bibliographically approved
In thesis
1. Characterisation of green-glued wood adhesive bonds
Open this publication in new window or tab >>Characterisation of green-glued wood adhesive bonds
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The gluing of unseasoned wood, called green gluing, is a relatively new sawmill process, implying a radically changed order of material flow in the production of value-added wood-based products. It facilitates the enhancement of raw material recovery and value yield by integrating defect elimination and gluing already before kiln drying. The present study evaluates green glued adhesive bonds in flatwise glued beams and finger joints. The main part of this work deals with green gluing using a moisture curing polyurethane adhesive (PUR). Standardised test methods and specially designed, small scale, specimens were used for the determination of the strength, fracture energy and the ductility of both dry- and green glued bonds in tension and in shear. Using the small scale specimens it was possible to capture the complete stress versus deformation curves, including also their unloading part. An optical system for deformation measurement was used for the analysis of bond behaviour. The influence of moisture content during curing and temperature after curing on the adhesive chemical composition and on the mechanical properties was investigated. Furthermore, the moisture transport through the adhesive bond during curing was tested. Finally, microscopy studies were performed for analysis of bond morphology and fracture. The results show that two significant factors influence the shear strength of green glued bonds: wood density and adhesive spread rate. Bonds which fulfil the requirements according to EN 386 could be obtained within a wide range of process parameters. The small specimen tests showed that green glued PUR bonds can reach the same strength and fracture energy, both in shear and in tension, as dry glued bonds with the same adhesive amount. The local material properties of the bonds could be determined, thanks to the failure in the tests taking place within the adhesive bond itself and not in the wood. Following process factors were shown to cause lower bond strength: a) a low adhesive spread rate, b) high pressure and c) short pressing time in combination with low wood density and high moisture content. Moreover, the heat treatment of the cured PUR adhesive during drying influenced the chemical composition of the adhesive, providing for higher strength, stiffness and Tg of the adhesive, caused by an increased amount of highly ordered bidentate urea.

Place, publisher, year, edition, pages
Växjö, Kalmar: Linnaeus University Press, 2012. p. 67
Series
Linnaeus University Dissertations ; 85/2012
Keywords
green gluing, finger jointing, durability, shear strength, wood failure percentage, fracture energy, tensile strength, PUR adhesive
National Category
Materials Engineering
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-18606 (URN)978-91-86983-57-4 (ISBN)
Public defence
2012-06-01, Myrdal, Hus K, Växjö, 09:00 (English)
Opponent
Supervisors
Available from: 2012-05-09 Created: 2012-05-08 Last updated: 2012-06-15Bibliographically approved

Open Access in DiVA

No full text in DiVA

Authority records BETA

Sterley, Magdalena

Search in DiVA

By author/editor
Sterley, Magdalena
By organisation
School of Engineering
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 335 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf