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Improved fire design model for cross-laminated timber and glulam
RISE Research Institutes of Sweden, Safety and Transport, Fire and Safety.ORCID iD: 0000-0002-8001-401x
Tallinn University of Technology, Estonia.
Tallinn University of Technology, Estonia.ORCID iD: 0000-0002-6623-9263
2022 (English)Report (Other academic)
Abstract [en]

Adhesives state the essential prerequisite for manufacturing large timber construction elements from rigidly bonded solid wood boards of growth and processing bound limited dimensions. In the first two decades after the invention of glulam up to the 1930s, adhesives based on natural organic substances like blood and proteins were used. Such adhesives can have high dry strength but are weak when applying water or temperature. These adhesives were then replaced by synthetic ones, firstly in the early 1930s by (phenol )-resorcinol-formaldehyde (RF/PRF) adhesives and then by urea-formaldehyde (UF) adhesives. Numerous tests have shown that the boiling water resistant duroplastic RF/PRF adhesives are very stable at high temperatures up to/beyond the charring of wood (Dorn and Egner, 1967; Klippel 2014). Contrary hereto, the UF adhesives later classified in Europe as type II adhesives have significantly reduced water resistance (e.g. Raknes (1997) and are less temperature stable and fire resistant, although the latter was not communicated sufficiently. The RF-, PRF- and UF- adhesives were exclusively used up until the 1980s when the presently existing timber standards for “cold” and fire design were being developed. From the 1980s onwards, adhesives with various chemical compositions have been added to the market. Firstly the duroplastic melamine-urea-formaldehyde and pure melamine formaldehyde (MUF/MF) adhesives, followed in the mid-90s by the moisture-hardening one-component polyurethane (1C-PUR) adhesives, then followed by the emulsion-polymer isocyanate (EPI) adhesives. In order to speed up curing times, being of utmost high economic importance, significant amounts of polyvinyl acetate (PVAc) have been added to the hardeners of MUF adhesives with drawbacks on temperature stability. Each of the developed adhesives has its advantages and disadvantages regarding strength, water and/or temperature resistance, application robustness and price. According to EN 1995-1-2:2004, chapter 3.5, the behaviour of a bond line in fire may not be considered explicitly if the bond line is made of phenol-formaldehyde and aminoplastic, Type I adhesives, according to EN 301. Regarding the general principle that adhesives shall produce joints of such strength that the integrity of the bond is maintained in the assigned fire resistance period, a footnote hints at the point that some adhesives show softening considerably below the charring temperature of wood.

Place, publisher, year, edition, pages
2022. , p. 10
Series
FIRENWOOD D2.3
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:ri:diva-61175ISBN: 978-91-89757-10-3 (electronic)OAI: oai:DiVA.org:ri-61175DiVA, id: diva2:1711855
Note

The FIRENWOOD project is supported under the umbrella of ERA-NET Cofund ForestValue byGermany (Federal Ministry of Food and Agriculture (BMEL); Agency for Renewable Resources (FNR)project number FKZ 2219NR120), Sweden (The Swedish Research Council for Environment,Agricultural Sciences and Spatial Planning (FORMAS); Swedish Energy Agency (SWEA); SwedishGovernmental Agency for Innovation Systems (Vinnova) project number 2018-04989) and Norway(Research Council of Norway (RCN) project number 298587). Fores tValue has received funding fromthe European Union's Horizon 2020 research and innovation programme under grant agreement No773324.

Available from: 2022-11-18 Created: 2022-11-18 Last updated: 2023-05-08Bibliographically approved

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Just, AlarMäger, Katrin Nele

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