Bonding performance of muf and pur adhesives for glued laminated timber

Šernek, Milan (author), Šega, Bogdan (author), Fašalek, Andrej (author)

Most adhesive systems for the production of glued laminated timber (GLULAM) are designed for softwoods and are therefore often not suitable for bonding hardwoods such as beech. Despite its good mechanical properties, beech wood still has a lot of untapped potential in timber construction. It has a high density and strength, but at the same time is not biologically durable and is dimensionally unstable. Beech wood can be successfully bonded with typical wood adhesives, but problems often occur in delamination tests due to unfavourable shrinkage and swelling when the bonded components are exposed to moisture fluctuations or immersed in water. The aim of this study was to determine the bonding performance of common melamine-urea-formaldehyde (MUF) and polyurethane (PUR) adhesives in the production of spruce GLULAM when applied to beech GLULAM or hybrid beech and spruce GLULAM. The experiment was divided into two parts. In the first part, beech lamellas were bonded with MUF, PUR and PUR in combination with a primer (PUR+P) to form a GLULAM. In the second part, hybrid GLULAMs made of beech and spruce were produced. The two outer lamellas were made of beech wood, while the three inner ones were made of spruce wood. For beech GLULAM only, all adhesive bonds were found to have a much higher shear strength (about 14 N/mm2) than required by the standard [1]. All adhesive bonds in a hybrid GLULAM made of beech and spruce also met the requirements, but the shear strength was lower (about 10 N/mm2). Adhesive bonds between spruce and beech achieved slightly higher average strength values than adhesive bonds between spruce only. The highest shear strengths were achieved with PUR adhesives in combination with a primer, followed by MUF and PUR adhesives without primer. The results show that beech and spruce wood can be successfully bonded to form a hybrid beam using MUF and PUR adhesives. The adhesive bonds between beech and spruce wood show an effective bonding performance and fulfil the standard requirements.

• Language: English
• Keywords: adhesives, beech, spruce, glulam, shear strength
• Work type: Scientific work
• Typology: 1.08 - Published Scientific Conference Contribution
• Organization: BF - Biotechnical Faculty
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: Str. 3576-3583
• PID: 20.500.12556/RUL-170763
• UDC: 630*8
• DOI: 10.52202/080513-0438
• COBISS.SI-ID: 242564099
• Publication date in RUL: 15.07.2025

Record is a part of a monograph

• Title: World Conference on Timber Engineering 2025 : advancing timber for the future built environment
• Editors: Kelly Rischmiller
• Place of publishing: [S. l.]
• Publisher: World Conference on Timber Engineering
• Year: 2025
• ISBN: 979-8-3313-2090-4
• COBISS.SI-ID: 239752963

Secondary language

• Language: Slovenian
• Keywords: lepila, bukev, lepljen lameliran les, strižna trdnost, bukev

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P4-0015-2020
• Name: Les in lignocelulozni kompoziti