ANALYSIS OF WATER VAPOR DIFFUSION IN STRUCTURAL WOOD ADHESIVE BOND
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Tartalom: http://doktori.uni-sopron.hu/id/eprint/988/
Archívum: SOE Doktori Repozitórium
Gyűjtemény: Állapot = Kéziratban
Típus = Disszertáció
Tudományterület = műszaki tudományok: anyagtudományok és technológiák
Cím:
ANALYSIS OF WATER VAPOR DIFFUSION IN STRUCTURAL WOOD ADHESIVE BOND
Létrehozó:
Zinad, Omar Saber
Tartalmi leírás:
Water-vapor diffusion in layer-bonded wood panels used for structural purposes plays a critical role in the long-term performance and durability of engineered wood products such as cross-laminated timber (CLT) used for residential houses and multistorey buildings. While the diffusion behavior of solid wood has been widely studied, far less is known about vapor diffusion through adhesive layers, the extent to which adhesives block diffusion, and the internal strains generated as a result. This thesis investigates these missing aspects by examining seven wood species: spruce, grey poplar, beech, oak, Smaragdfa, eucalyptus, and oil-palm wood under four surface conditions: uncoated, lasure-coated, commercial adhesive-coated, and coated with custom-made polymer resins of varying molecular weights (2000–6000 MW). Water-vapor diffusion was evaluated using an accelerated cup method following ISO 12572 and ASTM E96. A total of 315 specimens were tested, and permeability behavior was analyzed under both pre-steady-state and steady-state conditions. Although steady-state water vapor permeability among uncoated wood samples appeared similar (2.62–3.81 ×10⁻¹⁴ kg/(m·s·Pa)), the pre-steady zone revealed large differences strongly governed by structure and density, with mass change at the transition point serving as the most reliable indicator of early-stage permeability. Structural adhesives exhibited significant blocking effects. The commercial adhesive produced the lowest permeability values and the highest strains, confirming its strong vapor-blocking property. In contrast, lasure coatings specially formulated to moderate vapor transport allowed semi-permeable diffusion with smooth and stable strain profiles. Custom-made polymers showed systematic molecular weight (MW) dependent behavior: low-MW systems restricted permeability, intermediate MW enabled selective vapor passage, and high-MW systems supported enhanced vapor transport while reducing internal strains. Internal-strain measurements demonstrated a direct correlation between permeability resistance and strain development, with the highest strains occurring in impermeable adhesives and the lowest in uncoated or semi-permeable coatings. The findings reveal that vapor permeability in wood bonded in layer is governed by the coupled interaction of wood anatomy, density and adhesive molecular weight. The results suggest that the development of structural wood adhesives should account for molecular weight design to enable moderate water-vapor diffusion, which can reduce moisture-induced stresses and enhance the long-term performance of CLT and other bonded in layer engineered wood systems.
Nyelv:
angol
angol
Típus:
Disszertáció
NonPeerReviewed
Formátum:
application/pdf
application/pdf
Azonosító:
Zinad, Omar Saber ANALYSIS OF WATER VAPOR DIFFUSION IN STRUCTURAL WOOD ADHESIVE BOND. Doktori értekezés, Soproni Egyetem.
Kapcsolat: