Application
PUR adhesive for glulam and engineered timber
PUR wood adhesive cures by reacting with moisture in the wood and the air. That makes it strong and solvent-free, and it makes clamp time a function of the timber, not of the clock.
What 100% solids buys you
KA505 is 100% solids with a viscosity of 5,000–10,000 mPa·s at 25 °C. No solvent means no shrinkage gap in the glue line and no VOC in the press hall; it also means the spread rate is what you put on, not what is left after evaporation.
The catalogue cure is 1–4 hours, with a 30–70 minute skin time that moves with the season. In a cold workshop the skin time stretches and the cure slows; in a dry, hot one the opposite. Neither is a defect.
Moisture is the process variable
Because the reaction consumes water, the timber moisture content drives the bond. Kiln-dried stock at 8–12% is the normal window for structural work. Wet or frozen timber will produce a foamed, weak glue line that looks fine until it is loaded.
The same property is why PUR is good on treated timber: the treatment does not stop the reaction the way it can interfere with some water-based systems, provided the surface is dry.
Where it does not belong
PUR is not a gap filler. Joints need to close, and clamping pressure has to be even — a starved joint or a wide gap will fail regardless of the adhesive. It is also not a structural adhesive for steel; where the assembly mixes timber and metal, use a sealant designed for the metal bond or a mechanical fixing.
For sandwich panels and truck bodies, KA505 bonds the timber frame and the insulation; the skin-to-frame bond often wants a different product, and that is a conversation worth having before the drawing is fixed.
Models for this job
Typical values from the catalogue. Structural use requires the glue line to be specified by an engineer, not by a sealant supplier.
Questions that come up
What timber moisture content?
8–12% for structural glulam. Above that, the glue line foams and strength drops; below, cure slows and can be incomplete.
How long in the press?
The catalogue gives 1–4 hours cure. Clamp until the glue line is hard at the squeeze-out; cold or damp timber pushes that to the top of the range.
Can it be used outdoors?
The bond is water-resistant, but exposed timber needs its own protection. Do not treat the adhesive as the weatherproofing layer.
Other applications
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