# 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.

Source: https://karmindadhesive.com/applications/glulam-timber/

## 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

- KA505 PUR Wood Adhesive — undefined tensile, undefined elongation. https://karmindadhesive.com/products/ka505-wood-adhesive/

Note: Typical values from the catalogue. Structural use requires the glue line to be specified by an engineer, not by a sealant supplier.

## Questions

### 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.