A simple guide as to what a PU wood adhesive is, what it can bond, and how to use it.
PU adhesives. What are they, what do they bond, and how do you use them?
PU wood adhesives, (or MCPU – moisture cured polyurethane adhesive), are commonly used for bonding timber because of their excellent water resistance, and bond strength. The most common type is a single component version which is often supplied in a handy bottle for easy dispensing. PU adhesives will bond most wood and even the increasingly popular new products like Accoya .
If the adhesive is PU based (polyurethane) then by its very nature it is likely to be a good product. Common brands include Gorilla glue, Lumberjack and many other brands. Woodstikk D4 PU, D4 Rapid, Aro-Bond 920 and Aro-Bond 947 are a number of different grades we have in our range. Polyurethane chemistry is used in many markets for making all sorts of things in every day life. It is a very flexible system in the sense you can tweak it to be hard, soft, fast curing, slow curing, single component, two components, etc.
It is likely that all PU wood adhesives are waterproof as the bond line it creates is so strong and durable. The common PU wood adhesives comply with the D4 water resistance requirements, which effectively means that it is waterproof. More information on the different classifications (D1, D2, D3, D4) can be found here.
Yes it is. As it reacts with moisture in the air and on the substrate, a chemical reaction takes place meaning the adhesive will start bubbling up. It is the same base as the common builders expanding, or filler foam, but thankfully doesn’t expand that much. So always protect your hands, body and workpiece before applying it.
Accoya is wood, but not as you know it. It is modified timber in which a process called acetylation, a cutting-edge patented technology, enables it to resist rot, defy the elements and stay strong for decades. This process results in a stronger, more durable wood while reducing the maintenance frequencies for coatings. The change in cell structure also means that the wood is virtually rot and insect proof. Mould and fungi do not recognise Accoya as wood and therefore don’t attack, while the modified structure is indigestible to insects
The effect of this process on adhesives, is that traditional wood bonding adhesives struggle to give a satisfactory bond. Ureka have been working with Accsys, the producers of Accoya, for a number of years and have approved Aro-Bond 920 and Aro-Bond 947 for bonding Accoya
Unfortunately, PU adhesive is difficult to clean. Many users will have made the mistake of getting PU glue on their hands and it stays there for days! We would recommend that you use gloves and skin protection when using PU so that you don’t have this problem, as there aren’t many cleaners that we know of which effectively remove the residue.
Similarly, PU adhesive is difficult to get off substrates once it has cured. Really, the only effective way to remove overspill is to sand it off or chip it off. When producing your work, allow for the fact that you are likely to have to sand back to remove the overspill. You could protect the workpiece using a non-paper based masking tape.
PU wood adhesive can be applied by bead or roller, but bear in mind that the adhesive will cure off and is difficult to clean. Watch this video to see hints and tips on how to use it effectively.
Would you like more information about Woodstikk PU adhesives
Then here's where to find it:
PU adhesives. What are they, what do they bond, and how do you use them?
Got an adhesives problem? Let our sticky smarts work for you.
Call us0117 971 1364
Email ussales@thenamethatsticks.com
Get how-to advice, industry news and new innovations — straight to your inbox.