The pros and cons of PU glue
With carpentry, there are three main types of glue that you can use – polyurethane (PU), Grab/Panel or PVA glue.
All of them have their uses and all of them are hugely reliable, but they are all different and have their own unique strengths.
As such, we will be profiling all three of them and their pros and cons on an individual basis and the first glue we will look at is PU glue.
Polyurethane, or PU, glue is a type of glue that is best used for structural timber bonding, flooring or heavy load use. It can be used to glue timber to brickwork, plaster and concrete.
It comes in four different types – fast setting, slow setting, standard and thixotropic. These are mostly self-explanatory; fast setting can set within five minutes, slow setting can take 45 minutes and the standard is usually around half an hour.
Thixotropic, meanwhile, is for vertical applications as it doesn’t run. You can have a fast set thixotropic or a slow set thixotropic, but it still won’t run.
The reason why the thixotropic variant doesn’t run is because of its jelly-like formulation, which prevents it from trickling down.
The bond generated from PU glue is very strong and that is immediately a huge positive. When applied, the glue will fizz and expand, to the point it will fill irregularities or gaps in the bonding materials.
In addition, it reacts very well to moisture. In fact, if you lightly spray the bonding material with water, PU glue will not only set faster as it will draw water from the air rather than have water leave the glue itself to bond, but it will perform better too.
This makes it great when dealing with damp or frozen materials, as it will still thrive in those circumstances.
Because of how PU glue fizzes up when it is applied, you need to either bond the materials with machinery or by clamping them down. As a result of the glue’s reaction, the bonded surfaces are prised apart, so it is imperative that the workpiece is either clamped or mechanically fixed whilst the glue cures.
If you were to just rest one bonding material on top of the other using PU glue and then just leave it, you would come back to notice the materials had deviated slightly and were no longer lined up straight.
An example of this would be if you bonded two materials together but failed to clamp them, you could find that as the PU cured, the items would separate by around 5mm, which in turn results in a weak joint and a useless bond.
Also, PU glue is extremely hard to clean up whilst uncured and is a very messy product and as such, it may be wise to use PPE when using it. If it spills over and gets on your tools or your clothes, it’ll likely leave a permanent mark.
In the event uncured PU glue spills over, you can use a cleaning solvent – such as a foam gun cleaner – to clean it up, but the results are only fairly limited.
As such, anything important must be removed, covered over or masked up when using. When cured, the bulk of the glue can be cleaned off with a sharp knife, chisel or scraper, but there will be residue left behind.
Your best bet then is to remove the rest with an abrasive product, such as sandpaper or wire wool.
There is a reason why PU glue is revered and while caution is advised while using it due to how messy it can be, it’s a very good and reliable glue.
If you are working on a project where heavy load structural timber bonding is required, then it won’t let you down.
To speak to an advisor about what types of glue that we provide at Multifix or what may be best for your project, please get in contact with us here.
All of them have their uses and all of them are hugely reliable, but they are all different and have their own unique strengths.
As such, we will be profiling all three of them and their pros and cons on an individual basis and the first glue we will look at is PU glue.
Firstly, what is PU glue?
Polyurethane, or PU, glue is a type of glue that is best used for structural timber bonding, flooring or heavy load use. It can be used to glue timber to brickwork, plaster and concrete.
It comes in four different types – fast setting, slow setting, standard and thixotropic. These are mostly self-explanatory; fast setting can set within five minutes, slow setting can take 45 minutes and the standard is usually around half an hour.
Thixotropic, meanwhile, is for vertical applications as it doesn’t run. You can have a fast set thixotropic or a slow set thixotropic, but it still won’t run.
The reason why the thixotropic variant doesn’t run is because of its jelly-like formulation, which prevents it from trickling down.
What are the pros of PU glue?
The bond generated from PU glue is very strong and that is immediately a huge positive. When applied, the glue will fizz and expand, to the point it will fill irregularities or gaps in the bonding materials.
In addition, it reacts very well to moisture. In fact, if you lightly spray the bonding material with water, PU glue will not only set faster as it will draw water from the air rather than have water leave the glue itself to bond, but it will perform better too.
This makes it great when dealing with damp or frozen materials, as it will still thrive in those circumstances.
Those sound good! What about the cons though?
Because of how PU glue fizzes up when it is applied, you need to either bond the materials with machinery or by clamping them down. As a result of the glue’s reaction, the bonded surfaces are prised apart, so it is imperative that the workpiece is either clamped or mechanically fixed whilst the glue cures.
If you were to just rest one bonding material on top of the other using PU glue and then just leave it, you would come back to notice the materials had deviated slightly and were no longer lined up straight.
An example of this would be if you bonded two materials together but failed to clamp them, you could find that as the PU cured, the items would separate by around 5mm, which in turn results in a weak joint and a useless bond.
Also, PU glue is extremely hard to clean up whilst uncured and is a very messy product and as such, it may be wise to use PPE when using it. If it spills over and gets on your tools or your clothes, it’ll likely leave a permanent mark.
In the event uncured PU glue spills over, you can use a cleaning solvent – such as a foam gun cleaner – to clean it up, but the results are only fairly limited.
As such, anything important must be removed, covered over or masked up when using. When cured, the bulk of the glue can be cleaned off with a sharp knife, chisel or scraper, but there will be residue left behind.
Your best bet then is to remove the rest with an abrasive product, such as sandpaper or wire wool.
Forging a strong bond
There is a reason why PU glue is revered and while caution is advised while using it due to how messy it can be, it’s a very good and reliable glue.
If you are working on a project where heavy load structural timber bonding is required, then it won’t let you down.
To speak to an advisor about what types of glue that we provide at Multifix or what may be best for your project, please get in contact with us here.