A hot glue gun is waterproof.
But it isn’t just waterproof; it is also water-resistant. Hot glue is also resistant to temperature changes, eroding, chemicals, and solvents.
If you apply hot glue to a surface and pour water over it, the water will not mix with the adhesive. It will lay on top of it, or it will roll off of it.
Learning about glue guns is waterproof and water-resistant may seem pretty cool, but it also has some drawbacks.
Please keep reading to discover what makes hot glue guns waterproof and their water-resistance feature’s drawbacks.
What Makes Hot Glue Waterproof?
Hot glue guns have a high and effective resistance to water (including salt water) and various other solvents.
How is this possible?
Hot glue contains polymers, and these make it impenetrable. Water, or many solvent types, cannot penetrate it.
To some of you, this may raise the curiosity and question of whether hot glue works underwater.
When you apply hot glue underwater, this does lead to a weakening in the bond it forms.
Applying hot glue underwater could lead to cracks or holes between the surface and the adhesive.
This leads us to the drawbacks of hot glue being waterproof and water-resistant.
Water, vapors, moisture, or humidity are present in the air and on most surfaces.
Here is what this means.
The strongest bonds by glue are formed and created when they can permeate the surface on a molecular level.
This means that the glue doesn’t just bond superficially on the surface but brings its adhesion into the material.
Because hot glue is waterproof and water-resistant, and most surfaces contain different moisture levels, humidity, or water vapors, the bond isn’t formed on the molecular level.
Hot glue forms its bond on the surface.
This means that over time, as moisture, humidity, or water vapor makes its way between the material and the glue, it can lose its grip and detach itself from the bonded surface.
How Does An Increase In Temperature Affect Hot Glue?
Hot glue is influenced by temperature changes outside of its specific range.
An increase in temperature generally causes hot glue to expand. After that, it comes back to its original form. This process is known as thermoplasticity.
Typically, when temperature changes, both an increase and a decrease in temperature may cause the adhesive to lose some of its water-resistant ability.
Here is a kicker.
The water-resistant capability of hot glue does depend on the type of material you apply it to.
So let’s check these out.
Hot Glue On Wood
Wood contains some moisture. How much depends on the type of wood.
Being a porous material, it welcomes water, humidity levels, and temperature may influence it.
Wood soaks up water, moisture, or humidity from the air, causing it to expand and become bulkier over time.
This expansion can cause the hot glue, or even other glue, to become ineffective.
To avoid this, applying a water sealant to the wood is common for protection.
Hot Glue On Plastics
Hot glue is not enough to bond plastic with other materials, such as fabrics, glass, or other materials.
Hot Glue On Metal
Metal is a heat conductor.
So when the temperature increases in the metal (or heat being conducted through the metal), this will weaken the bond between the metal and hot glue.
Hot Glue On Glass
Glass is an amorphous material. When the surrounding temperature increases or decreases, this will cause the glass to expand or contract.
This will cause the hot glue to detach from the glass.
Hot Glue On Fabric
If you are working with a high-quality glue gun, the bond between the glue and the fabric will be strong.
Hot Glue: Meet The Polyurethane Reactive Hot Melt Glue
Polyurethane Reactive Hot Melt Glue (PUR) was created to be better and do better than regular or conventional hot glue.
This type of hot glue works the following way.
It creates a very strong structural bond. It cures over 48 hours to form an epoxy-level strong bond.
PUR hot glue reacts with the air and its elements to form a much stronger bond than regular hot glue.
Polyurethane Reactive Hot Melt Glue (PUR) is:
- Waterproof
- Resistant to temperature changes
- Dust-proof
- Insulating
- More UV resistant than traditional hot glue
So before you jump into getting PUR hot glue, here is something else you need to know about it.
Compared to traditional hot glue, it is more expensive and has a shorter shelf life.
Frequently Asked Questions
Can I use hot glue as a sealant?
Here is how a sealant works: it must adjust multiple times while remaining durable and strong. Hot glue is a non-flexible adhesive, so it can’t work as a sealant.
Can I use hot glue outdoors?
Hot glue doesn’t work outdoors.
Conclusion
Hot glue guns are waterproof and water-resistant.
They work best indoors and aren’t the best for outdoor use.
