Since they’re so versatile, it’s common to find glue on many surfaces.
However, many glues fail to reach their full potential when it comes to sticking to the inside of the bottle. That is, their outer surfaces seem to look great but inside is nothing but junk.
So, why doesn’t glue stick to the inside of the bottle? Glue consists of a thick liquid base, a powder, and excess water.
When the glue is poured, the powder sinks to the bottom of the bottle and the liquid flows upward. However, when the glue is squeezed out of the bottle, the powder is not evenly dispersed.
Instead, the powder collects at the top of the bottle and settles there. As the glue sits on its top, the powder dehydrates and hardens, preventing it from flowing downward.
Because of this, the glue never dries out completely and is always sticky to the touch.
Why Doesn’t Glue Stick to The Inside of The Bottle?
Contents
You may have thought that it is because the glue dries up, but this is not the case. The glue does not dry.
Instead, the molecules that make up the glue get entangled with each other and form a network called an amorphous solid.
To understand why glue does not stick to the inside of the bottle, you must understand the properties of amorphous solids.
Amorphous solids are characterized by the property of hardness, which means that they resist deformation.
Hard solids can be relatively brittle as well, meaning they can crack under pressure or impact.
When a solid is rigid, it consists of atoms whose arrangement is regular and symmetric. As a result, the atoms form a regular crystal lattice structure.
When a solid is amorphous, the atoms are arranged in a non-regular or random pattern.
This does not mean that the solid cannot hold itself together, but simply that the atoms are randomly arranged.
Now, glue is made up of molecules that consist of molecules and atoms. These bond to each other to form chains and rings.
These chains and rings are held together by hydrogen bonds between the atoms or between neighboring molecules.
This is why glue has an adhesive property that resists water.
Glue molecules are entangled with each other and cannot separate freely. Instead, these molecules form a network, which constitutes an amorphous solid. This means that the glue does not dry.
Instead, the molecules that make up the glue get entangled with each other and form a network called an amorphous solid.
What Makes Glue Not Stick to the Inside of Bottles?
If you’ve ever had a bottle of glue that won’t stick, then you know exactly what I’m talking about. No matter how much you try, the adhesive won’t stick to the inside. It sticks nicely on the outside, but if you try to stick it on the inside, it just doesn’t stick.
What causes glue not to stick to the inside of bottles?
There are many factors that can contribute to the glue not sticking well inside the bottle. For example, improper storage, the change in temperature, moisture, and pressure can affect how the glue sticks.
Temperature
When adhesive is exposed to temperature changes, the adhesive’s molecular structure changes. It can become too fluid and runny, making it a lot harder to stick to the bottle’s surface.
Moisture
Moisture can cause adhesive to swell and contract. When this happens, the glue loses its adhesive properties.
Pressure
The pressure inside the bottle can cause the glue to lose its adhesive properties. As air gets trapped inside the bottle, the adhesive’s properties tend to change and become weaker.
Storage
Storing your adhesive in a cool, dry area will help prolong its shelf life and prevent it from losing its adhesive properties.
If Cyanoacrylates React with Water, What Keeps Them Liquid?
Because cyanoacrylates (superglue) are known for the bonding property, it is interesting to know why they are liquid at room temperature.
Scientists have found that cyanoacrylates can react in water, but not as much as other adhesives can.
To understand this phenomenon, researchers ran a series of tests on cyanoacrylates using 25 different adhesives.
They found that the bonding strength between the adhesive and glass was proportional to the amount of water added.
The more water added to the adhesive, the stronger the bond. However, the amount of bonding water was limited. The more water added, the slower the adhesive’s bonding strength increased.
So, the bonding strength increased at a much slower rate with more water added to the adhesive.
Researchers also found that cyanoacrylates can form hydrogen bonds with water molecules at room temperature.
Due to this, water molecules become bound to the polymer chains, keeping the polymer chains together. This, in turn, keeps the adhesive liquid.
Other studies found that cyanoacrylates can also react with water differently.
Cyanoacrylates can form hydrogen bonds with water molecules at room temperature and can also form hydrogen bonds with water molecules that are frozen at -20 degrees Celsius.
However, when the temperature falls below freezing, the polymers in cyanoacrylates cannot form hydrogen bonds with frozen water molecules.
As an additional note, some cyanoacrylates can also react with water to form ice crystals.
This reaction does not only happen with room temperature water, but can also occur with hot water or hot water under pressure.
How Does Chemical Adhesion Differ from Mechanical Adhesion?
The adhesion of a chemical to a substrate is much stronger than the adhesion of a mechanical force.
This means that chemical adhesion is stronger than mechanical adhesion.
This can be explained with an example: the adhesion of a chemical force to a substrate is greater than the adhesion of a mechanical force to a substrate.
Mechanical adhesion involves contact between two surfaces and the force of attraction between them. The force of attraction can be temporary or permanent.
Chemical adhesion involves active process between the chemical and the substrate. The force of attraction in chemical adhesion is permanent.
In mechanical adhesion, the force is temporary and unstable. In chemical adhesion, the force is permanent and unstable.
Chemical adhesion is stronger than mechanical adhesion.
Are There Glues that Don’t Dry Even on Exposure to Air?
There are three types of glues: contact adhesives, hot melts, and pressure-sensitive adhesives.
While contact adhesives dry by evaporating solvent and are tacky only when they’re wet, hot melts dry by oxidation and become tacky as soon as they are flowing.
Pressure-sensitive adhesives dry by reacting with oxygen in the air.
Hot melts and contact adhesives suffer from oxidation and evaporation, respectively, just as regular glues do.
However, pressure-sensitive adhesives do not suffer from oxidation because air does not react with them. This is why they don’t dry when exposed to air.
Also Read: What Glue to Use for Paper Glass?
Final Words
Why doesn’t glue stick inside the bottle? The paste-type glue does not adhere to the bottle wall because the glue molecules are not fixed to the surface.
They cannot form a chemical bond with the surface. Instead, the glue molecules move independently on the surface.
The evaporation of a solvent in paste-type glue and the oxidation in hot melt glue can lead to the loss of adhesive properties.
While cyanoacrylates do not suffer from oxidation like hot-melt or paste-type glues, they are affected by moisture, especially water.
White glue contains water as a solvent and can dissolve in water; this also leads to the loss of adhesive properties.
On the other hand, superglue doesn’t have the solvent -water combination and so it doesn’t dissolve in water; it’s unaffected by moisture.
