Is Spray Adhesive Flammable? A Comprehensive Overview

This article will elucidate the question: “Is Spray Adhesive Flammable?” It will also explain other important information regarding adhesives, flammability, and sprays.

Is Spray Adhesive Flammable? 

Yes, spray adhesives are definitely flammable. The solvents used in adhesive sprays are flammable enough to be considered explosives. When a flammable substance is in the gas or aerosol state, the hazard is the highest.

But there are spray adhesives that have fire-retardant constituents. These should be fire-resistant if instructions are followed.

Spray adhesive constituents

A flammable spray adhesive is made of a polymer (check the following section for more information), and often has organic solvents on its constitution. 

These solvents have the essential function of carrying the glue constituents into the junction area while being able to fly away to let the glue dry, so adhesion can happen.

To do so, the solvent itself must be evaporable, which means it must assume a gas-like state, making it more prone to be set on fire. In fact, it might be so flammable that an explosion can take place.

Spray solvents

Here’s a list of common spray solvents:

  • Methyl Acetate
  • Propane
  • Butane
  • Heptane
  • n-Hexane
  • Acetone
  • Cyclohexane
  • Isobutane
  • Dimethyl Ether
  • Dichloromethane
  • Ethyl Alcohol

You probably recognized some of them as fuels. The thing is: commercially, fuel is something we burn to get energy from, but in fact, fuel is anything that can be burned.

If your spray has any of the constituents mentioned above, it is very flammable.

Solvent functions

In the case of spray adhesives, these compounds are considered to be solvents rather than fuels, but they can act like combustibles and that’s why we should take precautions.

Solvents help regulate the consistency of the active ingredient (the adhesive, in this case), so the particles come out of the can with optimal characteristics.

Any canned combustible has a high risk of explosions. This happens because the gas is compressed in the can. As a consequence, the pressure is high enough so the gas can get liquefied. That’s why it appears to be liquid if you shake the can.

When we squeeze the can button we open up a little space where the liquefied gas can escape. As an effect, this propulsion consumes some of the energy inside the tin, making it a little cold for a while. 

Once the liquified gas escapes, the pressure automatically decreases and makes it turn into gas. Its natural behavior is then to spread, just like any under pressure gas. 

So, the mechanism by which a spray adhesive works is by carrying out adhesive components by the impulsion of a solvent, which then flies away to leave only the adhesive in place, a process normally called cure.

Flammability chemistry

In this section, we will discuss in-depth questions regarding flammable chemical compounds and fire.

The solvents cited in the previous section are named hydrocarbons. Most of them have a petroleum origin.  

Chemically speaking, these compounds are basically made of carbon and hydrogen. Their names are given according to the amount of carbon each molecule has. 

You can construct the molecule in your head bonding a carbon next to each other, and then adding hydrogens until each carbon makes four bonds.

source: http://www.chemistryland.com/ElementarySchool/BuildingBlocks/BuildingOrganic.htm

The more length a carbon chain has, the less gas-alike it is. In fact, at room temperature, a carbon chain with more than 4 carbons is already liquid. 

If we continue to imagine more carbons being added to it, will eventually become solid, like paraffin.

As you can see from the picture above, a burnable molecule can’t get more simple than a hydrocarbon. To understand why let’s take a look at how fire happens.

Fires

Fire is nothing more than a consequence of a chemical reaction. This requires a hydrocarbon source, oxygen, and heat to sustain the reaction. 

As a result, carbon dioxide (CO2) and water(H2O) are produced, along with energy in the form of heat and light.

When a combustible source is big and available enough, a fire can sustain itself and even grow bigger. The heat produced by the starting fire can let even more oxygen become available, and the fire goes on, like in a bonfire.

When a fuel source is too much available, although, something a little different can happen. If the hydrocarbon molecules can react with oxygen too quickly, an explosion can occur. 

This simply means that the combustion took place in a small amount of time. But not all explosions require the combustion of a hydrocarbon.

Hydrocarbon gases can react quickly because their molecules are simple and can interact quickly with oxygen. Since they’re in the form of gas, the molecules are much more available to react at once. 

A canned gas is a liquefied gas. This means that even more molecules are put in one place, and the danger of explosion grows even bigger.

When a tin containing gas is used, although, the gas escapes, and suddenly the molecules become sparse. 

This is why the fabricants often state that their product must be applied with good ventilation of the installations. This way the fire hazard extinguishes quickly.

But the can is still hazardous. Storage instructions should always be followed.

Conditions to avoid fires

If combustion requires fuel, oxygen, and heat, all we have to do to prevent it is not allow one of these parts to happen. If you are using a flammable adhesive, the fuel requisite is already fulfilled, so you can only control the other things.

In the case of spray cans, the heat can inflate the tin rising the pressure, making it more willing to explode. Some of the liquefied gas can start leaking gradually, so a small flammable bubble can form. This can then light up and be the fuse to a bigger explosion.

How do adhesives work?

Adhesives are compounds capable of glueing different kinds of objects together. Several physical-chemical adhesion properties can promulgate the fixing, it all depends on the specific compounds the adhesive formula has.

Overall, adhesives are polymers, long hydrocarbon chain structures that have many different kinds of chemical structures attached to them, so their properties are wide. 

It’s hard to determine their flammability without analyzing each case.

Source: https://sites.google.com/site/microbesbyalice/what-is-a-hydrocarbon

As can be seen from the picture above, a plastic (polymer) has similarities to the solvents mentioned in this article. In chemistry, similar molecules tend to interact better with each other than different ones. 

When speaking about liquids, solvents are molecules that dissolve others. They are miscible. Talking about gases, their intermolecular interactions are much weaker, so the molecules just collide with each other. 

This collision helps to drag the adhesive out of the can. That’s why organic solvents are usually required since they interact better with the glue polymer. 

Spray adhesive flammability

As explained before, a spray adhesive is very flammable because of its ingredients, unless the product label has told otherwise (but of course, this is only valid for verified labels).

Once the spray it’s used, the glue part will attach to the surface and the solvent will fly away. This is why good ventilation is required (not only to prevent fires but because there might be toxic gases inside the can as well, which are highly harmful to humans).

The glue, although, is not considered flammable normally after the cure, it depends on every product. 

The biggest flammability problem when dealing with such products is the solvent hazard. It’s always safer to follow the instructions accordingly.

For example, the following spray adhesives are flammable according to the manufacturers: KRYLON® All-Purpose Spray Adhesive, 3M™ Super 77™ Multipurpose Adhesive (Aerosol), CRC Spray adhesive, and 400ML H/DUTY SPRAY ADHESIVE.

Conclusion

Spray adhesives are considered very flammable, even explosives. It’s not because of the adhesive itself, but the organic solvents used. These compounds are so flammable that are actually used as fuels, so correctly understanding the label is advised. 

Frequently Asked Questions (FAQS): Is Spray Adhesive Flammable? A Comprehensive Overview

Is spray adhesive flammable after the cure?

After the product dries, it shouldn’t be flammable anymore but it depends on the product. The bigger flammability issue really is the solvents used, but they disperse quickly.

Is any aerosol spray flammable?

If any of the spay constituents are flammable, the whole product is. If in doubt, always assume that the product is flammable and take necessary precautions. The label should contain all necessary instructions.

How can I be sure that an adhesive spray is flammable?

Conducting a quick side-search is the best choice. Simply input the whole name of your product in a search engine bar, and you will then be able to find official safety data, normally in PDF.

Citations

SAUNDERS, Keith J. Organic polymer chemistry: an introduction to the organic chemistry of adhesives, fibers, paints, plastics and rubbers. Springer Science & Business Media, 2012.

https://sites.google.com/site/microbesbyalice/what-is-a-hydrocarbon

http://www.chemistryland.com/ElementarySchool/BuildingBlocks/BuildingOrganic.htm

https://www.krylon.com/document/SDS/en/US/724504070108
https://multimedia.3m.com/mws/mediawebserver?mwsId=SSSSSuUn_zu8l00x482xN8mvNv70k17zHvu9lxtD7SSSSSS–

http://docs.crcindustries.com/msds/3018.pdf

https://www.tooled-up.com/artwork/ProdPDF/41918%20MSDS.pdf

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