Flammable vs non-flammable canister adhesives
There is a lot of confusion and misinformation around the difference between flammable and non-flammable canister adhesives and what their respective benefits and limitations are.
Non-flammable canister adhesives are non-flammable because they contain a non-flammable solvent called methylene chloride. Glue Guru Cantac High-Tac is an example of a non-flammable methylene chloride canister adhesive. Methylene Chloride is also heavier than conventional solvents consequently non-flammable canisters weigh more, typically 17kg compared to 13-14kg for flammable ones.
Methylene chloride is toxic to breathe and users must be careful to protect themselves from exposure by inhalation. Breathing protection can be provided by way of a respirator which includes a self-contained air-supply. Filter cartridge respirators are not suitable because methylene chloride can’t be filtered.
A feature of non-flammable canister adhesive is they have a short flash-off time. This is the time period required after applying the glue for the solvent to evaporate or “flash-off” before the two materials to be bonded can be joined. For non-flammable canister adhesives this time is typically two minutes. The short flash-off time means non-flammable canister adhesive can be well-suited to production environments where small time savings can be very beneficial. They are less suitable for construction environments or on-site work because of the breathing protection requirement as well as the hazard to other workers nearby.
A limitation of non-flammable canister adhesives is their short open time. Open time is the period between the solvent flashing off and the glue becoming too dry to adhere to itself. For non-flammable canister adhesives this period is typically less than 60 minutes. Bonds joined after this time will fail.
In summary non-flammable glues are:
- Fast flash-off so well suited to production environments where small time savings are critical
- Toxic by inhalation which is difficult to manage so not well suited to construction or site work
- Short open time
Flammable canister contact adhesives are flammable because they contain conventional flammable solvents. Glue Guru Cantac HSE-Tac is an example of a flammable canister adhesive. Flammability is obviously a hazard that needs to be managed but generally the flammability is low because the solvent is diluted with other material e.g. rubbers. Care should be taken in confined spaces or where there is inadequate ventilation or ignition sources are present.
The flash-off time of flammable canister adhesives is slightly longer than non-flammable ones – 2-5 minutes. This can mean non-flammable canister adhesives are less well suited to production environments where speed is critical and minutes can make a big difference.
A feature of flammable canister adhesives is longer open time. Cantac HSE-Tac can remain open for up to 24 hours which gives great flexibility in its application. It also reduces the risk of adhesive failure due to joining materials too late.
In summary flammable canister glues are:
- Slower flash-off – 2 to 5 minutes so may be less well-suited to production environments
- Non-toxic so very well-suited to construction or site work where self-contained breathing apparatus is not practical
- Flammability hazard to manage
- Long open time