Dispensing Dynamics -Fluid Types0 pages

I&J Fisnar Inc. Dispensing Dynamics - Part 2 - Fluids

Cyanoacrylate Dispensing
Bond Conditions
Cyanoacrylate is an “instant” adhesive with three (3) principal chemical components,
namely: methyl, ethyl, and butyl. Cyanoacrylate is generally a clear liquid with a
viscosity from 3 cps to 2000 cps. The higher viscosity cyanoacrylates are described as
“gap- filling”. There is also a cyanoacrylate, called Black-Max, with a rubber component
to provide elasticity. Bonding strength is 15 Kg per cm².
Polymerization
The polymerization of cyanoacrylate is a reaction which occurs when the adhesive comes
into contact with humidity.
Polymerization reaction starts at the surface of the adhesive toward the center of the
deposit. In order to have good adhesion (bond) between two substrates, the thickness of
the cyanoacrylate must be thin.
Example: If a large glob of glue is dispensed on a flat service, it will stay in liquid form
because only a very thin layer of adhesive contacts the surface and will polymerize.
Blooming
Blooming may occur when a large amount of cyanoacrylate remains in liquid form. Some
of the liquid material may vaporize and react with humidity. The result is a
polymerization, which appears as a white dusty marking on the surface near the adhesive.
To solve (or reduce) blooming:
- Ventilate to eliminate vapor
- Use an “activator” to polymerize at a faster rate
An “activator” is generally a liquid which is volatile and can be applied before or after
the assembly of the two parts being joined. When using an “activator”, the total
polymerization process occurs in seconds and not over a longer period if relying on
humidity alone to propagate the polymerization. The negative effect when using an
activator is that it slightly reduces the strength and adhesion of the “bond”.
Other conditions that can affect the bond strength and rate of polymerization are: