Menu

Carbonic Cleaning to Clear Contaminants Prior to Adhesive Bonding Shows Promise

Posted on 10/21/2020 8:25:35 AM By Assembly Magazine
  

The time and effort spent on preparing substrates prior to bonding with epoxy adhesives may have been a bit of a sore point in assembly because, while it is very necessary in order to ensure a strong and lasting bond, these preparation stages could also be viewed as affecting efficient and fast assembly. However, a new approach to removing these contaminates might change the whole picture.

The presence of contaminates which form their own weak bonds with substrates, has been known to affect the strength of epoxy bonds by reducing the size of surface left available and accessible to the epoxy if not removed.

The new approach takes the form of carbonic cleaning which uses very small amounts of compressed liquid CO2, an inert, non-flammable, non toxic and non-aqueous organic solvent which can be propelled in a temperature-controlled air stream through an insulated nozzle onto substrates.

asb0520clean1

As a result of the Joule-Thomson effect, the CO2 splits into a mix of gas and solid particles. While being propelled, the particles heat up and change shape, adopting a bullet-like profile with fine points. This shape enables them to transfer to the substrate easily, and at a higher velocity because of the kinetic energy added to it by the compressed air stream. Once on the substrate, the CO2 acts as a solvent, especially when dealing with hydrocarbon contaminates, and uses the thermal strains brought about by the temperature to boost its cleaning ability still further.

Testing the system’s effectiveness involved bonds being carried out with (and between) various materials, as well as setting up comparisons between it and other cleaning methods such as sanding, air, and alcohol wipes. The results indicated that the highest breaking force was required after carbonic cleaning was carried out prior to the bond.