You may be asking yourself what does surface preparation have to do with CO2?
Appropriate surface preparation is the essential first step in providing consistent and reliable adhesive or cohesive bond strength. In preparation of bonding surfaces, precision cleaning is required to achieve a high degree of surface cleanliness. Surface cleanliness is the absence of foreign materials deposited on bonding surfaces.
Conventional surface treatment options for joining substrates pose different constraints in terms cost of ownership, environmental compliance, and performance. Carbon dioxide (CO2) based processing alternatives offer an effective, eco-friendly and robust platform for preparing many types of substrates surfaces for numerous medical, aerospace, automobile, ophthalmic and microelectronic bonding applications.
Conventional Surface Preparation
How Clean is Clean?
Removing contaminants such as fingerprints, particles, manufacturing process residues, vapors, machining oils, loosely adhering oxides and other surface contaminant layers are crucial for creating a surface for bonding.
Conventional industrial cleaning techniques pose various constraints that allow for product damage, contamination, materials wastes and not many are adaptable to automated manufacturing tools. Bonding technologies are numerous and include: adhesive bonding, mechanical fastening, laser welding, soldering, brazing, acoustic bonding, diffusion bonding, isothermal solidification bonding, transient liquid phase bonding, exothermic bonding, dip coating and thermal spray coating.
Hence, there is a need to have a more comprehensive surface treatment process that can address contamination challenges using one method as opposed to secondary treatments.
The CO2 Factor
Why is bonding essential?
There are various industries that require strong joints or durable surface adherents such as paints and coatings that can survive challenging environments such as pressure, strain, heat, cold, UV, ozone, steam, moisture and the human body. CO2 surface treatment technology provides robust bond line surface preparation using numerous singular and hybridized treatments which are completely dry, selective, safe for the environment and easily adapted or integrated with new and existing manufacturing processes, tools, lines and automation.
Manufacturing a strong bond
Manufacturing a strong bonding surface requires three aspects:
1. Maximize mechanical interlocking - increase the surface roughness in order to physically anchor bond between adhesive and surface.
2. Matching cohesion energy - degree of cohesion energy matches the adhesive with surface to create a highly wettable bond.
3. Increasing surface absorption and reactivity - surfaces should have sites that are polar or contain chemistries for the adhesive reaction.
CO2 Surface Treatment Technology
Carbon Dioxide (CO2) based surface treatment technology can manufacture a consistent and reliable bond surface and address the various limitations of conventional cleaning and modification processes for bonding.
Precision CO2 cleans surfaces to remove hydrocarbon and silicone oil films, particles, and loose oxide layers, provides selective spray or bulk immersion treatments and pre-cleans surfaces for more uniform and effective atmospheric plasma surface activation.
There are three CO2 processes that precision clean surfaces for bonding:
- CO2 Composite Spray Treatments - CO2 composite sprays provide precise control of spray cleaning energy both mechanical scouring and chemical cleaning power. CO2 composite sprays are very useful for delicate substrate surfaces such as thin metallic or polymeric coatings, or surfaces containing fragile mechanical features.
- Centrifugal CO2 Immersion-Extraction Treatments - Centrifugal CO2 immersion treatment techniques utilize liquid or supercritical CO2 to remove both external surface and internal subsurface contaminants and are also used in cooperation with other dry techniques such as UV/Ozone, vacuum plasma and eco-friendly additive chemistries.
- CO2 Hybrid Treatments - the surface scouring and solvent cleaning actions of a CO2 composite spray are used in cooperation with atmospheric plasma CO2 to form a process called CO2 particle-plasma cleaning. The CO2 composite spray controls surface temperature and cleanliness working with plasma to simultaneously remove debris and excess heat from the treated surface.
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