The Plasma Treatment Revolution: CHRIS LINES, MANAGING DIRECTOR OF DYNE TECHNOLOGY, EXPLAINS HOW DEVELOPMENTS IN THE CAPABILITIES OF PLASMA SURFACE TREATMENT TECHNOLOGY HAS SEEN IT BECOME THE METHOD OF CHOICE FOR BONDING NON-STICK' POLYMERS.
When the use of these new 'non-stick' polymers began taking off in the 1980s, engineers were introduced to the growing need for surface modification. Popular methods at that time included high temperature flame torch treatment and environmentally damaging solvent-based primers and pre-treatments.
Although flame treatment methods provide a fairly good option for treating surface areas with simple geometries, such as two-dimensional web materials, it is not so well suited for parts with more complex geometries, wide surface areas and materials easily damaged by the high temperature output of the flame torch.
Manufacturers and engineers ultimately picked up on the shortfalls of flame treatment and harsh solvent based primers and pre-treatments. Alongside the high running costs of gas and compressed air, there are often high insurance costs and associated health and safety concerns due to the naked flame in a production environment of a plastics factory.
Why is surface treatment necessary?
Achieving any level of adhesion to low surface energy materials, such as PP, PE, PEEK etc. is difficult at the best of times, but more often than not, impossible. The low surface energy of these materials effectively renders them non-stick, gaskets and seals won't bond and adhesives, paints, inks and coatings will not adhere.
Due to their low surface energy, no matter how much you attempt to abrade or clean the material's surface, they remain difficult to paint, coat, print or bond to without resorting to flame torch treatment or environmentally damaging solvents.
With the ever increasing drive towards the use of UV curing or water-based adhesives, paints, inks and coatings, materials that have traditionally given acceptable adhesion results, such as ABS, nylon, glass filled nylon and composites to name a few, can also become difficult to bond to.
Plasma Treatment Explained
The last 10 years has seen a real shift towards the use of viable alternatives to the aforementioned surface treatments, particularly plasma treatment. This is mainly due to its ability to improve adhesion to 'non-stick' plastics but with low running costs, low temperature and, most importantly, the flexibility provided.
During plasma surface activation the component undergoes an environmentally friendly process which does not alter the bulk properties of the treated part. The relatively low temperature of the plasma discharge does not mark, discolour or damage the component in any way, eliminating problems experienced with flame treatment, where the high temperature causes surface damage or shrink back of composite materials exposing glass fibre reinforcing.
During the plasma treatment process, a gas, usually air, is excited by a strong electrical field; this strong electrical field ionises the air or other gas creating a plasma. When exposing the material to plasma for a predetermined amount of time, the polarity of the material is increased as the free radicals and other active particles that exist within the highly active plasma discharge attach to the material's surface, which forms additional polar groups. Polarity is key to adhesion as it enhances the chemical attraction to paints, adhesives, inks, etc., which therefore increases the strength of adhesion that can be achieved.
Unlocking a world of new materials development
As part of the growing acceptance of plasma treatment as a method of surface activation, the capabilities of the process have advanced incredibly.
For example, plasma is now widely accepted as the industry standard for the surface activation of 'non-stick' components throughout large-scale production. To best serve those with these large production processes, 'vacuum plasma' has been developed to become bigger and more powerful than ever before. A decade ago, a large chamber was considered to be one with a 200- litre capacity, now chambers with a 2,000-litre capacity are commonplace.
Not only chamber size but functionality of these units has dramatically increased, rotating vacuum plasma is now commonplace, which is excellent for the treatment of small size, high volume parts such as powders and granular materials.
Atmospheric plasma is ideal for targeted treatment and integration with automation and cannot be forgotten; the early systems of this cutting-edge technology offered little or no control, limited power, air operation only and had a large footprint. The latest atmospheric plasma units are only one third of the size of traditional units yet offer more power than ever before.
The introduction of 'rotating atmospheric plasma', which utilises two plasma nozzles on a spinning head, reduces the already relatively low heat exposure to the material being treated; Now, thin and heat sensitive materials, e.g. thin films and sheet materials can now undergo treatment, something that would have seemed impossible a decade ago.
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|Comment:||The Plasma Treatment Revolution: CHRIS LINES, MANAGING DIRECTOR OF DYNE TECHNOLOGY, EXPLAINS HOW DEVELOPMENTS IN THE CAPABILITIES OF PLASMA SURFACE TREATMENT TECHNOLOGY HAS SEEN IT BECOME THE METHOD OF CHOICE FOR BONDING NON-STICK' POLYMERS.(COMMENT)|
|Publication:||British Plastics & Rubber|
|Date:||May 1, 2017|
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