The landscape of manufacturing ultimately changed in 1957 with the start of large scale production of Polypropylene. Over the years, Polypropylene has become one of the most popular plastics in the world and is well known for the headaches it causes engineers when attempting to achieve good adhesion.
When the use of these new “non-stick” polymers began taking off in the 1980’s, engineers were introduced to the growing need for surface modification. Popular methods in that time included high temperature Flame Torch Treatment and environmentally damaging solvent based primers and pre-treatments.
Chris Lines, Managing Director of Dyne Technology, the UK and Ireland’s Number One Plasma Technology supplier explains “Around 35 years ago, I was working on an exciting project where a major luggage manufacturer needed to decorate polypropylene suitcases. Of course, we experienced problems when attempting to bond to the surface but at the time, the best solution was Flame Torch Treatment to improve adhesion qualities.”
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 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, such as the lack of consistency of results and the lack of flexibility to treat complex geometry components and wide surface areas. 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.
Dyne Technology was founded over a decade ago on the basis of discovering better solutions to surface treatment problems and to provide manufacturers with more options to broaden their access to new manufacturing materials. Over the past 10 years, there has been a real shift towards Plasma Treatment as a method of improving adhesion to “non-stick” plastics due to the low running costs, low temperature and most importantly the flexibility provided.
“Just recently a thermoplastic hose and tube manufacturer approached us looking for an alternative to their current flame system. The customer was understandably concerned about the unreliable results it offered due to the lack of control they had over the process. The lack of consistent results presented huge issues as their printing process was safety critical.” Chris Lines comments.
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 high temperature 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.
These problems of adhesion are experienced widely throughout the UK and Irelands manufacturing industries from automotive to aerospace, medical device to motorsport as they affect almost anyone who needs to bond, seal, coat, paint or print to “non-stick” materials.
The Dyne Technology team have witnessed this many times, such as when a major UK automotive component manufacturer introduced a new product moulded from glass filled nylon and needed to give the component a body-matching paint finish. It was quickly realised that the paint finish was failing to pass its customer’s paint adhesion tests and without surface treatment, achieving good adhesion would have been near impossible.
Plasma Treatment Explained
Used throughout a wide range of industries, Plasma Treating plastics and rubbers is the method of choice for solving their problems of adhesion. 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 pre-determined 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…
Over the past decade, the capabilities of Plasma Treatment have advanced incredibly to fit with the shifts of perception towards Plasma Treatment as a method of surface activation. Plasma is now widely accepted as the industry standard for the surface activation of “non-stick” components throughout large scale automotive production. To best serve those with a large scale production process, 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 including 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.
Surface Treatment is undoubtedly an exciting industry to be part of right now and the advances in technology are unlocking a wealth of new opportunity for those working with “non-stick” plastics, rubbers and more…
