The basics of plasma treatment – what is Plasma?
Until the 1950’s, matter was thought to exist in only three forms i.e. solid, liquid, and gas. But all that changed when a Danish engineer discovered plasma. But what is plasma?
What is Plasma and Plasma treatment?
Plasma is matter that exists in the form of ions and electrons. Basically, it is a gas that’s been electrified charged with freely moving electrons in both the negative and positive state.
The situation is actually a resultant of further energy being given to a gas which causes the breaking free of negatively charged electrons from the nucleus.
On a deeper level, plasma can be described as a gas that’s been partially ionized. It is a mixture of neutral atoms, atomic ions, electrons, molecular ions, and molecules present in excited and ground states. The charges (positive and negative) balance each other therefore; a good number of these charges are electrically neutral.
The charged particles present in plasma are responsible for its high electrical conductivity. Since plasma consists of electrons, molecules or neutral gas atoms, positive ions, UV light along with excited gas molecules and atoms, it carries a good amount of internal energy. And when all these molecules, ions and atoms come together and interact with a particular surface, plasma treatment is initiated.
Hence, by selecting a gas mixture, pressure, power etc. the effects of plasma treatment upon any surface can also be specified or precisely tuned.
How Plasma treatment is performed
A plasma treatment is usually performed in a chamber or enclosure that’s evacuated (Vacuum plasma). The air within the chamber or enclosure is pumped out prior to letting gas in.
The gas then flows in the enclosure at a low pressure. This is done before any energy (electrical power) is applied. It is imperative to know that plasma treatment performed at low temperature can easily process materials that are heat sensitive.
These types of plasma are sometimes referred to as ‘cold plasma’. Plasma treatment is mainly used for cleaning, surface activation, deposition, and etching – if you are interested in knowing more about plasma etching (plasma etch) we recommend you read our article about plasma etching. Also read about Plasma cleaning and what it is used for here.
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Useful for pretreatment of surfaces
On an industrial level, plasma treatments are used for treating surfaces of various materials prior to any coating, printing or adhesion. Therefore, it can also be referred to as a kind of pretreatment of surfaces. Treatment with plasma removes any foreign contaminants present on the surface of a material making it more suitable for further processing. Materials like plastics are prone to lose any type of printing or coating done on their surfaces because of their glossy texture unless treated.
Plastics are made up of polypropylene and are homopolar which means that they do not bond that easily.
Applying plasma treatment on such surfaces can result in an effective pretreatment of surface activation before any gluing, printing or lacquering could take place. Similarly, materials like ceramics and glass can also be treated with plasma. Usually, industrial oxygen is used in plasma treatment as a process gas, hence receiving the title of oxygen plasma.
However, atmospheric air is also used in many plasma surface treatments referred to as atmospheric plasma. Depending on the type of material that is being treated with plasma, effects can remain prominent for just a few minutes or even months.
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Plasma treatment FAQ
What is plasma?
Plasma is one of the four fundamental states of matter.
While the states solid, liquid and gas are well-known to all of us because they are part of our everyday life, plasma does not freely exist under normal conditions on earth, but it can be generated by adding energy to gas.
We generate plasma by exposing gas to electrical energy. In doing so, the involved gas molecules are ionized, which means that electrons start to leave the gas molecules, creating a plasma which is highly electrically conductive and can interact with any surface. Surface treatment can now be initiated by placing any surface in contact with the plasma. We can fine tune the effects of this treatment by choosing the right gas mixture and process parameters for each product.
What is plasma treatment used for?
Plasma treatment is used to modify the surface of an object.
Many solid materials have a low surface energy, which results in a poor wettability and poor adhesive properties. A plasma treatment can be used to prepare these materials for further processing by increasing their surface energy while simultaneously removing contaminations from the production process. This increases the quality and lifespan of any coating or printing applied to the surface and improves its adhesive properties.
A plasma treatment only modifies the surface of an object and does not change the object in any other way.
What are the main effects of Plasma treatment?
The major effects of a Plasma treatment are:
- Surface cleaning: Treatment with plasma removes any foreign contaminants present on the surface of a material leaving an ultra-clean surface and making it more suitable for further processing.
- Surface activation: A plasma treatment increases the surface energy of low-energy surfaces, which improves their wetability and adhesive properties.
- Surface characteristics: Other surface characteristics, such as liquid repellency or low friction, can be introduced, if required.
How does plasma treatment work?
Plasma consists of electrons, molecules or neutral gas atoms, positive ions, UV light along with excited gas molecules and atoms and carries a high amount of internal energy. When all these molecules, ions and atoms come together and interact with a particular surface, plasma treatment is initiated.
A plasma treatment is usually performed in a chamber or enclosure that is evacuated. The air within the chamber or enclosure is pumped out prior to letting gas in. The gas then flows in the enclosure at a low pressure. This is done before any electrical energy is applied.
The effects of plasma treatment upon any surface can be precisely tuned by selecting a special gas mixture, pressure, or power.
Can I treat heat sensitive parts with plasma?
Plasma treatments performed at low temperatures can easily process materials that are heat sensitive. These types of plasma are sometimes referred to as “cold plasma”.
How long does a plasma treatment take?
Treatment cycle times are often short, between 2-120 seconds depending on the treatment technology, the treated material and size of the part.
How long do the effects of a plasma treatment last?
The lifetime of a plasma treatment can last from hours to years depending on the material and the applied treatment as well as the subsequent storage conditions. In general, it is recommended to initiate further processing as soon as possible after a plasma treatment. However, tests with polymer surfaces, for instance, still show a significant remaining degree of activation 28 days after the treatment.
How good do plasma treated parts bond?
The enhancement can range from a 2-fold to a 10-fold improvement in lap-shear strength and peel- strength compared to untreated parts.
Is plasma treatment eco-friendly?
Plasma treatments are a lot more environmentally friendly than traditional surface treatment methods, which often rely on the use of high temperatures or wet chemicals.
The use of special process gasses is not necessary in most cases. By-products such as CO or CO2 are not present in toxic quantities. If NOx is produced, it can be removed with standard extraction hoods.