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Contact Information:

Tel:  +44 (0) 1543 411460
Fax: +44 (0) 1543 415140
Post: Dyne Technology Ltd
         Newton House
         5 Parkside Court,
         Greenhough Road
         Lichfield
         Staffordshire,
         WS13 7FE
         United Kingdom.
 
E-mail   
info@dynetechnology.co.uk
 
Web Site:
www.dynetechnology.co.uk

 

FAQ's                                                                                                       >> Dyne Home Page

What is Corona Treatment?

What materials can be successfully treated?

What parts can be treated?

What does Dyne Level / mN/m mean?

How can I measure the Dyne level of my parts?

Will the treatment wear off?

Does Corona Treatment generate any by-products?

Is any extraction required from a Corona treater?

Is it possible to treat metal surfaces?

Does line speed affect the results of corona treatment?

Is Corona Treatment an in-line or batch process?

Do you have another question?

 

 

What is Corona Treatment?

Corona treatment is a high-frequency, high-voltage electrical discharge. The discharge is generated between an electrode and a counter electrode. The corona discharge has such a powerful impact on the substance surface that the molecular structure changes in a way that improves the surface wettability.

In the presence of a high voltage discharge in an air gap, free electrons, which are always present in the air, accelerate and ionise the gas. When the electric discharge is very strong, collisions of high velocity electrons with molecules of gas result in no loss in momentum, and electron avalanching occurs. When a plastic part is placed in the discharge path, the electrons generated in the discharge impact the surface with energies 2 to 3 times that necessary to break the molecular bonds on the surface of most substrates. This creates very reactive free radicals. These free radicals in the presence of oxygen can react rapidly to form various chemical functional groups on the substrate surface. Functional groups resulting from this oxidation reaction are the most effective at increasing surface energy and enhancing chemical bonding to the resin matrix. These include carbonyl (-C=O-). carboxyl (HOOC-), hydroperoxide (HOO-) and hydroxyl (HO-) groups. Surface treatment with high voltage discharge modifies only the surface characteristics without affecting material bulk properties.

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What materials can be successfully treated?

Most base materials can be treated, the most common applications and in the plastics and rubber industries.

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What parts can be treated?

Dyne Technology supplies solutions to help our customers improve the surface energy of their plastic & rubber components to ensure improved bonding of printing inks, paints, adhesives etc. Our customers list includes many in the following industries: medical, electronics, automotive component, cable, ophthalmic, pipe, printing, packaging, domestic appliance, cosmetics packaging, food and beverage packaging.

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What does Dyne Level / mN/m mean?

The Dyne level reflects the surface wettability – the higher the Dyne level, the better the wettability/adhesion. The Dyne is the unit of force equal to the force that imparts an acceleration of 1cm/sec/sec to a mass of 1 gram.  1 dyne (mN/m) = 0.00001 Newtons,   or   = 1gm/sec˛ ,  or  1 Newton = 100,000 dynes.

It is often necessary to bond plastic materials to metals or other plastic materials, or simply paint or print onto a plastic surface. In order to successfully accomplish this, the liquid adhesive, paint or ink should be able to wet the surface of the material. Wettability depends on one specific property of the surface: Surface energy. The surface energy of the solid substrate directly affects how well a liquid wets the surface. To achieve good wettability the surface energy of the substrate needs to exceed that of the surface tension of the liquid by around 2 - 10 mN/m (Dynes).  Wettability is easily demonstrated by contact angle measurements. The contact angle is the angle between the tangent line at the contact point and the horizontal line of the solid surface (fig 1).

                             

When a liquid droplet is set on a smooth solid horizontal surface, it may spread out over substrate and the contact angle will approach zero if complete wetting takes place. Conversely, if wetting is partial, the resulting contact angle reaches equilibrium in the range material’s surface energy and positively affect adhesive characteristics by creating bonding sites. Various methods of measuring wettability are available: Contact Angle Measurement, Dyne inks, Dyne pens etc. The table below sets out typical values for a range of substrates and typically applied liquids (fig 2)

                    

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How can I measure the Dyne level of my parts?

The dyne level can be easily measured either through contact-angle measurement or by using dyne inks or pens.

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Will the treatment wear off?

The shelf life of pre-treated materials ranges from hours to years, depending on the plastic, its formulation, how it was treated and its exposure to elevated temperature after treatment. Material purity is the most important factor. Shelf life is limited by the presence of low molecular weight components such as antiblock agents, mould release, antistatics, etc. Eventually, these components migrate to the surface of clean polymers. It is therefore recommended to print or bond to the material soon after treatment. However, once the treated surface has been interfaced with a coating, ink, adhesive, or another material, the bond becomes permanent.

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Does Corona Treatment generate any by-products?

Ozone is generated during any high-voltage, high-frequency discharge. The ozone is easily neutralised using standard ozone filter systems.

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Is any extraction required from a Corona treater?

Yes, ozone is formed as a by-product of the corona-discharge process. It is an allotropic form of oxygen, and exists at room temperature as an unstable gas with a sharp, characteristic odour. It can usually be detected by its odour at concentrations as low as 0.01 to 0.05 ppm, which are below the permissible exposure level of 0.1ppm. We supply a standard range of ozone filters with flow sensors to control extraction air flows.

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Is it possible to treat metal surfaces?

We can treat metal surfaces by using our special insulated electrodes. Treating metal surfaces is primarily a surface cleaning issue.

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Does line speed affect the results of corona treatment?

Yes, the higher line speed, or the higher throughput of products, the more Corona power is required. We can easily calculate the need of treatment power, and specify the number of electrodes and size of Corona Generator required.

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Is Corona Treatment an in-line or batch process?

It can be either. In most cases, corona equipment is integrated into the existing production equipment.

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Do you have another question?   Then please contact us, we'll be pleased to assist.

Contact Information:

Phone:    +44 (0) 1543 411460
Fax:        +44 (0) 1543 415140
Post:        Dyne Technology Ltd, Newton House, 5 Parkside Court, Greenhough Road, Lichfield, Staffordshire, WS13 7FE, United Kingdom.
E-mail     info@dynetechnology.co.uk

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