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  1. Corona vs. Plasma Treatment

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    For more than 30 years, 3DT LLC has been a leading provider of specialized corona and plasma surface treatments for customers around the world. Our state-of-the-art systems can be used as stand-alone stations, incorporated into new and existing production processes, or integrated into fully or semi-automated production lines. With 3DT’s 2- and 3- dimensional treating systems and a wide variety of custom configurations, we have a solution for virtually any application. In addition to manufacturing our cutting-edge equipment, we offer services such as design, manufacturing, product handling, installation, training, and maintenance service.

    One of the more common questions we field about electrical surface treatment is, “What is the difference between corona and plasma treatment?” and then, “What best fits my application?” Both corona and plasma treatment increase the surface energy of numerous materials improving the adhesion of inks, adhesives, coatings, and other agents. However, they both have unique properties that require consideration in terms of applications.

    In this post, we discuss the advantages and uses of corona treatment vs. plasma treatment, to aide in your understanding. However, our sales team will actively guide you in selecting the best system for your material, process and application.

    This blog discusses the differences between corona treatment and plasma treatment, including how they work and the various systems that 3DT offers.

    What is Corona & Plasma Treatment?

    multidyne corona treatment

    How Does it Work?

    Corona and plasma treatment are both forms of electrical surface treatment. They use the power of electrical energy to change the chemical properties of material placed within an energy stream. This stream of electrically loaded molecules causes an intensified reaction with the material resulting in better wettability and stronger bonding traits. Electrical surface treatment is highly suitable for three-dimensional polymer parts, thin film, rubber profiles, glass labware, metal parts, coated paperboard and thicker materials such as foam and solid sheets of material.

    When this phenomenon is contained inside an electrically grounded chamber, an air stream can be introduced to this chamber to force the plasma outwards in a controlled fashion and onto materials in a process called plasma treatment or atmospheric plasma treatment. However, when an insulator is placed between the two electrodes, the avalanche effect is avoided and the result is a cloud of ionized air. This ionized air – Corona Discharge – can now be used for the surface treatment of a wide number of materials that show poor or no adhesion properties to media such as printing inks, adhesives, etc.

    What’s the Difference Between Corona & Plasma Treatment?

    Plasma discharge has a relatively narrow treating width but is capable of imparting enormous surface energies onto substrates. The plasma treating heads can also be quickly mounted onto existing lines with little setup. The plasma discharge is virtually potential-free so it can be used to treat conductive materials. Plasma also produces no ozone gas which is a natural byproduct of the corona process. Alternatively, corona discharge typically imparts less surface energy but can treat very large areas. Corona treatment also has the advantage of being able to treat inside parts or in the recesses of 3-dimensional parts.

    Our Most Popular Treatment Systems

    3DT designs and manufactures an extensive range of cutting-edge surface treatment products, including:

    multidyne MultiDyne™

    3DT’s MultiDyne™ corona treatment system creates optimal surface tension, or wettability, on a broad range of parts and materials. A highly repeatable and controlled process, MultiDyne™ is typically used to prepare blow molded, injection molded, and extruded parts and products. MultiDyne™ creates highly effective, uniform adhesion on surfaces for printing, coating, gluing, and lamination.

    MultiDyne™’s state-of-the-art corona discharge technology works by creating a short circuit between two high voltage electrodes. A constant flow of air between the electrodes facilitates even distribution of the corona field onto the surface of the treated material, creating a highly receptive adhesive surface. It is perfect for treating areas that are commonly a challenge for other surface treatments, including complex geometries, hard-to-reach areas, and metal-adjacent surfaces.

    PolyDyne™

    polydyne conveyer ceramic system for surface treatmentPolyDyne™ is one of 3DT’s most powerful corona treatment systems. This extremely dependable and reliable system is particularly useful in high-speed operations, such as printing, extrusion, assembly, and coating production lines. PolyDyne™ is exceptionally versatile and can be used to treat everything from the interior surface of needle hubs to automotive components. Using the latest technology, PolyDyne™ directs corona treatment with an exceptional degree of precision onto virtually any surface.

    PolyDyne™ is specifically designed with flexibility in mind. All of our systems can be customized to meet the particular needs of your application, including custom electrode systems, ozone eliminators, and a variety of material handling systems. For more resistant materials, we are pleased to offer our PolyDyne Pro™ system.

    PlasmaDyne Pro™

    PlasmaDyne Pro™ uses a stream of highly ionized plasma to modify the chemical properties of the surface material within the stream. The surface becomes highly receptive to chemical bonding. PlasmaDyne Pro™ enhances the adhesion of ink and adhesive to a wide range of components, from plastic tubing and medical devices to rubber automotive seals. 3DT’s PlasmaDyne Pro™ is a compact and energy efficient system, with an optimized control unit, adjustable treatment levels, and modular replacement parts that allow you to tailor the system to your particular needs.

    plasmadyne pro surface treatment

    Premium Surface Treatment Systems by 3DT

    At 3DT, we are committed to developing superior surface treatment systems for every industry.  We have spent decades at the forefront of corona and plasma technology and are dedicated to solving even the most complex adhesion challenges. To learn more about our surface treatment systems and related services, visit our product page, or contact our experts today.

     

     

  2. Reviewing Surface Treatments: Decorating, Printing and Bonding on Plastic IS Possible

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    Plastics Decorating Magazine's Enews
    This plastic bottle has been plasma-treated in the center only. Note how the ink bonds to the surface where treated but beads up where the bottle was not treated.

    From Plastics Decorating Magazine’s Enews July 2020

    By Gary Kohlnhofer, Senior Sales Engineer, 3DT LLC

    Polymers have many useful properties, making them the material of choice. Polypropylene and polyethylene are prime examples. However, polymers typically have insufficient surface energy and poor wettability for most printing and bonding applications. Fortunately, corona and plasma surface treatment modify the surface of polymer substrates and raise their surface energy for printing, coating, painting and adhesive applications. As a result, the usefulness of polymers greatly increases for decorating and bonding applications.

    Let’s take a look at each of these methods of surface treatment, their applications and benefits:

    What is corona treatment?

    Corona treatment makes use of a generator and high voltage transformer to create a high voltage/high frequency corona discharge applied through an electrode with small airgap onto the surface to be treated. The result is a cloud of ionized air – or corona discharge – which then is used for the surface treatment of plastics and other materials.

    A substance placed under the corona discharge is impacted by electrons with energy two to three times that necessary to break the molecular bonds on the surface. The resulting free radicals rapidly react with the oxidation of products in the corona discharge or with adjoining free radicals on the same or different chain, resulting in a cross-link. Oxidation of the surface increases the surface tension or surface energy, allowing for better wetting by liquids and promoting adhesion.

    In the photo to the right, MultiDyne’s discharge treats ampules before printing.

    How is corona used in relation to plastics decorating?

    Corona treatment often is used inline on web-based printing machines, such as for treating label materials. Films such as polypropylene and polyethylene, for example, are treated inline prior to the digital printing decks to increase the surface tension and improve wettability and adhesion of digital inks. With these inline corona treating systems, the web is threaded over a treater roller and high voltage/high frequency power is applied to the electrode resulting in corona discharge through a small airgap. Corona treating systems also can be used on a high-speed cup decorating line, treating the cup on a mandrel prior to the printing decks.

    What types of applications or surfaces is corona treatment better suited for and why?

    Corona discharge effectively improves the surface tension on numerous materials that show poor or no adhesion properties to media, such as printing inks and adhesives.

    Reviewing Surface Treatments: Decorating, Printing and Bonding on Plastic IS Possible
    This MultiDyne system with two treating heads and a conveyor is designed for improving adhesion on small parts.

     

     

     

     

    Corona treating systems lend themselves to many applications, such as inline printing presses, but discreet parts can be treated as well with custom conveyor-based systems. A conveyor-based system using rotating electrodes treats different shapes and sizes without set up changes.

    These systems are very user-friendly and provide for uniform, repeatable surface treatment and high production rates. Individual parts also can be treated in fixtures with corona treatment delivered by custom electrodes and generator configurations.

    What are the benefits and challenges of this particular treatment?

    The benefits of the corona treatment process include the ability to print on substrates that otherwise would not be possible. Users also benefit from better print quality and faster printing line speeds, resulting in higher production and output.

    What is plasma treatment?

    Plasma surface treatment (also called in-air and atmospheric plasma) improves the wetting properties of polymeric materials, rubber, metals, glass, ceramics, paperboard and more. The molecules of these difficult-to-bond materials are modified by the plasma process to obtain better adhesion without causing harm to the surface.

    3DT's PlasmaDyne plasma treatment system. Rotating heads provides full coverage of a metalized plastic part.
    PlasmaDyne PRO rotating head treats a metallized plastic part to improve adhesion of ink/paint.

    Atmospheric plasma is created by combining reactive gas molecules and an electric field. This technology uses one or more high voltage electrodes which charge the surrounding blown gas molecules, resulting in a highly ionized field that is forced onto a targeted surface. This highly ionized air stream creates a thermal property that reacts with the substrate and breaks the existing hydrogen bonds by introducing oxygen which recreates the chemical properties of the surface. The atmospheric plasma process causes an intensified reaction with the material, resulting in better wettability, stronger bonding traits and micro-cleaned surfaces, and eliminates the possibility for unwanted backside treatment.

    How is it typically applied/integrated into the workflow?

    Plasma treating systems often are placed just prior to printing on inline printing production lines. The plasma treating head is mounted above a profile allowing the material to pass under the treating head and then the printing head improving the adhesion of the digital inks. Alternately, individual parts can be placed in a fixture then inserted into a plasma treating system set up to index the treating head back and forth over the parts, treating the top surface of the parts. Once treated, this fixture can be inserted into the digital printer for improved printability thanks to plasma treatment.

    PlasmaDyne PRO rotating head treats a metallized plastic part to improve adhesion of ink/paint.
    Here PlasmaDyne PRO is fitted to a robotic arm to quickly plasma treat defined areas of parts.

     

    What are the benefits and challenges of this particular treatment?

    Because atmospheric plasma is nearly potential-free, one important advantage is that plasma treatment can be incorporated into conductive, semi-conductive and non-conductive applications.

    Plasma is effective for cleaning surfaces by removing impurities, contaminants, residue and organic compounds. This process, called micro cleaning or etching, provides another important aspect in improving adhesion. What’s more, surface activation by plasma treatment is exceedingly fast, effective, economical and environmentally safe.

    What are 3DT’s surface treatment options for printing and decorating on plastics?

    3DT LLC provides a complete line of corona and plasma surface treating systems designed to overcome many adhesion challenges.  We offer standard and custom-built systems and application development.

    FlexiDyne Pro corona treatment system for labware and plastic parts.

    Our 3DT FlexiDyne PRO system is a conveyor-based corona treating system that utilizes rotating electrodes to provide a wider treat area and uniform, repeatable treatment with high production rates.

    In order to treat individual parts and profiles, we can provide a corona treating system using our 3DT PolyDyne generator and high voltage transformer technology and electrode system designed specifically for the part/profile to be treated.  Especially useful is our 3DT UltraDyne generator package designed for high speed cup and tube printing and decorating applications. UltraDyne provides consistent, strong high-frequency treating where other systems can’t.

    UltraDyne cup treater

    For surface treatment utilizing plasma technology, we offer our 3DT MultiDyne low frequency plasma system as well as our recently updated 3DT PlasmaDyne PRO system.  The PlasmaDyne PRO system with adjustable power output is especially suited for today’s system requirements to be easily adjusted for process changes.

     

     

     

     

     

     

     

    Gary Kohlnhofer has 38 years of experience in the plastics industry, 15 of those as Senior Sales Engineer with 3DT LLC. 3DT LLC is a manufacturer of surface treatment equipment, offering standard and custom-built systems and application development. Established in 1991, 3DT has been developing solutions for adhesion and bonding challenges for enumerable applications in all industry sectors. 3DT manufactures a complete line of corona and plasma systems incorporating robust design, proven technology and exceptional customer service with every standard and custom-engineered system. 3DT’s systems are designed and manufactured in Germantown, Wisconsin. For more information, visit www.3DTllc.com.

  3. Principle of the MultiDyne: Gliding Arc Discharge

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    The MultiDyne system operates using the gliding arc discharge principle.  The electrode arrangement is the key to this type of discharge.  As shown in the diagram, the arc forms at the closest distance between the electrodes.  The electrodes are curved to allow the arc to travel between them while increasing in size.  The arc however does not travel along the electrodes without the assistance of airflow behind it.  The airflow is carefully set to maximize the size of the discharge without prematurely extinguishing the arc.

    Principle of the MultiDyne: Gliding Arc Discharge

    The other major component to maximizing the gliding arc discharge is the specialized high voltage transformer.  The transformer is a dry, oil free, transformer capable of providing over ten thousand volts.  The transformer also offers safety features.  The first of the safety features is the ability for the transformer to current limit itself in the event of a short circuit.  The other safety feature is a center tap connected to ground, reducing the potential between the high voltage leads and ground to 50%.

    Application

    Utilizing the MultiDyne, 3DT has been a solution for numerous industries.  Without the need for a separate ground plate, the MultiDyne is easily incorporated into existing or new product lines.  Adjusting the gap, along with product speed, allows for adjustability of the intensity and size of the discharge on the product.  This allows for most products, regardless of material sensitivity, to be treated.  The size of the arc discharge allows for treatment of three-dimensional objects in addition to flat linear applications.

    The diagram below shows how adjusting the gap alters the width of the discharge.

    Principle of the MultiDyne: Gliding Arc Discharge

    The MultiDyne system may be designed around a basic principle, but 3DT has developed it into a solid, reliable surface treatment system. Contact our sales team for more information and to discuss your application at 262-253-6700 or sales@3DTLLC.com.

    Principle of the MultiDyne: Gliding Arc Discharge

    3DT’s MultiDyne 1000 with 1 treating head. Systems are available with 1-4 treating heads depending on the application. Learn more about MultiDyne on our MultiDyne page.

    References:

    Bruggeman, Peter J. “2.6.3 Gliding Arc Discharge.” Low Temperature Plasma Technology: Methods and Applications, edited by Paul K. Chu and Xinpei Lu, CRC Press, 2014, pp. 27–28.