Powder coating on glass

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Powder coating on glass is a specialized procedure related to traditional powder coating, which is the technique of applying electrostatically charged, dry powdered particles of pigment and resin to a solid item's surface. It requires its own unique process, however, because glass is a poor electrical conductor in comparison to metal, the traditional powder coating substrate. [1]

Powder coating is a type of coating that is applied as a free-flowing, dry powder. Unlike conventional liquid paint which is delivered via an evaporating solvent, powder coating is typically applied electrostatically and then cured under heat. The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as household appliances, aluminium extrusions, drum hardware and automobile and bicycle parts. Newer technologies allow other materials, such as MDF, to be powder coated using different methods. The powder coating process was invented around 1945 by Daniel Gustin US Patent 2538562.

Electrical conductor object or material which permits the flow of electricity

In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge in one or more directions. Materials made of metal are common electrical conductors. Electrical current is generated by the flow of negatively charged electrons, positively charged holes, and positive or negative ions in some cases.

In chemistry, a substrate is typically the chemical species being observed in a chemical reaction, which reacts with a reagent to generate a product. In synthetic and organic chemistry, the substrate is the chemical of interest that is being modified. In biochemistry, an enzyme substrate is the material upon which an enzyme acts. When referring to Le Chatelier's principle, the substrate is the reagent whose concentration is changed. The term substrate is highly context-dependent. It essentially refers to the part of the molecule that is precursor to a product.

Contents

Markets for Glass Applications

Powder coating on glass is used in industries such as cosmetics, fragrances, wine and spirits, where the contents inside of the glass containers require protection from ultraviolet (UV) rays, particularly UVA electromagnetic radiation, which is capable of penetrating glass. When applied with a dual-coat method, powder coating techniques on glass provide an opaque shield against the light's effects.

Ultraviolet Electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays

Ultraviolet (UV) designates a band of the electromagnetic spectrum with wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation is present in sunlight, and contributes about 10% of the total output of the Sun. It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms, it can cause chemical reactions and causes many substances to glow or fluoresce. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules.

Cleaning Preparation

Powder coating on glass requires specialized equipment. The biggest challenge is getting the powder to adhere to the glass surface since there is no natural electrostatic attraction like there is with different metals.

A clean glass subsurface that will not interfere with the process is essential before beginning the powder coating procedure. [2] Washing to remove oil, dirt and grease can be accomplished with solvents, wipes or a traditional wash system. Proper temperature control is critical from the very beginning, including during the preparation stage. Certain temperature ranges are recommended, but they are proprietary at the moment to companies who have pioneered the technique.

The Coating Process

After cleaning, an opaque base coat of powder is applied to the glass substrate as the initial, most important layer of UV protection. Once the powder attracts, the product is heated to activate the process of gelling, which secures the adhesive bond. It is crucial to control the amount of powder that goes on to the surface. With too little, the coating becomes transparent and the protection is diminished. Too much can create a dripping effect or disperse uneven amounts, leading to one side of the glass container being heavier than the other. In the case of powder coating nail polish and other cosmetics bottles, experienced powder coaters typically use a highly chemical-resistant form of powder, which makes it impervious to the aggressive chemicals inherent with polish and primer.

As more heat is applied, the powder coater adds the top coat, which flows together with the base coat. Oven curing follows, and the two coats become one, locking themselves together and encapsulating the bottle or container as a singular protective casing. Not only should this process effectively block out UV rays, but the molecular structure of the powder should provide added chip resistance and scratch resistance to the bottle.

Generally speaking, the transfer of powdered paint to a glass substrate can be broken into four specific phases. Assuming the object is properly cleaned, this includes: 1) Attraction – achieving the electrostatic charge; 2) Gelling – transforming the powder from dry to wet; 3) Flowing – melding or cross-linking the coat applications together for a strong, hardened protective casing; and 4) Curing – heat drying the powder coated product to arrive at its finished form.

Coverage for Different Shapes and Dimensions

It is possible to powder coat a wide variety of glass forms and dimensions, including cylindrical, oval and square shapes, to name just a few. Care must be given toward achieving even coverage,[ tone ] which is accomplished through proper heat control and powder application.

Colors and Textures

Glass will accept an almost limitless number of powder coated colors. [3] Different textures and even metallics can also be applied. Professionals in this field have been able to achieve satisfactory silk screen printing and pad printing on the powder coated glass substrate, including in the case of difficult cylindrical shapes. Glass items compatible with powder coating include bottles and containers, decorative pieces, dinnerware, picture frames and more.

Screen printing printing technique

Screen printing is a printing technique whereby a mesh is used to transfer ink onto a substrate, except in areas made impermeable to the ink by a blocking stencil. A blade or squeegee is moved across the screen to fill the open mesh apertures with ink, and a reverse stroke then causes the screen to touch the substrate momentarily along a line of contact. This causes the ink to wet the substrate and be pulled out of the mesh apertures as the screen springs back after the blade has passed. One color is printed at a time, so several screens can be used to produce a multicoloured image or design.

Pad printing

Pad printing is a printing process that can transfer a 2-D image onto a 3-D object. This is accomplished using an indirect offset (gravure) printing process that involves an image being transferred from the cliché via a silicone pad onto a substrate. Pad printing is used for printing on otherwise difficult to print on products in many industries including medical, automotive, promotional, apparel, and electronic objects, as well as appliances, sports equipment and toys. It can also be used to deposit functional materials such as conductive inks, adhesives, dyes and lubricants.

Powder Coating as Green Technology

Powder coating is considered to be an environmentally-friendly application. Unlike solvent-based wet paint systems, the process uses no volatile organic compounds (VOCs). In addition, there is no release of chemicals into the air through evaporation, and over-sprayed powder is recoverable and easily and safely disposable. [4]

Related Research Articles

Paint colored composition applied over a surface that dries as a solid film

Paint is any pigmented liquid, liquefiable, or mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture to objects. Paint can be made or purchased in many colors—and in many different types, such as watercolor or synthetic. Paint is typically stored, sold, and applied as a liquid, but most types dry into a solid.

Varnish transparent, hard, protective finish or film used in painting

Varnish is a clear transparent hard protective finish or film. Varnish has little or no color and has no added pigment as opposed to paint or wood stain which contains pigment. However, some varnish products are marketed as a combined stain and varnish. Varnish is primarily used in wood finishing applications where the natural tones and grains in the wood are intended to be visible. It is applied over wood stains as a final step to achieve a film for gloss and protection. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss sheens by the addition of "flatting" agents.

Vitreous enamel Material made by fusing powdered glass to a substrate by firing

Vitreous enamel, also called porcelain enamel, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C. The powder melts, flows, and then hardens to a smooth, durable vitreous coating. The word comes from the Latin vitreum, meaning "glass".

A thin film is a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films is a fundamental step in many applications. A familiar example is the household mirror, which typically has a thin metal coating on the back of a sheet of glass to form a reflective interface. The process of silvering was once commonly used to produce mirrors, while more recently the metal layer is deposited using techniques such as sputtering. Advances in thin film deposition techniques during the 20th century have enabled a wide range of technological breakthroughs in areas such as magnetic recording media, electronic semiconductor devices, LEDs, optical coatings, hard coatings on cutting tools, and for both energy generation and storage. It is also being applied to pharmaceuticals, via thin-film drug delivery. A stack of thin films is called a multilayer.

Electrophoretic deposition

Electrophoretic deposition (EPD), is a term for a broad range of industrial processes which includes electrocoating, cathodic electrodeposition, anodic electrodeposition, and electrophoretic coating, or electrophoretic painting. A characteristic feature of this process is that colloidal particles suspended in a liquid medium migrate under the influence of an electric field (electrophoresis) and are deposited onto an electrode. All colloidal particles that can be used to form stable suspensions and that can carry a charge can be used in electrophoretic deposition. This includes materials such as polymers, pigments, dyes, ceramics and metals.

A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both. The coating itself may be an all-over coating, completely covering the substrate, or it may only cover parts of the substrate. An example of all of these types of coating is a product label on many drinks bottles- one side has an all-over functional coating and the other side has one or more decorative coatings in an appropriate pattern to form the words and images.

Silicate mineral paints or mineral colors are paint coats with mineral binding agents. Two relevant mineral binders play a role in the field of colors: Lime and silicate.

Fusion bonded epoxy coating, also known as fusion-bond epoxy powder coating and commonly referred to as FBE coating, is an epoxy-based powder coating that is widely used to protect steel pipe used in pipeline construction, concrete reinforcing bars (rebar) and on a wide variety of piping connections, valves etc. from corrosion. FBE coatings are thermoset polymer coatings. They come under the category of protective coatings in paints and coating nomenclature. The name fusion-bond epoxy is due to resin cross-linking and the application method, which is different from a conventional paint. The resin and hardener components in the dry powder FBE stock remain unreacted at normal storage conditions. At typical coating application temperatures, usually in the range of 180 to 250 °C, the contents of the powder melt and transform to a liquid form. The liquid FBE film wets and flows onto the steel surface on which it is applied, and soon becomes a solid coating by chemical cross-linking, assisted by heat. This process is known as “fusion bonding”. The chemical cross-linking reaction taking place in this case is irreversible. Once the curing takes place, the coating cannot be returned to its original form by any means. Application of further heating will not “melt” the coating and thus it is known as a “thermoset” coating.

ECTFE chemical compound

ECTFE was designed to provide chemical resistance in heavy duty corrosion applications. It is a partially fluorinated polymer, semi-crystalline and can be processed in the melt. Chemically it is a copolymer of ethylene and chlorotrifluoroethylene. It is marketed under the brand name Halar ECTFE by Solvay Specialty Polymers, a subsidiary of Solvay.

A UV coating is a surface treatment which either is cured by ultraviolet radiation, or which protects the underlying material from such radiation's harmful effects.

Thermal spraying materials processing technology

Thermal spraying techniques are coating processes in which melted materials are sprayed onto a surface. The "feedstock" is heated by electrical or chemical means.

Release agent

A release agent is a chemical used to prevent other materials from bonding to surfaces. It can provide a solution in processes involving mold release, die-cast release, plastic release, adhesive release, and tire and web release.

Plastic bottle bottle constructed of plastic

A plastic bottle is a bottle constructed from high density plastic. Plastic bottles are typically used to store liquids such as water, soft drinks, motor oil, cooking oil, medicine, shampoo, milk, and ink. The size ranges from very small sample bottles to large carboys. Consumer blow molded containers often have integral handles or are shaped to facilitate grasping.

Automotive paint coloring and resistance to corrosion of cars

Automotive paint is paint used on automobiles for both protection and decoration purposes. Water-based acrylic polyurethane enamel paint is currently the most widely used paint for reasons including reducing paint's environmental impact.

Electrostatic spray-assisted vapour deposition (ESAVD) is a technique to deposit both thin and thick layers of a coating onto various substrates. In simple terms chemical precursors are sprayed across an electrostatic field towards a heated substrate, the chemicals undergo a controlled chemical reaction and are deposited on the substrate as the required coating. Electrostatic spraying techniques were developed in the 1950s for the spraying of ionised particles on to charged or heated substrates.

Electrostatic coating is a manufacturing process that employs charged particles to more efficiently paint a workpiece. Paint, in the form of either powdered particles or atomized liquid, is initially projected towards a conductive workpiece using normal spraying methods, and is then accelerated toward the work piece by a powerful electrostatic charge.

An anti-graffiti coating is a coating that prevents graffiti paint from bonding to surfaces.

Beverage can printing refers to the art and practice of applying an image to a metal beverage can, to advertise its contents.

Industrial porcelain enamel is the use of porcelain enamel for industrial, rather than artistic, applications. Porcelain enamel, a thin layer of ceramic or glass applied to a substrate of metal, is used to protect surfaces from chemical attack and physical damage, modify the structural characteristics of the substrate, and improve the appearance of the product.

References

  1. Bottle Coatings Offers Stylized Bottle Packaging Solution; WineBusiness.com; June 24, 2013
  2. Powder Coating: The Complete Finisher's Handbook; The Powder Coating Institute; Page 47
  3. Get the Color Match That’s Right for You; Bottle Coatings.com; July 3, 2012
  4. Powder Coating Basics; Delta Industries

Further reading