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Powder Coatings and Formulation Tips

Powder coatings impart significant durability and resistance to abrasion, corrosion and chemicals in comparison to liquid coatings. Environmental advantages have led the way for the conversion of liquid coatings to powder coatings.

Become an expert by learning some basic information about powder coatings, their process, key features and benefits. Also get detailed information on various types of resins used to formulate powder coatings and popular application areas… So let’s get started!

Powder Coatings Technology


Powder Coatings TechnologyThe technology for coating products with dry powder rather than conventional liquids has been available since the 1950s. The powder used for the process is a mixture of finely ground particles of pigment and polymeric resin.

The powder is either:

  • Sprayed electrostatically onto a surface to be coated, or
  • The substrate is dipped into a fluidized bed of suspended powder

The powder adheres to a preheated substrate surface in the fluidized bed process, or they adhere electrostatically in the spray process. When heated further in a curing oven, the particles flow and fuse into a strong, adhering coating.

The result is a high quality coating with an attractive finish and excellent durability


Continue reading or click to go on specific section of the page:



Benefits of Powder Coatings


As compared to liquid coatings, powder coatings have been shown to offer several benefits such as:

  • They possess significant durability and resistance to abrasion, corrosion, scratching, and chemicals
  • They stay bright with less fading, and color selection is virtually unlimited with high and low gloss, metallic, and clear finishes available
  • Texture selections range from smooth surfaces to wrinkled or matte finishes, and rough textures are available for hiding surface imperfections
  • Thick coatings can be achieved quickly and efficiently
  • They contain no solvent, and thereby the process emits negligible, if any, polluting volatile organic compounds (VOCs) into the atmosphere
  • The processes used for powder coating do not require venting, filtering, or solvent recovery
  • Cost saving because there is less need for heating outside air to supply oven exhaust air, and
  • Most of the powder coating over-spray can be retrieved and re-used

» View All Commercially Available Ingredients for Powder Coatings in Our Database

This coatings database is available to all, free of charge. You can filter down your options by ingredient type, suitable resin, Trade name, application, supplier and regional availability.

Although the final properties of the powder coatings are often superior to liquid coating systems. The reason for the fast growth of this technology has been more related to the evidence that powder coatings:

  • Maximize production
  • Cut costs
  • Improve efficiencies, and 
  • Offer maximum compliance with increasing stringent environmental regulations

Environmental advantages have led the way for the conversion of liquid coatings to powder coatings

Let’s check out the advantages and disadvantages of powder coatings in brief...

ADVANTAGES DISADVANTAGES
  • No solvents so that VOCs are nil
  • Exhaust air from the coating booth can be returned to the coating room, thus less oven air is exhausted to the outside
  • Over-spray (up to 98%) can be retrieved and reused
  • No drying or flash time required so that parts can be racked closer together
  • Easily adapted to continuous, automatic processes
  • Coating does not run, drip, or sag, thereby lowering rejection rates
  • Minimum operator training and supervision
  • Thick coatings are easily possible
  • High throughput / output options
  • Simple clean-up and maintenance
  • Very thin coatings (less than 1.0 mil) are difficult because of pinholes
  • Frequent color changes could entail extensive downtime
  • Storage and handling of powder requires special climate controls
  • Color matching and color uniformity is somewhat more difficult than with liquid coatings
  • Uniformity of coating thickness is sometimes difficult to maintain
  • Cure temperatures required for some powders are too high for temperature sensitive parts
  • Powder coating is difficult on sharp corners
  • Conversion from liquid coating processes is expensive
  • Inside corners have low film thickness owing to the Faraday cage effect

Now when we have seen several benefits offered by powder coatings, it is equally important to understand its process in detail…

What is Powder Coating Process?


Powder coating is a dry finishing process, using finely ground particles of pigment and resin. These particles are generally electrostatically charged and sprayed onto electrically grounded parts.

The substrate is first pretreated similarly to conventional liquid coated parts. The pretreatment process is normally conducted in series with the coating and curing operations. The charged powder particles adhere to the parts and are held there until melted and fused into a smooth coating in a curing oven.

There is essentially two common ways of applying powder coating:


There are several other processes that have been developed, but they are far less used. These include flame spraying, spraying with a plasma gun, airless hot spray, and coating by electophoretic deposition.

Let’s discuss main technologies in detail:

Electrostatic Spray


Electrostatic spray method uses a powder-air mixture from a small fluidized bed in a powder feed hopper. The powder is supplied by a hose to the spray gun, which has a charged electrode in the nozzle fed by a high voltage dc power. In some cases, the feed hoppers vibrate to help prevent clogging or clumping of powders prior to entry into the transport lines.

Electrostatic Spray Powder Coating Process The electrostatic powder spray gun helps in:

  • Directing the flow of powder
  • Controlling the deposition rate
  • Controlling the pattern size, shape, and density of the spray
  • Charging the powder being sprayed 

The spray guns can be manual (hand-held) or automatic, fixed or reciprocating, and mounted on one or both sides of a conveyorized spray booth.

Electrostatic spray powder coating operations use collectors to reclaim over-spray. This reclaimed powder is then reused, adding significantly to the powder coating's high transfer efficiency.

There are various gun designs that mainly differ in the method of applying electrostatic charge to the powder. In some cases, the powder is electrostatically charged by friction. The advantage is that the powder is free to deposit in an even layer over the entire surface of the part, and deposition into recesses is improved.

The film thickness is dependent on the powder chemistry, preheat temperature, and dwell time.

  • Film thicknesses of 1.5 - 5.0 mils (37.5 - 125 µm) can generally be applied on cold products
  • If the products are preheated slightly, 20 - 25 mils (500 - 625 µm) coatings can easily be applied in a single coat

Fluidized Bed


Illustration of the fluidized bed process The fluidized bed coating process is a simple dipping process that can be either conventional or electrostatic.

#1 Conventional Fluidized Bed Process - The fluidized bed is a tank with a porous bottom plate.

The plenum below the porous plate supplies low pressure air uniformly across the plate. The rising air surrounds and suspends the finely divided plastic powder particles, so the powder-air mixture resembles a boiling liquid as shown in the figure.

Products that are preheated above the melt temperatures of the powder are dipped in the fluidized bed, where the powder melts and fuses into a continuous coating.

A high transfer efficiency results from little drag out and no dripping.

The fluidized bed powder coating method is used to apply heavy coats in one dip i.e. 3 - 10 mils (75 - 250 µm), uniformly to complex shaped products

It is possible to build a film thickness of 100 mils (2500 µm) using higher preheat temperatures and multiple dips.

Effects of preheat temperature and dipping time on the film build in coating a steel bar with epoxy resin


#2 Electrostatic Fluidized Bed Process - It is essentially a fluidized bed with a high voltage dc grid installed above the porous plate to charge the finely divided particles. Once charged, the particles are repelled by the grid, and they repel each other, forming a cloud of powder above the grid. These electrostatically charged particles are attracted to and coat products that are at ground potential. Film thicknesses are similar to what can be achieved in the electrostatic spray process.


ADVANTAGES DISADVANTAGES
  • Preheating of parts is generally not necessary
  • Small products, such as electrical components, can be coated uniformly and quickly
  • The product size is limited
  • Inside corners have low film thickness owing to the well-known faraday cage effect


Curing of Powder Coated Parts


There are four basic methods normally used in the curing of powder coated parts:

  • Convection
    • Convection ovens can be either gas or electric
    • Hot air is circulated around the powder coated parts, and the parts attain the temperature within the oven

  • Infrared
    • Infrared ovens, using either gas or electricity as their energy source, emit radiation in the IR wavelength
    • The radiated energy is absorbed by the powder and the substrate immediately below the powder, so the entire part need not be heated to the cure temperature. This allows a relatively rapid heat rise causing the powder to flow and cure when exposed for a sufficient time

  • A combination of the two
    • Combination ovens generally use IR as the first zone to melt the powder quickly. This process is termed near infrared (NIR) cure, and powders are formulated specifically to take advantage of this process
    • The part then progresses into a second zone, which is a convection oven

  • Ultraviolet (UV) curing
    • UV curing is commonly used with heat sensitive substrates
    • Specifically formulated UV powders flow at very low temperatures (121°C) and can be cured via UV radiation in a matter of seconds

Note: Thermoplastic powders require heat only to fuse the powder together into a continuous film while thermosetting powders often require additional heat to cure the film on the product

Below find a comparison of general curing conditions for heat curing of conventional thermosetting powders and UV curable powders using the various heating modes described above.

Heating / Curing Temperature, °C Total Curing Time, Minutes Substrate
Conventional Thermosetting Powders
Convection 140-220 30-15 Metal
Infrared + Convection 140-220 25-10 Metal
Infrared 160-250 15-1 Metal
UV Curable Powders
Infrared / Convection for heating
(1-2 mins) and UV for curing (secs)
90-120 3-1 Metal, wood, plastic, others


Types of Resins Used in Powder Coatings


The resin component in the formulation will largely determine the processing and end-use performance properties of powder coatings. There are two main classifications for powder coatings:

  • A thermoplastic powder coating melts and flows when heat is applied, but continues to have the same chemical composition once it cools to a solid coating.
  • A thermosetting powder coatings also melt when exposed to heat. However, after they flow to form a continuous film, they chemically crosslink on additional heating.

The final coating has a different chemical structure than the applied powder.

Thermosetting Powders Thermoplastic Powders


Thermoplastics Powders


Thermoplastic powders are typically high molecular weight materials that require high temperatures to melt and flow.

  • The primary advantage of thermoplastic coatings is that they form a smoother finish and require less energy
  • They are commonly applied by fluidized bed application, and the parts are both preheated and post-heated
  • Most of the thermoplastic powder coatings have marginal adhesion so that the substrate must be pretreated and sometimes primed prior to coating application

Vinyl Nylon Polyester
Primer Required Yes Yes Yes
Melting Point, °C 130-150 186 160-170
Typical Pre/Post Heat, °C 284 / 230 310 / 250 300 / 250
Adhesion G-E E E
Surface Appearance Smooth Smooth Slight Peel
Gloss, 60° 40-90 20-95 60-95
Pencil Hardness HB-2H B B-H
Salt Spray Resistance G E G
Weathering G G E
Humidity E E G
Acid Resistance E F G
Alkali Resistance E E G
Solvent Resistance F E F
E = Excellent, G = Good, F = Fair
Physical and Coating Properties of Thermoplastic Powders

Thermosetting Powders


Unlike thermoplastic powder coatings, thermosetting powders are heat stable and will not revert back to the molten stage when reheated after curing. They are also:

  • Tougher
  • Have better adhesion to metal substrates, and 
  • More resistant to solvents and chemicals

Thermosetting powders account for about 95% of all powder coatings.

Epoxy Epoxy Hybrids Urethane Polyester TGIC Polyester Acrylic
Hardness (Pencil) HB-7H HB-2H HB-4H HB-4H HB-4H
Impact Resistance (in-lbs) 60-160 40-100
Gloss (60° meter) 3-100+ 10-100+ 15-95 20-90 10-90
Color Al colors, clear, textures
Salt Spray 1000 hrs 1000 hrs min 1000 hrs 1000 hrs min
Condensing Humidity
Cure Range* 3 min at 232°C to 25 min at 121°C 10 min at 204°C to 25 min at 149°C 10 min at 204°C to 25 min at 177°C
* Typical 2 mil (50 µm) film – time at metal temperature


Now let’s see some of them in detail:

Epoxy Powder Coatings


  • Epoxy coatings are used wherever a hard, electrical insulating coating is required to provide protection over a wide temperature range
  • Depending on the particular epoxy selected, these coatings can be used up to 150°C or higher
  • Epoxy powder coatings have dielectric strength of up to 1200 volts / mil., in thicknesses over 10 mils (250 µm)
  • They are, therefore, ideal as functional electrical insulators as well as a protective coating
  • Chemical resistance to most solvents and mild acids and bases is good, and epoxy powder coatings provide excellent toughness and corrosion resistance
  • Adhesion to metal substrates is excellent, and generally epoxy powder coatings do not require a primer

» Check Out Several Epoxy Resin Grades Available Today for Powder Coatings

The major limitation of epoxy powder coatings is a tendency toward brittleness if the coating is over a few mils thick. They will also chalk when subjected to UV radiation. For this reason, they are rarely used for outdoor applications.

Epoxies are often used for decorative applications. They can be formulated to provide a variety of colors, glosses, and textures. Typical applications include metal office furniture, shelving, interior car parts, and toys.

Epoxy-Polyester Hybrid Powder Coatings


Epoxy-polyester hybrids combine epoxy resin with polyester resin to form a powder with many of the same characteristics as the epoxies. This group of powder coatings could be considered part of the epoxy family except for the high percentage of polyester utilized (often in excess of half the resin).

Property wise these resins are very close to their epoxy counterparts:

  • Epoxy-polyester hybrid coatings are generally tough, flexible, and competitively priced when compared to pure epoxy coatings
  • Hybrids provide some improvement in weatherability, but they will begin to chalk almost as fast as an epoxy coating. However, after initial chalking, the deterioration is slower
  • Some hybrids are less resistant to chemicals and solvents. Hybrids are likely to be used in many of the same applications as epoxies

Urethane Polyester Powder Coatings


Urethane polyester powders are one of the two polyester powder coatings being used commercially (the other is polyester TGIC). The primary type that has been used for several years is a urethane cured polyester powder, which is comparable chemically to the exterior quality urethane.

Coatings of this type offer:

  • Outstanding thin film appearance
  • Toughness with excellent weathering properties

It is common to block the crosslinker in urethane polyesters with e-caprolactam. To begin the crosslinking process, the material must reach a temperature above the blocking agent threshold. With e-caprolactam, unblocking occurs at approximately 182°C.

Urethane polyester powder coatings are true competitors to high quality liquid paints
in respect to thin film appearance

They are used for exterior applications such as patio furniture, automotive wheels and trim, lawnmowers, and a wide range of other products requiring high quality, decorative finishes.

Polyester TGIC Powder Coatings


Polyester triglycidyl isocyanurate (TGIC) powders are another type of polyester powder coatings being used commercially. In these coatings a very low molecular weight glycidyl or epoxy functional curing agent is used to co-react with the polyester. In this way, the polyester constitutes a very high percentage of the resin and provides weather and corrosion resistance incomparable to the urethane cured polyesters. However their resistance to chemical and solvents is lower.

  • TGIC powders have very good adhesion characteristics, corrosion resistance, and exterior durability
  • They can typically be cured at lower temperatures than urethanes and have shorter cure cycles
  • They also provide good edge coverage and tough, thick films

Typical applications of polyester TGIC powder coatings are where sharp edges and corners exist such as on automotive wheels, air conditioners, lawn furniture, and air conditioner cabinets.

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Acrylic Powder Coatings


Acrylic powders provide good appearance, tough surface, exceptional weatherability, and excellent electrostatic application characteristics. Common acrylic based powder coats include:

  • Urethane acrylics
    • Urethane acrylics require cure temperatures of 182°C
    • They offer excellent thin film appearance, good chemical resistance and hard films
    • Flexibility and impact resistance is usually poor

  • Arylic hybrids
    • They combine the acrylic resin with an epoxy binder
    • They are somewhat better than a polyester-epoxy hybrid but still not considered acceptable for exterior use
    • Acrylic hybrids generally have much better mechanical properties than the other acrylic powder coats

  • Glycidyl methacrylate (GMA) acrylics
    • GMA acrylics can be cured in less time or at lower temperature than the urethane acrylics, and they also can provide superior weathering characteristics
    • They make excellent clear coats over brass or chrome
    • Like the urethane acrylics, flexibility is somewhat limited

» Select the Right Acrylic Resin for Your Coatings

Polyvinyl chloride (PVC) Powder Coatings


Polyvinyl chloride (PVC) coatings are used for their excellent:

  • Softness, glossy surface & flexibility
  • Impact strength 
  • Resilience, and 
  • Salt spray and weathering resistance

PVC coatings have good chemical and water resistance. They can be formulated for:

  • FDA approved applications such as frozen food shelving and dishwasher baskets
  • General purpose electrical insulation
  • Chain link fence wire, outdoor furniture, and similar applications

Special primers are generally required for optimal adhesion. Two types of vinyl powder are used: dry blends and melt mixed. The dry blends are less expensive, but the melt mixed materials are superior in performance.

Polyolefin Powder Coatings


Polyethylene and polypropylene powder coatings provide soft and waxy films that have characteristics very similar to their plastic counterparts.

Polyolefin powder coatings are used primarily for their low cost and ease of application

However, they also have certain properties that are very attractive in many applications. In addition to toughness common to other thermoplastics, they have:

  • Low water absorption
  • Excellent chemical resistance 
  • Good electrical insulation characteristics
  • High durability, and
  • Resistant to many chemicals and detergents; however, some solvents can break them down quickly

Polyolefins are often used to coat laboratory equipment because the surface is easily cleaned. They are also used for food handling equipment and for automotive applications such as battery hold-downs.

Nylon Powder Coatings


  • Nylon powders are practically all based nylon 11
  • Nylon 6/10 is sometimes used but at high cost

Nylon powders are used to produce powder coatings which:

  • Are tough
  • Have excellent abrasion, wear, and impact resistance
  • Have a low coefficient of friction
  • Have good chemical and solvent resistance
  • Provides smooth surface finish

Generally, a primer must be used with nylon powder coatings to achieve the adhesion level needed for higher performance applications

Nylons can be formulated for food contact applications, outdoor applications such as light fixtures or seating and marine applications where they completely encapsulate fittings, bolts, and other hardware items.

Polyester Powder Coatings


Thermoplastic polyester powder materials have better than average adhesion properties without the need for a primer. They also exhibit good UV resistance and weatherability. Polyester powder coatings are somewhat more difficult to apply than nylon materials and are not as resistant to abrasion or solvent.


Find Suitable Resin Grade As per Your End-use Requirements

Find Suitable Resin Grade As per Your Application Needs

Polyester coatings are often applied to such items as outdoor metal furniture due to its good weatherability, corrosion resistance, and general durability.

Polyvinylidene Fluoride Powder Coatings


Polyvinylidiene fluoride (PVF) based coating resins have:

  • Excellent weathering characteristics
  • Excellent resistance to chemicals with the exception of certain hydrocarbon solvents

They are used to coat piping and valves used in the chemical process industries. Usually a chromate primer is recommended.


How to Formulate Powder Coatings?


As with any coating, formulation variables are critical to the processing and performance characteristics. The powder coating formulation is much like a liquid coating formulation except that most of the components are in solid, melt processable form.

The main raw material components used in powder coatings are:

  1. Resins are the key component of powder coatings. The range of resins used is increasing steadily in an attempt to meet the more demanding needs of new market sectors… Learn more about resins used 

  2. Curing agents are used according to the type of resin system employed and the final properties required of the coating

  3. Accelerators are used to increase the cure reaction rate

  4. Pigments are generally solid particulate materials such as titanium dioxide or carbon black

  5. Fillers are used to reduce the cost of the coating formulation and / or to improve specific properties such as flow, surface texture, lubricity, etc. Common fillers are barytes, calcite, mica, talc, whiting, and wollastonite

  6. Extenders, such as aluminum silicate, are used to provide opacity and act as a filler

  7. Degassing agents are particularly important in low-bake systems. They are used to eliminate / dissipate gas bubbles that may cause film porosity and embrittlement or poor finish

  8. Dry Flow agents improve the free flow of powders within the production delivery systems

  9. Flow agents enhance film properties and minimize / eliminate surface defects by improving the flow of the molten coating. Examples of flow agents include polyacrylates, silicones, surfactants, and fluorinated alkyl esters

  10. Matting agents are used to reduce the gloss of the cured film

  11. Texturing agents are used to control / enhance the gloss level of cured films

  12. Rheological additives provide viscosity control to molten coatings for improved edge coverage or for textured surface effects

  13. Waxes are added to the formulation to provide slip, hardness, scratch and mar resistance, and to act as free flow powders and anti-bridging agents in processing

The raw powder coating materials are generally mixed dry and then fed into an extruder for melt mixing. Once cooled, the extrudate is then chipped and ground into the final product. The chips are ground to a very specific particle size distribution depending on the application.

The particle size is important to the performance and appearance of the coating

The size of the powder particle can have an influence on the:

  • Behavior of the material in the delivery system
  • Charging systems, and 
  • the final film characteristics

When reclaimed powder is used, the coater must maintain a consistent particle size distribution. There are several methods by which particle size distribution can be measured.

Powder Coatings Application


Today, powder coatings have replace solvent-based coatings and have found the greatest commercial success in applications such as: (Click on application for a summary)


Automotive

Applications of Powder Coatings in Automotive Industry

The automotive industry is increasing its use of powder coatings for economic, quality, and environmental reasons.

Powder is being used in the automotive industry for the:

  • Exterior bond intermediate coat known as a "primer surfacer", as well as for finishing of underhood components
  • Exterior body intermediate coat
  • Wheel finishing (Clear powder coatings)

Clear coats are also now being used over automotive exterior basecoats by some European manufacturers such as BMW and Volvo.

» View Several Powder Coatings Ingredients for Automotive Uses

A special area is powder slurries. Here powder particles are wet ground to 3µm size and stabilized in an aqueous environment. Typically these compositions are then being wet-spayed. Then flash-dried and fully cured in the second curing step.

Powder coatings for body parts are partially replaced back by liquids. This as wet-on-wet combines the curing of two applied film layers simultaneously.

Powder Coated Car Wheels Grow areas for powder coating in automotive are alloy wheels, breaking parts, plastic / heat sensitive substrates and parts that require extra protection as well as a decorative finish. Wheels, hubcaps, door handles, radiators, decorative trim, bumpers, shock absorbers, mirror frames, oil filters, engine blocks, battery trays, and coil springs are some of the many automotive products being powder coated.

Other transportation application areas are (motor) bike frames or ski cabins, bars and handles inside of trams, buses or trains etc.

Appliances


The appliance industry benefits from the use of thermosetting powder coating in applications requiring the combination of:

  • Appearance
  • Resistance to abrasion & chemicals, temperature cycling, and abusive ware

The appliance industry makes use of powder coating on:

Powder Coatings Applications in Appliances
  • Front and side panels of ranges and refrigerators, 
  • Washer tops and lids, 
  • Dryer drums, 
  • Air-conditioner cabinets, 
  • Water heaters,
  • Dishwasher racks, 
  • Freezer cabinets, and 
  • Cavities of microwave ovens
Powder coatings has also replaced porcelain enamel on many washer and dryer parts. However powders are being replaced partially by liquid coil coatings.

Thermoplastics powder coatings generally have a higher molecular weight compared to thermosetting powders. Their “softening point”, or glass transition temperature, is generally lower than with the classic amorphous thermosettings.

Being partially crystalline compensates this. Thermoplastic need only to be molten and can be found on the inside of dishwashers. Polyamide thermoplastics have better chemical resistance than polyester based. But cost increases too.

Thermoplastic and thermosetting powder coatings for food applications can be found on the inside of three-piece food and aerosol cans. To cover and protect the weld. Full body inside protection of food canisters have been tried, but with epoxy being phased out, this is still a long way to go. Coating speed is also slow.

Outdoor Furniture, Lawn, and Garden Products


Excellent durability, UV stability, hardness, abrasion resistance and corrosion resistance combined with higher film thicknesses of powder coatings make them ideal for outdoor furniture and equipments which see rough use outdoors.

Lawnmower
  • The farm segment has powder coated tractors and agricultural equipment. 
  • Golf clubs and carts, ski poles and bindings, snowmobiles, bicycles, and exercise equipment represent applications in the recreation market segment. 
  • Homeowners have powder coatings on lawn mowers, snow blowers, barbecue grill, patio furniture, garden tools, bird feeders and pet cages.

Thermoplastics are being used also for outdoor public play furniture. The metal frames are pre-heated and powder coating is tumbled on the substrate and melt-coat.

Indoor Furniture - School furniture such as tables and chairs are easy to powder coat. Doorknobs can be powder coated for inside or outside. But also powder coatings for kitchens and bathrooms are very suitable and decorative. Having high film weight, they give good abrasion and chemical resistance and humidity protection.

Architectural and Building / Construction


Painter The architectural and building market is growing for powder coated products because of the:

  • Excellent durability 
  • Variety of finishes and colors that are available

The recent advances in polyester-TGIC and fluoropolymer powders have enabled powder coatings to compete with liquid architectural coatings in durability, weatherability, and resistance to fading.

  • These are being used on outdoor stadium seating and other exterior applications that were previously susceptible to degradation from ultraviolet rays

  • Aluminum extrusions used on frames for windows and doors are powder coated as are building facades, fixtures, and modular furniture

  • Many highway and building projects use powder coating on products such as light poles, guard rails, signs, posts, and fencing

  • Light poles, lawn furniture, shopping carts and shelving often benefit from powder with fluorocarbon (polytetrafluoroethylene) additives for increased resistance to abrasion

  • Clear coat powders are often used as an external protective layer on many brass products such as door knobs, hinges, railing, lamps, and plumbing fixtures. There are also powders that can substitute for chrome and brass plating in certain applications

Electrical / Electronics


Powder coatings are used for exterior housings in the electrical and electronic industries. However, they are also being evaluated for unique, functional applications.

Wires
  • Powder coating of copper and aluminum magnet wire significantly reduces environmental problems in the wire industry
  • The toughness and durability of powder coatings in applications such as transformer and motor windings provide an added bonus

Makers of electronic components sometimes use electroconductive and electrodissipative powder coatings.
These coatings provide electrostatic discharge protection of the components - critical during the manufacture, testing, and transport of electronic goods. These powder coatings are often based upon of the Epoxy-Polyester chemistry.

» Select Suitable Ingredient for Your Powder Coatings for E&E Applications

Non-Metal Products


Originally powder coatings were applied as metal finishing coatings only. However with the development of powder that can be applied and cured at low temperatures, the market has opened to heat sensitive substrates such as plastics and wood.

  • Radiation curing (UV or electron beam) allows the curing of powder on heat sensitive substrates by reducing the curing temperature to below 121°C. Reducing the curing temperature is not without risk. Either flow or leveling are reduced which impact the appearance in a negative way
  • On the other hand the “softening point” or glass transition temperature of the powder coating particles is reduced. For special applications only, powders can be stored under lower ambient temperatures to prevent caking

Powder Coating on Wood is Growing Significantly

Wood manufacturers and their customers are now able to powder coat a wide range of wood products by developing:

  • Powders with reduced heat requirements, and
  • A uniform density wood product

Powder Coating on Wood is Growing Significantly

MDF is very suitable for powder coating because of its low porosity and homogeneous surface. Curing of powder on MDF can be accomplished by infrared, or UV light in conjunction with infrared or convection ovens.

Powder Coatings for Plastics

Plastics need to have some kind of conductivity to be able to powder coat.

  • Special techniques have been developed to make the surface temporarily conductive
  • The charged powder particles will then adhere electro-physically to the substrate
  • Next step is to melt-cure the powder particles

The advantage! No color difference occurs or aging differs of the coated substrates

Powder coatings for heat sensitive substrates require a dual cure treatment.

  • First, powder particles must melt to form a homogeneous and pore-free surface. Often the substrate is pre-heated too. This to reduce any trapped humidity in the substrate (wood!) and to support the leveling later on
  • Second step is the curing. This can be the already mentioned NIR, which can be optimized to preferential heat the coating and not the substrate. Or by UV

Caution is required to find the correct catalyst for the UV curing in case of pigmented coatings. White powder coatings have only a limited window in their spectrum for UV light penetration. The catalyst must be excited just in this window to start up the polymerization.

Raw Materials for Powder Coatings





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1 Comments on "Powder Coatings and Formulation Tips"
Budsaraporn S Dec 17, 2016
Course problem solving and new innovation trend 2017-2020 for powder coating

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