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Powder
Coating
Basics
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We
are replacing our demo powder oven - you can save big on this one- details
here!
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This information was edited from the
Wagner Powder Systems Training Manual
Types of Powder Coatings
Powder is basically dry paint consisting of 4 or 5 components:
- Resin
- Crosslinker (not used in Thermo plastic powders)
- Pigments
- Flow Aids
- Degassing Solvent (Solid)
Two basic types of powders:
Thermoset Powders –Curing or crosslinking takes
place so that once cured, the coating will not remelt.
The majority of powder coatings today are thermosetting type powder.
Typical Thermosetting type powders are:
- Epoxies
- Acrylics
- Most polyesters
Thermoplastic Powders – Do not crosslink and
can remelt after curing when exposed to sufficient heat.
Typical Thermoplastic powders are:
- Vinyls
- Nylons
- Fluorocarbons
Five Basic Kinds of Powder (Table 1):
Epoxies, Epoxy/Polyester (Hybrid), Polyester Urethanes, TGIC Polyester, Acrylic
Urethane
| Table 1 Typical Properties of Thermosetting
Powder Coatings |
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Properties
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Epoxy
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Epoxy/polyester
Hybrid
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TGIC
Polyester
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Polyester
Urethane
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Acrylic
Urethane
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| Application mils |
1-20 mils |
1-10 mils |
1-10 mils |
1-3.5 mils |
1-3.5 mils |
| Cure Cycle |
450F 3 min |
450F 3 min |
400F 7 min |
400F 7 min |
400F 7 min |
| Weather-Ability |
Poor |
Poor |
Excellent |
Very Good |
Very Good |
| Pencil Hardness |
11B-511 |
11B-211 |
11B-211 |
11B-311 |
11B-311 |
| Adhesion |
Excellent |
Excellent |
Excellent |
Excellent |
Excellent |
| Chemical Resistance |
Excellent |
Very Good |
Good |
Good |
Very Good |
Functional vs. Decorative Powders
Most Decorative Coatings are applied as relatively thin (1-4 mils) thermoset
powder coatings and typically used for:
- Various automobile parts
- Appliances
- Clear coatings
Functional powders are typically used for protective purposes.
Kinds of Powder:
Epoxy Polyester Hybrid Powders
Not suitable for outdoor applications.
Resistant to over-baking.
Typical Applications:
- Shelving
- Hot water heaters
- Power tools
- Fire extinguishers
Polyester TGIC Powders
Maintains excellent mechanical properties at film build above 3 mils.
Good edge coverage
Typical Applications:
- Aluminum extrusions
- Automotive wheels
- Air conditioners
- Lawn furniture
Polyester Urethane Powder
Combine very smooth, thin film, excellent mar and chip resistance, and
good weathering properties.
Applications include:
- Light fixtures
- Lawn and garden equipment
- Electrical enclosures
- Air conditioners
- Automotive trim
Acrylic Urethane
Offers better weathering, and improved chemical resistance compared to
polyester urethanes.
Flexibility and impact resistance is poor.
Typical Applications:
- Plumbing fixtures
- Automotive wheels
- Vending machines
GMA Acrylic Powders
Faster cure and improved weatherability than acrylic urethanes.
Well suited for clear top coats.
Typical Applications:
- Plumbing fixtures
- Automotive wheels
- Microwave cavities
Acrylic Hybrid Powders
Offer good weatherability, mechanical properties, and flexibility, but
not outdoor durable.
Typical Applications:
- Metal furniture
- Lighting fixtures
Thermoplastic Powder Coatings
Require high temperature (300-750 degree F) to achieve melt and flow.
Have poor or marginal adhesion to most substances.
Surface preparation prior to powder coating is critical.
Polyamides
Nylon based coating with outstanding functional characteristics such as:
- Hardness
- Toughness
- Abrasion resistance
- Solvent resistance
- Can be formulated to be FDA compliant for food contact applications.
Polyolefins
- Chemical resistance is good.
- Can deteriorate quickly in contact with some solvents and detergents
due to stress cracking.
- Not suited for outdoor applications.
- Poor adhesion to most metal substrate.
Vinyls
- Have to use a primer.
- Good detergent and water resistance.
- Some are acceptable for good grade applications.
- Good outdoor weathering – durability.
Polyester
- Look and feel similar to nylon coatings.
- Lack of solvent and abrasion resistance.
- More difficult to apply and have not achieved market acceptance of
nylons.
- Good adhesion to most substrates.
- Can be used without a primer.
- Good exterior durability.
Polyvinyl Fluoride (PUDF)
Outstanding exterior durability, better than any other powder coating material.
Needs a chromate primer.
Have excellent electrical insulating properties and chemical resistance.
Typical Applications:
- Pumps and valves
- Piping
- Equipment used in chemical process industries
POWDER VS LIQUID COATING COST ADVANTAGES
Energy cost differences due to heating a conveyor, tooling, and product
being coated sometimes comes out in favor of liquid coating due to high temperature
of curing powder (average 400 degree F).
Labor and Maintenance
- Less time spent on clean up.
- Maintenance hours are reduced.
- No need for a paint kitchen.
- No solvent to reduce or thin the powder.
- Skill of the coaters can be less than that of liquid.
POWDER STORAGE AND HANDLING
Issues affecting storage are:
- Moisture in air absorption
- Cross contamination of partially used powders
- Exposure to heat
Keep boxes and containers closed.
Do Not re-use powder containers for the storage of new products.
Do not store powder near the coating line, washers, or ovens.
Conditioning
When storage conditions are not the same as application conditions:
- Powder needs a 24 hours acclamation period.
- Sieve if possible to reduce or remove lumps from the powder.
Industrial Hygiene
Powder should not be inhaled – wear a dust mask.
Check the MSDA sheets before using.
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PowderOvens.com
is a division Spray Tech Systems, Inc. Oklahoma City, OK 73127
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Phone:
800.777.7729 or 405.948.8696 / Fax: 405.948.8160
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