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Powder Coaters Manual 1/98I/10

Acrylic hybrids combine the acrylic resin with an epoxy binder. Theyare somewhat better than a polyester/ epoxy hybrid but still not con-sidered acceptable for outdoor use. The mechanical properties thatare characteristic in epoxies are a benefit of these materials and theyhave much better flexibility than other acrylics.

Because of their good appearance, tough surface, exceptional weather-ability, and excellent electrostatic application characteristics, acrylicsare frequently used for applications on products that have very highquality standards. Appliances, automobiles and other products that

require durability and long life in a harsh environment are good candi-dates for acrylic powder coatings. Typical applications include auto-motive wheels, plumbing fixtures and vending machines.

Research has been conducted to determine the suitability of acrylicpowder coating as a clear coat on automotive bodies. While the UnitedStates automobile manufacturers continue to evaluate this applica-tion, one European manufacturer is using it in production.

3 Coating Comparison

The decision on what powder to use depends on the specific appear-ance and performance requirements of the end product. The end usermust determine what specific properties they want in the coating andcommunicate that to the formulator.

When selecting a powder, several variables must be considered.

Cost of the powder (applied)

Performance characteristics

Application characteristics

Appearance

The proper coating is a balance of these variables. Coating manufac-turers can help the applicator in the selection process. Given a par-ticular specification, they can often formulate a powder to meet aspecific application at a reasonable cost, particularly if the volume is

high.

The comparison charts below show some of the performance proper-ties and typical uses of the various resins.

Coating Comparison

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Powder Coaters Manual 1/98 I/11

Epoxy

Property Range

Hardness (pencil) HB7H

Impact Resistance (in.-lbs) 60160

Gloss (60 deg. meter) 3100+

Color All colors, clear and textures

Salt Spray 1,000 hrs.

Condensing Humidity 1,000 hrs.

Cure range (Typ. 2 mil (0.05mm) film 3 min at 450F (232C) to

time at Metal temp.) 25 min at 250F (121C)

Epoxy hybrids

Property Range

Hardness (pencil) HB2H

Impact Resistance (in.-lbs) 60160

Gloss (60 deg. meter) 10100+

Color All colors, clear and textures

Salt Spray 1,000 hrs. minimum

Condensing Humidity 1,000 hrs. minimum

Cure range (Typ. 2 mil (0.05mm) film 10 min at 400F (204C) to

time at Metal temp.) 25 min at 300F (149C)

Urethane polyester

Property Range

Hardness (pencil) HB4H

Impact Resistance (in.-lbs) 60160

Gloss (60 deg. meter) 1595

Color All colors, clear and textures

Salt Spray 1,000 hrs.

Condensing Humidity 1,000 hrs.

Cure range (Typ. 2 mil (0.05mm) film 10 min at 400F (204C) to

time at Metal temperature) 25 min at 320F (160C)

TGIC

Property Range

Hardness (pencil) HB4H

Impact Resistance (in.-lbs) 60160

Gloss (60 deg. meter) 2090

Color All colors, clear and textures

Salt Spray 1,000 hrs. minimum

Condensing Humidity 1,000 hrs. minimum

Cure range (Typ. 2 mil (0.05mm) film 10 min at 400F (204C) to

time at Metal temp.) 30 min at 300F (149C)

Coating Comparison

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Powder Coaters Manual 1/98I/12

Acrylics

Property Range

Hardness (pencil) H4H

Impact Resistance (in.-lbs) Excellent, 40100

Gloss (60 deg. meter) 1090

Color All colors, clear and textures

Salt Spray 1,000 hrs. minimum

Condensing Humidity 1,000 hrs. minimum

Cure range (Typ. 2 mil (0.05mm) film 10 min at 400F (204C) to

time at Metal temp.) 25 min at 350F (177C)

Note: All of the performance properties are dependent on proper pretreatment of thesubstrate, proper application, and proper curing.

4 Coating Selection

The first step in the coating selection process is to define your finishedproduct requirements. With a specification, a manufacturer can workwith a coating supplier to get just the right coating formulated for theirspecific need.

In selecting a thermosetting powder type from a powder coating sup-plier, it is advised that the following thoughts be kept in focus through-out the selection process and during negotiation with suppliers.

The key selection factors are:

Demonstrated film performance

Demonstrated application characteristics

Cost performance balance

Testing of performance issues is important. For example, if the prod-uct will be used outdoors, resistance to UV light and outdoorweatherability should be tested.

The exposure chart on page I/12 shows the results of testing forcomparative gloss retention of different powder formulations.

The properties of any particular powder will vary even if they are thesame chemistry. Formulators can produce materials to meet specificneeds.

Coating Selection