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What is
Powder Coating?
Powder Coating
was invented in the 1950's. It is a method of finishing a
metallic surface by the application of dry powder. When the
powder is fused to the metal with a heat source, the coating
forms a continuous and integrated bond with the substrate.
Initially, only thermoplastic resins were used in a
fluidized bed application system. The development of
thermosetting epoxy, polyurethane & polyester resins in
the 1960's and 70's, combined with new spray application
techniques opened up a much wider segment of the metal
finishing industry to powder coatings.
Powder coatings have several significant advantages over
solvent-based liquid paints.
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No
Solvents
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Liquid
paints can contain up to 70% solvent.
Powder coatings contain no solvents, and
therefore eliminate solvent release into
the environment. |
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Recyclable
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Oversprayed
powder can be reclaimed and reused,
allowing up to 95% material
utilization, reducing waste. |
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Fewer
variables in film properties
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The
more uniform properties of powders and
the elimination of thinners and
solvent balancing lead to a more
consistent paint film in just one
coat. |
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How are powder coatings made?
There are 4 key stages in the manufacture process of
powder coatings.
Formulation
The formulation of powder coatings involves the use of 4
key raw material types: resins, pigments, curing agents and
additives. Resins provide strength, durability and adhesion;
pigments add color; curing agents ensure that the resins
bond to the substrate and harden, and additives give further
coating properties such as enhanced application, improved
flow, etc.
Premix
Once a product has been formulated, raw materials are
carefully weighed and measured. These raw materials are then
blended together, either by mixing or tumbling, to ensure a
consistent dispersion of raw materials throughout the
mixture.
Extrusion
The mixed raw materials are then fed into an extruder.
The extruder applies pressure and heat to melt the resins
and thoroughly incorporate the pigments, curing agents and
other ingredients into a homogenous substance. The extrudate
is then cooled and chipped.
Grinding
Once the extrudate has been cooled and chipped, it is
ready to be ground into a fine powder. This powder is then
sieved and classified to ensure an even particle size
distribution. Particles that are under 10 micrometers or
over 120 micrometers can cause application problems and are
restricted by the sieving and classification process.
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