B
Back Ionization.
A
condition that
can occur during
electrostatic
application of
powder in which
an excessive
build up of
charged powder
particles limits
further powder
from being
deposited from
the
substrate and
can be reverse
the electrical
charge of the
surface layer of
powder
particles. Also
called electro
static rejection
or repelling.
Bulk density.
Mass per unit of
volume in powder
form, including
the air trapped
between
particles.
C
Cloud chamber
technique.
A
method of moving
charged or
uncharged
object through a
charged or
uncharged
cloud of powder
in enclosed
chamber.
Compatibility.
The
capacity of
powder coatings
from indifferent
sources of
different
compositions to
be combined
and applied
so as to yield
no visible or
mechanically
measurable
differences in
the cured film
or application
properties.
Corona charging.
The process of
inducing a
static electric
charge on powder
particles by
passing the
powder coating
film is
determined to
have developed
specified
properties.
Cure schedule.
The
time/temperature
relation
required to
properly
crosslink a
thermosetting
powder coating.
Cut-Through
resistance.
A
powder coating
film resistance
to penetrate
from the
combined
application of
sharp edges,
heat, and
pressure. A
formalized test
used by
applicators of
isolative powder
to electrical
motors.
D
Delivery.
The
process of
moving the
powder coating
through the
application
equipment to the
end product.
E
Edge coverage.
A
powder coating’s
capability to
flow over,
build, and
adhere to sharp
corners, angles,
and edges.
Electrostatic
deposition.
A
technique of
moving and
charging powder
so that it is
deposited on a
grounded
substrate.
Electrostatic
fluidized bed
technique.
A
deposition
method of
charging
fluidized powder
so that it is
deposited onto a
grounded
substrate.
Electrostatic
spray technique.
A
deposition
method of
spraying and
charging powder
so that it is
deposited on to
a grounded
substrate. See
Corona charging
and
Tribocharging.
F
Faraday cage
effect.
A
condition that
can exist on a
substrate
because of its
geometric
configuration,
which can
inhibit the
electrostatic
application of
powder particles
at that specific
localized area.
Film formation.
The
forming of a
continuous film
by melting
powder particles
and coalescing
them
By the
application of
energy.
For
thermosetting
materials, a
chemical
reaction,
through the
further
application of
energy, also
takes place. The
fused and cured
film has the
uniformity,
color,
toughness, and
other properties
associated with
protective and
decorative
coatings.
Flocking
deposition
technique.
A deposition
method of
applying powder
by spray to a
substrate heated
above the melt
point of the
powder material.
Fluidized bed.
A fixed
container in
which powder is
suspended in a
continuous
stream of air.
Preheated
objects can be
coated by
dipping directly
into a fluidized
bed. The
fluidized bed
can also be used
to facilitate
transfer of
powder materials
to an alternate
application
site.
Fusion.
The melting &
flow of
individual
powder particles
under the
influence of
heat to form a
continuous film.
G
Gel time.
Interval
required at a
given
temperature for
a powder to be
transformed from
a dry solid to a
gel-like state.
Gloss plate
flow.
See Plate
flow.
Grounding.
An
electrical
grounding of
item to be
coated.
I
Impact fusion.
The
tendency of
finely divided
powders to
combine with
other particles
in the
application
equipment during
the application
process.
Inclined plate
flow.
See plate
flow.
Intercoat
adhesion.
A powder
coating’s
capability to
adhere to
previously
applied films.
L
Lower explosive
limit (LEL).
The lower
point for a
range of
concentrations
of organic
particles
suspended in air
that can be
ignited by a
sufficient
energy source.
Also called
minimum
explosive
concentration
(MEC).
M
Melt mixing.
A
predominant
process for the
manufacture of
powder coatings
involving the
continuous
compounding of
the pigments,
fillers,
catalysts, and
resins at
elevated
temperatures.
Melt point.
The
temperature at
which a finely
divided powder
will begin to
melt & flow.
Micron/mil.
Common
units of
measurement of
coating
thickness: 25
microns
(micrometers)
equals 1 mil. (one
thousandth of an
inch).
Minimum
explosive
concentration.
See lower
explosive limit.
N
No electrostatic
depositions.
A
technique of
depositing
powder on to a
substrate, which
may be heated
above the melt
point of the
powder material.
Some methods are
flocking and
fluidize bed.
P
Particle size.
The
average diameter
of an object
having irregular
boundaries,
which can be
determined
various test
methods.
Pill flow.
See Plate
flow.
Plasma
deposition
technique.
A method
of applying
powder by using
compressed gas
and by melting
the powder in a
flame before the
powder impinges
on the surface.
Plate flow.
The
distance a
powder coating
flows in the
molten state
before gel. Also
called inclined
plate flow, and
pill flow.
Pourability.
The capability
of a dry powder
to flow
uniformly or to
be continuously
poured from a
container at a
steady rate.
Powder coatings.
Coatings
that are
protective,
decorative, or
both; and that
are formed by
the application
of a coating
powder to a
substrate fused
into continuous
films by the
application of
heat or radiant
energy. Coating
powders are
finely divided
particles of
organic polymer
that generally
contain
pigments,
fillers, and
additives and
that remain
finely divided
during storage
under suitable
conditions.
R
Reclaim.
A process to
recycle
non-deposited
powder through
the delivery
system for
reuse.
Recovery.
The process of
removing non
deposited powder
through the
delivery system.
Repelling.
See Back
ionization.
S
Sintering.
The tendency of
some powders and
powder coating
materials to
agglomerate
during storage.
Spray/reclaim
booth.
A
specially
designed
enclosure in
which coating
powders are
introduced,
contained and
recovered during
the coating
process.
Storage
stability.
The capability
of powder
coatings to
maintain uniform
physical &
chemical
properties after
being subjected
to the
manufacturer’s
specified
storage
conditions.
Surface appearance.
Generally
refers to the
smoothness and
gloss of
powder-coating
films and the
presence or
degree of
surface defects.
T
Thermoplastic.
A powder coating
that will
repeatedly melt
when subjected
to heat and
solidify when
cooled. Typical
examples are
vinyl(PVC),
nylon, and
polyolefin.
Thermosetting.
A powder
coating designed
to undergo an
irreversible
chemical change
during the cure
schedule.
Typical examples
are acrylic,
epoxy, and
polyester.
Transfer
efficiency.
The ratio
of the powder
deposited
compared with
the amount
directed at the
part to be
coated.
Transportability.
A powder
coating’s
capability to be
carried in an
airstream and be
passed through
tubing and ducts
designed to
transfer the
powder.
Tribocharging.
The process of
creating a
static electric
charge on powder
particles by
friction against
a nonconductive
material.
V
Virgin powder.
Unsprayed powder
as opposed to
sprayed or
reclaimed
powder.
Volatile content.
The quantity,
expressed as a
weight percent
of the powder,
that is lost
under specified
conditions of
temperature and
time.
W
Wrap.
A characteristic
of powder
coatings in
electrostatic
application to
seek out and
adhere to parts
of the substrate
not in direct
line of sight of
the delivery
system end
point.
Adapted with the
kind permission
of the Powder
Coating
Institute from
Technical Brief
# 2 ( Alexandria,
Va.: Powder
Coating
Institute,
1986).
