Spray Coating
Technology of Plastic Prototype
Spray coating characteristics:
in coating craft project. Air spraying makes use of compressed air
which form negative pressure when flow spray gun. The paint vehicle
is absorbed form sucker by negative pressure, and is sprayed out by
spray gun as coating mists. When spraying, coating mists become
even film on the surface of prototype. Air spraying can paint even film,
and smear layers are very smooth. It can spray the hidden parts such
as gaps and unevenness. The utilization rate of dope is low in this way,
which is about 50 to 60 percent. There are some effect after coating
on plastic
prototype.
1. Spray coating
can cover the deficiency of prototype surface.
2. The plastic itself is difficult to color. Spray coating
can paint many
kinds of color on plastic.
3. Spray coating improves the electrostatic properties of
plastic,
which can reduce dusty-adsorption.
4. Spray coating strengthens hardness and mar-resistance
of plastic.
5. Spray coating improves weather resistance of plastic.
6. Spray coating can adjust the gloss of plastic surface.
7. Some special lacker such as sand paint, fluff paint
can achieve
effect of good appearance and hand feeling.
Moreover , the
surface confition after plastic formed has great impact
to appearance quality.
The technological
process of plastic spray painting technology
1. Annealing : It
is easy to form internal stress when plastic molding
and processing, so after
coating, the stress concentration position
is easy to crack. Therefore , the annealing
treatment or post nital
treatment can be adopted to relieve stress.
Annealing treatment is to
heat ABS formed parts to heat below distortion
temperature, that is 60℃
and heat preservation for 2 hours.
However, those technology need
a lot of equipment investment. For this reason, post
nital treatment
can be adopted, that is to deploy liquor which can relieve
plastic stress,
and immerse the plastic parts into liquor for 15～20minn to anneal.
2. Degreasing : plastic parts often stick with greasy
dirt, hand
perspiration and release agent, which make coating adhesion worse
and the
coating would crack, blister and fall off. It need to degrease
before apply
coating. For plastic parts, gasoline or alcohol is often be
used , and then alkaline
degreasing. After clean out alkali liquor,
the pure water should be used to
clean up at last.
3. Static electricity removal and dust removal:
Plastic parts are
nonconductor and its surface
resistance is about 1013Ω which is easy
to produce static electricity. It is
easy adsorb tiny dust and attached
appearance when it electrify. The dust
attached surface because of static
electricity is very difficult to wipe out. High
pressure ionization air flow
has very good effect to Static electricity removal
and dust removal.
4. Spraying coating:The thickness of plastic coating
is 15~20μm and
it need to spray 2 or 3 times to finish.One time spray spraying
coating
need to dry for 15miniutes and the do the second spraying coating.
If
the surface need to be glossy , the surface must spray transparent
coating. The
spraying coating have nofluence to flame retardant property.
5. Stoving：After spray coating, plastic parts can be
dried under
natural condition and they can also be baked under 60℃ temperature
for 30 minutes.
