Spray Coating Technology
of Plastic Prototype
Spray coating characteristics:
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.
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.
