Application of Paints
Supervised by : Dr/ El-Sayed Mansour
Presented by : Ahmed Abdullah Balbaa
Introduction
• Paint can be thought of a pigmented
liquid which protects and beautifies
substrates.
• Paint any liquid, which after application
to a substrate in a thin layer is converted to
an opaque solid film
• Various raw materials are utilized to
make this pigmented liquid.
Composition of Paints
A paint is formulated as a mixture of three
ingredients:
• Binder
• Solvent
• Pigment
Besides the three ingredients, paint
can have a wide variety of :
• Additives
• Extenders or Fillers
1- Binder
• Binder is the main ingredient of paints.
• Binders are polymers (resins) forming a
continuous film on the substrate surface.
• Binders are responsible for good adhesion of
the coating to the substrate. The binder holds
the pigment particles distributed throughout
the coating. The binder is dispersed in a carrier
(water or organic solvent) either in molecular
form (the solution) or as colloidal dispersions
(emulsions)
• Binder also known as non-volatile vehicle
• Binder can be classified according to drying or
curing into four mechanisms :
- Simple solvent evaporation.
- Oxidative cross linking.
- Catalyzed polymerization.
- Coalescence.
2- Solvent
• Solvent (water or organic solvent) is a medium
where the binder, pigment and additives are
dispersed in molecular form or colloidal form.
• Solvent (thinners) are also used for modification
of the paint viscosity required for the application
methods :brush, roller, spray….
• The solid coating is formed due to evaporation
of solvent therefore the evaporation rate is one
of the important properties of solvents.
• Other important properties are the ability to
dissolve the paint ingredients and toxicity.
3- Pigment
• Pigment is a solid substance dispersed
throughout the coating to import it a colour
opacity (hide the substrate surface).
• Pigment may protect the substrate from UV
light.
• Pigment change the paint appearance (gloss
level)
• Pigment increase hardness and decrease
ductility
• Pigment may be natural, synthetic, inorganic or
organic.
4- Additives
• Additives are small amounts of substances
modifying the paints properties.
• Examples of additives: dryers, plasticizers,
fungicides, flow control agents, defoamers,
emulsifiers, UV stabilizer, anti skinning
agents, adhesion promoters, corrosion
inhibitors and texturizers.
5- Extenders or Fillers
• Filler serve to thicken the film, support its
structure and simply increase the volume
of the paint. Not all paints include fillers.
Pigments that also function as fillers are
called simply pigments.
• Fillers are generally colour-neutral and
opaque.
The Application of Paints
Which can be classified into 3 terms
Type
Solid•
Gas•
liquid•
Purpose
Decoration•
Protective layer•
Ease of cleaning•
Technique
Brush•
Roller•
Air spray•
Airless spray•
Electrostatic spray•
Rotating disc or •
bell
1st Term : Types of Paints
• As a solid usually used in industrial and
automotive applications, the paint is applied as a
very fine powder, then backed at a high
temperature . This melts the powder and cause it
to adhere (stick) to the surface.
• As a gas or gaseous suspension, the paint is
suspended in solid or liquid form in a gas that is
sprayed on an object, The paint stick to the object.
• As a liquid application, paint can be applied by
direct application using brushes, roller, blades,
other instrument, or body parts.
2nd Term : Purpose of Painting
• Decoration to interiors and exteriors of a
building, they are used to enhance a building by
adding pigments, lightness or darkness.
Reflective surfaces can be also obtained.
• Protective layer paint are also used to protect the
outer surfaces of a building or metals to protect
them against : sunlight, dust, corrosion and
weathering.
• Ease of cleaning :
- to provide easily cleaning surfaces.
- to keep the substrate clean and tidy.
3rd Term : Paints Techniques
- Paint is applied onto a substrate surface which
has been previously treated by the methods of
enhancement of adhesion (surface preparation ):
cleaning, surface roughening, primers, adhesion
promoters, plasma treatment.
- The following techniques are used for
application of paints:
• Brush :
- Brush application is used decorative coating of
relatively small and complex areas.
- Brush painting is a slow application method but
it provide good penetration of the paint.
- Brush application prevents paint losses.
• Roller :
- Roller technique is applied for coating large
flat surfaces, this method is faster than brush
application.
- In contrast to brush method roller paint is not
suitable for applying high film build.
• Air spray :
- In the air spray application method the paint in form
of atomized droplets is delivered by a stream of
compressed air.
- Spray application is a simple and inexpensive method
which is capable to coat objects of various shapes and
dimensions.
- High quality coatings are achieved if the paint
composition provides the required level of viscosity
and drying rate.
- The disadvantages of the air spray application is
unavoidable over spray (paint losses) and expensive
organic solvents and thinners. The method requires
additional investments in safety equipments in order
to protect the workers exposed to the hazardous
solvent vapors.
Air spray technique
• Airless spray :
- In the airless spray (in contrast to the air spray)
the paint is not mixed with air. The liquid paint
is delivered to the gun by hydraulic pump
producing a high pressure (300-7000 psi).
- Using a high pressure pump and preheated
paints allow to apply high viscosity paints
having a decreased amount
of solvent and thinners
(lower solvent content).
• Electrostatic spray :
- Electrostatic spray application is based on the
electrostatic attraction of electrically charged
atomized (either dry powder or liquid paint
droplets) to the grounded (having earth
potential) work piece.
- The charged particles coming out from the gun
hit the whole surface of the object including
the back surface.
- Electrostatic spray is characterized by very low
over spray. The method utilizes at least 95% of
the paint.
Electrostatic Spray
• Rotating Disc or Bell :
- In the rotating disc/bell application technique the
liquid is pumped to the center of the disc/bell
rotating at high speed (at least 10000 rpm)
- The centrifugal force drives the liquid to the
edge where it is atomized and spun off.
- Rotating disc/bell method is used for automatic
application of high viscosity paints (e.g. high
solid paints).
Rotating Disc or Bell painting
References:
- Paints, Dr. El-Sayed Mansour
- Civil engineering Portal , http://www.aboutcivil.org.
- California paints is a division of California products
corporation.
- SubsTech for Substances & Technologies
httb://www.substech.com
(Application of Paints, Dr. Dmitri Kopeliovich)