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1-
1.1
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Description of
product
P.T.F.E water borne
tow-coat system comprises
a) the RAH Floun 6611 base coat
b) and the RAH Floun 221 top coat.
RAH Floun 6611 (bse coat)
RAH Floun 6611 is an aqueous dispersion based on a
fluoropolymer and an inorganic adhesion promoter.
suitable as a base coat for the production of highly
adherent coatings on aluminium, aluminium alloys and
steel by the two-coat process. The use of this process
is not confined to these materials. However, if other
materials are used, modifications to the process may be
necessary and these should be determined by preliminary
trials in each case.
The following table shows the most important properties
of the starting material.
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1.2 |
RAH FLOUN 220
is a PTFE-based aqueous dispersion supplied in
various colours. It is used to produce highly adherent,
glossy top coating by the two-coat process. In addition
to the main constituent PTFE and the pigment to give the
required shade, contains additives to improve
wetting, film formation and flow properties. Because of
the pigment, the substrate is completely obscured at
coating thicknesses greater than 17micron.
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1.3
1-
2-
3-
4-
1-
2-
3-
4-
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Starting material
properties
Property
Unit
Test method
6611
6610
4410 Gray
Density
g/cm3
DIN
53479
1.1
1.2
1.1
Solid content
%
32
36
36
PH
value
9.9
9.9
9.9
viscosity
sec
cup
14
15
16
Top coats
Unit
Test
method
221 silver 220
silver light
420 Gray
Density
g/cm3
DIN
53479
1.4
1.4
1.4
Solid content
%
48
47
48
PH
value
10
13
13
Viscosity
sec
cup
14
13
13
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2. |
Processing
instructions
Coating with the two-coat system involves the following
operation:
a) Preparation of the substrate
b) Application of the RAH Floun 6611 base coat
dispersion
c) Drying the base coat in warm air
d) Application of the top coat dispersion
e) Drying and sintering the coating
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2.1 |
Pretreating the
articles to be coated
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2.1.1 |
Degreasing
The most important requirement for perfect coating
is an absolutely clean and uniform substrate. Light
contamination of the substrate, particularly oil or
grease, discolours the RAH Floun coating while heavier
contamination causes.
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a)
b)
c) |
Loss of adhesion to the substrate. The all parts to be
coated need careful degreasing.
Vapour-phase degreasing with organic solvents (e.g.
trichloroethylene)
Degreasing in aqueous baths - e.g. in a 3 % solution of
( suitable for aluminium alloyes). Any traces of the
solution adhering to the part must be removed by rinsing
with de-ionized water.
A universally suitable degreasing method involves
heating the part over an extended period up to 400-420
C.
In choosing the temperature, the nature of the substrate
must be taken into consideration.
This method is particularly recommended for porous
materials (e.g. ceramic products ) because it enables
other volatile materials lift up the coating form
underneath during sintering and destroy it.
Slight discoloration of the coating due to variation in
the composition or in the crystalline structure of the
substrate is sometimes unavoidable.
The method described under c) also serves as a test to
determine whether the material is suitable fo coating
with RAH Floun.
If the surface scales, then poor adhesion of the RAH Floun coating may be expected. one solution to this
problem is to sinter thr the coating in an in an inert
gas atmosphere, if possible.
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2.1.2 |
Roughening the
substrate
After degreasing, the articles to be coated are
roughened to obtain good This can be done by etching (in
the case of aluminium and Al-Mg alloys) or sandblasting
which is technically simpler. The roughness depth should
be about 5-10 micron. Another very important requirement is a
fissured surface profile. This can easily be achieved
with commercially available sandblasting equipment using
corundum a the blasting agent.
The roughness depth obtained will in each individual
case depend very much on the crystalline structure and
hardness of the substrate. Preliminary tests should thus
be carried out to determine the most suitable blasting
agent.
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2.1.3 |
Second degreasing
Since the compressed air used in sandblasting is
rarely free of oil, a second degreasing process should
be carried out after sandblasting if high demands are
made on the appearance of the coating.
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2.1.4 |
Avoidance of contamination
In most sandblasting machines, the blasting agent is re-circulated .Thus to avoid rapid contamination of the blasting agent, no greasy, waxy or painted objects should be blasted.If this is unavoidable, then the blasting agent should be changed immediately afterwards. Blasting agents used to roughen steel or non-ferrous metals should not then be employed on light metals because steel dust etc.can cause spots on light metals during coating.
Before coating prepared surfaces, great care must to taken to avoid re - contamination.Contact with the bare fingers should be avoided. Although finger prints are hardly visible before coating, they becomeclearly evident after sintering. It is therfore advisable to wear clean white cotton gloves when handling the pretreated surfaces.
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2.2 |
Application of adhesion - Promoting base coat dispersion
The dispersion is applied by hand or automatically by spraying. For hand spraying, a nozzle orifice
1.2 to 1.6 mm in diameter and a spray pressure of about 1.5 to 2.5 bargauge have proved successful.
Care should be taken to ensure Oil-Free compressed air and effective extraction of spray mist. Goggles and an effective face mask with aerosol filter should be worn.spray guns and other equipment coning into contact with
RAH floun should be made from alkali -resistant materials. The usual commercially available spray guns oftem contain suction pipes and other parts made from chrome - or nickel -plated brass. These should be replaced with parts made from stainless steel, PTFE or polyethylene.
If fairly large supply containers are to be used for spraying,the dispersion must be carefully stirred to prevent sedimentation and separation. The stirrers should be run slowly ( about 25 rpm) and kept at a suitable distance (1.5 to 3 cm) from the walls. Bearing or shaft guides and stuffing boxes should not come into contact with the liquid.
The dispersion should if possible be pneumatically conveyed and not pumped. Hoses must be made of materials resistantto solvents and alkalis
The base coat dipersion should be sprayed .
The coat thickness should not exceed15 micron.m so ensuring that the coated surface retains the sandblasted profile of the substrate ready for application of the top coat.
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2.3 |
Cleaning spray equipment
Afte spraying, all equipment should immediately be rinsed thoroughly with water. there is no solvent for dried residues. They can only be removed mechanically ( by brushing). This can produce small , soft PTFE particles which must be removed very carefully so that they do not contaminate future
RAH floun coatings or block up nozzles when the spray equipment is next used. It is
advice
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2.4 |
Drying the RAH floun 6611
The RAH floun base coat can simply be air-dried at 80 - 130 C temperature. A drying time of about 5-10 minutes is generally sufficient.
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2.5 |
Application of the
RAH floun 221
The RAH floun 221 top coat can be applied when the RAH floun 6611 coating appears dry to the naked eye.
The same spraying conditions should be used as for preparation of the base coat.
RAH floun 6611 . Immediately before
use, RAH floun 221 ( top coat) should be filtered through an 80 -110 um mesh screen.
Spray application should be adjusted to achieve a top coat thickness not exceeding 25-30 um after sintering. with greater coat
thickness there is risk of "mud " craks.
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2.6 |
Drying and sintering the top coat
The top coat is first dried at 90 C , then at 250 - 290 C and is then sintered at 400 - 410 C . with thick coatings in particular, care should be taken to ensure that before sintering the coating has completely dried through and has stopped giving off vapours.
The RAH floun coating system has a matt appearance after sintering. By rubbing with a soft cloth or polishing with lambskin, an attractive gloss can be obtained, particularly with two-coat systems.
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3. |
Storage specifications and special
Precautions in processing
RAH floun 6611 and RAH floun 220 should be stored at temperatures between +5 and + 25C. When left standing for a prolonged period,the dispersions tend to settle out. To prevent formation of a solid unhomogenizable sediment,
RAH floun cooting should be homogenized twice a month by slow rolling ( around the longitudinal axis of the bottle) at a temperature of about 20C. To prevent the dispersions flocculating, the following points should be observed in rolling.
a) bottle rotation speed about 25 min-1
b) rolling time about 15 minutes.
The dispersions must also be homogenized immediately before use, if only part of the container contents are to be removed. Opened containers in daily
USE need to be rolled for a short time. Any unused dispersion should not be returned to the original container but stored separately . in handling and storing these solvents, the precautions normally taken for paints should be applied. In particular, prolonged contact with the skin and inhalation of vapours should be avoided.
Residues of sintered dispersion are non-toxic and non - flammable but should not be burnt with other materials
This could give rise to decomposition products which in some cases may be harmful to health.This applies particularly to impregnated rags etc.
Spots on clothing may be rinsed out with plenty of water or solutions of non-ionic or anionic wetting agents,proviede the dispersion is still moist. Dry spots cannot be removed.
When handling RAH floun . Any splashes on the skin should be washed off immediately with plenty of water.
Any splashes in the eye should be thoroughly rinsed out with water and a doctor should be summoned.
This inforamtion is based on our present state of knowledge and is intended to provide general notes on our products and their uses. It should not therefore be construed as guaranteeing specific properties of the products described or their suitability for a particular application. Any existing industrial property rights must be observed.The quality of our products is guaranteed under our General conditions of sale.
TEHRAN - IRAN
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