| Caswell powder coatings
are suitable for application by: |
-
electrostatic spray,
-
Tribo charging,
-
or by fluidized bed.
|
| Avoiding Contamination by
Oil or Water - |
When compressed air is used
to fluidize or propel the powder, it is essential that
the air is completely filtered to avoid contamination
by oil or water. Certain conditions may necessitate the
installation of an air refrigeration unit. Jigs should
be clean in order to maintain a good ground. |
| Overspray Recovery |
Overspray powder, not attracted
to the article being sprayed, should be recovered by
means of a powder recovery system, and can be incorporated
with virgin powder for re-use, only after sieving. |
| Avoiding Contamination of
Mixing Colors |
To avoid contamination when
using different colors, thorough cleaning of the system
must be carried out between each color. Too much care
cannot be exercised in keeping different colors and types
of powders apart, whether in storage or in the process
itself. Other sources of contamination include inadequate
pretreatment, and silicones and lubricants from mechanical
conveyor tracks. |
| Cure Time Dependencies |
The total curing time of the
film is dependent on several factors: substrate material,
gauge or mass of the substrate, the shape of the substrate,
i.e. sheet, tube, hollow objects. Large articles will
take longer to heat up before curing commences. The color
of the coating may also affect the cure schedule slightly,
as some pigments absorb heat more effectively than others.
Large articles may be susceptible to non-uniform curing
if a temperature gradient exists across the oven. Changes
in the cross-section of the articles themselves can also
result in temperature differences and incomplete cure
on parts of the coating. |
| Required Temperature & Curing |
It is important to remember
that the effective curing time commences when the object
has reached the required temperature. This process allows
for the flowing out and chemical reaction necessary to
complete the cycle. Recommended baking times are always
quoted after the substrate has reached the said temperature. |
| Storage |
Powders should be kept in
a cool, dry area, and the stock rotated. If the temperature
exceeds 20°C, the storage life will be reduced. |
| Safety |
Smoking, flames or sparks
should not occur near the powder. Leather footwear should
be worn. |
