Technical Resources Area
Technical Resources Area |
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PLASCOAT
PPA571ES
Plascoat PPA571ES is a
thermoplastic powder coating
which
melts to
form a
fusion-bonded coating. Polyester powders, however, must first melt and
then
chemically cross-link to
develop their physical properties and
adhesion. The "curing" schedule is
therefore
critical for polyester powder coatings. PPA571 only has to melt onto the surface
to
provide adhesion, and when the coating is cooled
full physical properties are
ensured.
Plascoat PPA571ES has been formulated to give excellent
resistance to UV
light and water including acid rain and
salt spray. Furthermore it offers excellent
corrosion
resistance when applied over mild steel,
galvanised steel or aluminium.
Plascoat PPA571ES is applied at 150 to 250 microns
or more in a
single
application. Polyesters are applied at 50 to 100 microns. The thicker PPA571ES coating ensures
that the edges
are well covered and that the interstices of any
wire sections are pinhole free.
Polyesters are by their chemical nature
water-permeable. Water passing through
the coating will bring with it acids or salts from
the environment. These will attack
the
substrate beneath and cause blistering and
cracking of the coating. PPA571ES
is
hydrophobic and so water will not be absorbed by
the coating. Therefore salts
cannot
attack the substrate below unless the coating is
damaged. Even if the coating
is
damaged the adhesive mechanism resists under-film creep and the coating is so
flexible
it
cannot crack and fall off.
Polyesters have a similar chemistry to paints used by
Graffiti
"artists". Therefore solvents carry the colour into the polyester
coating. The solvents used to
dissolve
the graffiti paint also remove layers of the
polyester powder coating. PPA571ES,
however,
is non-porous to the graffiti paint solvents and so
they do not penetrate into PPA571ES coatings.
Therefore graffiti can be easily
wiped off
using
a clean rag or cloth dipped in solvents (such as toluene or MEK)
with little or no affect on the coating.
Plascoat PPA571ES is extremely
flexible even down to -78°C. Polyesters even
when
fully cured do not have good
flexibility.
From the coater's viewpoint, the thermoplastic nature of PPA571ES means
that the
shelf life of the product is many years but
polyester powders will slowly
cross-link and
may become
unusable
after a few months, especially in hot climates.
Plascoat PPA571ES can be
over-sprayed with PPA571ES to give a thicker
coating or alternatively with polyester if the thickness
and corrosion properties or PPA571 are
required but the hardness of polyester is also
desired. In both cases inter-coat adhesion is assured.
Plascoat PPA571ES coatings can be easily
repaired
using the same polymer system. Plascoat can supply repair rods of PA571ES, which
can be melted into the coating to
produce an invisible repair. Polyesters can only be repaired with a
solvent based paint
which may not have the same physical or
weathering properties as offered by the
coating powder.
WGO.18/07/02
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| © Plascoat Systems Limited, MMIII |
Plascoat Systems Ltd. Trading Estate, Farnham, Surrey GU9 9NY, UK Tel: +44 (0) 1252 733777, Fax: +44 (0) 1252 721250 email: sales@plascoat.com |
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