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TABLE
A - COMPARISON WITH COMPOSITE LAMINATES
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AGAINST
MIRAWALL
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IN
FAVOUR OF MIRAWALL
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1) Composite laminates are extremely flat and produce faultless
wall surfaces, thanks to their plastic core. Solid aluminium
sheet is not perfectly flat, and produces an unpleasant wavy
effect on large surfaces. |
1)
flatness has been the winning argument for composite sheet as
long as solid aluminium could not be stress-leveled in the thick
gages needed for large panels. New leveling equipment now produces
perfectly flat 3 mm thick aluminium. |
| 2)
The finish on composite sheet is coil coated PVDF (Kynar) which
is accepted as the best for exterior exposure. |
2) The PCC finish
on Mirawall is 2-3 times thicker, does not crack or thin down
excessively when deformed, has a wider colour range, and has
an outstanding record in service.
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| 3)
Composites have superior insulating properties because 60-80%
of their thickness is plastic.. |
3) The thickness
of the plastic core in composite sheet 3-4 mm, which has no
appreciable effect on the overall K coefficient in a ventilated
wall system (Calculations available from Otefal).
A similar argument applies to acoustic
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| 4)
Composites are easy to fabricate |
4)
Mirawall is even easier to fabricate, because it can be bent
without previous milling on the back, whilst composites cannot
dispense with black milling. |
In
addition, Mirawall behaves better in case of fire, because it contains
no plastic. For the same reason, Mirawall panels and fabrication
scrap are totally recyclable, whilst composite panels and scrap
have disposal problems.
TABLE
B - COMPARISON WITH SOLID ALUMINIUM
PANELS PAINTED
AFTER FORMING AND CORNER WELDING
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AGAINST
MIRAWALL
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IN
FAVOUR OF MIRAWALL
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1) Painting after fabrication provides complete coverage of
the surface. Mirawall has not a complete coverage because the
cut borders are bare metal. |
1)
Window and curtainwall frame bars have been cut for 40 years
from prefinished aluminium profiles, with no problems. The bare
cut edges are protected by self-passivation. The aim of painting
is maintaining the decorative aspect. Corrosion itself is no
problem on bare aluminium. |
| 2)
Painting of tray panels after forming permits welding of the
corners, so improving rigidity and making the panels watertight. |
2) Rigidity may
only be a (minor) problem for very wide (over 3 sq.mt.) panels.
Water-tightness is no must: water can be flushed away by proper
design even with unwelded corners.
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| 3)
Painting after fabrication permits to apply 2 or 3 coats of
PVDF (Kynar-like) paint, i.e. the top-quality finish that has
been proven in service for 20 years on architectural exteriors. |
3) Polyester
powder paints also are well proven after 25 years in Europe,
and an improved variety is applied on Mirawall by the PCC
process. Powder paint offers a much wider colour range at
much lower cost.
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| 4)
When prepainted sheet is bent to fabricate tray panels, it will
crack and discolour on deformed areas. |
4)
Mirawall has an extra-thick (>50 MM) polyester skin, specially
formulated for withstanding bending wihtout damages. |
In
conclusion, panels fabricated from Mirawall are considerably less
expensive than those fabricated from bare aluminium and subsequently
painted. Mirawall cuts costs by 25-50 $/sq.mt. without any loss
in performance.
TABLE
C - COMPARISON WITH PANELS MADE
FROM SHEET
PREVIOUSLY COIL COATED WITH A PVDF (KYNAR) PAINT
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AGAINST
MIRAWALL
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IN
FAVOUR OF MIRAWALL
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The PVDF (Kynar) is the only one that meets the ASTM Standards
requirement of 5 years' exposure in Florida. |
Kynar
(PVDF) has excellent physio-chemical qualities, however:
1) The thickness of common PVDF "wet" films is 1/2-1/3
of the Mirawall coating, and will thin down dangerously on bending. |
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2) The performances
of the special polyester coatings on Mirawall are very near
to those of PVDF and the advantages of much thicker films.
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3) Mirawall has
a much wider colour range.
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| 4)
Mirawall shows no directional effect. On the contrary, the surface
texture of the metal shows off through the thin films ("checquered"
effect). |
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