Top Quality Finishes for Architectural Metal:
The Right Chemistry for High-performance, Long-lasting Building Envelopes
Chip Bisignaro,
Posted
05/01/2008
Today's building designers continue to challenge manufacturers
of building envelope components to provide unorthodox shapes,
styles and colors. Simple straight lines, corners and smooth
surfaces are being replaced with curvatures, textures and
complexities. At the same time, architects and building owners
expect the envelope components to hold up in blistering heat,
humidity, urban grime, acid rain, corrosive salt and abrasion over
decades of exposure.
Metal has rapidly become the material of choice for exterior use
due to its rugged durability, design versatility and aesthetic
possibilities. Metal roof and wall components, extrusions and
preformed shapes can be bent, crimped and twisted to meet the most
challenging building design requirements. They can also save
energy, increase property values and hold their beauty far longer
than other building materials.
For all its performance advantages and beauty, however, metal
doesn't necessarily have a tough skin and is only available in a
single color. To satisfy a designer or owner's needs, architectural
metal must be coated with a rugged protective finish that not only
beautifies with color but also doesn't chalk; lose its color and
sheen; or pit, chip and age for a long time.
Weatherability Is Paramount
Color creates a mood and makes that desired first impression
quickly and more effectively than almost any other architectural
component. But while architects like to use color to create a
statement or image with a building, retaining its beauty and
vibrancy can be very difficult. Exterior paints naturally degrade
from exposure to heat, humidity and harmful ultraviolet rays.
Sunlight can quickly turn brown to tan, red to pink or a deep blue
to sky blue. Deterioration can also be evident in the loss of gloss
and adhesion, as well as the appearance of chalking. More than 95
percent of architects in a recent national survey considered
weatherability as "critical" or "very important" to specifying for
metal roof and wall panels. Nearly nine out of 10 of these same
architects rated Kynar 500 PVDF resin-based metal coatings as "good
or excellent" in terms of weatherability and color retention and
said they prefer coatings formulated with Kynar 500 PVDF resins.
Additional results from the survey can be found at
www.kynar500.com/ma.
A key reason for this strong brand preference among architects is
the Kynar 500 resin-based coating's outstanding resistance to film
degradation. The high-performance chemistry behind these premium
exterior finishes is transparent to UV rays and, when combined with
durable pigments, creates a coating system that prevents color from
fading. Coatings formulated with Kynar 500 resins also withstand
extended exposure to water, humidity, temperature, UV rays, oxygen
and atmospheric pollutants.
Green Building Solutions
With energy codes becoming more rigorous, cool roofing is becoming
a more popular means of energy-efficient building. Sustainable
design calls for the reduction in energy consumption as a cost
savings to the building owner and as a direct reduction in the
greenhouse gas emissions at the power plant generating the energy
for the building.
The choice of roofing material has the greatest impact on the
energy conservation of a building. Cool metal roof systems, which
feature a finish such as a Kynar 500 PVDF resin-based coating, can
reduce energy consumption by up to 40 percent as part of a total
system design (as reported by the Oak Ridge National Laboratory,
Oak Ridge, Tenn.).
Kynar 500-based painted metal roofing, which offers advanced
resistance to UV degradation, can achieve solar reflectance of over
70 percent. Reflected solar energy allows the roof surface to
remain cool, which means less heat is transferred into the
building. As a result, use of cool metal roofing products featuring
Kynar 500 PVDF-based paints is one proven way to limit the urban
heat island effect.
Kynar 500 PVDF-based coatings offer superior long-term color
retention, allowing the building owner to enjoy the original color
specified over the life of the building with little to no change
over time. Unlike conventional products, which are regularly
destructed by UV energy, heat and moisture, colors in a Kynar
500-based paint system remain rich and vibrant due to the resin's
resistance to UV solar radiation. With restoration not being
required as often as it is with competitive products, environmental
impact is reduced. The reduction in restoration and reconstruction
results in lower amounts of VOCs emitted into the atmosphere. These
features of a Kynar 500 PVDF system make it a sustainable green
building product.
The Kynar
Technology Platform
Kynar 500 PVDF, or polyvinylidene fluoride, homopolymer is
universally known within the architectural community as a
weatherable coating resin. All coating systems contain a specific
resin that acts as the first line of defense against weathering.
Ultimately, the resin determines robustness. The durability found
in PVDF is a result of the chemical composition of the resin
relying on the carbon-fluorine molecular bond-one of the strongest
bonds known. It is the C-F bond that provides the resilience, color
and gloss retention for which Kynar 500 PVDF-based coatings are so
well known.
The structure of PVDF contains alternating carbon/fluorine and
carbon/hydrogen bonds, which provide a polarity that enables the
formulation of a practical coating that resists environmental
degradation and dirt retention. This structure enables PVDF to
resist oxidation, photochemical deterioration, fading, chalking,
cracking and airborne pollutants. Thus, PVDF has a balance of
properties that make it particularly suitable for use in coatings,
especially for architectural uses.
The National Coil Coating Association, Cleveland, rates the
performance of PVDF coatings very favorably to the other common
paint systems used in the metal construction industry. A portion of
its Comparative Properties and Performance Chart, shown in Table 1
(above), illustrates that PVDF coatings, such as resin-based Kynar
500 paint systems, excel in most every category of importance to a
building owner. In all cases, NCCA used the opinions of industry
experts to accurately capture the performance of each technology.
The properties are measured using recognized standards and test
methods from West Conshohocken, Pa.-based ASTM International and
Schaumburg, Ill.-based American Architectural Manufacturers
Association.
Strong Performance
Record
Kynar 500 PVDF resin-based coatings have been thoroughly analyzed
since they were first introduced to the market over 40 years ago.
Coatings made with this fluoropolymer are time tested in harsh
climates, internationally evaluated and rewarded by being the
product of choice for architects and designers who specify durable
prepainted metal components in the construction industry.
The performance of Kynar 500 PVDF resin-based coatings compared to
other common paint systems used in the metal construction industry
is illustrated in Figure 1 (above). The superior resistance to fade
exhibited by the Kynar 500 resin-based coating is obvious after 17
years of exposure at an independent test-fence facility in southern
Florida. It is difficult to retain dark colors over time, and yet
even in the dark color used, fading was insignificant with the
Kynar 500 resin-based coating.
In other colors,
the performance of Kynar 500 PVDF-based paint finishes is noted in
Figure 2 (above).
Taiyo Steel Performance Study
Customers of Kynar 500 PVDF resin-based coatings in other parts of
the world have agreed with the excellent performance seen in North
America. To test the weatherability of its precoated metal
products, Taiyo Steel of Funabashi, Japan, established an exposure
test fence by using the south-facing wall of a new plant it was
building. Thirty-three-foot- (10-m- ) high steel panels were coated
with acrylic, polyester, silicone polyester and Kynar 500 PVDF
resin-based coatings in 1981. After 14 years, the Kynar 500
resin-based coating was the only system that kept its original
appearance.
Quality Control Through Licensing
The number and variety of building components that are commonly
protected with Kynar 500 resin-based coatings continue to grow.
Examples include spandrel panels, wall panels, curtainwalls, metal
roof systems, storefronts, column covers, entranceways, louvers,
mullions, window and doorframes, metal trim and fascia. When
specifying a Kynar 500 resin-based paint system for ultimate
performance on a building project, the following terminology should
be used: "The final coating for aluminum, galvanized steel or
aluminized steel shall be a factory-applied, oven-baked finish
based on 70 percent KYNAR 500 polyvinylidene fluoride resin."
Product consistency, quality and availability are managed on a
worldwide basis through a rigid licensing program. A license is
granted only to quality coating companies and only after a rigorous
testing program is completed. This program encompasses both outdoor
exposure testing and extensive laboratory testing. The license
grants the licensee the right to identify their products formulated
from Kynar 500 PVDF resins with the Kynar 500 trademark. Licensees
must use nothing less than 70 percent Kynar 500 PVDF resin. This
minimum establishes the base level of performance for licensed
Kynar 500 resin-based coatings that the industry has come to
expect.
Chip Bisignaro is business manager for Arkema Inc.,
Philadelphia.
www.arkema-inc.com; www.kynar500.com/ma