The proven durability of Kynar 500® resin type paint systems allows for stable color and film integrity over decades of exposure. This durability is also seen in the retained amount of initial solar reflectance. Thus, paint systems based on the Kynar 500® resin have a surface that does not retain dirt, remains cool, and retains its original color better than any other resin type.
In the design and performance of a building, the owner wants to know that the initial energy cost savings projections are maintained over the life of the roof. Most other roof types have been documented to lose some percentage of their initial solar reflectance due to dirt pick up and overall degradation from the weather. In those cases, the aged performance of these cool roofs is far from what the building experiences in the early years. The strong performance of Kynar 500® based paint system which is maintained over time is especially apparent in the retention of the initial solar reflectance of cool Kynar 500® based prepainted paint systems. In research conducted by Oak Ridge National Laboratory on behalf of the Cool Metal Roofing Coalition Kynar 500® based prepainted metal test panels exposed in South Florida were found to retain 95% of their original solar reflectance over more than 30 years. Typically, dirt pick-up and retention is responsible for many roof products’ solar reflectance dropping over time. This is also true for some conventional resins used for prepainted metal roofing. However, Kynar 500® based prepainted metal roofing readily sheds dirt and does not promote the formation of algae or other microbial growth on the surface which could lower the solar reflectance.
Chart 1
In the Metal Construction Association’s roofing certification program, the Kynar 500® based paint systems achieve the highest performance certification – Premium. No other prepainted metal roofing product has the high levels of gloss retention, color and chalk performance that are required for a MCA Certified Premium Painted™ product. So again, the aesthetic appeal of using a Kynar 500 based prepainted cool metal roof is second to none when a building owner is considering what type of cool metal roof to specify.
ARKEMA’s research indicates that there are many reasons why Kynar 500® based paint systems are the product of choice for cool roofing applications. The most weatherable coatings for metal roofing are based on polyvinylidene difluoride resin technology. These resins have superior resistance to photo-chemical degradation. They maintain their gloss and color better than any other resin technologies used in today’s exterior paint systems used in the metal roofing industry. Actual exposure of panels in South Florida’s harsh climate after nearly 40 years substantiates the outstanding performance of the Kynar 500® resin.
To achieve superior resistance to weathering, Kynar 500® based paint systems commonly use durable grades of inorganic pigments and tough acrylic resins. The structure of a Kynar 500® based paint system is thermoplastic in nature, thermodynamically stable and based mainly on the photochemically inert PVDF resin. This combination has been shown to retain the aesthetic and cool properties of Kynar 500 based paint systems for decades. This durability is in stark contrast to the common cross-linked binder chemistries used in polyester and silicone modified polyester paint systems often used in the metal construction industry.
TSR Values of PVDF Coatings |
|
22 Year Florida Panels |
Color |
Lab Retain |
Washed |
Unwashed |
Black |
0.052 |
0.053 |
0.047 |
Green |
0.209 |
0.218 |
0.210 |
Blue |
0.278 |
0.271 |
0.200 |
Brown |
0.471 |
0.515 |
0.480 |
Yellow |
0.530 |
0.538 |
0.502 |
White |
0.760 |
0.733 |
0.688 |
NOTE: These data were obtained from the ORNL study. TSR values were obtained using a portable solar spectrum reflectometer per ASTM C1549 (D&S Solar spectrum reflectometer model SSR-ER). The device uses a tungsten halogen lamp to illuminate the sample. Four detectors, each fitted with differently colored filters, measure the reflected light in different wavelength ranges. The four signals are weighted in appropriate proportion to yield the solar reflectance.
Source: "Hot Solutions for Cool Roofs", Finishing Today Magazine, February 2007
Other research has found that 70% Kynar 500® based paint systems actually achieve higher solar reflectance when compared to identical colors of polyester and urethane resin based paint systems.
TSR Values of Orange Paints |
|
22 Year Florida Exposure |
Resin |
Unexposed |
Washed |
Unwashed |
70% KYNAR 500 PVDF |
0.463 |
0.439 |
0.426 |
Polyester |
0.375 |
0.346 |
0.312 |
Urethane |
0.446 |
0.436 |
0.412 |
Total solar reflectance values of color-matched orange paints based on different resin chemistries before and after 22 years of Florida weathering.
Source: "Hot Solutions for Cool Roofs", Finishing Today Magazine, February 2007
This significant advantage is in addition to the expected superior retention of gloss and fade, and the prevention of chalking of the paint film.
Hence, a cool Kynar 500® based prepainted metal roof product has the best protection against color fade, chalk and erosion of gloss AS WELL AS having the highest solar reflectance of a color formulated in any other paint resin type. There is no better choice than Kynar 500 resin when selecting a durable exterior paint system for cool metal roofing