Above: An example of SMP coatings was used on the roof of this luxury cabin in the woods.

May, 2024- In recent years, the rising costs and availability of polyvinylidene fluoride (PVDF) resins have made the generational advancements in resins used in silicone-modified polyester (SMP) coatings a more economical and attractive option. Manufacturers should weigh the cost, end-use application and environment to determine which system is optimal for each situation.

Because these polymers are engineered to withstand extreme weather conditions, each provides a formidable barrier against UV exposure, humidity, salt spray and chemicals that can degrade the coating system.

While both are excellent choices for preserving the structural integrity and aesthetics of metal building products, their performance and mechanical properties differ due to their distinct resin systems. While PVDFs remain the gold standard for metal protection and aesthetics, SMP systems that are engineered with newer, premium resins and pigments are making it a viable option for a growing array of building applications at a more competitive price point.

BENCHMARK

PVDF is a semicrystalline, highly inert and stable thermoplastic fluoropolymer. PVDF resin-based coatings are one of the most widely used ultra-durable coating systems on the market and set the benchmark for performance in the metal coating industry.

PVDF polymers consist of alternating carbon-hydrogen and carbonfluorine groups. The carbon-fluorine bonds are one of the strongest in the chemical world, providing PVDF with exceptional chemical and photochemical resistance to UV radiation, moisture and atmospheric pollutants.

What drives this gold-standard level of protection is a formulation that is comprised of 70 percent polyvinylidene fluoride polymer and 30 percent proprietary acrylic resins. This balance offers optimal adhesion, weatherability and UV durability properties.

LONG-LASTING GLOSS

SMP coating systems are created by combining a durable polyester resin backbone with silicone-based polymers to achieve longer-lasting gloss and color retention than what would be achieved by the polyester resin alone.

SMP molecules are based on carbon-hydrogen, carbon-oxygen, carbonsilicone and silicon-oxygen bonds. While these chemical bonds are strong, they are generally less robust than those found in fluoropolymers, making them more vulnerable than PVDFs to long-term UV exposure that can degrade the coating.

COST & MARKET APPLICATIONS

From both a performance and price perspective, fluoropolymers are a premium coating system. For applications that demand the highest durability, 70 percent PVDF fluoropolymer coatings are regarded as the top choice due to their strong resistance to UV exposure, humidity and pollution. They are the preferred system for use on metal roofing, curtain walls, wall panels and monumental applications like skyscrapers, stadiums and high-end commercial buildings.

PVDFs have a long lifespan and require less maintenance over time, but they do come with a higher applied cost.

Based on both cost and performance, silicone-modified polyesters are considered to be a solidly strong mid-tier market solution, positioned between standard polyesters and PVDF formulations. Competitively priced SMPs have an attractive price-to-performance ratio, making it the favored coating for the pre-engineered building industry for functional structures like warehouses, storage, pole buildings, barns and residential applications.

PHYSICAL PERFORMANCE

PVDF formulations are known for their color retention properties, as well as unmatched resistance to UV radiation, moisture, dirt, airborne particles, acids, pollutants and chemicals. Because the PVDF polymer is highly fluorinated and inert, PVDF-based coatings offer superior resistance to weather, even in extreme climates.

PVDF-based coatings also are very flexible, which helps to prevent fractures that can occur during manufacturing and roll-forming process. In some instances, however, the thermoplastic nature of PVDF may have a higher propensity to damage from handling or installation, requiring a higher level of care.

One of the primary benefits of a silicon-modified polyester coating is a hard, durable finish that has excellent resistance to scratches and abrasions. Depending on the application and its environment, SMPs are increasingly becoming a viable, lower-cost alternative to PVDFs. Plus, recent advancements in resin and pigment technologies are making it applicable for a wider range of architectural, residential and commercial projects.

WEATHERING

In terms of long-term weathering, film integrity, color change and chalking are three primary concerns. The type of coating system used has a direct impact on these performance measures.

Film integrity is defined as the absence of peeling, chalking, chipping or cracking over an extended period.

Chalking is a powder-like substance on the surface of a coating, a result of the breakdown of resins and pigments from UV radiation. Chalking eventually leads to loss of color and gloss and the ultimate degradation of film integrity. In accordance with ASTM D4214- 98 test procedures, it is measured by rubbing the weathered coated surface with a soft fabric and measuring the amount of powder that is picked up on a scale from 1 (extremely poor) to 10 (perfect).

PVDF coatings are typically used on monumental buildings

COMPARISON

BREAKING DOWN BENEFITS

PVDFs

• Well-suited for extreme environments

• Best for intense sun exposure

• Proven performance across a wide color space

• Color stability for decades

• Optimal warranty for chalking and fading

• Good film adhesion

SMPs

• Superior film adhesion

• Available with cool coating technologies

• Attractive price-to-performance ratio

Fade is measured in terms of the change in color and gloss from its original application state, per ASTM D2244-02 procedures. After extended years of UV exposure, PVDF coatings and polyester coatings will react differently in exterior environments. In the initial years of exposure, both systems will have a slight shift in color fade and chalk values, yet, over time, their differences become more apparent.

SMPs and PVDFs both have similar, excellent film adhesion and surface performance, but SMPs are less durable over the same extended period than PVDF coatings in terms of weatherability, colorfastness, gloss retention and chalking.

Manufacturers need to weigh the loss in aesthetic and protective performance against premium priced PVDF systems.

TESTING HISTORY

When it comes to proven performance in the field, PVDF coatings reign supreme. Since their debut in the 1960s, they have been continuously subjected to exposure testing in South Florida’s subtropical climate and analyzed against multiple coatings chemistries. Monumental buildings around the world protected with PVDF systems illustrate the value of these formulations.

Although SMPs lack 50 plus years of testing data, they have undergone exposure testing in South Florida for over 25 years, giving manufacturers and coating companies valuable insights and confidence in the long-term weatherability of their products.

PVDFs have a long, well-documented history as one of the most widely used coating systems for the premium building products exterior market, heralded for performance, film integrity and long-lasting resistance to chalking, fading and extreme weather conditions.

SMP coating systems are a strong choice for a wide market of building end uses with robust film properties that are engineered to last and meet the demands of roll formers and installers. While they provide a tough finish and are more economically priced than PVDFs, SMPs are more vulnerable to chalking and fading with longterm exposure. Due to their competitive pricing and durable finish, they are popular options for residential, industrial and agricultural uses.

PPG Industrial Coatings, 888/774-4332, ppg.com

 

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