UL Grants RTI Rating to Arkema's Black Kynar® Film Used for PV Backsheet

Arkema Inc. announces that Underwriters Laboratory (UL) has granted a final Relative Thermal Index (RTI) rating of 150°C mechanical and 140°C dielectric for its black Kynar® film, used in the construction of photovoltaic backsheet. This RTI rating is among the highest that has been granted by UL. The new, black version of Kynar® film will enable solar panel module makers to source black Kynar®-based backsheets to produce modules which can be more visually appealing and consistent in color to the dark silicon cells.

The backsheet provides insulation and protection from electric shock. The Kynar® film typically is the outer layer of the backsheet laminate structure, where PET film is used as the primary dielectric layer. However, PET weathering performance and hydrolysis resistance is poor.

"The primary function of the Kynar® film is to protect the PET such that the backsheet does not degrade over the life of the module," said Ron Partridge, senior business development engineer for Arkema's North American fluoropolymers photovoltaic market. "Kynar® film provides outstanding protection for the PET layer and resists degradation because it is extremely resistant to weathering and provides long-term UV protection for the underlying PET film. Kynar® film also resists moisture and environmental pollutants, Partridge noted. The low surface energy of the film provides excellent dirt shedding properties and is inherently resistant to mold and mildew growth," he added.

Kynar® PVDF polymer has been widely used in architectural coatings for more than 40 years and is an exceptional resin for weather-resistant coatings. Kynar® PVDF coatings showed excellent weathering performance after 42 years of continuous exposure in South Florida, based on Arkema's long-term weathering studies. This same weathering performance can be expected from Kynar® film and is seen in very aggressive and accelerated QUV-B weathering tests.

"The excellent thermal stability, coupled with the long-term weathering protection, will provide extremely durable protection for photovoltaic backsheets," said Partridge.