With China’s 14th Five-Year renewable energy plan progressing, cumulative PV installations exceeded 500 GW in 2025. For outdoor service life beyond 25 years, the reliability of module frame sealants has become a major focus. The key to long-term performance lies in an often-overlooked ingredient—high-end silicone—which determines whether the sealant can withstand UV exposure, humidity, and thermal cycling.
Traditional methyl silicone oils are low-cost but prone to main-chain breakage under intense UV, causing hardening, cracking, and yellowing, which leads to moisture ingress, cell corrosion, and power loss. In contrast, phenyl-modified silicone oils, with their benzene ring structure, effectively absorb and dissipate UV energy, significantly enhancing polymer chain stability.
Accelerated QUV aging tests (ASTM G154, 3000 h) show:
Sealants with standard methyl silicone yellow noticeably (Δb* > 8), retain only 62% tensile strength, and elongation drops from 400% to 150%.
Formulations with high-purity phenyl silicone (≥15 % phenyl) show almost no yellowing (Δb* < 2) and maintain >85% elasticity with good stress buffering.
“PV modules in desert regions can reach 85 °C in summer and drop to –40 °C in winter. Sealants must stretch and compress like a ‘rubber spring’ without failing,” says a leading sealant R&D director. “Phenyl silicone not only enhances weather resistance but lowers the glass transition temperature (Tg), ensuring low-temperature elasticity.”
Top-tier sealant manufacturers now standardize phenyl silicone for high-end products and require batch-level UV resistance data and low volatile content (<1 % @150 °C/4 h). Some collaborate with silicone suppliers to develop custom narrow-distribution phenyl silicones, optimizing crosslink density and long-term modulus stability.
As high-efficiency N-type TOPCon and perovskite modules demand greater encapsulation reliability, sealants have evolved from “supporting materials” to “lifetime protectors.” In this 25-year durability race, a single drop of high-end silicone may be the key barrier preventing premature failure of megawatt-scale solar plants.
