Technology Trends in Aging Resistance of Rubber Components for Photovoltaic Products

As key sealing and structural materials in photovoltaic products, rubber components are long-term exposed to complex outdoor environments (such as ultraviolet radiation, extreme temperatures, humidity, ozone, etc.), and their aging resistance performance directly affects the reliability and service life of the modules.

1. Molecular structure advantage: With Si-O bonds as the main chain, the bond energy is as high as 452 kJ/mol, much higher than that of C-C bonds (348 kJ/mol), providing excellent thermal stability and weather resistance.
2. Temperature resistance range: Operating temperature can reach -65℃ to 204℃, significantly better than EPDM (-50℃ to 120℃), suitable for high-temperature environments.
3. UV and ozone resistance: Can withstand long-term UV radiation and ozone erosion without additives, and the surface is not prone to cracking.
4. Typical applications: Sealing strips for photovoltaic modules (e.g., LZ1501 series), junction box seals, which can withstand over 25 years of outdoor aging.

1. Cost advantage: Price is about 1/3 of silicone rubber, suitable for cost-sensitive scenarios (e.g., bracket gaskets).
2. Weather resistance limitations: Prone to oxidative hardening at high temperatures (>100℃), requiring antioxidants; ozone resistance depends on formula design, and surface cracks may occur during long-term outdoor use.
3. Improvement direction: Nano-composite technology (e.g., adding TiO₂ particles) can enhance its UV resistance and delay aging.

1. Water vapor barrier performance: Water vapor transmission rate is only 1/200 of natural rubber, suitable for edge sealing of new battery modules sensitive to humidity such as HJT and perovskite.
2. Limitations: Low mechanical strength, requiring composite use with other materials.

1. Ultraviolet rays (290-400 nm) induce molecular chain scission of rubber, generating free radicals and accelerating oxidation reactions. The Si-O bonds of silicone rubber have weak absorption of ultraviolet rays, while the carbon-carbon double bonds of EPDM are vulnerable to attack.
2. Typical manifestations: Surface yellowing, hardening, and cracking (e.g., EPDM strips in coastal salt spray environments show cracks within 3 years).

1. High temperatures (>85℃) accelerate oxidation reactions, leading to decreased crosslink density (silicone rubber) or molecular chain scission (EPDM), and a significant increase in compression set.
2. Test verification: Hardness change of silicone rubber after 200℃×1000h is <5%, while that of EPDM increases by 15% after 120℃×1000h.

1. High humidity environments (e.g., double 85 test: 85℃/85% RH) may cause rubber swelling and hydrolysis, reducing mechanical properties; salt spray in coastal areas accelerates corrosion of metal inserts, leading to interface failure.

1. Long-term thermal expansion and contraction (diurnal temperature difference up to 50℃) cause rubber stress relaxation and increased compression set (e.g., the elastic modulus of EPDM at -40℃ increases to 3 times that at room temperature).

1. Hardening or cracking of rubber leads to water ingress into modules, causing corrosion of battery cells (e.g., annual power generation loss of 12% in a power station due to aging of strips).
2. Critical indicator: Compression set must be ≤25% (ASTM D395, 70h×150℃); otherwise, elastic recovery is insufficient after long-term compression.

1. Reduced bonding strength at the interface between rubber and aluminum alloy profiles (e.g., pull-out force <40N) leads to module displacement or detachment.
2. Improvement measures: Surface treatment with γ-aminopropyltriethoxysilane can increase bonding strength by more than 30%.

1. Decreased volume resistivity after aging (<10¹²Ω·cm) may cause leakage risks.

1. The hardness of silicone rubber should be controlled at 35-45 Shore A (ISO 48) to ensure tight fit with the contact surface; tensile strength ≥8MPa (ISO 37) to prevent tearing.

1. Tested by ASTM D395: set of silicone rubber after 150℃×70h ≤25%; set of EPDM after 100℃×70h ≤35%.

1. Silicone rubber must pass 200℃×1000h test, with hardness change ≤5% and tensile strength retention ≥80%.
2. Standard reference: GB/T 3512-2014 (equivalent to ISO 188).

1. Simulating 10 years of outdoor aging (1000h test), requiring no surface cracks and color difference ΔE ≤3 (ISO 16474-3).
2. Key parameters: Irradiance 550 W/m² (290-800 nm), black panel temperature 65℃, humidity 65%.

1. Stretched by 20% and exposed to 50pphm ozone concentration for 48h: silicone rubber shows no cracks; EPDM needs ozone-resistant additives to meet the standard (ISO 1431-1).

1. Silicone rubber has no brittleness at -60℃ (ASTM D746); EPDM must pass the -50℃ test.

1. Salt Spray Corrosion
   Coastal areas must pass 500h neutral salt spray test (ISO 9227) with surface corrosion grade ≥8.
2. Damp Heat Aging
   After 1000h of double 85 test (85℃/85% RH), volume resistivity decrease ≤20% and dielectric strength ≥20kV/mm.

1. Adding 5%-10% nano-TiO₂ particles to silicone rubber can increase UV absorption rate from 60% to 95%, and optimize interface bonding through molecular dynamics simulation (e.g., Rutile-type TiO₂ rearranges methyl groups in PDMS segments, reducing diffusion rates of water and hypochlorous acid).
2. Performance breakthrough: Tensile strength retention after aging increases from 70% to 85%, and weather resistance life extends by 5-8 years.

1. Using platinum-catalyzed addition-cure silicone rubber, crosslinked with tetramethyltetravinylcyclotetrasiloxane and hydrogen-containing silicone oil, can reduce compression set from 30% to 15%.
2. Typical case: A photovoltaic strip achieves compression set ≤20% within a 25-year warranty period through this technology.

1. Designing 0.5-0.8mm high sawtooth on the rubber surface (spacing ≥3.5mm) can increase glass pull-out force from 20N to over 60N.
2. Application scenario: Edge sealing of double-sided modules to prevent displacement caused by wind load.

1. Composite use of butyl rubber and silicone rubber (e.g., inner butyl for water resistance + outer silicone rubber for anti-aging) can simultaneously meet water vapor barrier (transmission rate <0.1g/m²·d) and weather resistance requirements.

1. Superhydrophobic Coating
   Using nano-silica coating (thickness 50-100nm) with contact angle ≥150% can reduce dust adhesion by over 90% and lower cleaning frequency (e.g., Jierui nano-coating reduces annual power generation loss from 8% to 2%).
2. UV-resistant Coating
   Coatings containing zinc oxide quantum dots can absorb over 90% of ultraviolet rays below 380nm, protecting rubber substrates and delaying aging.

1. Core requirements: Silicone rubber must pass 200℃×1000h thermal aging, 1000h xenon lamp aging without cracks, and compression set ≤25%.
2. Testing process: 6 core indicators including hardness, tensile strength, and ozone resistance must be inspected for each batch; pre-production test cycle is 5 years.

1. Ozone resistance test: Silicone rubber shows no cracks after 48h exposure to 50pphm concentration; EPDM needs ozone-resistant additives to meet the standard.

1. Accelerated aging: Xenon lamp aging test must simulate 10 years of equivalent outdoor aging (1000h) with surface cracking grade ≤1.

1. Flame retardancy requirement: Rubber components must reach V-0 level to prevent fire spread.