As the global shift to renewable energy speeds up, photovoltaic (PV) and energy storage systems (ESS) face severe long-term outdoor environmental risks. With a 25-year service life, these installations endure extreme temperature cycles, strong UV radiation, high humidity and repeated mechanical stress. High-performance adhesives are far more than simple fasteners: they prevent critical failure, providing electrical insulation, moisture protection, thermal control and structural stability.
Part 1: Photovoltaic (PV) Solar Systems
| Application Point | Substrates / Components | Recommended Model / Type | Core Chemistry | Viscosity / Form | Key Performance Targets & Certification Benchmarks |
| Junction Box Encapsulation | PCB, Bypass Diodes, PPO/PC Shell | JOMS5230 Series | Two-Component Silicone | Low viscosity, self-leveling potting liquid | Thermal conductivity $\ge 0.6 \text{ W/m·K}$; Dielectric strength $\ge 20 \text{ kV/mm}$; UL 94 V-0 flame retardant; Operating temp: $-50^\circ\text{C}$ to $+180^\circ\text{C}$. |
| Junction Box Edge Sealing | PPO/PC Box Flange to PV Backsheet (PET/PVDF) | JOMS5339 Series | One-Component Neutral Alkoxy Silicone | Thixotropic paste, non-sag | Tensile strength $\ge 2.0 \text{ MPa}$; Elongation at break $\ge 300\%$; Excellent adhesion to unprimed plastics and fluoropolymer backsheets; Passed IEC 61215 damp heat test (85% RH / $85^\circ\text{C}$ for 1000 hrs). |
| PV Frame & Glass Edge Sealing | Anodized Aluminum Alloy to Tempered Glass | JOMS5339 Series | One-Component Structural Silicone | High tack, thixotropic paste | Shear strength $\ge 1.5 \text{ MPa}$; Shore A hardness: 40–50; UV-induced yellowing resistance ($\Delta E < 2.0$ after 2000 hrs UV exposure); Accommodates CTE mismatches. |
| Backsheet Auxiliary Components | Reinforcement Strips, Cable Clamps to Backsheet | Weather-Resistant PET Tape | Modified Acrylic Double-Sided Tape | Solid film carrier tape | Initial tack $\ge 15 \text{ N/25mm}$; Continuous peel strength $\ge 20 \text{ N/25mm}$; Resistant to plasticizer migration; Maintains adhesion under high wind loads. |
| Inverter Shell & Thermal Interfaces | Cast Aluminum/Steel Enclosure to Power Modules | JOMS5339 Thermal | Conductive Silicone Thermal Sealant | Dispensable gap filler / paste | Thermal conductivity: $1.5\text{–}3.0 \text{ W/m·K}$; Volume resistivity $\ge 1 \times 10^{14} \;\Omega\cdot\text{cm}$; Moisture vapor transmission rate (MVTR) $< 10 \text{ g/m}^2\cdot24\text{h}$; IP67/IP68 ingress protection compliance. |
Part 2: Energy Storage Systems (ESS) & Lithium Battery Modules
| Application Point | Substrates / Components | Recommended Model / Type | Core Chemistry | Viscosity / Form | Key Performance Targets & Certification Benchmarks |
| Cell-to-Cell Fixed Spacing | Prismatic/Pouch Lithium Cells (Al/PET film) | Polyurethane Foam Tape | Microcellular PU Foam + Acrylic Adhesive | Compressible tape rolls | Compression deflection resistance; High dielectrical insulation ($> 5 \text{ kV}$ breakdown voltage); Functions as an expansion cushion for cell breathing/swelling. |
| Cell-to-Cell Thermal Filling | Battery Cells to Cooling Plate / Chassis | JOMP 2651 Series | Two-Component Polyurethane | Thixotropic gap filler, structural paste | Thermal conductivity $\ge 2.0 \text{ W/m·K}$; Structural lap shear strength $\ge 6.0 \text{ MPa}$; Low volatile organic compounds (VOC); Low assembly stress injection formulation. |
| Structural Battery Supports | High-Strength Metal Brackets, Composite Trays | JOMP 2103 Series | Two-Component Structural Epoxy | High-viscosity structural paste | Lap shear strength $\ge 18 \text{ MPa}$; Impact resistance $\ge 15 \text{ kJ/m}^2$; Minimal shrinkage ($< 0.5\%$); High vibration fatigue resistance matching automotive standards (ISO 16750). |
| BMS PCB Conformal Coating | Electronic Circuitry, SMT Components | JOMS 5921 Series | Silicone Conformal Coating | Low viscosity spray/dip liquid | Dielectric constant $\le 3.0$ at $1 \text{ MHz}$; Moisture, salt spray, and sulfur resistance; Fluorescent tracer included for automated optical inspection (AOI). |
| BMS Heavy Encapsulation | Power Distribution Units, Relay Blocks | JOMP 2608 Series | Flame-Retardant Electronic PU | Medium pourable potting compound | UL 94 V-0 recognized; Thermal shock resistance (cycles from $-40^\circ\text{C}$ to $+125^\circ\text{C}$ without cracking); High volume resistivity. |
| Storage Cabinet Sealing | Enclosure Doors, Sheet Metal Joints | JOMS5339 Series | Neutral Waterproof Silicone | Non-slump elastomeric sealant | Joint movement capability $\pm 25\%$; Weathering resistance index matching ISO 11600; Total VOC emission minimized; Validated for IP66 enclosure ratings. |
| Wiring & Connector Sealing | Cable Glands, Molded Plastic Connectors | JM3302 | UV-Moisture Dual-Cure Silicone | Medium-viscosity liquid paste | Rapid UV fixture (3–5 seconds under $365\text{ nm}$ LED light) followed by deep moisture cure in shadowed areas; High elongation ($> 250\%$). |
Part 1: Comprehensive Adhesive Solutions for Photovoltaic Solar Panels
[Front Glass] —> Sealing: JOMS5339 Structural Silicone
[Solar Cells & EVA Encapsulation]
[Backsheet] ——> Component Fixation: Weather-Resistant PET Tape
[Junction Box] —> Box-to-Backsheet Sealing: JOMS5339 Series
Internal Potting/Diodes: JOMS5230 Thermal Silicone
1. Photovoltaic Junction Box Assembly
The junction box is the electrical hub of the PV module. It houses bypass diodes that prevent localized hot-spot heating.
Internal Potting (JOMS5230 Series): Diodes generate significant heat during partial shading. The JOMS5230 two-component silicone features low viscosity to flow easily around tightly packed components without creating air pockets. Its high thermal conductivity ($>0.6 \text{ W/m·K}$) transfers heat directly to the exterior, keeping diode junction temperatures below critical thresholds.
Perimeter Box Sealing (JOMS5339 Series): The interface between the junction box housing (typically modified PPO or PC) and the module backsheet is prone to mechanical stress from wind and snow. JOMS5339 provides a primerless bond to both engineering plastics and fluoropolymer backsheets (such as PVDF or Tedlar). Its exceptional moisture vapor barrier properties protect electrical contacts from corrosion over a 25-year lifespan.
2. PV Frame and Glass Panel Edge Sealing
Solar panels face severe mechanical loads from wind lifting forces and heavy snow accumulation. The perimeter seal between the glass face, backsheet, and anodized aluminum frame must act as both a structural load-bearing member and an environmental barrier.
Structural Integrity: JOMS5339 structural silicone absorbs the shear stress caused by the radically different Coefficients of Thermal Expansion (CTE) of glass ($\approx 8.5 \times 10^{-6}/\text{K}$) and aluminum ($\approx 23 \times 10^{-6}/\text{K}$).
Weathering Proofing: This formulation features an fully saturated inorganic silicone backbone ($\text{Si-O-Si}$ bonds), which possesses bond energy higher than the energy of terrestrial UV radiation. It prevents chalking, cracking, and loss of adhesion from prolonged outdoor exposure.
3. Backsheet Auxiliary Components Fixation
Fixing cables, routing clips, and structural reinforcement rails requires rapid, reliable initial assembly.
PET Double-Sided Tape: Utilizing a high-performance cross-linked acrylic adhesive chemistry on a stable PET carrier film, this tape provides immediate green strength during assembly. It resists environmental degradation, plasticizer migration from cable jackets, and does not yellow or degrade under prolonged high-humidity and UV exposure.
4. Photovoltaic Inverter Enclosures
Inverters convert DC power to grid-ready AC power, experiencing significant thermal flux and electromagnetic interference (EMI) risks.
Sealing & Heat Dissipation: JOMS5339 modified conductive thermal sealant seals cabinet seams against rain and dust (IP66 or higher). Simultaneously, it serves as a dispensable thermal interface material when applied between high-power IGBT modules and internal heat sinks, facilitating continuous cooling.
Part 2: Advanced Adhesives for Energy Storage Systems (ESS)
[ESS Cabinet Outer Shell] —> Sealing: JOMS5339 Neutral Silicone
[Battery Module Chassis] —-> Structural Assembly: JOMP 2103 Epoxy
[Cell-to-Cell Array] ——–> Spacing/Cushion: Polyurethane Foam Tape
|————————-> Thermal Management: JOMP 2651 PU Adhesive
[BMS Controller PCB] ——–> Moisture/Salt Protection: JOMS 5921 Conformal Coating
1. Battery Pack Module Assembly
Lithium-ion battery packs require a balancing act of rigid structural hold, efficient heat removal, and impact absorption.
Cell Expansion Management (PU Foam Tape): Lithium-ion cells naturally expand and contract during charge and discharge cycles (cell breathing). Microcellular polyurethane foam tape provides a precise physical gap, absorbing these volumetric changes while maintaining constant pressure across the cell faces to prevent delamination.
Thermal Structural Bonding (JOMP 2651 Series): The JOMP 2651 two-component polyurethane adhesive bonds cell groups to liquid-cooling plates. It provides dual functionality: high mechanical structural strength to eliminate heavy mechanical fixtures, and optimized thermal pathways ($\ge 2.0 \text{ W/m·K}$) to keep cell temperatures uniform, preventing localized thermal runaway.
Frame and Bracket Support (JOMP 2103 Series): For heavy structural sub-assemblies, JOMP 2103 structural epoxy provides premium shear and tensile strength ($>18 \text{ MPa}$). It exhibits low shrinkage during cure, avoiding induced stresses on cells, and tolerates high dynamic shock and vibrational forces encountered during transport and operations.
2. BMS PCB Encapsulation and Protection
The Battery Management System (BMS) controls balancing circuits and communication protocols. It must be protected from condensation, dust, and corrosive gases.
Conformal Coating (JOMS 5921 Series): Applied as a thin, uniform layer, this silicone coating insulates the PCB against micro-droplet condensation and salt spray.
Heavy Potting (JOMP 2608 Series): For sections of the BMS or power distribution unit exposed to high vibration or high voltage, JOMP 2608 polyurethane potting compound provides a robust, flame-retardant barrier. Its elastomeric nature minimizes mechanical stress on delicate surface-mount components during thermal cycling (from $-40^\circ\text{C}$ to $+125^\circ\text{C}$).
3. Energy Storage Cabinet and Wiring Seals
Cabinet Sealing (JOMS5339): Large outdoor containerized energy storage systems rely on robust outer gaskets and liquid-applied sealants. JOMS5339 neutral silicone maintains elasticity under extreme weather, sealing cabinet doors, HVAC ports, and sheet metal joints against wind-driven rain and dust.
Connector Weatherproofing (JM3302): JM3302 dual-cure UV/Moisture silicone ensures high-throughput sealing for external wiring harnesses and multi-pin connectors. The UV mechanism cures exposed fillets instantly for immediate handling, while moisture-activated curing penetrates deep into shadowed, hidden geometries over the following hours to complete the sealing process.
Outdoor Materials Selection Guide
Choosing the right adhesive core chemistry depends heavily on the specific outdoor stress factors of the application environment.
[OUTDOOR ADHESIVE SELECTION MATRIX]
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[UV / Extreme Weather] [Mechanical Loads]
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(Silicone Chemistry) (Epoxy Chemistry)
• JOMS5339 (Frame Sealing) • JOMP 2103 (Structural Metal)
• JOMS5230 (Box Potting) |
| [Thermal Management]
[Electronics Protection] |
| (Polyurethane Chemistry)
(Silicone / PU Potting) • JOMP 2651 (Cell Structural Thermal)
• JOMS5921 (BMS Coating) • JOMP 2608 (Flame Retardant Potting)
• JM3302 (UV Connector Seal)
- Silicone Base Chemistry: Ideal for components directly exposed to sunlight and broad temperature swings. Silicones offer unmatched UV stability and retention of elasticity, making them the default choice for PV Frame Sealing, Junction Box Attachment, and Cabinet Outer Interfaces.
2. Polyurethane (PU) Base Chemistry: Combines tough structural properties with targeted elastomeric behavior. PUs provide structural bonding while accommodating thermal expansion mismatches, making them ideal for Internal Battery Cell Thermal Filling and BMS Potting.
3. Epoxy Base Chemistry: Designed for rigid, high-load configurations. Epoxies deliver maximum mechanical cross-linking density for exceptional shear strength, making them the standard for Heavy Structural Racks and Storage Cabinet Brackets.
Field Application & Troubleshooting Q&A
Q1: How do you prevent adhesion failure on unprimed anodized aluminum PV frames when applying JOMS5339?
A: Adhesion failure on anodized aluminum typically results from surface contamination (such as cutting oils, processing lubricants, or dust) or incomplete oxide layer preparation.
Solution: Implement a strict “two-wipe” cleaning protocol using an oil-free solvent like Isopropyl Alcohol (IPA). Use a lint-free cloth soaked in solvent to lift contaminants, followed immediately by a second dry lint-free cloth before the solvent evaporates. Check that the anodization layer thickness is stable ($\ge 10\ \mu\text{m}$), as loose oxide structures can fail cohesively.
Q2: What causes voids during two-component junction box potting (JOMS5230), and how do they impact PV performance?
A: Voids or bubbles are generally caused by air entrapment during high-speed automated mixing, or by moisture reacting with unreacted components. Voids create localized air pockets that drastically lower thermal conductivity, causing bypass diodes to overheat. They can also lead to electrical tracking and dielectric breakdown under high-system voltages ($1500\text{V DC}$).
Solution: Optimize the automated dispensing equipment’s dynamic or static mixing nozzle geometry. Keep the dispensing tip close to the bottom of the junction box cavity to allow a bottom-up filling pattern. Ensure components A and B are stored sealed to prevent moisture absorption prior to mixing.
Q3: Why is polyurethane (JOMP 2651) preferred over epoxy for battery pack cell-to-cell structural thermal filling?
A: While epoxy adhesives deliver higher overall lap shear strength, they cure into a highly cross-linked, rigid matrix. Lithium-ion cells experience volumetric expansion during rapid charge/discharge cycles. A rigid epoxy places high compressive stress on the cell walls, which can warp internal separator films and accelerate cell degradation.
Solution: Polyurethane chemistry provides structural bonding (tensile shear $\ge 6\text{ MPa}$) alongside necessary elasticity (elongation typically $30\text{–}80\%$). This balances mechanical containment with a flexible cushion that absorbs cell expansion stress while maintaining an unbroken thermal pathway to the cooling plate.
Q4: How does moisture-shadow curing work in the UV dual-cure adhesive JM3302 for connectors, and why is it necessary?
A: UV-curable adhesives require direct line-of-sight light to activate their photoinitiators. In complex multi-pin electrical connectors or dense wiring harnesses, deep recess areas are shadowed by pins or plastic housings, leaving standard UV adhesives liquid and uncured.
Solution: JM3302 contains a secondary moisture-curing mechanism. When exposed to UV light ($365\text{ nm}$), the outer, visible fillets cure instantly (in 3–5 seconds) to securely fixture the parts. The uncured adhesive hidden in the shadowed internal zones reacts with ambient atmospheric moisture over 24 to 72 hours, completing cross-linking to ensure a reliable waterproof seal throughout the connector.
Q5: What parameters must be controlled to prevent delamination of the PET double-sided tape on backsheet components?
A: Delamination of pressure-sensitive acrylic tapes on PV backsheets is typically driven by low wet-out during application, surface energy mismatches, or plasticizer migration from components like flexible PVC cable clips.
Solution: First, ensure the application surface is clean and dry. Second, because acrylic tapes require mechanical pressure to flow into microscopic surface roughness, apply a consistent wet-out pressure of at least $20\text{ N/cm}^2$ using a roller or press. Finally, verify that the backsheet surface energy is above $38\text{ mN/m}$ to guarantee proper bonding.
Q6: Can JOMS5339 silicone sealant be applied in freezing winter conditions for outdoor storage cabinet repair?
A: Applying one-component room-temperature vulcanizing (RTV) silicones like JOMS5339 at temperatures below $4^\circ\text{C}$ introduces two primary risks: frost/condensation layers on substrates and a severely slowed cure rate. RTV silicones require atmospheric moisture to cross-link. Cold air holds very little absolute humidity, which can extend tack-free times from 30 minutes to several days.
Solution: If outdoor winter application is required, surfaces must be pre-heated with hot air blowers to remove microscopic ice or frost films. Ideally, perform repairs using a temporary heated enclosure to maintain temperatures above $10^\circ\text{C}$ and ensure sufficient ambient humidity for the silicone to cure properly.