Potting compound

一、Comparison of the three mainstream systems (most commonly used in the energy storage/power supply industry)

1. Epoxy resin sealant (epoxy EP)

• High hardness (Shore D70~85), high adhesive strength, excellent insulation, chemical solvent resistance, moderate cost, and bright surface;
• Easy to achieve UL94 V-0 flame retardancy and mature high thermal conductivity modification solutions.
  ❌shortcoming
• The texture is brittle and prone to cracking under cold and hot shock；
• After curing, it becomes hard and almost impossible to repair；
• Narrow temperature range: conventional -40~130 ℃。
  Applicable: Transformers, inductors, capacitors, ordinary drive power supplies, equipment that does not require post maintenance, and equipment with small environmental temperature differences.

2. Silicone potting adhesive (silicone rubber/silicone gel SI)

• Elastic colloid, extremely low stress, excellent resistance to thermal shock；
• Wide temperature resistance: -60~220 ℃, long-term high temperature stability；
• Extremely low shrinkage rate, repairable (peelable/pry open for repairing circuit boards)；
• Can achieve high thermal conductivity, high temperature resistance, flame retardancy, and non corrosive components。
  ❌shortcoming
• Weak adhesion to plastics and metals；
• Price higher than epoxy; The surface is prone to getting dusty。
  Applicable: Energy storage BMS, power battery module, vehicle electronic control, outdoor power supply, high-power module, scenarios requiring after-sales maintenance and large temperature differences (mainstream selection of energy storage cabinets)。

Silicon gel: super soft, self-healing, extremely low stress, mostly used for precision sensitive components。

3. Polyurethane sealant (PU)

• Good toughness, excellent shock absorption, excellent adhesion, outstanding moisture and mold resistance；
• Excellent low-temperature performance, adjustable hardness。
  ❌shortcoming
• Long term low temperature resistance limit (generally ≤ 85~120 ℃)；
• Curing is sensitive to humidity, and high humidity can easily cause foaming; Outdoor long-term UV aging resistance is generally good。
  Applicable to: small sensors, photovoltaic junction boxes, and low heat vehicle components。

二、Key functional subdivision models

1. Thermal Potting Compound
   Adding aluminum oxide and aluminum nitride fillers, with a thermal conductivity of 0.6-5.0 W/m · K, to solve the heat dissipation of power devices, energy storage PCS, and inverters are widely used。
2. Flame retardant sealant
   Requirement UL94 V-0, essential for energy storage and lithium batteries; Prioritize halogen-free flame retardant to meet the safety standards for new energy vehicles/energy storage。
3. Low viscosity sealant
   Strong liquidity, suitable for dense components, narrow gaps, and vacuum sealing that is not prone to bubble accumulation。
4. Transparent potting adhesive (epoxy/silicone)
   Use of LED light sources and optical modules。

三、Standard sealing process flow

1. Component/shell cleaning, dehumidification and baking
2. A. Mix component B accurately in proportion
3. Vacuum degassing (key! Prevent internal bubbles from causing poor pressure resistance)
4. Vacuum glue injection/slow injection under normal pressure
5. Room temperature curing for 24 hours or accelerated curing by heating (60-80 ℃)
6. Electrical testing after cooling (insulation, withstand voltage)

四、Quick selection reference for energy storage cabinet industry (suitable for your industry)

1. BMS control board, acquisition board → addition of organic silicon thermal conductive flame-retardant sealant (repairable)
2. Power inductor, power frequency transformer → epoxy thermal conductive sealant (pursuing structural strength and low cost)
3. Cell module encapsulation/thermal barrier → high thermal conductivity organic silicon/foamed polyurethane
4. Do not allow later opening and maintenance, pursue strength → epoxy
5. Large temperature difference, outdoor working conditions, requiring maintenance → Organic silicon

五、Common Failure Issues

• Internal bubbles: lack of vacuum degassing, rapid infusion speed
• Colloidal cracking: Excessive thermal shock stress on epoxy and incorrect selection of adhesive
• Adhesive delamination: Oil stains on the surface of the shell have not been cleaned, and there is a lack of primer for the silicone coating
• Incomplete curing: incorrect ratio, insufficient mixing, insufficient curing temperature

  Foshan Zhiwei Adhesive Products Co., Ltd. has professional matching solution experience regarding sealing adhesive materials. We welcome inquiries from major manufacturers and contact email：yang@fszw-tapes.com。