Full Bubble Elimination for Silicone! Defoaming Field Test for Potting & Sealing

Solve bubble issues in silicone potting, sealing and thermal pads, covering low-viscosity LSR to high-viscosity pastes


Silicone is an elastic polymer based on polydimethylsiloxane (PDMS). It features outstanding high & low temperature resistance (-60℃~250℃), electrical insulation, hydrophobicity and biological inertness. Classified by curing mechanism into addition-curable (platinum-catalyzed) and condensation-curable types. Widely used in electronic potting, LED encapsulation, thermal interface materials (TIM), building sealing, medical devices, cosmetics and personal care products. Air is easily entrapped during silicone stirring, filler dispersion and dispensing. Some systems feature ultra-high viscosity and strong thixotropy. Residual bubbles may trigger poor insulation, decreased thermal conductivity, sealing failure and surface defects. SIENOX delivers efficient defoaming solutions for various silicone materials via self-developed planetary mixing & defoaming technology.


◆ Material Properties

Matrix Type

Addition-curable (platinum catalyst), Condensation-curable (tin-catalyzed / oxime-type / alcohol-type)

Filler System

Fumed silica, thermally conductive alumina / boron nitride, calcium carbonate, color pigment

Viscosity Range

500~500,000+ cps, from free-flowing liquid to high-viscosity paste

Mixing Ratio

One-component RTV / two-component 1:1~10:1 / LSR injection molding

Curing Condition

Room temp curing / heating 100-150℃ / high temp vulcanization 170-200℃

Defoaming Challenges

High-filled thermal silicone with strong thixotropy; platinum-catalyzed systems highly sensitive to air bubbles


◆ Mature Application Fields

🔌 Electronic Potting

Potting protection for power modules, LED drivers, sensors, connectors and other electronic components (viscosity 1,000~15,000cps)

💡 LED Encapsulation

Encapsulation lens for LED chips/strips/modules, requiring high transmittance and resistance to high-temperature yellowing (low-viscosity high-transparency system)

🔥 Thermal Interface Materials

Thermal silicone pads, thermal conductive gels, thermal gap fillers (high-filled alumina/boron nitride, viscosity 50,000~300,000cps)

🏗️ Building Sealing

Curtain wall structural adhesive, door & window sealant, stone bonding adhesive, insulating glass sealing (high-viscosity high-thixotropy system)

🏥 Medical / Daily Chemical

Medical-grade silicone tubes, catheters, nipples, cosmetic injection fillers, defoaming for cosmetic formulations

🔋 New Energy Battery

Thermal pads for battery modules, battery pack sealing & potting, three-proof coating for BMS circuit boards (flame-retardant thermal conductive system)

🎨 Crafts / Molds

Silicone mold reproduction, silicone molds for resin/candle/soap, food-grade silicone products (low & medium viscosity system)

🚗 Automotive Sealing

Lamp sealing, windshield bonding, engine gasket forming, wire harness waterproof sealing (oil & weather resistant system)

⚡ PV Modules

Potting for PV junction boxes, terminal sealing, module frame sealing (weather-resistant & anti-UV system, 25-year service life requirement)


◆ Core Problems Caused by Bubbles

⚡ Degraded Insulation / Thermal Performance

Internal bubbles create thermal resistance / electrical weak points. Thermal conductivity drops by 30-50%, breakdown voltage decreases significantly and heat dissipation deteriorates

🔘 Surface Defects & Sealing Failure

Burst surface bubbles form pinholes and pits. Risk of leakage on sealing interface increases, failing waterproof & moisture-proof requirements

🧪 Abnormal Curing

Bubbles hinder full contact of A/B components, resulting in incomplete local curing, tackiness, soft spots and uneven rebound

💡 Deteriorated Optical Performance

Bubbles scatter light in LED encapsulation lenses and optical-grade silicone, reducing transmittance, causing uneven light spots and lower luminous efficiency


◆ Recommended Process — Planetary Mixing & Defoaming

Step 1 Material Preparation

Weigh silicone base material and curing agent/crosslinker according to ratio. Ensure accurate proportion of A/B for two-component systems; preheat high-viscosity materials to 40-60℃ to reduce viscosity

Step 2 Vacuum Mixing & Defoaming

Put mixture into mixing cup, set vacuum at -95KPa and planetary mixing parameters. The machine completes mixing and vacuum defoaming synchronously in one cycle

Step 3 Dispensing / Pouring

Dispense or pour immediately after defoaming. Pour slowly along container wall to avoid re-entrapped air; finish operation within pot life

Step 4 Curing & Forming

Cure under specified temperature & duration. For addition-curable silicone, avoid platinum catalyst poisoning from sulfur or phosphorus-containing materials


◆ Recommended Equipment

  1. MIX60 — Capacity 5~60g, suitable for lab R&D and small batch potting sample defoaming; excellent effect for low-viscosity silicone (500~10,000cps)

  2. MIX90 — Capacity 20~500g, suitable for medium-batch production and medium-viscosity thermal silicone (10,000~80,000cps) defoaming; uniform planetary mixing

  3. MIX1000PLUS — Capacity 100~1,000g, suitable for mass production and defoaming of high-viscosity high-filled thermal gel / sealant (80,000~300,000+ cps)

  4. MIX2000 — Capacity 500~2,000g, suitable for industrial continuous production and batch defoaming of large potting parts


◆ Test Cases

▶ Case 1: Low-viscosity Electronic Potting Silicone Defoaming

Test Material

Two-component addition-curable silicone potting compound (for LED driver power supply potting, A/B=1:1, transparent free-flowing liquid)

Initial Viscosity

3,000 cps (25℃)

Test Model

MIX60

Vacuum Level

-95 KPa

Rotation Speed

1,500 rpm

Defoaming Time

3 min

Material Temp.

25℃ (Ambient)

✅ Defoaming Result: Mixing + defoaming finished in 3 minutes. No visible bubbles on cross-section of potting part, transmittance＞95%, Shore A hardness 25 after curing, breakdown voltage＞20KV/mm, meeting potting requirements for LED driver power supplies.


▶ Case 2: Medium-viscosity Thermal Silicone Defoaming

Test Material

Thermal conductive silicone gel (for CPU/GPU heat dissipation, high-filled alumina thermal powder, A/B=1:1, grey paste)

Initial Viscosity

35,000 cps (25℃)

Test Model

MIX90

Vacuum Level

-95 KPa

Rotation Speed

2,000 rpm

Defoaming Time

5 min

Material Temp.

40℃ (preheat for viscosity reduction)

✅ Defoaming Result: Mixing + defoaming finished in 5 minutes. Cross-section porosity of thermal gel＜1%, thermal conductivity stable at 3.5 W/m·K, interfacial thermal resistance reduced by 40%, meeting requirements for consumer electronics heat dissipation modules.


▶ Case 3: High-viscosity Building Sealant Defoaming

Test Material

One-component dealcoholized silicone building sealant (curtain wall structural adhesive, high-thixotropy paste, with calcium carbonate reinforcing filler)

Initial Viscosity

150,000 cps (25℃)

Test Model

MIX1000PLUS

Vacuum Level

-95 KPa

Rotation Speed

2,500 rpm

Defoaming Time

8 min

Material Temp.

50℃ (preheat for viscosity reduction)

✅ Defoaming Result: Mixing + defoaming finished in 8 minutes. Sealant extrudes continuously without bubble breakage, smooth surface free of pinholes, elongation at break＞400%, no cracking after weathering test (1000h UV aging), meeting standards for building curtain wall sealing.


◆ Before & After Comparison

Comparison Item

Before Defoaming

After Defoaming

Internal Density

Cross-section porosity 5-15%, uneven distribution

Cross-section porosity＜1%, uniform & dense structure

Thermal Conductivity

Bubbles cause thermal insulation, low & fluctuating measured values

Stable thermal conductivity, interfacial thermal resistance reduced by 40%

Curing Integrity

Local tackiness & soft spots, uneven curing

Fully & evenly cured, consistent hardness/elasticity data

Sealing & Waterproof Performance

Bubble channels cause leakage, IP rating failure

Complete sealing interface, stable IP67 protection rating

Transmittance (Optical Parts)

Light scattered by bubbles, hazy & whitening

Transmittance＞95%, optically clear & uniform

Yield Rate

High rework rate, poor batch consistency

Yield＞99%, stable & controllable batches


🎯 Free Sample Testing    
      Send your silicone samples to us. We will test defoaming parameters and issue test reports.