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Differences in Production Equipment for Silicone Products and Rubber Products

Notes: Rubber: Generally refers to solid synthetic rubber (NR natural rubber, SBR, NBR, EPDM, CR neoprene, etc.) vulcanized at high temperature. Silicone: Normally divided into High-Temperature Vulcanized solid silicone rubber (HTV) and Liquid Silicone Rubber (LSR). Although internal mixers, extruders and vulcanizing presses can be shared in some cases, there are distinctions in configuration, temperature control, auxiliary machines and process parameters.

1. Overview Comparison of Core Equipment

表格

Equipment Category	Conventional Rubber Production Line (EPDM/NBR/NR etc.)	Solid Silicone HTV Production Line	Liquid Silicone LSR Production Line
Mixing Equipment	Banbury Internal Mixer + Open Mill 1. The internal mixer withstands high filling and high shearing; 2. Two-wing/four-wing rotors with powerful ram; 3. Mixing temperature ranges from 120℃ to 160℃, requiring intensive cooling; 4. Heavy dust emission (carbon black, calcium carbonate), equipped with carbon black feeding system and dust removal device; 5. Wear protection: large-area hardfacing with wear-resistant alloy.	Kneader + Open Mill (small production may use internal mixer) 1. Silicone features high viscosity and low heat generation; mild shearing is required. High-strength internal mixers are not recommended (prone to air entrapment and molecular degradation); 2. Rare use of carbon black; mainly silica which tends to agglomerate; 3. Mixing temperature controlled ≤110℃ to strictly limit temperature rise; 4. High cleanliness requirement to avoid metallic contamination; polished mixing chamber to prevent rust; 5. Kneader performs better for silica dispersion.	No internal mixer / open mill required A/B two-component liquid feeding unit & static mixer for direct injection molding.
Extrusion Equipment	Hot-feed extruder / cold-feed extruder for rubber 1. Extrusion temperature: 60~110℃; 2. Screw with relatively large length-diameter ratio, suitable for rubber plasticization; 3. Mainly barrel water cooling; 4. Widely used for rubber strips, hoses and tread.	Silicone-specialized cold-feed extruder 1. Optimized screw structure to reduce shear heat; 2. Lower barrel temperature control; 3. Mirror-polished head and flow channel to avoid material accumulation; Matched with hot air continuous vulcanization tunnel.	LSR metering extrusion & injection unit with closed conveying to avoid air entrapment.
Main Vulcanizing Equipment	Plate Vulcanizing Press (Hydraulic Press) 1. Vulcanization temperature: 145~170℃; 2. Relatively long molding cycle; 3. Optional water cooling for hot plates; 4. Conventional precision of mold cavities; Widely adopted for miscellaneous rubber parts and seals.	Plate Vulcanizing Press (mechanically interchangeable but different configuration requirements) 1. Vulcanization temperature: 160~185℃; 2. Higher temperature uniformity requirement of hot plates (±2℃); 3. Silicone easily sticks to molds; mold release agent spraying system is often equipped; 4. Silicone products tend to form bubbles, demanding higher mold clamping precision; Vacuum plate vulcanizing presses are preferred for high-end silicone products.	LSR Liquid Silicone Injection Molding Machine High-pressure closed injection with vacuum venting; structurally different from rubber compression molding presses.
Post-Curing / Secondary Baking	Secondary vulcanization is unnecessary for most rubber types (except partial EPDM grades).	Post-curing oven is mandatory Temperature: 200~220℃, holding time: 2~4 hours, for removing low-molecular volatiles and stabilizing physical properties.	Post-curing oven is also required.
Dust Removal & Environment	Heavy carbon black dust; independent dust extraction and separated workshop area.	White silica dust; co-production with black rubber is prohibited to avoid cross-contamination.	Highest requirements for clean workshop environment.
Material Conveying System	Carbon black conveying system & automatic powder feeding system.	Silica feeding system with sealed dust suppression; mirror-polished equipment inner surface.	Closed fluid conveying, no dust generation.

2. Detailed Key Differences in Equipment

2.1 Mixing Process (Largest Variation)

✅ Conventional Rubber (NBR/EPDM/NR) Main Equipment: Banbury Internal Mixer

High shear force breaks carbon black; substantial heat generation during mixing, requiring powerful cooling system.
Heavy ram pressure; rotors adopt wear-resistant hardfacing to resist abrasion from hard fillers.
Allowable temperature of mixed compound reaches 140~160℃.
Carbon black contained in formula; high surface finish of equipment is not required.

✅ Solid Silicone Rubber (HTV) Main Equipment: Kneader

Silica is prone to agglomeration; high-torque & low-shear slow kneading is required.
Overheating must be avoided. Temperature exceeding 115℃ may cause premature scorch and polymer degradation.
Inner cavities, rotors and rams are mirror-polished to prevent material buildup and rust contamination to silicone.

Important Note: An internal mixer can be temporarily used for silicone mixing, but it is not suitable for mass long-term silicone production. A kneader cannot handle high-intensity mixing of carbon black-filled rubber.

2.2 Plate Vulcanizing Press (Common Basic Structure, Different Supporting Requirements)

Similarity: The frame, oil cylinder and hydraulic system share identical basic structure. Differences:

Temperature control: Silicone production requires smaller temperature deviation of hot plates.
Vacuum configuration: Most high-end silicone sealing parts require vacuum system to evacuate air inside molds and prevent bubble defects; vacuum is unnecessary for many conventional rubber products.
Molds: Higher surface finish standard for silicone molds.
Energy consumption: Higher heating power configuration due to higher silicone vulcanization temperature.

2.3 Continuous Vulcanization Extrusion Line

Rubber extrusion: Hot-feed extruder matched with salt bath or steam vulcanization tank.
Silicone extrusion: Cold-feed extruder + hot air vulcanization tunnel. Contact with water or salt bath is forbidden, as silicone easily foams under high temperature with water contact.

2.4 Auxiliary Equipment Differences

Oven Silicone production is equipped with post-curing oven as standard; most rubber products do not need it.
Cleaning Requirement Extremely strict color change requirement for silicone production lines. Black rubber production line and silicone production line must be separated without shared equipment. Trace carbon black will cause black speck defects on silicone parts.
Cooling System Larger cooling water flow required for rubber internal mixers; silicone kneaders focus on precise temperature control to avoid local overheating.

3. Selection Summary (Concise Version for Foreign Customer Proposal)

Manufacturing conventional rubber products (NBR, EPDM, NR, CR) Recommended process flow: Banbury Internal Mixer → Open Mill → Extruder / Plate Vulcanizing Press
Manufacturing solid HTV silicone miscellaneous parts & silicone seals Recommended process flow: Vacuum Kneader → Open Mill → Vacuum Plate Vulcanizing Press + Post-Curing Oven
Liquid Silicone LSR Products Adopt dedicated LSR injection machine; no internal mixer or open mill is needed.

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