Silicone Rubber for Cable Insulation

Silicone Rubber for Cable Insulation and Jacketing

Silicone rubber cable insulation and jacketing compounds are the solution when operating temperature, flexibility, or service environment requirements exceed what PVC, XLPE, or thermoplastic elastomers can deliver. The combination of the widest operating temperature range of any elastomeric insulation (−60 °C to +200 °C continuous), inherent flexibility at extreme cold, and outstanding electrical properties makes silicone the default choice for industrial, automotive, military, and medical cable applications.

Why Choose Silicone for Cable Insulation?

Temperature range: Silicone cable compounds operate from −60 °C to +200 °C continuously, compared to PVC (−10 °C to +70 °C), standard XLPE (−30 °C to +90 °C), and fluoropolymers (−65 °C to +200 °C but at much higher cost). In furnace and kiln environments, silicone cables operate at surface temperatures that would destroy PVC wiring within minutes.

Cold temperature flexibility: At −60 °C, PVC jacketing becomes rigid and brittle. Silicone cable retains full flexibility and can be bent, coiled, and routed without cracking. This is critical in cold-climate industrial installations, aircraft exposed to high-altitude cold-soak, and refrigeration system wiring.

Halogen-free flame retardancy: Silicone base polymer is inherently halogen-free. With alumina trihydrate (ATH) or platinum-based flame inhibitor addition, silicone cable compounds can achieve UL 94 V-0, IEC 60332 flame test, and low smoke zero halogen (LSZH) ratings. In cable fires, silicone produces a ceramic ash residue that maintains cable integrity and prevents re-ignition — a property unique to silicone among rubber cable materials.

Electrical properties: Volume resistivity >10¹⁴ Ω·cm, dielectric constant 2.8–3.0 (stable across frequency from 50 Hz to 10 GHz), and low dielectric dissipation factor make silicone suitable for both power and high-frequency signal cables.

Typical Applications by Industry

Industrial process: Furnace and kiln wiring, process control cables near heat sources, heating element connections, thermocouple extension wire insulation. Rated per IEC 60227 (polymeric insulated cables) or IEC 60245 (rubber insulated cables).

Automotive: High-temperature wiring harness connections to exhaust sensors, turbocharger controls, and ignition systems. Meets FLRXX automotive cable standards (SAE, ISO 6722) for temperature classes F (+155 °C) and G (+180 °C) or above.

Military and aerospace: MIL-W-16878 type E (200 °C) and MIL-C-17 coaxial cables use silicone insulation for aircraft and military ground vehicle applications requiring −65 °C to +200 °C performance.

Medical: Medical device power cords and internal cables where silicone's biocompatibility, cleanroom processability, and gamma sterilization compatibility are valued.

Renewable energy and building services: High-temperature photovoltaic (PV) string cables, underfloor heating cables, and building wiring in high-temperature mechanical rooms.

Compound Design: Key Formulation Parameters

Base polymer: High-molecular-weight PDMS (500,000–800,000 g/mol) for good physical properties and processing consistency.

Filler: Fumed silica (primary reinforcing filler, 30–50 phr) for tensile and tear strength. Additional fillers (precipitated silica, calcium silicate) for specific property optimization.

Cure system: Peroxide cure (most common for extrusion applications); platinum cure for medical and pharmaceutical cable grades. Post-cure is typically required for peroxide-cured compounds.

Flame retardant: ATH (alumina trihydrate) at 30–60 phr for LSZH grades. Platinum-based FR for self-extinguishing grades without halogens and with minimal smoke.

Processing: Continuous Vulcanization

Silicone cable compounds are extruded as insulation or jacket over copper conductor by continuous wire extrusion and vulcanized inline by one of three methods: liquid curing medium (LCM) salt bath (most common), hot-air oven, or microwave + hot air. Production speeds range from 5–80 m/min depending on gauge and cure system.

Contact us to verify cable compound specifications and request silicone cable insulation compound samples for your application.