Cables and wires with silcones

Silicones

High Flexibility Even at Extreme Ambient Temperatures

Silicones or silicone rubbers belong to the class of elastomers, but differ in that the main chain is not composed of carbon compounds, but of alternating silicon and oxygen atoms. The silicon atoms carry organic substituents, preferably methyl groups.

Silicones are chemically crosslinked and as a result form a network structure. The inorganic polymer chain of silicon and oxygen has a greater binding energy, which means that the properties are significantly stronger than those of purely organic elastomers.

Operating temperatures of 180 °C long-term or 200 °C for short-term use are therefore possible.

Typical Areas of Application for Silicone Are:

 

Thermal properties

Mechanical properties

Electrical properties

 Fire properties

Abbreviation​

 Chemical name

VDE Ref,

 Continuous operating temperature 3000h [°C]

Continuous operating temperature 20.000h [°C]​

Melting area [°C]​

Tensile strength [Mpa]​

Stretch [%]​

Hardness

 Volume resistivity at 20°C Dielectric strength Dielectric constant at 1MHz, 20°C

LOI​

 Flame retardancy

Halogen-free​

SIR​

Silicone rubber​

2G​

200​

-50 to 180​

networked​

6-14​

>250​

50A - 85A​

>10^15​

30​

3,0 - 4,0​

25 - 30​

 very good

Yes​

Manufacturing Competencies Silicone

Depending on their molar mass, silicone rubbers can be divided into liquid silicones (LSR) and solid silicones (HTV), resulting in different processing methods.

 

Solid silicones (HTV)

Solid silicones are copolymers of dimethylsiloxanes (main chain) and isolated vinylmethylsiloxanes (functional group). Due to their low intermolecular interaction, they have a soft, pasty consistency. With a viscosity of 10,000 to 50,000 Pa-s, solid silicones are easy to process at room temperature.

In the first step, the silicone is mixed with the crosslinker and other additives (such as stabilizers, color, fillers, etc.) on a roller or in a kneader. The silicone compound obtained in this manner is then cold extruded onto the conductor by means of an extruder and then crosslinked by heat input.

The amount of crosslinker and the proportion of functional (vinyl) groups determines the crosslink density and thus the final properties (such as tensile strength, tear resistance, elongation, hardness, etc.) of the silicone compound.

Peroxides (including halogen-free peroxides) or platinum-catalyzed systems are usually used as crosslinkers. By means of modern extruders or extrusion heads, several silicone layers can be applied to the conductor simultaneously in co-extrusion.

Fluid Silicon

Liquid silicones (LSR)

Liquid silicones are usually 2-component systems consisting of the platinum catalyst (component A) and the Si-H crosslinker (component B), which are crosslinked exclusively by addition. Due to short-chain linear polysiloxanes with a viscosity of approx. 5-500 Pa-s and a relatively low filler content (max. 30%), liquid silicones have a pourable to pasty consistency and are mainly processed by injection molding.

Thanks to its low viscosity, LSR can be applied to the cable at room temperature. For this purpose, the cables are fed horizontally or vertically through the LSR and then crosslinked via heat input. Unlike HTV, LSR does not have to be rolled or compounded beforehand. Both components arrive in different containers and are processed directly. Due to the addition crosslinking by means of a platinum catalyst, the crosslinking is residue-free and halogen-free, which makes LSR very popular for applications in medicine.

HEW-Silindo Cable

HEW Silindo® - For noticeably improved silicone haptics

For highly sensitive applications, mainly in the medical field, the Silindo® surface developed by HEW-KABEL offers key advantages.

HEW Silindo® noticeably and permanently improves the conventional silicone feel. Completely free of foreign material in the silicone or on the surface, HEW Silindo® prevents "sticking" to other materials. This surface property is retained even after more than 400 autoclave cycles.

Properties of HEW Silindo®

  • Completely new finish:
    (no foreign material in the silicone or on the surface).
  • Permanent improvement of the surface haptics
    (anti-adhesive, no "sticking")
  • Minimized sliding friction even after more than 400 autoclave cycles
  • Suitable for the following sterilization options:
    • Steam sterilization (autoclave)
    • STERRAD® NX®
    • Disinfection washing machine
    • Gas sterilization (ethylene oxide)
    • Gamma sterilization
    • Wipe disinfection

Klingsiepen 12

D - 51688 Wipperfürth