Insulated wire construction for fire safety cable

1. An electric wire comprising:

a metal conductor;

a first insulation layer, wherein the first layer is a non-ceramifiable silicone compound;

a second insulation layer, wherein the second layer is a ceramifiable silicone compound, wherein the second layer is on the outside of the first layer, wherein no mica is used in the second insulation layer, wherein the first layer is between about 5 mils and about 15 mils and the second layer is between about 30 mils and about 40 mils; and,

an extruded jacket, wherein the extruded jacket surrounds the first and second insulation layers.

2. The wire of claim 1 , wherein the first and second layer are coextruded into inseparable layers, wherein no mica is used in the first insulation layer.

3. The wire of claim 2 , wherein the first layer has an acceptable 90° C. wet insulation resistance performance and acceptable current leakage performance at 1850° F.

4. The wire of claim 2 , wherein the first layer has a diameter of between about 10% to about 40% of the diameter of the combined first and second layers.

5. The wire of claim 4 , wherein the minimum thickness of the layers is about 40 mils.

6. The wire of claim 4 , wherein the first layer is between about 10 mils to about 12 mils and the second layer is about 20 mils.

7. The wire of claim 1 , wherein the metal conductor is chosen from the group comprising stranded copper, stranded silver plated copper, stranded nickel plated copper, stranded nickel, solid copper, solid silver plated copper, solid nickel plated copper, and solid nickel, wherein the conductor has a cross sectional area between about 0.823 mm 2 and about 253.35 mm 2 .

8. The wire of claim 1 , wherein the first insulation layer is addition or peroxide crosslinked.

9. The wire of claim 8 , wherein the second insulation layer is addition cured or peroxide crosslinked.

10. The wire of claim 9 , wherein the silicone compound of the first and second insulation layers is a polyorganosiloxane and is crosslinked with a peroxide compound or a crosslinking agent.

11. The wire of claim 10 , wherein the ceramifiable silicone compound is a polydimethylsiloxane and has a density of about 1.05 to about 1.60 g/cm 3 , a Shore A hardness of about 3 to about 90, a tensile strength of about 5 to about 11 N/mm 2 , an elongation at break of about 100% to about 1,100%, a tear strength of about 5 to about 55 N/mm, a compression set of about 5 to about 25%, and a rebound resilience of about 30% to about 70%.

12. The wire of claim 11 , wherein the ceramifiable silicone compound is a polydimethylsiloxane and has a density of about 1.20 to about 1.29 g/cm 3 , a Shore A hardness of about 70 to about 72, a tensile strength of about 6.6 to about 9 N/mm 2 , an elongation at break of about 330% to about 430%, and a tear strength of about 18 to about 26 N/mm.

13. The wire of claim 8 , wherein the non-ceramifiable silicone compound is a polyorganosiloxane.

14. The wire of claim 13 , wherein the non-ceramifiable silicone compound is a polydimethylsiloxane.

15. The wire of claim 1 , wherein the jacket is thermoplastic.

16. The wire of claim 1 , wherein the wire further comprises a fiber reinforcement between the two silicone insulation layers.

17. An electric wire comprising:

a metal conductor, wherein the metal conductor is chosen from the group comprising stranded copper, stranded silver plated copper, stranded nickel plated copper, stranded nickel, solid copper, solid silver plated copper, solid nickel plated copper, and solid nickel, wherein the conductor has a cross sectional area between about 0.823 mm 2 and about 253.35 mm 2 ;

a first insulation layer, wherein the first layer is a non-ceramifiable platinum-crosslinked polydimethylsiloxane, wherein the first layer is between about 10 mils to about 12 mils, wherein the first layer has an acceptable 90° C. wet insulation resistance performance;

a second insulation layer, wherein the second layer is a ceramifiable peroxide-crosslinked polydimethylsiloxane, wherein the second layer is on the outside of the first layer, wherein the second layer is about 35 mils, wherein the first and second layer are coextruded into inseparable layers, wherein the thickness of the layers is a minimum of about 40 mils, wherein no mica is used in the second insulation layer; and,

a thermoplastic, halogen free, fire-retardant, olefinic extruded jacket, wherein the extruded jacket covers the layers.

18. An electric wire comprising:

a metal conductor, wherein the metal conductor is chosen from the group comprising stranded copper, stranded silver plated copper, stranded nickel plated copper, stranded nickel, solid copper, solid silver plated copper, solid nickel plated copper, and solid nickel, wherein the conductor has a cross sectional area between about 0.823 mm 2 and about 253.35 mm 2 , wherein the second layer is directly on the outside of the first layer;

a first insulation layer, wherein the first layer is a ceramifiable silicone compound, wherein no mica is used in the first insulation layer;

a second insulation layer, wherein the second layer is a non-ceramifiable silicone compound, wherein the second layer is on the outside of the first layer, wherein the thickness of the layers can be as low as about 40 mils; and

an extruded jacket, wherein the extruded jacket surrounds the first and second insulation layers.

19. The wire of claim 18 , wherein the first and second layers are coextruded into inseparable layers, wherein no mica is used in the second insulation layer.

20. The wire of claim 19 , wherein the second layer has an acceptable 90° C. wet insulation resistance performance and acceptable current leakage performance at 1850° F.

21. The wire of claim 19 , wherein the two silicone layers are applied in two separate extrusion layers and inseparably bonded together.

22. The wire in claim number 19 where a third silicone layer is applied over the first two extruded layers, wherein the extruded jacket surrounds the first, second, and third silicone layers.

23. The wire of claim 18 , wherein the layers are addition or peroxide crosslinked.

24. The wire of claim 23 , wherein the ceramifiable silicone compound is a polydimethylsiloxane and has a density of about 1.05 to about 1.60 g/cm 3 , a Shore A hardness of about 3 to about 90, a tensile strength of about 5 to about 11 N/mm 2 , an elongation at break of about 100% to about 1,100%, a tear strength of about 5 to about 55 N/mm, a compression set of about 5 to about 25%, and a rebound resilience of about 30% to about 70%.

25. The wire of claim 24 , wherein the non-ceramifiable silicone compound is a polyorganosiloxane.

26. The wire of claim 18 , wherein the wire further comprises a fiber reinforcement between in the two silicone insulation layers.