Coating material

1. An intumescent coating material, the material comprising first and second parts mixable together so that the material will cure by an addition reaction in the presence of a metallic catalyst; the first part including a polydiorganosiloxane polymer having at least two unsaturated groups per molecule, the first part also including the metallic catalyst and a reinforcing filler; and the second part including an organohydrogensiloxane crosslinker described by formula R 1 3 Si(OSiR 2 2 ) x (OSiMeH) y OSiR 1 3 , where each R 2 is independently selected from saturated hydrocarbon radicals comprising from 1 to 10 carbon atoms or aromatic hydrocarbon radicals and each R 1 is independently selected from hydrogen or R 2 , x is zero or an integer and y is an integer, the organohydrogensiloxane having at least three Si—H bonds per molecule, wherein the first part includes graphite, wherein two grades of graphite are included in the first part, with a first grade with a low thermal expansion, and a second grade with a high thermal expansion, in which the first grade of graphite has a particle size of less than 75 μm and the second grade of graphite has a particle size of 80% greater than 300 μm, in which the first grade of graphite has a thermal expansion of between 20 and 100 cm 3 /g.

2. A material according to claim 1 , in which the polydiorganosiloxane polymer constitutes between 35 and 65% by weight of the material.

3. A material according to claim 1 , in which the first grade of graphite has a thermal expansion of between 40 and 80 cm 3 /g.

4. A material according to claim 1 , in which the second grade of graphite has a thermal expansion of between 100 and 600 cm 3 /g.

5. A material according to claim 1 , in which the second grade of graphite has a thermal expansion of between 250 and 450 cm 3 /g.

6. A material according to claim 1 , in which the second grade of graphite has an ignition temperature of greater than 150° C.

7. A material according to claim 1 , in which the material includes between 5 and 25% by weight of the first grade of graphite.

8. A material according to claim 1 , in which the material includes up to 10% by weight of the second grade of graphite.

9. A material according to claim 1 , in which the first part of the material includes ceramic fibres.

10. A material according to claim 9 , in which the material includes between 1 and 5% by weight ceramic fibres.

11. A material according to claim 1 , in which the first part includes one or more flame retardant additives, the flame retardant additive being one or more of magnesium hydroxide, Huntite, hydromagnesite, Mica, zinc borate, aluminium trihydrate or boric acid, wherein the flame retardant additive is present in an amount of from 0.1 to 15% by weight.

12. A material according to claim 1 , in which the second part includes fumed silica.

13. A material according to claim 12 , in which the fumed silica is present in an amount of from 1% by weight to 5% by weight.

14. A material according to claim 1 , in which the second part includes glass microspheres.

15. A material according to claim 14 , in which and the glass microspheres are present in an amount of from 0.1% by weight to 5% by weight.

16. A material according to claim 1 , in which the ratio of first grade and second grade graphite is 1:1.

17. An intumescent coating material, the material comprising first and second parts mixable together so that the material will cure by an addition reaction in the presence of a metallic catalyst; the first part including a polydiorganosiloxane polymer having at least two unsaturated groups per molecule, the first part also including the metallic catalyst and a reinforcing filler; and the second part including an organohydrogensiloxane crosslinker described by formula R 1 3 Si(OSiR 2 2 ) x (OSiMeH) y OSiR 1 3 , where each R 2 is independently selected from saturated hydrocarbon radicals comprising from 1 to 10 carbon atoms or aromatic hydrocarbon radicals and each R 1 is independently selected from hydrogen or R 2 , x is zero or an integer and y is an integer, the organohydrogensiloxane having at least three Si-H bonds per molecule, the first part including graphite, wherein two grades of graphite are included in the first part, with a first grade with a low thermal expansion, and a second grade with a high thermal expansion, in which the ratio of first grade and second grade graphite is 1:1.

18. A material according to claim 1 , in which the ratio of first grade and second grade graphite is from 1:1 to 3:1.

19. An intumescent coating material, the material comprising first and second parts mixable together so that the material will cure by an addition reaction in the presence of a metallic catalyst; the first part including a polydiorganosiloxane polymer having at least two unsaturated groups per molecule, the first part also including the metallic catalyst and a reinforcing filler; and the second part including an organohydrogensiloxane crosslinker described by formula R 1 3 Si(OSiR 2 2 ) x (OSiMeH) y OSiR 1 3 , where each R 2 is independently selected from saturated hydrocarbon radicals comprising from 1 to 10 carbon atoms or aromatic hydrocarbon radicals and each R 1 is independently selected from hydrogen or R 2 , x is zero or an integer and y is an integer, the organohydrogensiloxane having at least three Si—H bonds per molecule, the first part including graphite, wherein two grades of graphite are included in the first part, with a first grade with a low thermal expansion, and a second grade with a high thermal expansion, in which the ratio of first grade and second grade graphite is from 1:1 to 3:1.

20. An intumescent coating material, the material comprising first and second parts mixable together so that the material will cure by an addition reaction in the presence of a metallic catalyst; the first part including a polydiorganosiloxane polymer having at least two unsaturated groups per molecule, the first part also including the metallic catalyst and a reinforcing filler; and the second part including an organohydrogensiloxane crosslinker described by formula R 1 3 Si(OSiR 2 2 ) x (OSiMeH) y OSiR 1 3 , where each R 2 is independently selected from saturated hydrocarbon radicals comprising from 1 to 10 carbon atoms or aromatic hydrocarbon radicals and each R 1 is independently selected from hydrogen or R 2 , x is zero or an integer and y is an integer, the organohydrogensiloxane having at least three Si-H bonds per molecule, wherein the first part includes graphite, wherein two grades of graphite are included in the first part, with a first grade with a low thermal expansion, and a second grade with a high thermal expansion, in which the first grade of graphite has a particle size of less than 75 μm and the second grade of graphite has a particle size of 80% greater than 300 μm, in which the second grade of graphite has a thermal expansion of between 100 and 600 cm 3 /g.

21. A method of applying an intumescent coating onto a substrate, the method including applying a coating material according to claim 1 , 17 , 19 , or 20 onto the substrate.

22. A body of intumescent material, the body comprising a cured body of intumescent coating material according to claim 1 , 17 , 19 , or 20 .

23. A material according to claim 1 , in which the first part of the material includes glass frit, wherein the material includes between 5 and 20% by weight glass frit.