Roofing membranes with expandable graphite as flame retardant

1. A rooting membrane comprising:

i. a first layer including a cured network of ethylene-propylene-diene rubber, where the cured ethylene-propylene-diene rubber is in the form of a crosslinked network, where said first layer includes from about 20 to about 50% by weight cured ethylene-propylene-diene rubber, from about 70 to about 100 parts by weight carbon black, from about 78 to about 103 parts by weight clay, from about 55 to about 95 parts by weight extender, and from about 1 to about 50 parts by weight expandable graphite, where the parts by weight are based upon 100 parts by weight of the cured ethylene-propylene-diene rubber, where the carbon black, clay, extender, and expandable graphite are dispersed throughout the crosslinked network, and where the expandable graphite has an onset temperature of at least 160° C.; and

ii. a second layer including a cured network of ethylene-propylene-diene rubber, where said second layer is substantially devoid of expandable graphite.

2. The membrane of claim 1 , where said expandable graphite has an onset temperature of at least 170° C.

3. The membrane of claim 1 , where said second layer includes at least one of silica, titanium dioxide, and clay.

4. The roofing membrane of claim 1 , where the first layer includes from about 3 to about 35 parts by weight expandable graphite per 100 parts by weight of the cured ethylene-propylene-diene rubber.

5. The roofing membrane of claim 1 , where the first layer includes from about 5 to about 30 parts by weight expandable graphite per 100 parts by weight of the cured ethylene-propylene-diene rubber.

6. The roofing membrane of claim 1 , where the first layer includes from about 7 to about 25 parts by weight expandable graphite per 100 parts by weight of the cured ethylene-propylene-diene rubber.

7. The rooting membrane of claim 1 , where the expandable graphite is optionally only partially expanded.

8. The roofing membrane of claim 1 , where the expandable graphite is optionally expanded to at most 50% beyond its original unexpanded size.

9. The roofing membrane of claim 1 , where the expandable graphite is optionally expanded to at most 20% beyond its original unexpanded size.

10. The roofing membrane of claim 1 , where the expandable graphite is optionally expanded to at most 10% beyond its original unexpanded size.

11. A roofing membrane comprising:

a first layer including about 20 to about 50% by weight cured ethylene-propylene-diene rubber, from about 70 to about 100 parts by weight carbon black, from about 78 to about 103 parts by weight clay, from about 55 to about 95 parts by weight extender, and at least 2 parts by weight expandable graphite, where the parts by weight are based upon 100 parts by weight of the cured ethylene-propylene-diene rubber; and

a second layer including cured ethylene-propylene-diene rubber, where said second layer is substantially devoid of the expandable graphite.

12. The membrane of claim 11 , where the expandable graphite is characterized by a pH of at most 7.

13. The membrane of claim 11 , where the expandable graphite is characterized by an onset temperature of at least 170° C.

14. The membrane of claim 11 , where the expandable graphite is characterized by an onset temperature of at least 180° C.

15. The membrane of claim 11 , where the expandable graphite is characterized by an average particle size in the range from about 30 μm to about 1.5 mm.

16. The membrane of claim 11 , where the first layer is black in color and the second layer is non-black in color.

17. The membrane of claim 11 , where the first layer having expandable graphite dispersed therein is substantially devoid of a halogen-containing flame retardant.

18. The membrane of claim 11 , where the membrane meets performance fire standards as tested by UL 94 and/or UL 790.

19. The membrane of claim 11 , where the membrane is substantially devoid of Decabromodiphenyl oxide (DBDPO).

20. The membrane of claim 11 , where the membrane is substantially devoid of flame retardants other than expandable graphite.

21. The membrane of claim 11 , where the ethylene-propylene-diene rubber is cured with a sulfur cure system.

22. The membrane of claim 11 , where the ethylene-propylene-diene rubber is cured with a peroxide cure system.

23. The membrane of claim 11 , where the ethylene-propylene-diene rubber is cured with a quinone cure system.

24. The roofing membrane of claim 11 , where the expandable graphite has an onset temperature of at least 160° C.

25. The roofing membrane of claim 24 , where the carbon black, clay, extender, and expandable graphite are dispersed throughout a crosslinked network of the cured ethylene-propylene-diene rubber.

26. The roofing membrane of claim 25 , where the first layer further includes from about 5 to about 60 parts by weight talc per 100 parts by weight of the cured ethylene-propylene-diene rubber.

27. The roofing membrane of claim 25 , where the first layer includes from about 3 to about 35 parts by weight expandable graphite per 100 parts by weight of the cured ethylene-propylene-diene rubber.

28. The roofing membrane of claim 25 , where the first layer includes from about 5 to about 30 parts by weight expandable graphite per 100 parts by weight of the cured ethylene-propylene-diene rubber.

29. The roofing membrane of claim 25 , where the first layer includes from about 7 to about 25 parts by weight expandable graphite per 100 parts by weight of the cured ethylene-propylene-diene rubber.

30. The roofing membrane of claim 25 , where the expandable graphite is optionally only partially expanded.

31. The roofing membrane of claim 30 , where the expandable graphite is optionally expanded to at most 50% beyond its original unexpanded size.

32. The roofing membrane of claim 30 , where the expandable graphite is optionally expanded to at most 20% beyond its original unexpanded size.

33. The roofing membrane of claim 30 , where the expandable graphite is optionally expanded to at most 10% beyond its original unexpanded size.