Pressure-sensitive adhesives including expandable graphite

1. A building material comprising:

(i) a polymeric sheet having first and second opposed planar surfaces;

(ii) a pressure-sensitive adhesive layer disposed on the second planar surface of the polymeric sheet thereby forming an interface where the adhesive layer contacts the second planar surface of the polymeric sheet;

(iii) a concentrated region of expandable graphite proximate to the interface; and

(iv) a release liner, where the pressure-sensitive adhesive layer includes first and second planar surfaces, where the first planar surface of the pressure-sensitive adhesive layer is fixedly attached to the polymeric sheet, and where the release liner is removably attached to the second planar surface of the pressure-sensitive adhesive layer.

2. The building material of claim 1 , where the building material is a moisture barrier.

3. The building material of claim 1 , where the building material is a roofing underlayment.

4. The building material of claim 1 , where the pressure-sensitive adhesive layer includes a polystyrene block copolymer.

5. The building material of claim 1 , where the pressure-sensitive adhesive layer includes butyl rubber.

6. The building material of claim 1 , where the concentrated region of expandable graphite is formed by applying the expandable graphite onto the first planar surface of the pressure-sensitive adhesive layer, the then pressure-sensitive adhesive layer is mated to the polymeric sheet to thereby locate the expandable graphite proximate to the interface formed by joining the polymeric sheet to the first planar surface of the pressure-sensitive adhesive layer.

7. The building material of claim 1 , wherein the concentrated region of expandable graphite may be partially dispersed within said pressure-sensitive adhesive layer to form a concentration gradient whereby the concentration of the expandable graphite within the pressure-sensitive adhesive layer moves from a region of maximum concentration proximate to the first planar surface of the of the adhesive layer to a region of minimum concentration at the second planar surface of the adhesive layer.

8. The building material of claim 1 , where the expandable graphite has an onset temperature of at least 160° C.

9. The building material of claim 8 , where the pressure-sensitive adhesive is an extrudable pressure-sensitive adhesive.