A system for sealing a cavity of an automotive vehicle frame, comprising: (a) a wall associated with an automotive vehicle structure; and (b) an expandable material being a heat activated thermoplastic foamable_material disposed by an extruder over at least a portion of said wall and in contact with said wall prior to expansion of said expandable material, wherein the expansion rate of the expandable material is at least 400% when exposed to heat usually provided to the vehicle frame during automotive vehicle production and wherein the expandable material is prior and after its disposition to said wall dry to the touch at ambient temperature, and wherein the expandable material is a hot melt adhesive formulation comprising (i) one or more solid polymers (ii) a thixotropic filler (iii) a blowing agent system (iv) a cross linking system comprising - a first cross linking agent having an activation temperature within the temperature range at which the adhesive is heated up to the foaming temperature to increase the melt viscosity of the adhesive to at temperatures within the bake phase and - a second cross linking agent with an activation temperature within the range of the foaming temperature to cause the foamed formulation to cross link. (a) a wall associated with an automotive vehicle structure; and (b) an expandable material being a heat activated thermoplastic foamable_material disposed by an extruder over at least a portion of said wall and in contact with said wall prior to expansion of said expandable material, wherein the expansion rate of the expandable material is at least 400% when exposed to heat usually provided to the vehicle frame during automotive vehicle production and wherein the expandable material is prior and after its disposition to said wall dry to the touch at ambient temperature, and wherein the expandable material is a hot melt adhesive formulation comprising (i) one or more solid polymers (ii) a thixotropic filler (iii) a blowing agent system (iv) a cross linking system comprising - a first cross linking agent having an activation temperature within the temperature range at which the adhesive is heated up to the foaming temperature to increase the melt viscosity of the adhesive to at temperatures within the bake phase and - a second cross linking agent with an activation temperature within the range of the foaming temperature to cause the foamed formulation to cross link. wherein the expansion rate of the expandable material is at least 400% when exposed to heat usually provided to the vehicle frame during automotive vehicle production and wherein the expandable material is prior and after its disposition to said wall dry to the touch at ambient temperature, and wherein the expandable material is a hot melt adhesive formulation comprising (i) one or more solid polymers (ii) a thixotropic filler (iii) a blowing agent system (iv) a cross linking system comprising - a first cross linking agent having an activation temperature within the temperature range at which the adhesive is heated up to the foaming temperature to increase the melt viscosity of the adhesive to at temperatures within the bake phase and - a second cross linking agent with an activation temperature within the range of the foaming temperature to cause the foamed formulation to cross link. (i) one or more solid polymers (ii) a thixotropic filler (iii) a blowing agent system (iv) a cross linking system comprising - a first cross linking agent having an activation temperature within the temperature range at which the adhesive is heated up to the foaming temperature to increase the melt viscosity of the adhesive to at temperatures within the bake phase and - a second cross linking agent with an activation temperature within the range of the foaming temperature to cause the foamed formulation to cross link. - a first cross linking agent having an activation temperature within the temperature range at which the adhesive is heated up to the foaming temperature to increase the melt viscosity of the adhesive to at temperatures within the bake phase and - a second cross linking agent with an activation temperature within the range of the foaming temperature to cause the foamed formulation to cross link.