Cavity sealing system for automotive vehicles

A method for sealing a cavity of an automotive vehicle frame, comprising:

• (a) providing a wall associated with an automotive vehicle structure, wherein said wall defines a cavity of an automotive vehicle body in white and is an interior wall surface of a vehicle pillar;
• and
• (b) locating an expandable material being a heat activated thermoplastic foamable material by an extruder over at least a portion of said wall and in contact with said wall prior to expansion of said expandable material;
• (c) heating the expandable material so that the expandable material foams to form a foamed formulation that is at least 800% of its original volume so that it fills the cavity when exposed to the heat, wherein the heat is provided to the vehicle frame during automotive vehicle production;
• 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;
• and
• (iv) a cross linking system comprising:
• a first cross-linking agent having an activation temperature within a temperature range at which the adhesive is heated up to a foaming temperature, but below the foaming temperature to increase a melt viscosity of the expandable material;
• and
• a second cross-linking agent with an activation temperature within a range of the foaming temperature to cause the foamed formulation to cross link.