Constrained layer, composite, acoustic damping material

Abstract

A constrained layer, composite structure for damping acoustic vibrations includes an extensional layer comprised of a first polymeric material, and a constraining layer of a second polymeric material. The modulus of elasticity of the constraining layer is greater than that of the extensional layer. In use, the structure is disposed on the surface of an article in which acoustic vibrations are to be damped so that the extension layer overlies the surface. Also disclosed are methods for preparing the structure, including automated methods.

1 . A constrained layer, composite structure for damping acoustic vibrations in an article, said composite structure comprising:
 an extensional layer comprising, on a weight basis:
 3-10% of an epoxy resin 
 3-10% of a rosin ester tackifier 
 5-12% SBR rubber 
 5-15% polybutadiene rubber 
 2-20% of a phthalate plasticizer 
 2-20% of an aromatic hydrocarbon plasticizer for said rubbers 
 1-5% asphalt 
 1-5% of a polyester resin (Dynapol) 
 1-5% of an ethylene methacrylate copolymer 
 0.3-0.8% of a crosslinker for said epoxy resin 
   
       said first polymeric material having a first modulus of elasticity, wherein in the use of said composite structure, said extensional layer is disposed upon a surface of an article in which acoustic vibrations are to be damped; and
 a constraining layer comprising a second polymeric material which comprises, on a weight basis:
 10-25% of an epoxy resin 
 5-15% of an ABS powder 
 0.5-2% of an aromatic tackifier resin 
 0.5-5% of a polyester resin 
 5-15% of propylene glycol diglycidyl ether 
 0.5-3% of a crosslinker for said epoxy resin 
 
 
       said second polymeric material having a second modulus of elasticity which is greater than the first modulus of elasticity of said first polymeric material, said constraining layer being disposed atop said extensional layer. 
     
     
         2 . The composite structure of  claim 1 , wherein the first polymeric material further comprises, on a weight basis, 0.2-1% of sulfur. 
     
     
         3 . The composite structure of  claim 1 , wherein at least one of said first polymeric material and said second polymeric material further includes, on a weight basis, 1-40% of a mineral material, said mineral material being selected from the group consisting of fillers, pigments, thixotropy control agents, and combinations thereof. 
     
     
         4 . The composite structure of  claim 1 , wherein said second polymeric material further includes, on a weight basis, 2-10% of an epoxidized cashew nut shell liquid. 
     
     
         5 . The composite structure of  claim 1 , wherein the thickness of said extensional layer is in the range of 1-6 millimeters, and the thickness of said constraining layer is in the range of 0.5-3 millimeters. 
     
     
         6 . The composite structure of  claim 1 , wherein neither the first polymeric material nor the second polymeric material is a foamed polymeric material. 
     
     
         7 . The composite structure of  claim 1 , wherein neither the first polymeric material nor the second polymeric material includes polyvinylchloride or methylmethacrylate. 
     
     
         8 . A method for damping acoustic vibrations in a sheet metal body panel of a motor vehicle, said method comprising:
 applying said constrained layer, composite structure of  claim 1  to said body panel.   
     
     
         9 . The method of  claim 8 , including the further step of painting said panel after said composite structure has been applied thereto. 
     
     
         10 . The method of  claim 8 , wherein the step of applying said composite structure is implemented utilizing a robotic applicator. 
     
     
         11 . The method of  claim 8 , including the further step of heating said panel to a temperature of at least 200° C. after said composite structure has been applied thereto.