Dual layered light weight fire resistant PU foam-based composite for acoustical insulation

In today's automotive industry, sound package design and optimization is important considering the mounting need for weight reduction and achieving targeted sound absorption and sound transmission loss values. The present paper relates to dual layered light weight (LW) fire resistant (FR) Polyurethane (PU) foam-based composite for engine room insulation, referred herein as Ωµ2 foam comprising of two layers of foam having different densities and flexibility. The composite consists of one layer of semirigid FR PU foam acting as a carrier with sound absorptive property and another layer consisting of flexible FR PU foam acting as higher acoustical absorptive property. This concept is intended for enhancement of acoustical performance by the synergistic effect of dual foam layers besides being FR and LW material, specially designed for passenger vehicles' engine compartment insulations such as firewall/dash panel, bonnet/hood liner insulation and other diverse applications in commercial vehicles. The paper presents material properties and in-depth comparative assessment of sound absorption properties of dual layer (Ωµ2) LW FR PU foam with respect to conventional materials like single layer light weight semi-rigid PU foam and resinated cotton shoddy felt, etc.