Acoustic absorption polymer foam having improved thermal insulating performance

Abstract

Polymer foams having a good balance of high sound absorption, low thermal conductivity and generally low water absorption are disclosed which are obtainable by perforating (i.e., hole punching) a polymer foam having a moderately large cell size (1.5 mm to 4 mm) and an open content not greater than 40 percent to increase the open cell content of the foam by at least about 10 percent relative to the non-perforated foam, the polymer foam matrix preferably made of a thermoplastic foam, such as a low-density polyethylene (LDPE) resin, a high melt strength (HMS) polypropylene resin (PP), or a blend of an HMS PP resin and an LDPE resin, optionally containing a cell size enlarging agent such as glycerol monostearate, an antioxidant, carbon black and/or flame retardant additives, using a volatile organic compound, e.g. isobutane, as blowing agent. These foams are useful for applications in which a combination of acoustic absorption, thermal insulation and possibly low water absorption is needed, such as outdoor, motor vehicle and marine applications. They exhibit a noise reduction coefficient greater than 0.3, a thermal conductivity not greater than 90 mW/m° K measured at an average temperature of 10° C. according to DIM52616 and a low (less than 10, such as less than 1.5, percent by volume) water absorption when measured according to EN 12088 at a 50° C. temperature gradient for an exposure test period of 14 days.