A method for accelerating the release of a flammable blowing agent from an expanded foam is disclosed. According to the method, an expanded foam structure is perforated to form a first series of channels extending partially through its thickness from a first surface and a second series of channels extending partially through its thickness from a second surface opposite the first surface. The channels provide paths enabling the blowing agent to escape more rapidly from the interior of the expanded foam structure.
A foam plank laminate of thermoplastic material comprises at least two expanded foam sheets, both partially perforated, and laminated with the perforated surfaces facing each other and the smooth non perforated surfaces as the outer plank surfaces. The foam plank laminate can be obtained by an industrially acceptable production method as the partial perforation of the forming foam sheets accelerates the removal of a majority of the blowing agent from the foam structure, thus drastically reducing the curing time, and at the same time it has impermeability, good mechanical properties, and an attractive appearance.
A method for accelerating the release of a flammable blowing agent from an expanded foam is disclosed. According to the method, an expanded foam structure is perforated to form a first series of channels extending partially through its thickness from a first surface and a second series of channels extending partially through its thickness from a second surface opposite the first surface. The channels provide paths enabling the blowing agent to escape more rapidly from the interior of the expanded foam structure.
A cover for an air bag module is provided. The cover comprises a polymeric sheet and one or more thinned portions. The polymeric sheet has a first surface and a second surface and includes a plurality of cells formed therein. A skin is formed on at least the first surface. The thinned portions are formed in the second surface and define a weakened region of the cover.
This invention provides an expanded open-cell foam polymer composition comprising at least one linear or modified linear polyolefin, at least 50% of the cells being open, and the cells having an average size of at least 1 millimeter. It is desirable that the composition have a sound absorption coefficient as determined by ASTM D 1050 at 1,000 Hz which is greater than 0.15. In preferred foams the composition has an airflow resistivity of less than about 800,000 Rayls/m.
Thermoplastic polymer foams having sound deadening properties satisfactory for demanding applications are provided which have mechanical strength, which are economical to manufacture, and which are hydrolytically stable. Methods of preparing these foams are also provided. The foams are useful in sound management, cushion packaging, filtering, and fluid absorption and exhibit one or more of the following properties: 1) average cell size greater than about 2 mm; 2) substantially open-cell structure and 3) relatively large pores connecting the cells. In order that the foam be acoustically active, the foam should possess a substiantially open-cell structure and a relatively low airflow resistivity. Foams with substantially open-cell structure and relatively low airflow resistivity are prepared by mechanically opening a foam having an average cell size greater than about 2 mm. In most cases, such mechanical opening creates relatively large pores connecting the cells.
