Impact resistant underbody shield materials and articles and methods of using them

A method of forming a composite article comprising:

• combining a polypropylene resin having a melt flow index of 300 g/10 min or more, reinforcing glass fibers and a lofting agent in an aqueous solution, wherein the lofting agent comprises a binary lofting agent that expands from no loft to full loft after application of heat, wherein the binary lofting agent does not loft at 180 degrees Celsius and lofts at a lofting temperature above 210 degrees Celsius, wherein the polypropylene resin is present at 50% by weight or more in the aqueous solution;
• mixing the aqueous solution comprising the polypropylene resin, reinforcing glass fibers and lofting agent to disperse the reinforcing glass fibers and the microsphere lofting agent in the polypropylene to provide an aqueous foam dispersion;
• disposing the aqueous foam dispersion onto a forming element;
• removing liquid from the disposed aqueous foam to provide a porous core layer comprising a web formed from the polypropylene, the reinforcing glass fibers and the lofting agent trapped in void space of the formed web;
• heating the porous core layer above a softening temperature of the thermoplastic polymer resin of the porous core layer and below the lofting temperature of the binary lofting agent;
• disposing an impact resistant film on a first surface of the porous core layer, wherein the impact resistant film is a copolymer polyolefin film, wherein the impact resistant film comprises a thickness of at least 10 mils;
• disposing a scrim on a second surface of the porous core layer to provide a composite article;
• compressing the composite article to a selected thickness;
• and
• lofting the binary lofting agent by heating the compressed composite article above the lofting temperature to provide a lofted composite article, in which a ratio of the polypropylene resin to reinforcing glass fibers in the porous core layer is selected so the lofted composite article can withstand at least 50 individual impacts according to a SAE J400 protocol without damage to the disposed impact resistant film, wherein the SAE J400 protocol subjects the polyolefin copolymer film of a 100 mm×300 mm plaque of the lofted composite article to individual 90 degree impacts using 8 to 16 mm diameter road gravel with the lofted composite article placed against a ⅛ inch steel backing, wherein the road gravel is provided at 8+/−2 second intervals using an air pressure of 70 psi, and wherein damage to the polyolefin copolymer film comprises delamination of the polyolefin copolymer film from the post lofted core layer or cracking of the polyolefin copolymer film.