Abstract: A glass fiber reinforced building panel is made by extruding molten first and second webs of polymer compounds through spaced die openings, positioned a glass fiber mat between the first and second webs, pressing the webs and mat together, and cooling to form a building panel. The building panel of the invention has improved fire retardance and better field cutting and sawing performance compared with conventional, unreinforced building panels.

Abstract: Microwave frequencies in the range of 0.5 GHz to 10 GHz are used to weld thermoplastic substrates by interposing a carrier strip. The strip is formed of a polymer carrier which is miscible in the substrates. Electrically conductive submicron carbon black susceptor particles are chosen with specified properties such that they generate enough heat within a specified time to produce a weld in which the heat generated is confined to the weld zone. The resulting weld is such that the welded assembly has essentially the same dimensions as the clamped assembly. Glass fiber reinforced substrates are welded without breaking glass fibers in the weld zone. Lap strength of welded substrates is greater than that of substrates joined by prior art methods, whether by welding or adhesive bonding. Articles microwave welded in accordance with the invention are useful for manufacturing and repairing vehicle components such as automobile bumpers and dashboards and other structural parts of automobiles, aircraft, and spacecraft.