This invention relates to methods for manufacturing plates bonded to resilient layers, wherein the plate is made of a polypropylene and the resilient layer is made of a polyethylene. Ultrasonic welding used to bond the resilient layer to the plate. In some embodiments, a thin film is applied to a layer of the resilient layer before ultrasonic welding. While the film layer may be located adjacent the plate when welding, the film layer may also be advantageously located on the opposite of the resilient layer from the plate when welding. The film may also be applied to both sides of the resilient layer.
