An improved thermal curtain for separating a food service cart into hot and cold regions is disclosed. The thermal curtain is composed of composite foam structural elements which have enhanced insulating capability, toughness and the ability to provide structural support for food service trays placed thereon. The thermal curtain is composed of a plurality of vertically superposed tray support/thermal barrier sections which attach to a support bracket which further attaches to the back of the food service cart. The upper portion of the support/barrier is adapted to provide a tray support and conforms to the design of the food service tray to minimize migration of heated or cold air to the opposite compartment. The lower edge of the support/barrier section is composed of a blade seal floating in a retention channel which allows vertical movement of the seal. When a tray is inserted, the blade seal travels upward so that the tray may be inserted and the lower edge of the blade seal contacts the upper edge of the tray. When a tray is removed, the blade seal lowers into contact with the upper edge of the next lower support/barrier to form a thermal seal.