Abstract: Disclosed is a slidable duct assembly for conducting air from a fixed component to a component that is movable with respect to the fixed component by conducting air from a fixed supply of air, associated with the fixed component, to an air delivery member, movable along with the movable component. The duct assembly contains at least two metallic telescoping, tubular conduit sections for rotatably interconnecting the air supply to the air delivery member, and a pair of electrically-conductible, spaced-apart slide bearings positioned between the inner surface and the outer surface of each adjacent conduit section to electrically bond the duct assembly.

Abstract: An aircraft surface for use on composite structure. The detail surface includes a conductive foil, a conductive double pulled expanded screen, and an adhesive for joining the conductive foil and screen to a composite material. The conductive screen is layered between the conductive foil and composite structure, providing electrical contact between the foil and the composite structure.

Abstract: A cowling assembly for a vehicle comprises a general external surface having secured to or adjacent thereto, an elongate lightning diverter element which, at least when subjected to a high electric field, is electrically conductive, wherein a portion of the diverter element is arranged to project from the general external surface.

Abstract: The present invention provides a method of fastening an outer composite aircraft skin (12) to an inner substructure (14), which may be the wall of a fuel tank. The method includes the steps of incorporating an electrically conductive layer (26) in an outer surface of the outer composite skin (12), inserting a bolt (11) through the electrically conductive layer (26) and the outer composite skin (12) and through the inner substructure (14), securing the bolt (11) by means of a nut (22) directly or indirectly engaging the inner surface of the inner substructure (14), and applying insulating material (34) over the head (16) of the bolt.

Abstract: The installation for removing electrostatic charge and passing lightning current between a conductor of each blade of the rotor and a metallic part of the hub comprises at least one conductive member integral with the member for linking the blade to the hub in its angular deflections, and in electrical continuity with the conductor of the blade and held elastically in permanent contact with a conductive terminal integral with the hub and in electrical continuity therewith.

Abstract: An anti-spark structure includes first and second elements of composite material which are at least partially superimposed and assembled together with a screw and nut. The nut has a recess which defines a storage chamber for storing gases formed at the interface of the screw and the elements. A passage is provided in the structure for allowing gases stored in the chamber to escape from the structure.

Abstract: An electrically conductive bridge is formed over a non conductive joint between two or more adjacent electrically conductive panels. The bridge provides a continuous conductive path between the panels. In an exemplary embodiment, the panels form part of a shield against electromagnetic and/or lightning strike energy. The bridge is formed by taping an expanded conductive mesh over exposed conductive portions of the panels and applying an epoxy adhesive. During a following cure cycle, vacuum compression is applied. The expanded mesh of the bridge has an out-of-plane cross sectional configuration which remains in contact with the panel conductive portions during cure so that when the adhesive has cured, the bridge mesh and the panel conductive portions are held in contact with each other.

Abstract: A spacecraft includes a spacecraft element, such as a deployable antenna, and a black paint on the spacecraft element. The paint has a composition of 100 parts by weight of a methyl phenyl silicone-based polymer, and from about 1.35 to about 3.5 parts by weight of an electrically conductive carbon pigment having a porous, sponge-like structure. The paint is applied by mixing these constituents with a solvent such as naphtha or xylene in an amount sufficient to permit the paint to be applied by a selected technique such as brushing or spraying.

Abstract: A laminated window includes at least one rigid external substrate (5) and a sheet made of flexible plastic material (6) which is adjacent to the substrate (5). The window is equipped with an electrostatic protection circuit which is capable of dissipating the charges which have accumulated on the external sheet (7). This circuit includes conducting elements (2) which cross through at least the substrate and at least one part of the sheet made of plastic material (6). The conducting elements (2) are connected to a collector element (3) which is connected to the ground (4) and embedded in the sheet made of flexible plastic material (6).

Abstract: A passive intermodulation shield (10) for a spacecraft is made from a substrate (12) and a vacuum deposited aluminum layer (14) over the substrate (12). The substrate (12) can include a polyimide sheet such as Kapton. The vacuum deposited aluminum layer (14) has a thickness (16) to produce a surface resistivity which maintains both the inherent passive intermodulation generation and the passive intermodulation passthrough below a predetermined value. Preferably, the surface resistivity is selected between 10 ohms per square and 40 ohms per square. Spacecraft multilayer insulation blankets (30, 40, 50, 60) are formed by disposing the passive intermodulation shield (10) between a pair of outer layers.

Abstract: Lightning strike protection for an aircraft or part of an aircraft is provided by mounting metal (aluminium) rods adjacent but spaced from the inner surface of the aircraft wall. The rods are provided with ball joints from which extensions through the wall stand proud of the aircraft outer surface and within the material of static dischargers. The rods are coupled to bus bar which run the length of the aircraft in turn are coupled to lightning strike dischargers (again in the form of metal rods carried on but spaced from the wall of an aircraft and having extensions which pass through the aircraft wall). The application of the lightning strike protection system to radomes, antennas, pitot tubes carbon fiber reinforced plastics structures is discussed, in the former two cases metal rods being provided to extend in the null field of a device within the radome or the antenna.

Abstract: A lightning shield comprising a fiber reinforced plastics laminate (13, 14), a fixed leading edge structure (12) and an aircraft wing (1) comprising said laminate shield are provided. The laminate shield comprises a series of laminae (21, 22) of fibre reinforcing material held together by plastics matrix material, the laminate including a layer of electrically conductive material (19) interposed between an outer lamina (21) and its next adjacent lamina (22) for conducting lightning current attaching to the laminate to conducting fasteners (31, 32) passing through the laminate (13, 14).

Abstract: An antisparking structure, in particular for aircraft, comprises two components made of composite electrically conductive material which overlie each other at least in part and which are assembled together by using an electrically conductive screw having a countersunk head. A conduction-improving arrangement is provided for improving the conduction of electricity between the overlying portions of the two components. Electrical insulation is provided for electrically insulating the screw from the second component, at least in the vicinity of the nut. Thus, when lightning strikes the head of the screw, the lightning current flows between the screw and the first component, and then between the first component and the second component through the conduction-improving arrangement, without there being any arc between the nut and the second component.

Abstract: A structural component exposed to lightning strikes comprises a bonded assembly of a first component part (18) which has a cellular structure and a front face (20) and a second component part (22) extending across the front face (20) of the first component part (18), the second component part (22) comprising an electrically conducting first sheet (23), an electrically non-conductive second sheet (25) at the rear of the first sheet (23) and a fibre reinforced composite third sheet (26) at the rear of the second sheet (25) and positioned between the second sheet (25) and the front face (20) of the first component part (18). In one form, the electrically conducting first sheet (23) is a non-ferrous metal or metal alloy expanded foil, the electrically non-conducting second sheet (25) is a glass fibre fabric, the third sheet (26) is a carbon or graphite fibre reinforced composite sheet and the first component part (18) is an aluminium alloy honeycomb core.

Abstract: Novel fastener assemblies self-conforming to contoured surface panels being fastened to support members and minimizing radar cross-section by providing a non-reflective surface shield component over the basic fastening component or bolt. The invention provides a method for reducing the amount of microwave radiation normally reflected back to its source by aircraft panel fasteners or bolts and/or by the recessed walls of bolt access openings at contoured surface areas. The invention comprises a novel fastener assembly of a threaded shield bolt engaged within a main fastening bolt, the shield bolt having a flexible, surface-conforming head of a metal alloy having high temperature stability properties.

Abstract: A device for dissipating and discharging undesired electric charges, especially from airplanes. The device is formed from nonmetallic conductive material, such as carbon loaded plastic, and comprises a number of regions having varying conductivities. A region at a first end where the device is connected to a mass to be discharged has a lower conductivity than a region at a second end. The device includes a coating comprised of insulating material, which coats the entire surface of the nonmetallic material except for a portion of the nonmetallic material on the second end of the device. A magnetic flux is created which pulls charges from the mass through the device. The charge is in part dissipated in the nonmetallic material and is in part discharged into the air through the exposed portion.

Abstract: Highly conducting lightweight hybrid materials are obtained by weaving strands of carbon or graphite fibers into a 2-dimensional fabric-like structure, depositing a layer of carbon onto the fibers of the fabric-like structure, heating the fabric-like structure to graphitize the carbon layer and intercalating the graphitized carbon layer. Composite materials for use in lightning strike protection are composed of at least one layer of the highly conducting lightweight hybrid material and at least one layer of traditional composite materials.

Abstract: Composite assemblies prepared from thermosettable matrix resin-impregnated fiber-reinforced prepregs, conductive metal screens, and film adhesives are provided which do not develop microcracks after extensive thermal cycling. The composite assemblies are particularly useful in the manufacture of vehicles in the transportation industry, especially aircraft.

Abstract: A lightning resistant composite structure, particularly for aircraft, in which a composite skin panel, for example of carbon fibre, is attached to an inner composite structure by one or more lightning resistant fastener assemblies. The fastener assembly comprises a nut and bolt, the bolt being in good conductive contact with a conductive sleeve engaging the skin panel and a non-conductive sleeve engaging the inner structure. The nut is contained within a capped nut assembly located to the undersurface of the inner structure.The non-conductive sleeve and the capped nut assembly isolate the inner structure from the effects of lightning strike, the conductive sleeve providing a high quality conductive interface between the bolt and the skin panel. By this means adverse penetration of lightning current into the inner structure is prevented.

Abstract: A device for shielding composite material surfaces of aircraft from the destructive forces associated with lightning strikes and for protecting avionics from electromagnetic interference (EMI) and radio frequency interference (RFI), is provided, consisting of a thin metallic foil having uniformly spaced polygonal apertures formed therein. The polygonal apertures are so shaped as to provide at least one axis along which the shield material can expand or lengthen, permitting the shield material to better fit the irregular or compound curved surfaces found on aircraft. The foil shield can also be used to protect the filler material used between joints and to repair breaks and openings formed in the aircraft surface. When fashioned out of aluminum and applied to a composite material, such as graphite epoxy, the shield may be plated with nickel to prevent galvanic corrosion caused by the contact between dissimilar materials. When manufactured from copper the shield provides a solderable surface.

Abstract: A method and apparatus for grounding multi-layer insulations (MLI) by electric contact, of either of each layer with the other or of all the layers with the underlying structure by means of one or more points of attachment of mechanical type. This makes it possible to simplify the construction procedure and increase the reliability.This method is essentially carried out in the following manner: The layers (FIG. 1) which form the multi-layer insulations (6), (7) (8) are metalized on both faces and have holes (9) which are also metalized. All layers are contacted with each other and with a part of the attachment system (3) which is also electrically conductive.The other part of the attachment system (2) is positioned on the structure (1) in such a manner as to permit the passage of electric charges. By contacting the two parts of the attachment system (2) (3), the multi-layer insulation is grounded with the structure.

Abstract: The invention is a flush head fastener for joining two or more structural elements together. The structural elements have a fasterner hole therein with one of the structural elements being countersunk to accommodate the head of the fastener. The fastener includes head and shank portions and a layer of material joined to the top of the head of the fastener which can readily be deformed to fill any gaps between the head and the countersink. Thereafter, the excess material can be removed leaving an aerodynamically smooth surface. The surface also will have no electrical discontinuities. The procedure for installing the fastener includes the steps of (1) providing two or more structural elements having a countersunk fastener hole therein (2) thereafter the fastener is installed in the hole (3) the layer of material is deformed so as to fill any gaps between the head of the fastener and the countersink, and (4) thereafter, excess material is removed leaving a smooth external surface.

Abstract: Two composite structures are fastened together using an electrically conductive, threaded fastener. The composite structures have insulating surface regions and inner regions which contain conductive fibers. The threaded fastener is provided with large contact areas through the inner regions to facilitate discharge of high curent densities from the composite materials while minimizing localized heating. This significantly increases the life of the composite material.

Abstract: An integral lightning protection system and method for its use with an aircraft graphite epoxy structure. If a repair is to be made to an aircraft composite structure, the hole to be repaired is first cleared of broken composite material and replaced with a bonded adhesive patch. Over the patch and conformal to the surface of the aircraft composite structure, a dielectric layer is placed, and over the dielectric layer, at least one metal-plated graphite fiber fabric ply is placed. Where fasteners are inserted through an aircraft composite panel, the heads of the fasteners are left flush with the outer surface of the composite material, and the composite material and fastener heads are adhesively covered by a dielectric cover. Thereafter, at least one metal-plated graphite fiber fabric ply is placed over the dielectric layer. Subsequently, either structure may be given a primer and paint coating.

Abstract: A method and composition which provides both thermal; control and electrostatic discharge protection to bodies in the space environment. The composition comprises: (a) a chosen polymer or resin that forms a polymer that is an electronic insulator and is suitable for space applications; and (b) a selected lithium salt as a dopant wherein said composition, when formed into a film or coating, provides a semiconductive film or coating having a volume resistivity of about 10.sup.6 to 10.sup.11 ohm-centimeter and a value of solar absorptance/total normal emittance within the range of about 0.305 to 0.595. In an alternative embodiment, the composition may optionally include tantalum pentoxide.

Abstract: A volume of gas is enclosed by a cap around a fastener that is through a composite structure on an aircraft. The gas provides spark suppression for arcing that may occur between the composite structure and the metal fastener during a lightning strike. The volume of gas is sufficiently large to absorb the energy of small, very hot particles of graphite, epoxy, etc., that may be present resulting from arcing. High-pressure gas regions between the fastener and composite member vent to the larger volume of gas and are absorbed. This provides effective spark suppression for particular areas in an aircraft, such as a fuel tank, etc.

Abstract: A method for conditioning a composite structure to have an increased sparking current threshold. The method calls for the treatment of the joint in a composite structure by injected currents for predetermined periods of time at a sequence of voltages which are initially less than the present sparking voltage threshold of the structure. The voltage levels can be increased during the treatment to be greater than the sparking voltage threshold of the original structure. If the composite structure contains fasteners, the sparking voltage threshold can be conveniently increased by injecting the current from a timed voltage source through a variety of pairs of the fasteners.

Abstract: A fastener for use with aircraft structures comprising composite materials has improved electrical characteristics designed to reduce damage by lightning strikes. The fastener comprises separate nut and bolt portions and a cage member (4, 1, 6). The nut (4) and the head portion of the bolt 1 both have beveled edges which in use are countersunk in the composite materials to enhance electrical contact between the fastener and aircraft structural members (2, 5). The nut (4) is captively mounted inside the cage member (6) and is moveable, within pre-determined limits, inside the cage (6) so that it may be axially aligned with and the bolt screwed therein, thus compensating for any initial non-aligment of the nut (4) and bolt (1) due to a complex shape of the aircraft structure necessitated by aerodynamic or other considerations.

Abstract: A charge control apparatus for a flightcraft uses an inherent droplet charging mechanism to remove unwanted charge from the distal portion of a reference body mechanically connected to, and external to the craft, and a driven ion attachment mechanism to adjust the potential of the craft to that of the reference.

Abstract: The invention is a flush head fastener for joining two or more structural elements together. The structural elements have a fastener hole therein with one of the structural elements being countersunk to accommodate the head of the fastener. The fastener includes head and shank portions and a layer of material joined to the top of the head of the fastener which can readily be deformed to fill any gaps between the head and the countersink. Thereafter, the excess material can be removed leaving an aerodynamically smooth surface. The surface also will have no electrical discontinuities. The procedure for installing the fastener includes the steps of (1) providing two or more structural elements having a countersunk fastener hole therein (2) thereafter the fastener is installed in the hole (3) the layer of material is deformed so as to fill any gaps between the head of the fastener and the countersink, and (4) thereafter, excess material is removed leaving a smooth external surface.

Abstract: An improved tether having a central strength member comprised of layers of synthetic fibers surrounded by a thin weatherproof plastic barrier. A current carrying metallic braid surrounds the weatherproof barrier and in a portion of the tether is of a higher strength and denser weave copper than in other areas. An outer protective jacket surrounds the metallic braid and one or more windows are formed by removing a short longitudinal section of the outer jacket above an area of the tether which has the high density metallic braid. The weatherproof barrier, at least in the area where windows are formed, is heat sealed to form a seamless barrier. A relatively soft copper wire is wound around the metallic braid in the window area so as to transfer lightning induced currents in the metallic braid of the tether to a grounding system.

Abstract: An improved composite structure is disclosed for a lightning protective skin member of an aircraft vehicle surface. The skin member includes first and second graphite panels separated by a wire grid. The grid enhances the strength and elasticity of the skin member while also providing a conductive path for lightning current. Each of the graphite panels includes a plurality of graphite plies laminated with an adhesive, preferably epoxy.

Abstract: A device for dissipating static charge collected on the surface of an aircraft window having a plurality of electroconductive film elements on the outboard surface of the aircraft window. The elements are electrically interconnected and grounded such that charges accumulated by the film elements passed there along to the ground. An electrical window heating system may be incorporated into the plies of the window.

Abstract: Lightning protection apparatus for an exterior structural surface includes an electrically insulating protective coating adhered to the exterior surface, and a plurality of conductive particles supported in the coating. The particles are spaced at distances greater than the dimension of the particles in a direction parallel to the surface. The dielectric strength of the coating is thereby weakened by bridging the thickness of the coating with the particles. This enables lightning attachment to occur at a multiplicity of points rather than at one point, thereby reducing interior sparking in an aircraft and minimizing structual damage to the surface of the aircraft.

Abstract: A method of manufacturing a dielectric material for use in spacecraft, comprising the operation of coating a dielectric substrate with a layer comprising a metal oxide dispersed in a solution of a polymer material of a thickness such that when the polymer solvent has evaporated the resultant layer has a thickness comparable with the expected maximum range of incident electrons.

Abstract: An apparatus provides lightning protection for the radome of an aircraft, or the like, by providing an electrically discontinuous path having a plurality of separated electrically conductive segments that upon exposure to a high voltage field, form an inonization channel in the air above the segments. The conductive segments are so formed that the gap separating adjacent segments is narrower along the outer, exposed surfaces of the segments than is the case between surfaces of the adjacent segments anchored to a dielectric material. Such a design ensures the electrical separation of adjoining segments while permitting the breakdown voltage between adjacent exposed surfaces to be minimized.

Abstract: A lightning protection repair system for graphite epoxy structures. An aircraft graphite epoxy structure is repaired by fastening a repair plate over the hole to be covered, followed by a dielectric sheet covering the outer surface of the metal repair plate. An electrically conducting lightning diversion sheet, conforming to the outer surface of the repair plate, is fastened to the repair plate through the dielectric sheet. The edges of the lightning diversion sheet are bent toward the outer surface of the aircraft graphite epoxy structure to be adjacent or touching its outer surface. Sealing compounds can be used around the repair plate to prevent moisture intrusion, and the repair can be faired into the aircraft graphite epoxy structure by means of a fairing compound.

Abstract: Apparatus and method for efficiently and economically reducing and removing static charge from a surface of a dielectric material. One device is a window assembly comprising a window having an outer surface and a perimeter. The outer surface comprises a dielectric material. A frame is around the window and houses the perimeter. The frame has an outer surface which terminates along the outer surface of the window at a border. At least one corona point is attached to the window assembly proximate the border. Means for grounding the corona point is in electrical communication with the corona point. The number of corona points required to dissipate the static charge is minimized by a method that locates arc attracting regions and installs the corona points proximate these regions. Also provided are a corona point assembly and a kit comprising (1) the corona point assembly and (2) means for attaching the corona point assembly to the frame.

Abstract: The conductivity of the outer surface of skin (2) is enhanced by providing an outer layer of conductive material. The outer surfaces of each external metal fastener (8) and the skin around it are covered with a patch (6) of a strongly dielectric material. Patch (6) is dimensioned to cause current flow from lightning strikes to diffuse to a current density below an arcing threshold before reaching fastener (8). Preferably, further protection against arcing between the outer surface of skin (2) and metallic fasteners and fittings is provided by coating with a dielectric any surface portions of such fasteners and fittings that contact the skin (2) or an integral continuation thereof. When load requirements permit, fasteners made from dielectric materials are used instead of dielectric coated fasteners.

Abstract: A multilayered electronics protection system includes a first ablator layer providing thermal protection that is sprayed on to a non-metallic surface of an electronics enclosure. A second ablator layer comprised of highly conductive material is sprayed on to the first ablator layer and provides protection against strategic environmental threats.

Abstract: A composite material skin (42) is attached to a composite material support structure (26) by a plurality of metal lock bolts (64). A foraminous metal material (44) is embedded in the matrix of the outer layer of the skin (42) and positioned outwardly of reinforcing graphite fibers. The metal (44) is preferably copper in a knitted, woven, or expanded metal configuration. The metal (44) is in direct electrical contact with the graphite fibers to disperse current throughout the skin (42) and is sufficiently proximate to the lock bolts (64) to divert current away from the bolts (64). Each bolt (64) is surrounded by an expanded sleeve (74) and fits tightly within the sleeve (74) to provide good electrical contact between the bolt (64) and the skin (42). The inner end (70) of the bolt (64) has parallel grooves (72) thereon, and a collar (76) is swaged onto the end (70) to prevent arc plasma from escaping into the interior of the aircraft.

Abstract: A rescuer (1) is lowered at the end of cable (2) from a helicopter having a winch (4) on which the cable is wound. The rescuer is provided with a electric field sensor (20) which is downwardly directed and which is connected to a radio transmitter (22). The helicopter (3) has a corresponding radio receiver (24) which serves to actuate an active static discharger which is servo-controlled to the electrical magnitude supplied by the sensor (20). The servo-control is such that the potential difference between the rescuer (11) and the person to be rescued (10) is progressively reduced as the rescuer approaches the person to be rescued. Practically all risks of an electric shock on making contact are thus avoided.

Abstract: A method for protecting composite structures from electrostatic discharge. This method includes limiting resistive heating in conductivity enhanced layers of composite material to prevent delamination due to pyrolytic reactions. Only sufficient metal is used in external conductivity enhanced layers to cause dielectric breakdown to occur before delamination due to pyrolytic reaction results.

Abstract: A plurality of metal conduits for fuel for hydraulic fluids extend through an aircraft fuel tank made of non-metallic materials such as carbon-epoxy. The conduits are attached to wall portions of the tank at spaced apart locations. The conduits are spaced apart from each other and are each spaced away from such wall portion of the tank. A dielectric insulator such as teflon or polyimide is provided on each conduit.

Abstract: A fastener (36,58) attaches a composite material external skin (2) of an aircraft structure to another structure (4). Fastener (36,58) has a metallic head (44,62) and shaft (38,60) and a dielectric cap (50,70) covering a top portion of head (44,62). Head (44,62) and cap (50,70) are received into a countersink hole (6) in skin (2). Cap (50,70) is resilient and fills gap (16) between the top portion of head (44,62) and the inner sidewalls of hole (6). Cap (50,70) forms, with skin (2), an aerodynamic surface which is sufficiently continuous to receive and maintain a crack-free coat of paint having a uniform thickness. The top (52) of cap (50) of internally wrenching fastener (36) is an integral layer of uniform thickness. The top (72) of cap (70) of fastener (58) includes a uniform layer covering the head's top surface around a tool receiving recess (66) and a body of material (74) filling recess (66) and positioned therein after structures (2,4) are attached.

Abstract: Conductive coating (20) is a thorough mixture of 0.03 parts per weight of carbon black together with 0.003 to 0.01 parts per weight of wetting agent and 20 parts of solvent, and further mixing in by low shearing mixing 1/2 to 1 part per weight of thermosetting resin. This is then sprayed into place on the substrate and thermoset. In this particular case, the substrate is exterior face sheet (12) of honeycomb structure (10) which may serve as part of a spacecraft, to electrically conduct away surface charges.

Abstract: A static discharger for discharging charge accumulation from the surface of the wing of an aircraft, comprises a generally flat layer of non-conductive material which is dimensioned and configured so that it can be secured to a portion of the wing surface and so as to conform generally to the shape of the wing surface. A generally flat base member is dimensioned and configured so as to be capable of being placed in conforming relationship with at least a portion of the surface of the layer of non-conductive material which insulates the base member from electrically contacting the surface of the aircraft. A plurality of strands formed of a discharging material are embedded in the base member. The plurality of strands are electrically connected to the wing surface of the aircraft so that charge accumulation may pass from the wing surface of the aircraft to the plurality of strands and be discharged at the trailing ends of the strands.

Abstract: A device for dissipating static charge collected on the surface of a laminated aircraft window having an outboard plastic ply includes a plurality of electroconductive static charge collecting wicks extending through the thickness of the outboard ply from the outboard surface of the ply to its inboard surface where the wicks are interconnected by wire runs adapted for connection to ground. The device may be laminated to additional transparent structural plies to form a composite aircraft transparency. The device is advantageously used to protect heating facilities in a composite transparency from static discharge damage, as well as to prevent damage to the plies of the transparency from static discharge through the plies.

Abstract: A conductive strip for attachment to an aircraft radome to provide protection against the effects of a lightning strike to the radome, wherein the conductive strip has a series of holes formed in it.

Abstract: Polyurethane foam is modified by a post-treatment process comprising the steps of contacting the polyurethane foam with a swelling agent for the polyurethane foam and interpenetrating the swollen foam with a chemical additive, then shrinking the interpenetrated foam by removing the swelling agent under conditions where the chemical additive remains trapped in the polymeric structure of the foam.