FR3102436A1 - COMPOSITE STRUCTURE FOR VEHICLE INSULATION - Google Patents

Abstract

The invention relates to a composite structure for the interior insulation of a vehicle, the structure having a surface, called external, oriented towards a wall of the vehicle to be dressed and a surface, called internal, oriented towards the interior of the vehicle, and comprising a flame-retardant closed-cell polyethylene foam, said structure comprising, on at least the internal surface, a layer of at least one material selected from polyurethanes, polyureas, poly (urethane-urea) copolymers and any mixture of said polyurethanes , said polyureas and / or said poly (urethane-urea) copolymers. The invention also relates to insulation panels made with this structure and to a vehicle so equipped.

Description

COMPOSITE STRUCTURE FOR VEHICLE INSULATION

The present invention relates to the field of the insulation of the interior walls of a vehicle and more particularly that of military land vehicles.

By vehicle according to the invention, is meant any land machine, in particular armored, such as a car, a light or heavy truck, a combat vehicle, a command or troop transport vehicle, a tank, a logistics truck, a trailer..., the interior of which needs to be insulated mainly from the extreme temperatures encountered in theaters of operation, but also from the flames resulting from the attacks to which the vehicle is exposed, accidental fires, incendiary ammunition, improvised explosive devices (EEI or IED Improvised Explosive Device), in order to protect the occupants of the vehicle, but also the equipment.

The bodies of armored vehicles are essentially metallic and more precisely made of materials based on metals including iron, aluminum, and metal alloys of which steel remains the main one. In order to provide protection against various threats and to stiffen the structure of the body, these metallic materials are particularly thick and highly conductive. The temperature inside such a vehicle can reach 75°C in certain areas of intervention, air conditioning off. The problem of thermal insulation is therefore crucial.

The thermal insulation solutions are provided by composite structures comprising polymer foams of the polyurethane, polypropylene, polyethylene, solid type, which are cut to obtain panels which are then fixed to the walls or parts of the wall of the vehicle, directly on the metal wall or parts of the wall or on the interior spall shield plates. These panels are fixed in a removable manner by means of Velcro, one fastener being glued to the wall of the vehicle or to the splinter-guard liner, the other being glued to the so-called external face of the structure which is oriented towards the wall of the vehicle . It is not common to use screws to fix these insulators, because the through screws, themselves made of metal, would constitute a thermal bridge. Adhesives used for Velcro adhere poorly to polymer foams, especially to non-polar, low surface energy polymers such as polyethylene and polypropylene; also the outer face of the panel is often coated with an intermediate layer which will serve as an interface.

The present invention is specifically concerned with a composite structure comprising a closed-cell polyethylene foam, or cellular polyethylene. This foam is chosen because in addition to its thermal insulation performance, its low surface energy and its closed cells allow it to ensure airtightness, as well as liquids, and can be treated to increase its properties. or give it others. Thus, a closed-cell polyethylene foam according to the invention has been subjected to a fire-retardant treatment to enable it to prevent, or at least limit, the spread of flames resulting from a fire outbreak or a fire in the vehicle, which can be caused by an accident or the impact of a homemade bomb, rocket or incendiary bullet to which the vehicle is exposed in theaters of operation. Such treatment is all the more important since the cabin is a very confined place and military vehicles have very few exits, in particular for passengers who often only have a rear ramp and a roof hatch. It can also be treated with one or more agents and/or one or more processes aimed at improving this fire resistance property, and/or providing any additional characteristic increasing the performance of the foam with a view to its use. Among these foams, preference will be given to those which are stable with regard to said extreme conditions, so that they release little or no volatile organic compounds into the interior of the vehicle in order to comply with the regulations in force concerning the limits of exposure, as well as sufficiently flexible foams for easy cutting of the insulation elements which will have to adapt perfectly to the walls or parts of the wall of the interior of a vehicle, including the most inaccessible and/or the less flat such than the wheel offset zones. Suitable foams are well known to those skilled in the art and are commercially available.

This polymer foam lining is however exposed on the inside of the vehicle to numerous attacks such as repeated friction by users and knocks from their equipment such as helmets, gun butts, the frequency of which is increased in a cramped passenger compartment, but also chemical attacks associated with cleaning, decontamination, for example nuclear, radiological, biological and chemical (NRBC) decontamination, leaks or spills of aggressive automotive liquids such as gasoline, hydraulic oil, coolant. Currently, the interior insulations of military vehicles are obtained from cutting composite structures comprising a polymer foam and a polymer layer in the form of a film, adhesive on the so-called internal surface of the structure which is oriented towards the inside the vehicle, this layer fulfilling the finishing role and making it possible to protect the polymer foam. This topcoat must be fire resistant; it is usually a chlorosulphonated polyethylene (CSM) film or fabric available under the trade name Hypalon, due to its wear resistant qualities. Since the edges of the structural panels can also be stressed, they too are coated with a finishing coat; a self-adhesive strip is generally applied around the entire perimeter of the edge of the composite structure, then it is folded over the external and internal faces in order to improve adhesion.

The problems encountered by the use of such materials, films or fabrics, to constitute a finishing layer are their lack of adhesion to the polymer foam and the low durability of the structure, these problems being accentuated by the assembly and disassembly successive insulation panels and by the shocks and friction they undergo during use. This results in a decohesion of the finish and the foam, with the appearance of permanent wrinkles and premature wear that alter the properties of the composite structure and give the surface an unattractive appearance. It is indeed observed that after a few years of exposure of the vehicle to normal conditions of use on military terrain, the finishing layer separates from the foam at least partially creating an appearance of orange peel or embossing, up to complete decohesion. Sometimes such defects are even found in a new vehicle resulting from folding the composite structure to introduce it into the vehicle; this fold is irreversible and can be the starting point of premature wear.

According to the invention, this difficulty has been overcome by resorting to a finishing layer of a material which, once combined with the polyethylene foam, no longer dissociates from it despite the stresses. This association between the finishing layer and the polyethylene foam is achieved and maintained throughout the life of the panel, on the complete internal surface, improving its aesthetic appearance and extending its lifespan.

The solution provided according to the invention consists of a composite structure comprising at least on the internal surface a layer of a material chosen from polyurethanes, polyureas, poly(urethane-urea) copolymers and any mixture of said polyurethanes, said polyureas and/ or said poly(urethane-urea) copolymers.

Thus an object of the invention is a composite structure for the interior insulation of a vehicle, the structure having a surface, called external, oriented towards a wall of the vehicle to be dressed and a surface, called internal, oriented inwards. of the vehicle, and comprising a flame-retardant closed-cell polyethylene foam, the latter being directly coated, on at least the internal surface, with a layer of at least one material chosen from polyurethanes, polyureas, poly(urethane- urea) and any mixture of said polyurethanes, said polyureas and/or said poly(urethane-urea) copolymers. By any mixture is meant mixtures of 2, 3, 4 polymers and/or copolymers, or more, of the same nature as polyurethane, polyurea or copolymer, or of different natures, for example a polyurethane and a polyurea, a polyurethane and a copolymer poly(urethane-urea)…

The material intended to constitute the finishing layer can easily be applied directly to the polyethylene foam by any means and for example by spraying, for example by means of an air gun, with a brush, with a roller. Whatever technique is used, the bond is effective and durable. This significantly reduces labor time compared to usual practice. A person skilled in the art has sufficient knowledge to know how to apply this material; in particular, polymerization can be achieved when applying a two-component system. Thus, in a preferred variant, the material of the topcoat is applied in the liquid state, in particular in the form of its precursors, and the polymerization reaction takes place in contact with the foam, or shortly thereafter, to ensure strong adhesion. According to the invention, an intimate bond is created between the foam and the finishing layer which makes it possible to overcome the problems of separation encountered in the existing solutions which consisted in simply assembling a finishing film on the foam by means of an adhesive.

This result is quite unexpected because a closed-cell polyethylene foam is particularly resistant to the durable fixing of a coating due to its impermeable, apolar and low surface energy character. The attachment of the material to the polyethylene foam according to the invention being carried out on the surface, the properties of the foam, in particular its fire-retardant treatment, are not affected.

The finishing coat can also be applied to the edges of the composite structure without interruption since the liquid coating, sprayed or deposited with a roller, is applied in a single pass, both on the surface and the edges. This is an advantageous variant, since the polyethylene foam panels are obtained by cutting from a large plate and then see the opening of the closed cells along the cut line. The application of the finishing coat on the edges thus makes it possible to avoid the penetration of fluids, in particular the aforementioned aggressive fluids. On the edges, the same better adhesion of the coating applied in one pass and forming one with the coating of the surface, is observed compared to the self-adhesive strips used conventionally and which are simply superimposed on the finishing film assembled by means of an adhesive protecting the surface.

The desired resistance effect can be achieved with a layer thickness of only 1.5 mm; this thickness can vary from 0.5 mm to 6 mm.

According to variants of the invention, in particular preferential variants, the materials of the topcoat will be chosen from polyurethanes, polyureas and copolymers having the following characteristics, considered alone or in combination:

polyurethanes, polyureas and copolymers (urethane-urea) have a density in the range of 0.9 to 1.3 kg/L;

polyurethanes, polyureas and copolymers (urethane-urea) are of the aliphatic or aromatic type, preferably aliphatic because they are more resistant to UV;

urethane and urea copolymers are homogeneous, random, periodic or random copolymers, or heterogeneous, block or graft copolymers;

polyurethanes, polyureas and copolymers (urethane-urea) are rigid enough to resist abrasion and friction; for this purpose, they have an elongation at break of less than or equal to 200%;

polyurethanes, polyureas and copolymers (urethane-urea) are solvent-free in order to limit the release of toxic compounds, in particular volatile organic compounds (VOCs) in a generally cramped passenger compartment and covered over a large part with such a composite structure;

the mixtures are obtained from the polyurethanes, polyureas and copolymers (urethane-urea) described above.

The material of the finishing layer can also comprise any additive, for example any additive making it possible to improve its adhesion, its resistance to peeling, to friction and generally to wear, but also its appearance, or to confer any other property on it. additoinal.

The closed cell polyethylene foam involved in the composite structure is flame retardant; this operation is preferably carried out by additives or flame retardant treatments free of halogenated compounds. Indeed, the latter effectively limit ignition, but in the event of combustion, they release extremely corrosive and toxic halogenated acids.

A suitable polyethylene foam according to the invention advantageously has a density of 5 to 100 kg/m ³ .

The closed cell polyethylene foam has a thickness in the composite structure in the range of 5 mm to 50 mm, preferably 10 mm to 30 mm. For some uses it may be less than 10mm, especially in areas of the vehicle interior less exposed to temperature extremes; it can also be higher, especially for the insulation of the ceiling of a vehicle, which happens to be the part of the vehicle most exposed to the sun, as well as the areas in contact with the engine compartment, which emits a lot of heat.

In order to allow its fixing, a composite structure according to the invention advantageously comprises, on its external surface, a Velcro allowing its fixing on the vehicle without metal screws and therefore without thermal bridge.

The invention also relates to a panel for the interior insulation of a vehicle, comprising or consisting of a composite structure as defined previously. Such a panel is according to the invention advantageously intended to furnish all or part of a door, a ceiling, the side walls and/or a floor of a vehicle, such as a vehicle exposed to extreme conditions. temperatures and fire hazard, such as a military vehicle.

Another object of the invention is a vehicle of which all or part of the interior is covered with a coating as defined above or comprising at least one panel of the invention.

Claims (12)

Composite structure for the interior insulation of a vehicle, the structure having a so-called external surface oriented towards a wall of the vehicle to be covered and a so-called internal surface oriented towards the interior of the vehicle, and comprising a polyethylene foam with fireproof closed cells, characterized in that it comprises, on at least the internal surface, a layer of at least one material chosen from polyurethanes, polyureas, poly(urethane-urea) copolymers and any mixture of said polyurethanes, said polyureas and/or said poly(urethane-urea) copolymers. Composite structure according to Claim 1, characterized in that the said layer is a finishing layer, the thickness of which varies from 0.5 mm to 6 mm. Composite structure according to Claim 1 or 2, characterized in that the said material is chosen from polyurethanes, polyurethanes, polyureas and copolymers (urethane-urea) whose density is of the order of 0.9 to 1.3 kg/L. Composite structure according to any one of Claims 1 to 3, characterized in that the said material is chosen from polyurethanes, polyurethanes, polyureas and copolymers (urethane-urea) having an elongation at break less than or equal to 200%. Composite structure according to any one of Claims 1 to 4, characterized in that the said material is applied in the liquid state (spray, roller) and polymerizes on the foam in order to ensure strong adhesion. Composite structure according to any one of Claims 1 to 5, characterized in that the polyethylene foam is fireproofed by means of a treatment free of halogenated compounds. Composite structure according to any one of Claims 1 to 6, characterized in that the said layer comprises one or more additives. Composite structure according to any one of Claims 1 to 7, characterized in that it is coated on its edges with a said finishing layer. Composite structure according to any one of Claims 1 to 8, characterized in that it comprises, on its external surface, Velcro allowing it to be fixed to the vehicle without metal screws and therefore without a thermal bridge. Panel for the interior insulation of a vehicle, characterized in that it comprises or consists of a composite structure according to any one of the preceding claims. Panel according to Claim 10, characterized in that it is intended to line all or part of a door, a ceiling, the side walls and/or a floor. Vehicle of which all or part of the interior is covered with a composite structure according to any one of claims 1 to 9 or comprising at least one panel according to claim 10 or 11.