RU2493057C1 - Thermostatic material - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: invention relates to space materials science and optical hardware, particularly, to thermostatic materials intended for space structure passive thermal control systems. Thermostatic material comprises outer facing layer of nonwoven material with electrically conducting threads interlaced in lengthwise and crosswise directions. Substrate of polyamide film metalised on inner surface is introduced in thermostatic material. Outer facing layer interwoven electrically conducting threads produced by twisting metal 30-50 mcm-thick wire with polymer thread of linear density of 1.5-11 tex and interweaving with thread density of 6-12 g/cm² as to warp and weft. Thermostatic layer based on polyimides or polyether imides, or polyethers, or polysulfone is arranged between substrate and facing layer.

EFFECT: decreased weight of thermostatic material.

1 dwg

Description

The invention relates to the field of space materials science and optical technology, in particular, to thermoregulating materials intended for use in systems of passive thermoregulation of space objects, for example, for thermal protection of instruments and equipment of spacecraft.

In addition, the proposed technical solution can be used as a heat-shielding and thermoregulating material in a sealed evacuated volume.

A number of negative factors affect space objects (KO) flying both in near-Earth and in geostationary orbits, which interfere with the normal functioning of on-board systems and equipment, as well as the safety of the crew, which puts forward a number of requirements for temperature-controlled materials:

- electromagnetic radiation (EMR) of the Sun requires ensuring radiation resistance of protection materials;

- UV radiation acts on the surface of space objects, as well as hot gas streams of working rocket engines that adversely affect the spacecraft’s hull, equipment and crew; in this regard, it is necessary to maintain the temperature of their regular functioning;

- corpuscular radiation also acts on the outer surface of the spacecraft body — the fluxes of electrons and protons of the Earth’s radiation belts (RPGs), under their action, an inhomogeneous electrostatic charge accumulates on the dielectric surfaces of the spacecraft, and discharges occur between the surface areas with different electric potentials, causing electronic on-board disruptions equipment and contributing to the deterioration of the characteristics of optical surfaces, this factor puts forward its requirements for the electrical conductivity of the protection material;

- the outer surface of the body of the KO is exposed to the negative effects of atomic oxygen, leading to destructive changes in the surface of the KO, which requires the presence of a protective layer in such material;

- the thermoregulating material should work well for “tearing”, i.e. possess the necessary strength;

- another important property should be possessed by the KO protection material - it should be lightweight, as any increase in mass reduces the weight of the payload delivered into orbit.

- an important requirement for a protective material is its flexibility, flexibility, because KO case has a complex configuration;

- the thermoregulatory coating used in outer space in a vacuum should not "dust" and have gas evolution, which is unacceptable for optical on-board devices.

Known layered shell for thermal and electrostatic protection according to Russian patent No. 2087392 (IPC: B64G, 1/58), consisting of an electrically conductive layer of a semiconductor (for example, Germany) with a thickness of 5 ^... 25 · 10 ^-8 m, a thermoregulating layer, a substrate of a polyimide film , an intermediate layer of a polyamide network (which can be impregnated with epoxy resin and vulcanized), attached to the substrate, and a thermally reflective coating of a polymer film material based on silicon or polyvinyl fluoride.

The disadvantages of this coating are the easy damage to the thin surface layer during installation, insufficient reflectivity, and also the rigidity, which does not allow it to be used for complex composite structures.

A multilayer coating is known for operation at cryogenic temperatures and / or under conditions of aerodynamic heating according to RF patent No. 2298480 (IPC: B64G, 1/58), consisting of a metal shell, an anticorrosive layer, an amortization layer, a heat-insulating layer in the form of foam, which is fixed by a network with glue and anti-static coating.

The main disadvantages of this coating are very large weight and insufficiently high thermal insulation properties.

Known multilayer material for thermal control according to British patent No. 2062189 (IPC: B64G, 1/58), consisting of internal and external thermally insulating layers, which can be made flexible from plastic or rigid from glass and an intermediate conductive layer of aluminum or silver. On the inside, there may be a second electrically conductive layer of aluminum or silver.

The disadvantages of this material are low strength, damage, poor optical characteristics.

Known multilayer material consisting of metal (at least two) and polymer layers, containing a sublayer of two metal layers and a fiber reinforced polymer, described in international application (PCT) WO 2007/061304 (IPC: B64G, 1/58).

The disadvantages of this material are very large weight and insufficiently high thermal insulation properties due to the tight contact of the metal and polymer layers, poor optical characteristics: high reflective properties, but a low degree of blackness.

Known multilayer insulation according to US patent No. 7252890 (IPC: B64G, 1/58), consisting of layers of metallized aluminum or silver polymer (polyimide or polyester), between which are layers of fiberglass or nylon, coated on the upper side of the IR-emitting material (quartz , glass, silicon nitride or oxynitride), then with a photocatalytic layer of metal oxide and from the outside with an electrically conductive layer of indium or tin oxide.

The disadvantages of this material are insufficient tensile strength when stitching heat-protective mats and slight damage to abrasion, contamination of the outer layer during the manufacture and transportation of spacecraft.

Known multilayer coating for mats of screen-vacuum thermal insulation of spacecraft according to Russian patent No. 2269146 (IPC: B64G, 1/58), consisting of a substrate with a transparent electrically conductive multilayer (2 or more layers) coating on the outer surface and a reflective coating in the form of a metal film on the back surface.

The disadvantages of this material are very low mechanical tensile strength, damageability, and contamination.

Known multilayer coating according to French patent No. 2681078 (IPC: B64G, 1/58) containing a polymer substrate, on which an adhesive layer is applied, followed by the application of a metal optical layer.

The main disadvantage of this analogue is the high value of the ratio of the absorption coefficient of solar radiation of the resulting coating to the emission coefficient (degree of blackness) As / ^∈ = 2 with the required ratio of less than 1.0 for thermostatic coatings of the "solar reflector" class.

A multilayer thermoregulatory coating of the “solar reflector” class is known according to RF patent No. 2168189 (IPC: B64G, 1/58), containing a polymer substrate with an optical layer deposited on it with whisker or fibrous zinc oxide crystals with high reflectivity in the wavelength range of 0, 3-2.4 µkm, while the polymer substrate is made elastic.

The main disadvantages of this analogue are the low stability of optical characteristics (due to the use of an organic binder) and low electrical conductivity. In this case, the coating accumulates an electrostatic charge under the action of charged particles, which leads to the appearance of electric discharges, which cause failures in the on-board equipment of KO.

A coating is known according to US Pat. No. 5,400,986 (IPC: B64G, 1/58) comprising a thin dielectric sheet, the outer surface of which is coated with a transparent conductive layer, the back surface is coated with a reflective layer, and the end surface of the sheet is coated with an electrically conductive coating so that at least partially overlaps the reflective layer and is electrically connected to the outer transparent conductive layer, the layer of adhesive material, mainly of constant thickness, and the outer surface of the adhesive layer is larger than the back surface dielectric sheet; the adhesive layer is fixed with the back side to the surface of the spacecraft body, and the external surface fixes the back side of the dielectric sheet, while the adhesive layer is electrically conductive and electrically connected to the specified end coating to provide a current path between the outer surface of the specified sheet and the outer surface of the spacecraft body through the specified end coating.

The disadvantages of this solution are brittleness, stiffness, mechanical abrasion, high weight.

Known thermoregulation device according to US patent No. 4618218 (IPC: B64G, 1/58), which is a three-layer coating, the outer layer of which is made of a transparent (for given wavelengths) electrically conductive material, for example Ge; the intermediate one is made of a solid electrolyte with predominantly ionic conductivity, and the inner one is made of silver. Depending on the potential difference between the outer and inner layers, the coating can absorb or reflect radiation of a certain wavelength range.

The main disadvantages of this analogue are: the need for an energy source and a control circuit; the impossibility of combining high emissivity and high reflectivity in the wavelength range of 0.3-2.4 µkm. Rs (Rs = 1-As), mechanical abrasion resistance.

There is a thermostatic coating according to US Pat. No. 5,296,285 (IPC: B64G, 1/58), which is a two-layer coating formed by creating a first layer by anodic oxidation of an aluminum base and applying a second top layer consisting of a silicate coating.

Relative fragility, insufficient elasticity, laborious application are the main disadvantages of this coating, mechanical abrasion resistance.

There is a temperature-controlled coating according to RF patent No. 2356074 (IPC: B64G, 1/58), attached to the outer surface of the spacecraft’s body using an electrically conductive adhesive layer, containing a substrate made in the form of individual elements from an optically transparent radiation-resistant material, the back surface of which covered with a reflective and protective layer, and on the outer surface there is a transparent electrically conductive coating covering the end surfaces of the substrate and in contact with the protective layer, while separate The substrate was made with a thickness of at least 0.08 mm, the conductive coating was made with an electrical resistance of at least 2 and not more than 1 · 10 ⁵ kOhm / m ² , and an adhesive layer was applied over the protective layer.

Disadvantages - fragility, inelasticity, high weight, mechanical abrasion.

Known screen-vacuum thermal insulation of a spacecraft with an external combined coating according to RF patent No. 2397926 (IPC: B64G, 1/58), consisting of a polymer substrate, an electrically conductive layer with a wear-resistant layer on the outer surface and a reflective layer on the inner surface. The insulation contains a temporary protective layer on the outer surface and a reinforcing polymer network on the inner surface.

The disadvantages of this thermal insulation are the large mass of the external combined coating (140 g / m ² ), insufficient radiation resistance due to the use of adhesive compositions, insufficient reliability due to insufficient bonding strength of the polymer film, significant gas evolution from dissimilar thermal insulation materials, and also strong warping of the working surface due to due to uneven heat shrinkage of dissimilar heat insulation materials.

Known screen-vacuum thermal insulation by AS 1840181 (IPC: B64G, 9/00), containing the outer and inner facing layers and screens located between them with a one-sided metallized surface, separated from each other by separators of low-heat-conducting material, in which the screens are oriented with a metallized surface to the inner facing layer.

The disadvantage of this solution is the low resistance to electrification of the outer facing layer, which leads to the appearance of electrostatic discharges on the surface of this layer.

As a prototype of the claimed decision, the material according to the patent of the Russian Federation No. 2344972 (IPC: B64G, 1/58) was adopted in which the outer facing layer is made of a dielectric woven material with a weaving density of 0.34-0.7 g / cm ² woven in the longitudinal and transverse directions by electrically conductive threads.

The disadvantages of the prototype are the large mass, the inability to obtain effective thermal insulation for devices and assemblies of complex configuration, low resistance to electrification of the outer facing layer, which leads to the appearance of electrostatic discharges on the surface of this layer, mechanical abrasion.

The objective of the invention is to reduce the mass of the material, the exclusion of electrostatic discharge both in operating conditions and during installation and assembly works, as well as maintaining surface conductivity due to the absence of influence on these characteristics of abrasion and other mechanical influences during installation and assembly operations, while maintaining the optical characteristics of the material.

This problem is solved in that in a thermostatic material containing an outer facing layer of woven material with electrically conductive threads interwoven in the longitudinal and transverse directions, a substrate is inserted into it from a polyimide film metallized, at least on one side, and the outer one the facing layer is made with weaving electrically conductive threads obtained by twisting a metal wire with a thickness of 30-50 μm with a polymer thread of linear density 1.5-11 tex and weaving with a density of nit 6-12 minutes / cm ² in warp and weft, wherein between the substrate and the cover layer injected thermoplastic layer based on polyimides or polyetherimides or polyesters or polysulfones.

The drawing shows the design of the proposed material, where:

1 - outer facing layer;

2 - combined conductive threads;

3 - polymer threads;

4 - thermoplastic layer;

5 - metallized substrate.

The proposed material consists of an outer facing layer 1 made of woven fabric for weft and warp of polymer threads 3 and combined threads of conductive threads 2, obtained by twisting a metal wire 30-50 μm thick with a polymer thread of linear density 1.5-11 tex and weaving with a density 6-12 filaments / cm ² in warp and weft, in addition, the material introduced metallized substrate 4, and between the substrate 5 and the cover layer 1 is entered thermoplastic layer 4 based on polyimides or polyetherimides or oliefirov or polysulfones, and the substrate 5 may be metallized as soon as the inner side and both sides.

We give examples of the implementation of the proposed solution.

Example 1

For the outer facing layer, a fabric is made of two types of filament: an arimide thread with a linear density of 6 tex and a combined twist consisting of an arimide thread with a density of 6 tex and a silver-plated copper wire 50 μm thick.

At the same time, the combined thread is arranged in increments of 8-10 mm along the weft and the base, and the tissue density is 12 ÷ 14 g / m ² , which is significantly less than in the prototype (340 g / m ² ), and therefore significantly less in mass.

The fabric is thermally welded using a thermoplastic polyimide film, for example, PI-PK-200, with a thickness of 8-10 mm to a metallized substrate of a polyimide film with a thickness of 12.5 μm. With double-sided coating with aluminum with a thickness of 500-700 A ° and black factor ≤0.06.

The total mass of the material will be only 45 ÷ 55 g / m ² , and the mass of the prototype is 350-700 g / m ² .

To protect against atomic oxygen, a layer of indium oxide or silicon oxide can be deposited on the outer facing layer, for example, by a vacuum magnetron method.

Example 2

The outer facing layer consists of fabric, for example, made of monofilament polyester yarn with a linear density of 1.6 tex and a combined twisted yarn of polyester yarn with a density of 1.6 tex and cobalt wire 30 μm thick, while the combined yarn and warp spacing is 8 -10 µkm, and the density of the fabric with openwork weaving 8-10 g / m ² .

The fabric is welded onto a polyimide metallized film, film thickness 12.5 µkm.

As a thermoplastic layer for welding, a film of polyester resin TF-55 or TF-60 with a thickness of 8-12 microns is used.

A film can also be formed on the surface of a metallized PET film from a solution of resin in methylene chloride.

The total mass of the material will be 35-40 g / m ² , which is significantly less than that of the prototype.

The proposed material excludes the possibility of the appearance of electrostatic discharges, as the position of the threads in the facing layer is fixed during welding of the thermoplastic layer and, thereby, local breakdowns of electrostatic discharges are excluded.

The proposed material works much better on abrasion, because the wire is much stronger than metal spraying (as in the prototype).

The optical characteristics of the invention are also better than that of the prototype due to the use of a polymer film of small thickness and sparseness of the fabric of the facing layer due to weaving with a density of threads 6-12 / cm ² for weft and warp. In the visible range, the absorption coefficient is A _s = 0.35-0.45, and the degree of blackness in the IR range is ε = 0.7-0.85, which reduces the surface temperature of the object, for example, KO.

Claims (1)

Thermoregulating material containing an outer lining layer of woven material with electrically conductive threads interwoven in the longitudinal and transverse directions, characterized in that a substrate is made of metallized from at least one of the inner side of the polyimide film, while the outer lining layer is made with weaving electrically conductive threads obtained by twisting a metal wire with a thickness of 30-50 microns with a polymer thread of linear density 1.5-11 tex and weaving with a density of threads 6-12 / cm ² on the weft and the base, and between the substrate and the facing layer, a thermoplastic layer based on polyimides or polyetherimides, or polyesters, or polysulfones is introduced.