FR2461688A1 - THERMAL INSULATING MATERIAL BASED ON MINERAL FIBERS AND SYNTHETIC RESIN - Google Patents

Abstract

THERMAL INSULATION COMPOSITE MATERIAL CONTAINING INSULATING MINERAL FIBERS TAKEN IN A MATRIX FORMED BY A POLYMERIZED THERMOSETTING RESIN, CHARACTERIZED IN THAT THE FIBERS ARE CHOSEN FROM THE GROUP CONSTITUTED BY SILICA FIBERS FROM GRAND CERUMIN FIBERS AND PURETE FIBERS, , ARE APPROXIMATELY 25 TO 65 BY WEIGHT OF THE FIBER-POLYMERIZED RESIN COMPOSITE MATERIAL, AND HAVE A DIAMETER LESS THAN ABOUT 15 MICRONS AND A LENGTH GREATER THAN ABOUT 3 MM, AND THE MATRIX IS A CARBON PRODUCT LIKELY TO LEAVE MATRIX ON THE FIBERS. OF PYROCARBON IN CASE OF PYROLYSIS OF THE MATERIAL. APPLICATION IN PARTICULAR TO THERMAL INSULATION USED IN AVIATION.

Description

The present invention relates to an insulating composite material

  thermal device of the type comprising insulating mineral fibers taken from a matrix formed by

  a polymerized thermosetting resin.

  The fields of application targeted by the present invention are those in which a product is sought.

  having a good fire behavior, excellent properties

  thermal insulation tees at high temperature and,

  a very good answer. t a nc e to chemical agents.

  As an indication, these areas are, for example, the iso-

  thermal insulation in aeronautics and aerospace systems, firewall in aviation,

  marine and building, protection of soles, .....

  At present, the materials combining the properties mentioned above are generally based on asbestos fibers. Asbestos fibers are

  dangerous to health and their use, in parti-

  their manipulation requires precautions

  health and safety.

  Also, a first object of the present invention is to provide a thermal insulating composite material having the aforementioned properties without using

  asbestos fibers. The present invention also obtains

  to obtain a material that can be put into

  machined and whose mechanical properties can be adapted to the envisaged conditions of use,

  without alienating its thermal properties. Finally, the presentation

  Another object of the invention is to provide a material

  thermal insulation composite whose thermal conductivity

  can be lowered well below minimum values.

currently obtained.

  According to the invention, the composite material

  is of the type defined at the beginning of the present description

  and is characterized in that: the fibers are selected from the group consisting of silica fibers of -2

  high purity, alumina fibers and cerebral

  about 25% to 5% by weight of the material.

  fiber-resin composite polymerized, and have a dia-

  meter less than about 15 microns and a maximum length

  less than about 3 mm, and the matrix is a carbon product likely to leave on the fibers

  a pyrocarbon matrix in case of pyrolysis of the material.

  Not only do you get a flame and chemical resistant product with a very good high temperature insulation

  known products based on asbestos fibers, but

  does this product maintain its integrity and its proprietary

  insulation after pyrolysis and in addition to the conductibility

  thermal can / lowered to very low values.

  Thus, according to a preferred embodiment of

  the invention, the mineral fibers used are

  alumina containing at least 90% A1203 or

  silico-aluminous ceramic bees containing about 40

  60% A1203 and about 40 to 60% SiO2. Conductivity

  thermal stability of the material can then reach a

  value less than 0.3 W / m.0K, a value well below

  above the minimum threshold of 0.7 W / m.0K currently obtained

  naked with asbestos-based products, this threshold can be matched by using high silica fibers

  purity in the material according to the invention.

  The percentage by weight of fibers is chosen

  greater than 25% to obtain sufficient mechanical strength

  by the fibrous reinforcement and less than 65% to avoid difficulties of penetration of the resin in the heart of the fiber reinforcement during the manufacture of the material. The diameter of the fibers is chosen to be sufficiently small, that is to say less than about 15 microns, to prevent the fibers from being brittle. This diameter is, moreover, generally greater than about 1 micron.

  because of the conditions for obtaining the fibers.

  The length of the fibers is chosen higher

  about 3 mm for the fibers to perform a function

  mechanical reinforcement within the insulating material.

  There is no critical maximum value for fiber length other than that dictated by the method of manufacture of these fibers. It can be admitted, however, that the use of fibers longer than 300 mm does not bring any significant improvement in the

  mechanical strength of the composite material.

  The arrangement of the fibers in the material is

  whatever: it can be random, the fibers are

  loose, or not random, the fibers are

  in tablecloths, fabrics or any other marketable form.

  The matrix coating the fibers is a resin

  thermosetting polymerized carbon.

  A formulated resin is preferably used

  polymerizable phenol at a polycondensation temperature

  between 150 and 2000 C or polymerizable at

  cold by the addition of a catalytic system.

  Other thermosetting resins can also

  may be used, eg cresol resins

  or xylenols, the amino resins of the urea-formaldehyde type

  dehyde or melamine formaldehyde, polyimide resins, .....

  In order to lighten the final material obtained, it is possible to incorporate in the resin elements allowing a reduction in density. Thus, a liquid blowing agent (for example freon or heptane) can be incorporated into the

  5 to 20% by weight of liquid resin, before

  fiber, so that the fibers can be expanded

  resin between the fibers. Another lightening process is to disperse homogeneously in

  the solid or liquid resin of the hollow particles

  mant micro-balloons or micro-spheres for example silica or carbon, these particles having a larger diameter - 4-

  at about 30 microns and being added in the correct amount

  corresponding, by weight, to 5% to 30% of the weight of the resin.

  The manufacture of the composite material is carried out

as follows.

  The fibers are arranged in bulk, in layers

  or in layers of tissue to form a fibrous reinforcement.

  Before the shaping of the material in the desired configuration, the synthetic resin chosen is dispersed in

  the solid phase fibrous reinforcement, in the case of a

  pulverulent, or in the liquid phase, in the case of a resin diluted in a solvent or in aqueous solution. In

  solid phase, for example the mixing of

  and in the liquid phase, the fibers are for example impregnated by immersion in a dilute resin bath, the solvent being evaporated after wringing. We could still resort to the spreading of the solid or liquid resin on the fibrous reinforcement, the penetration of the resin between the fibers being achieved

  during the shaping of the material.

  This formatting is carried out by a technique

  Conventional molding technique: for example molding

  by vacuum, compression, or transfer-

  compression (preheating followed by compression), or by centrifugation, or bag molding (the product

  being enclosed in an envelope) in a hydroclave or

  clave. The polymerization of the resin at room temperature or hot with catalyst is carried out at least partially during molding. The conditions of

  therefore depend on the type of resin and polymerisation

  tion. These conditions also depend on the configuration

  of the product to be molded (lightened or not).

  The resulting composite material has a set

  characteristics that make it particularly

performance.

  Thus, the density can vary from 0.5 to 1.5

  in particular, depending on whether the product is lightened or not.

  The thermal conductivity can, as already

  indicated, achieve values that are largely

  below the minimums currently achieved.

  The behavior of the material at erosion (resistance

  ablation rate) is higher than that of

asbestos base known.

  The material retains good integrity and thermal insulation properties after pyrolysis. It can therefore be subjected to high temperatures during a

  time limit in the case where the fumes produced by the pyrolysis

  lysis are tolerated or are imprisoned as a result of

  finely of the material made allow the possible pyrolysis.

  The material has sufficient structural integrity to enable the machining of complex shapes and to withstand shocks, vibrations and accelerations. Some of the properties: of the material can be improved by adding reinforcing element and / or

protection.

  Thus, the mechanical properties of the material

  can be improved by means of a single or double

  directional nature of the same or different nature of the

  basic fibrous reinforcement. These reinforcements may be incor-

  pores during the manufacture of the material or reported surface after manufacture. For example, we can use silica, glass or carbon fabrics that are incorporated during manufacture to be taken

  in the matrix. We can also use reinforcements

  metallic (for example, stainless steel, lithium, titanium,

  in the form of sheets (or foils) or deposited by

  jection, by electrolysis or under vacuum.

  Moreover, a coating can be reported

  on the surface of the material for different functions:

  - 6- strong material mechanically, protection of the surface against products eg chemical or

  abrasives, containment of the material in a vacuum to improve

  improve its resistance properties to oxidation at high temperature, and allow any pyrolysis, dressing

  material to produce a particular aesthetic effect.

  Surface protection may be related

  during or after manufacture. To achieve the surface protection, it will be possible to use single or bidirectional materials, such as carbon, silica or glass fabrics, or metallic materials (steel

  stainless, aluminum, titanium, .....) in the form of foil

  or deposited by spraying, by electrolysis or under vacuum, or laminates or decorative films such as fabrics,

  laminates, veneers, wood, paints, varnishes, .....

  The examples given below illustrate the

  of the material according to the invention.

Example l

  A composite material according to this example is prepared from ceramic fibers having a diameter of between 2 and 5 microns and a length varying between 150 and

  250 mm, and a phenolic resin of the resol type.

  The fibers are impregnated by the technique

  spreading impregnation. The resin is then poly-

  condensed at a temperature of 160 I 5 C under pressure of 10

I l fuck for 2 hours.

  The characteristics of the material are as follows - fiber content 60% by weight - density 1.35 - compressive strength: 70 MPa resilience: 0.20 J / cm2 - flexural strength: 55 MPa - flexural modulus: 6800 MPa - tensile strength: 24 MPa - 7- - tensile modulus 6100 MPa - elongation 0.51% - thermal expansion 16.7.106 thermal conductivity: 0.25 W / mK - onset of thermal degradation 4000 C

  With the exception of hydrofluoric acids and

  it offers excellent inertia for

  mineral acids and neutral metal salts or

  an acid reaction by hydrolysis. It is not

  ordered for alkaline caustic solutions nor

for their hydrolysable salts.

  The material has high heat stability with early thermal degradation at 400 ° C

  about. This material also has a good behavior in

and thermal shock.

  When a specimen of 50 mm diameter and 20 mm thickness receives a heat flow of 110 calories / cm.sec, the temperature of the opposite side to the flow is 5000 C after two minutes, the specimen then lost 40% of its weight, the remaining part retains good material integrity. For a flow of 20 calories per cm. dry, the temperature of the opposite side to the flow is 5000 C after five minutes then goes into regime

  the test piece loses 25% of its weight after 30 minutes.

  losses, mainly due to the pyrolysis of the resin,

  the material retains good material integrity.

Example 2

  Reinforced material according to Example 2

  is produced under the conditions of Example 1 with

  placing 5% by weight of the ceramic fiber with a gauze-woven glass cloth weighing about 55 g

  at i2, distributed evenly in the material.

  The mechanical characteristics are very much improved, the other properties remain

unchanged.

-8-

______--- ---- - -: - - -

  - tensile strength (MPa: - flexural strength (MPa)

_________-------: -

- Flexural modulus: (MPa)

__________------: -

- Compressive strength (MPa)

- ------ ------ ----- 2:

  - Resilience (J / cm2): material. following

example 1

_____________

_____________

_____________

0.20: next material

: example 2

: ---30

*30

_____________

_____________

--0,40-:

0.40:

Example 3

  A test piece obtained according to the example of 2 mm thickness of the material 1 is covered on each side with a protective coating constituted by a foil

  made of 5/100 mm thick stainless steel. That dream-

  significantly strengthens the material and protects it

  effectively against oxidation since the test specimen

  serve all its material integrity and is not pierced when it is subjected to a flame of 1100 C for more than 30 minutres. The temperature of the cold face is below 400 C and stabilizes rapidly during

  the duration of the fire reaction test.

Example 4

  A composite material according to this example is prepared from ceramic fibers having a diameter of between 2 and 5 microns and a length varying between 150 and

  3p 250 mm, and a phenolic resin of the resol type

  10% catalyst and 15% freon by weight.

  The polymerization is carried out in a shaker at room temperature, followed by an annealing of 2 hours at C. The characteristics of the material are as follows: - density 0.7 - tensile strength: 16 MPa - tensile modulus: 4000 MPa - flexural strength: 45 MPa flexural modulus: 4700 MPa - compressive strength: 28 MPa resilience: 0.14 J / cm2 - thermal conductivity: 0.2 W / mK - thermal expansion: 20.10- 6

  Of course, the foregoing description is not

  not limiting and the invention can be implemented according to other variants without leaving the frame

  protection defined by the appended claims.

- 10 -

Claims (8)

  1. A thermal insulating composite material comprising insulating mineral fibers taken from a matrix formed by a polymerized thermosetting resin, characterized in that the fibers are selected from the group consisting of silica fibers of high purity.   alumina fibers and ceramic fibers,   present about 25- to 65% by weight of the composite material   polymerized resin-fiber site, and have a smaller diameter   approximately 15 microns and longer than   about 3 mm, and the matrix is a carbon product sus-   able to leave on the fibers a matrix   pyrolytic material in case of pyrolysis of the material.   2. Material according to claim 1, characterized in that the mineral fibers are fiber-based   of alumina containing more than 90% Al 2 O 3.   3. Material according to claim 1, characterized in that the mineral fibers are silico-aluminous ceramic fibers containing about 40 to 60% of A1203. and about 40 to 60% SiO2.   4. Material according to any one of the claims   1 to 3, characterized in that its thermal conductivity   is less than 0.3 W / m.0K.   5. Material according to any one of the claims   tions, characterized in that it is provided with a   protective coating on the surface.   6. Material according to any one of the preceding revendicai tions, characterized in that it comprises a   mechanical reinforcement in addition to said mineral fibers.   7. Material according to any one of the claims   tions, characterized in that the matrix is   formed by a polymerized expanded resin.   8. Material according to any one of the claims   tions, characterized in that the matrix is   formed by a polymerized resin containing particles hollow spheres. J