RU2288925C1 - Sealing composition - Google Patents

Abstract

FIELD: sealing materials.

SUBSTANCE: sealing composition comprising fluorosiloxane rubber, mineral filler, tin diethylcaprylate, and polyethylhydrosiloxane is characterized by that above fluorosiloxane rubber is, more specifically, polydimethylmethyltrifluoropropylsiloxane rubber and composition additionally contains calcium stearate and iron oxide with following amounts of components, wt parts: rubber 100, mineral filler 90-300, tin diethylcaprylate 1-4. polyethylhydrosiloxane 4-8, calcium stearate 0.2-0.5, and iron oxide 0.5-1.

EFFECT: increased resistance to heat and fuel and reduced coefficient of linear thermal dilatation allowing composition to be used as intrajoint hermetic.

3 cl, 1 tbl, 4 ex

Description

The invention relates to the field of macromolecular compounds, and in particular to sealants used in the aviation industry for sealing units of aircraft structures (plug connectors, fuel compartments, sensors, pressure glands, etc.) operating in a wide temperature range from -60 to 250 ° C .

Known fluorinated silicone compounds filled with oxides of silicon, iron, zinc or soot in an amount of 35 parts by weight filler per 100 parts by weight fluorosiloxane, which are resistant to oil, fuel, are used in aeronautics and automotive industry at temperatures from -40 to 200 ° C (PCT application WO 01/32750).

The disadvantage of these compositions is the insufficient temperature range of health.

Fluorosiloxane rubber compounds based on high molecular weight rubbers are known that have low shrinkage under compression and low swelling in polar solvents (Japanese Patent No. 2729871).

The disadvantage of these compositions is their high viscosity, which does not allow their use as a sealing composition.

Known sealing composition containing fluorosiloxane rubber with m.v. 20000, polyoxybutylene urethane diepoxide, hardener, ethyl silicate and tin octoate (ed. St. USSR No. 979481).

This composition has a sufficiently high elasticity, frost resistance, oil resistance, but is not functional in the temperature range from -60 to 250 ° C, which limits its use.

The closest in composition and purpose to the claimed invention is a heat-resistant sealant for intracutaneous sealing (i.e. for sealing without air access) based on fluorosiloxane rubber, having the following composition (parts by weight):

Fluorosiloxane rubber - polymethyl trifluoropropylsiloxane-SKTFT one hundred mineral filler - titanium dioxide 70-100 tin diethyl dicaprylate 2-3 polyethyl hydride siloxane (GKZH-94) 4-6

The sealant may additionally contain soot furnace in the amount of 3 wt.h. (ed. St. USSR No. 473732).

This sealant, used for intra-seam sealing of aircraft fuel compartments, has a pasty consistency without the use of solvents and the ability to vulcanize at room temperature. The disadvantage of this sealant is the high coefficient of thermal linear expansion (KTLR).

In modern aircrafts, higher KTLR requirements are imposed on this type of sealant for the use of a sealant for internal sealing.

Sealants for surface sealing cannot be used for intra-seam sealing, since during operation without access of air in a closed volume, the destructive stability of the sealing composition is violated and they also have a high thermal coefficient of linear expansion.

The technical task of this invention is the creation of heat-resistant sealant with a reduced coefficient of thermal linear expansion, which has physical and mechanical properties, frost resistance, the ability to vulcanize at room temperature and working capacity from -60 to 250 ° C at the level of the prototype for use as an intra-sealant, t .e. for sealing without access of air.

To solve this problem, a sealing composition is proposed that contains fluorosiloxane rubber, a mineral filler, tin diethyl dicaprylate and polyethyl hydride siloxane, characterized in that it contains polydimethyl methyl trifluoropropyl siloxane rubber and additionally contains calcium stearate (iron oxide). :

polydimethylmethyl trifluoropropylsiloxane rubber one hundred mineral filler 90-300 tin diethyl dicaprylate 1-4 polyethylsiloxane 4-8 calcium stearate 0.2-0.5 iron oxide 0.5-1.0

As a mineral filler, the composition contains titanium dioxide, zinc oxide, silicon dioxide, basalt.

The composition may further contain carbon black in an amount of 1-5 parts by weight

The use of calcium stearate and iron oxide, contributing to a better structure formation of the composition, in combination with other components of the sealing composition leads to a significant decrease in the coefficient of thermal linear expansion (CTE) of the sealant. This allows it to be well syringed in a closed volume, which is extremely important for groove sealing and sealing by filling the volume, as well as for the successful functioning of the sealed product during operation, including during cyclic heating.

The proposed sealant is vulcanized at room temperature, syringes well, which allows it to be used for groove sealing. This type of intra-seam sealing is less laborious, since it eliminates the need for preliminary assembly and disassembly of the structure and provides improved working conditions for workers.

In order to impart color, the composition may further comprise carbon black in an amount of 1-5 parts by weight.

Examples of carrying out the invention

Example 1

To obtain the proposed sealant composition, SKTNFT-50 polydimethylmethyltrifluoropropylsiloxane rubber (TU 38.10 3124-80) was used in an amount of 100 parts by weight, a mineral filler titanium dioxide (TU 6-10-1252-86) was added at room temperature with constant stirring. in the amount of 300 parts by weight, then tin diethyl dicaprylate (TU - 6-02-1-013-89) was added in the amount of 1.0 parts by weight and 5.0 parts by weight polydiethylhydride siloxane (GKZh-94) (GOST 10834-76), then 0.2 parts by weight were added with constant stirring. calcium stearate (TU 6-09-17-017-98) and 0.5 wt.h. iron oxide (TU 2611-023-05761-270-01).

Example 2

The same fluorosiloxane rubber - SKTNFT-50 (TU 38.10 3124-80) was used in an amount of 100 parts by weight, and a mineral filler — zinc oxide (GOST 202-84) in an amount of 150 parts by weight was added to it at room temperature. ., then added tin diethyl dicaprylate (TU 6-02-1-013-89) in an amount of 4.0 parts by weight and 7.0 parts by weight polyethylsiloxane (GOST 10834-76), then 0.5 parts by weight of calcium stearate (TU 6-09-17-017-98), 0.75 parts by weight, were added with constant stirring. iron oxide (TU 2611-023-05761-270-01) and 3.0 wt.h. carbon black (GOST 7885-86).

Example 3

We used the same fluorosiloxane rubber - SKTNFT-50 (TU 38.10 3124-80) in an amount of 100 parts by weight, a mineral filler - basalt (TU 5762-031-05328981-01) in an amount of 90 was added to it with constant stirring parts by weight, then tin diethyl dicaprylate (TU 6-02-1-013-89) was introduced in an amount of 3 parts by weight and 8.0 parts by weight polyethylsiloxane (GOST 10834-76), then 0.3 parts by weight of calcium stearate (TU 6-09-17-017-98) and 1.0 parts by weight were added with constant stirring. iron oxide (TU 2611-023-05761-270-01).

Example 4 (prototype).

We used polymethyl trifluoropropylsiloxane rubber - SKTFT in an amount of 100 parts by weight, titanium dioxide (TU 6-10-1252-86) in an amount of 100 parts by weight, tin diethyl dicaprylate (DEDCO, TU 6-) was added to it with constant stirring at room temperature. 02-1-013-89) in an amount of 2.0 parts by weight and 4, 0 parts by weight polyethylsiloxane (GOST 10834-76).

The properties of these sealants are shown in the table, where 1-3 examples of the proposed sealant, 4 example is a prototype.

The data in the table shows that the proposed sealant has a 2.5-3 times lower thermal coefficient of linear expansion (KTLR) and at the same time physical and mechanical properties at the level of the prototype.

Thus, the use of the proposed sealant can improve the reliability and service life of the fuel compartments and other units of new generation aircraft.

Table Indicators Examples of the invention Prototype one 2 3 Initial conditional tensile strength, MPa 1.8 2.0 1.8 1,6 Initial elongation,% 160 170 165 one hundred Initial shore hardness, conventional units fifty fifty fifty fifty Without air access, 250 ° С, 3 h, conditional tensile strength, MPa 1.3 1,0 1,1 0.9 Without air access, 250 ° С, 3 h, elongation,% 150 150 140 140 Without air access, 250 ° С, 3 h, hardness in us.ed. Shore 36 35 36 36 After the action of fuel, 250 ° C, 24 hours, conditional tensile strength, MPa 1,2 1.4 1.3 1,1 After the action of fuel, 250 ° C, 24 hours, elongation,% 160 180 185 120 After the action of fuel, 250 ° C, 24 hours, hardness in us.ed. Shore 38 40 45 46 CTLR, × 10 ^-6 1 / С ° 80 60 60 180

Claims (3)

1. A sealing composition comprising fluorosiloxane rubber, a mineral filler, tin diethyl dicaprylate and polyethyl siloxane, characterized in that it contains polydimethyl methyl trifluoropropyl siloxane rubber and additionally contains calcium stearate and iron oxide in the following ratio: Polydimethylmethyl trifluoropropylsiloxane rubber one hundred Mineral filler 90-300 Tin diethyl dicaprylate 1-4 Polyethyl Hydride Siloxane 4-8 Calcium stearate 0.2-0.5 Iron oxide 0.5-1 2. The sealing composition according to claim 1, characterized in that it contains titanium dioxide, zinc oxide, silicon dioxide or basalt as a mineral filler. 3. The sealing composition according to claim 1 or 2, characterized in that it further comprises carbon black in an amount of 1-5 parts by weight