Friction material composition

FIELD: polymer materials.

SUBSTANCE: invention relates to polymeric composite materials for various-destination friction articles. Composition of invention contains, wt %: powderlike binder (SFP-012 and AK-30), which is mixture of novolac phenol-formaldehyde binder and nitrile rubber obtained via joint coagulation of their latexes, 15-18; barite concentrate 30-40; alumina 10-15; bronze chippings 3-5; graphite 3-5; non-stoichiometric titanium compound 2-5; and polyoxadiazole fiber (Oksalon) or mixture thereof with glass fiber at ratio 1:2 - the balance.

EFFECT: enhanced adhesion strength of material to metallic framework, increased friction coefficient, and reduced high-temperature wear and price of material.

3 tbl, 4 ex

 

The invention relates to mechanical engineering and transport, and in particular to polymer composite materials intended for friction products for various purposes. The invention can be used for the manufacture of friction elements of drum and disk brakes, clutch car, friction elements of the tire is a pneumatic couplings, friction elements of the belt brakes, etc.

Known friction materials appointments made by impregnation of aqueous emulsions or alcohol solutions of phenol-formaldehyde resins, mixtures of different mineral fillers containing as the fiber constituting the asbestos (V. V. Korshak. Technology of plastics. - M.: Chemistry, 1985, s-278). Materials have satisfactory strength properties. Their disadvantages are difficult and time-consuming technology for material requiring long-term mixing, processing the mixture in the mill, molding bricks, drying in the vacuum drying, low and unstable friction coefficient of the obtained materials, usually not exceeding of 0.30-0,33 and, in addition, the presence in the formulation of carcinogenic asbestos.

Partially the drawbacks of the materials described above are eliminated another similar, friction polymer composition described in (SU # 1552617, CL 08 L 61/10, 1987). The composition contains is it a polymeric binder, mineral and fibrous fillers in the following ratio, wt.%: modified phenol-formaldehyde resin 13-16; butadiene-nitrile rubber 2-4; barite concentrate 10-20; alumina 8-15; metal powder of copper-based 10-19; graphite 1-15; diammonium phosphate 0.5 to 2.0; fibrous filler (asbestos or a mixture of asbestos with basalt fiber or mineral wool mass ratio of 1.9 to 6 to 1) - the rest. The process of obtaining material several times less time consuming, as the composition was prepared by direct mixing of all components in a closed mixer. The coefficient of friction of the material stabilizes and increases to 0.42-0.45 respectively. However, in the formulation of the composition is still asbestos, and the resulting materials have a low wear resistance.

The closest technological nature of the claimed composition (prototype) is a material containing a polymeric binder, mineral, fiber and other fillers (RU # 2034869, CL 08 J 5/14, 1995). The composition comprises, in wt.%: phenol-formaldehyde resin 12-14; butadiene-nitrile rubber 2-4; barite concentrate 16-20; alumina 9-11; bronze shavings 4-6; copper powder 9-10; blocked with caprolactam 2,4-toluylenediisocyanate of 0.5-3; graphite 1-2; and basalt fiber - rest.

The prototype eliminated the use of asbestos in composition composition and and increases the wear resistance of materials. However, the presence of basalt fiber in the composition reduces the strength of the clutch friction material with a metal frame. The disadvantages of the prototype are also low coefficient of friction, increased wear of the material at temperatures above 500°and the high cost of the material for containing in its structure a large number of copper powder.

The technical result, which is aimed invention is to improve the strength of adhesion of the material with a metal frame, increasing the coefficient of friction, reducing wear at high temperatures and reducing the cost of material.

The result is achieved that, in the composition for a friction material containing a polymeric binder, mineral and fibrous fillers, according to the invention as a binder is a powder binder TFP-012 AK-30, as fiber is present polyoxadiazole fiber axalon (or its mixture with fiberglass in the ratio 1 : 2) and additionally uses strengthening and structuring additive is a non-stoichiometric compound titanium carbide, carbonitride and the like) in the following ratio, wt.%: powder binder TFP-012 AK-30 from 15 to 18; barite concentrate from 30 to 40; alumina from 10 to 15; bronze shavings from 3 to 5; graphite from 3 to 5; estacionamento compound of titanium is from 2 to 5; fiber Exelon or its mixture with fiberglass in the ratio of 1 to 2 - rest.

For the preparation of compositions used the following raw materials: powder binder TFP-012 AK-30, which is a mixture of Novolac phenol-formaldehyde binder TFP-012 AND THE 6-05751768-35-94 and nitrile rubber SKN-40 am, THE 38.10354-76, received the joint coagulation their latex and containing 30 wt.% rubber in terms of dry substance ("K-30" in letter form)obtained in the pilot plant; barite concentrate KB-6, GOST 4682-84; alumina, GOST 6912.1-93; bronze shavings BRS-30, GOST 493-79; graphite, GOST 5279-74; polyoxadiazole fiber axalon, which is a polycondensation product of hydroinsulation and terephthalic acid, THE 6-12-00204056-56-90, with a fibre length of 5-10 mm; the fiber, THE 6-11-240-77.

Used in the composition of non-stoichiometric compound titanium carbide, carbonitride and the like) produced by interaction of sponge titanium powder brand PTOM with soot, nitrogen, organic matter containing carbon and nitrogen, etc. in the mode of self-propagating high temperature synthesis (SHS).

The friction material is made by mixing the above components at atmospheric pressure in the faucets of any structure: vane, screw, pan, etc. for 10-30 minutes Produced a mixture of the press who are at a temperature of 165-175° C and a pressure of 100-150 MPa. Vulcanization of the material lasts 15-20 min with two podpressdivname without disclosure of the mold for 2-3 minutes and 5-8 minute cycle.

According to this scheme of the obtained material were made part of the disk brake of the car VAZ 2101 (det. 2101-3501090-01A) on a metal frame, which is then subjected to physico-mechanical and tribological tests on THE 38.114-187-87. The strength of adhesion of the material with a metal frame was determined by a standard method on a tensile testing machine UMM-5, tribological properties were evaluated on the machine friction CMT-1 at a load of 50 kgf, the sliding speed of 4 m/s with increasing temperature up to 700°by the end of the tests according to GOST 23210-80, the counterbody - iron mid-15-32.

The invention is illustrated in the following examples.

Example 1. Obtaining non-stoichiometric compounds titanium

a) obtaining a non-stoichiometric carbides of titanium. In a ball mill for 1-2 h mixed powder of titanium grade PROM with soot marks PW-50 in a molar ratio of 1 to n, where n is greater than or equal to 0.5 but less than 1. The resulting mixture is pressed to tablets with a diameter of 1-2 cm and a height of 2-3 cm, which are then burned in a stream of argon. The materials obtained were pulverized in a ball mill and a selected fraction with particle diameters less than 100 microns.

b) obtaining a non-stoichiometric titanium nitride. In a cylindrical quartz re ctor cooling load pellets of titanium hydride (t.), the reactor stoppered with drainage tubes through one of the tubes in the reactor serves gaseous nitrogen at 5 l/min, initiate reaction by burning, eye-catching hydrogen divert through another tube. The resulting material was crushed and used the fraction with particle size less than 100 microns.

C) obtaining a non-stoichiometric titanium carbonitride. Act similar to part (a) of the example, with the difference that instead of the carbon black used organic substance containing both carbon and nitrogen, such as hexamethylenetetramine (methenamine). The mixture is moistened volatile solvent, pressed tablets, which are then dried and burned in a stream of argon. The resulting material was crushed and used the fraction with particle size less than 100 microns.

Characteristics of the obtained non-stoichiometric titanium compounds shown in table 1.

Example 2. A composition for a friction material with a non-stoichiometric titanium carbide

In a paddle mixer for 3-5 min mix powder binder TFP-012 AK-30, barite concentrate, alumina, non-stoichiometric titanium carbide composition TiC0,75and graphite, then add the bronze chips and fiber axalon, stirring is continued for another 10-15 minutes of Finished material is a homogeneous gray mass with inclusions bronze shavings. Composition the composition is given in table 2.

From the obtained material was obtained briquettes, which are then placed on metal frames and subjected to hot pressing, as described above. The finished product removed from the mold, free from burrs, grind and subjected to testing. The test results of the compositions are given in table 3.

Example 3. A composition for a friction material with a non-stoichiometric titanium carbonitride

In the preparation of the composition act analogously to example 2, with the difference that the mixing is carried out in a pan mixer for 10-15 minutes, all components are loaded at once, and as non-stoichiometric compounds use titanium carbonitride composition TiC0,7Nfor 0.4obtained in example 1. The composition is given in table 2.

The finished products are produced analogously to example 2. The test results of the compositions are given in table 3.

Example 4. A composition for a friction material with a non-stoichiometric titanium carbonitride and a mixture of okalona and fiberglass

Separately, prepare a mixture of okalona and fiberglass in the ratio of 1 to 2 wt., mixing them for 5-7 minutes in a pan mixer.

Next, do the same as in example 2 preparing a composition in a paddle mixer, with the difference that as non-stoichiometric compounds of titanium use the carbonitride composition TiC 0,7Nfor 0.4obtained in example 1, and at the end of mixing in a mixer add the mixture of fiber and Exelon and fiberglass in the ratio of 1 to 2, prepared as described above. The composition is given in table 2.

The finished products are produced analogously to example 2. The test results of the compositions are given in table 3.

The technical result of the application of the invention is to increase the adhesion strength of the material with a metal frame, increasing the coefficient of friction, reducing wear at high temperatures and reducing the cost of material.

Change of basalt fiber on polyoxadiazole fiber Exelon or its mixture with fiberglass (1 to 2) can significantly increase the strength of adhesion of the material made of the proposed composition, with a metal frame in comparison with the prototype (table 3).

Using the proposed composition as the polymeric binder powder TFP-012 AK-30, which is a mixture of Novolac phenol-formaldehyde binder and nitrile rubber, obtained by joint coagulation their latexes, lets keep up the good tribotechnical characteristics of the material, both at high and at low temperatures, characteristic of the rubber-resin materials, and at the same time to apply high-tech powders is Yu technology in the manufacture of friction material.

Used as a strengthening and structuring additive in the proposed composition of non-stoichiometric compounds of titanium allow you to adjust adhesive interaction in the system of the composite material, because in addition to stock excess surface energy due to their nestekhiometricheskie they are characterized by a special surface morphology of their particles formed at SHS. These compounds not only have a high adhesion to high-molecular substances, but also significantly affect the polymerization of the organic binder in the material, which in the case of highly filled composite, which are friction materials, leads to a significant change in properties.

Thus, the use of a binder TFP-012 AK-30 and strengthening and structuring additives - non-stoichiometric compounds of titanium in the proposed composition allows, in comparison with the prototype, to increase the coefficient of friction of the material and its durability at high temperatures (table 3).

The cost of the proposed material, compared with the prototype, is reduced due to the exclusion of his recipes expensive copper powder (table 2).

Introduction to material non-stoichiometric compounds of titanium in amount more than 5 wt.% it is impractical because it leads to the increase of the abrasive properties of the compo is icii and increased wear of the counterbody in friction, when its content in the material is less than 2 wt.% strengthening and structuring properties are exhibited slightly.

Content in the composition of the fiber 12 to 37%, an optimum ratio of its reinforcing ability with the strength of adhesion of the material to the frame. The increase in the content of glass fiber in a mixture of Exelon : fiberglass above 1 to 2 leads to a decrease in strength of the connection.

When the content of the binder in the composition is from 15 to 18 wt.% best solidity of the material and its high mechanical strength and friction properties.

Table 1.

Characterization of non-stoichiometric titanium compounds
The formula of the compoundThe titanium content, %The carbon content, %The nitrogen content, %Specific surface area, m2/g
TiN0,5of 87.3-a 12.75,2
TlC0,7584,215,8-a 4.9
TiC0,7Nfor 0.477,413,59,13,2

Table 2.

Formulations of the friction composition is th
ComponentsThe placeholderThe composition of the material, wt.% examples
123
Phenol-formaldehyde resin14---
The NBR2---
Binder TFP-012 AK-30-151718
Barite concentrate20353040
Alumina10101015
Bronze chips5355
Copper powder10---
Graphite2335
Non-stoichiometric compound titanium-235
Mineral fiber37---
Axalon or mixture castelbolognese (1:2)-10010 100

Table 3.

The frictional characteristics of songs
IndexThe placeholderThe composition of the proposed material for the examples
123
The strength of the grip frame, MPa without heatthe 4.729,527,230,4
after exposure temperature (140±10° (C) within (1±0,1) ha 4.912,811,713,5
The coefficient of friction0,380,470,480,46
Energy wear And cm3/kg×m1,50,60,80,5
Energy wear, cm3/kg×mnot as well.1,91,21,9
Note: - test up to 500°;

In - test up to 700°C.

The composition for a friction material comprising a polymeric binder, mineral and fibrous fillers, characterized in that as the polymer binder compositions which s contains a powdered binder TFP-012 AK-30, representing a mixture of Novolac phenol-formaldehyde binder and nitrile rubber, obtained by joint coagulation their latexes; as a fibrous filler - polyoxadiazole fiber Exelon or its mixture with fiberglass in the ratio (1:2) and further comprises a non-stoichiometric compound of titanium in the following ratio, wt.%:

Powder binder TFP-012 AK-3015-18
Barite concentrate30-40
Alumina10-15
Bronze chips3-5
Graphite3-5
Non-stoichiometric compound titanium2-5
Fiber Exelon or its mixture with
the fiber in the ratio (1:2)100



 

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