RU2403269C2 - Method of producing polymeric nanocomposite material and material produced using said method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing composite nanomaterials for antifrictional purposes. The materials can be used in systems working under high deformation loads and in friction assemblies. The method involves mechanical activation of powder filler in form of sheet silicate in a ball mill in high-speed mode. Further, the powder filler is then mixed with powdered ultra-high molecular weight polyethylene for 10-60 minutes in a high-energy mill combined with mechanical activation.

EFFECT: obtained mixture is starting material from which articles with improved tribological characteristics, high mechanical strength and elasticity are moulded.

2 cl, 9 dwg, 2 tbl, 1 ex

Description

The invention relates to the field of technology for producing polymer nanocomposites and can be used to obtain materials used in products operating at high deforming loads, in friction units with reduced combustibility.

A composite material and a method for producing it are known, according to which a mixture is obtained by mechanically activating a pre-ground filler and a binder (RF patent No. 2160856, IPC F16C 33/14, publ. 20.12.2000).

As a powdery filler in the known method, a composition of natural minerals based on complex oxygen-containing compounds of magnesium, silicon, iron, molybdenum, sulfur is used.

The disadvantages of this method include a fairly high complexity, complexity, as well as the lack of the ability to obtain high physical and mechanical properties such as elasticity and mechanical strength.

As the closest in technical essence to the claimed method is known for producing a composite material by mixing pre-mechanically activated powder filler - synthetic spinel - with a binder - polyethylene, mixing the filler with a binder in a high-speed mixer, with the final molding by pressing and sintering (RF patent No. 2296139, IPC C08J 5/16, published March 27, 2007).

The disadvantages of the prototype include the inability to obtain high physical and mechanical properties of materials such as elasticity and mechanical strength, tensile strength while ensuring low fragility.

The present invention provides a method for producing a nanocomposite polymer material of antifriction purpose, characterized by wear resistance, high strength properties and elastic modulus, low brittleness.

A new technical result achieved using the proposed method is to improve the tribological characteristics, increase the mechanical strength of the finished material, the elastic modulus, maintaining high deformability.

A new technical result is ensured by the fact that in the method for producing a polymer nanocomposite material with antifriction properties, including mechanically activating a powdered filler, mixing the mechanically activated powdered filler and a powdered polymer binder - polyethylene, and subsequent molding of the mass by compression, ultra-high molecular weight polyethylene (UHMWPE) is used as polyethylene as a filler - layered silicate, its mechanical activation is carried out in high speed mixer, mixing - with joint mechanical activation in a high-energy mill for 10-60 minutes, with the following ratio of ingredients, wt.%:

Laminated Silicate - 1-70

Ultra-high molecular weight polyethylene - the rest,

and pressing - by direct hydraulic pressing.

Products of a given shape are molded by pressing at a temperature that is commonly used for the manufacture of products from ultra-high molecular weight polyethylene.

Montmorillonite, palygorskite, hydromica, vermiculite, kaolinite, talc can be used as layered silicate.

Known polymer composite material based on a polymeric binder, powder filler (RF patent No. 2172751, IPC C08L 23/06, publ. 08/27/2001).

The disadvantages of the prototype include the lack of the ability to obtain high physical and mechanical properties such as elasticity, mechanical strength, tensile strength and at the same time low fragility.

A new technical result is ensured by the fact that the polymer nanocomposite material contains as a polymer binder a powdery ultra-high molecular weight polyethylene, as a powdery filler - layered silicates, in the following ratio of ingredients, wt.%:

layered silicates - 1-70;

powdered ultra-high molecular weight polyethylene - the rest,

and obtained as described above.

The invention is illustrated as follows. Layered silicates are preliminarily subjected to intensive mechanical activation in ball mills in the high-speed rotation mode. As a result of grinding, a homogeneous fine powder is obtained. Accurate determination of the particle size of the powder is difficult. However, they can be judged by the data of x-ray analysis. If the initial layered silicates have basal reflexes characterizing the distance between the silicate plates, and non-basal ones reflecting the internal structure of the silicate plates, then after grinding the powders are X-ray amorphous - any reflexes are absent (Figure 1).

This indicates the destruction of both the layer structure and the initial silicate plates themselves, the thickness of which is only 9.6 angstroms. As a result of the destruction of the silicate plates, the mechanical activation of the formed particles should take place — they may contain free valencies.

To obtain the polymer / filler powder compositions, a mixture of UHMWPE and pre-mechanically activated clay is processed in a high-energy mill. The resulting mixture is the starting material from which the product is pressed.

The resulting composite materials can be used in products operating at high deforming loads, in friction units with reduced flammability.

The requirements for the polymer matrix in antifriction materials are high (or sufficient) mechanical strength (30-35 MPa), resistance to aggressive media, satisfactory tribological characteristics, primarily antifriction properties (friction coefficient not higher than 0.25), sufficient heat resistance and antiwear resistance (wear in relative units no more than 140).

The nanostructured filler should be characterized by higher hardness and strength than that of the matrix material, high or satisfactory antifriction properties, high thermal conductivity, satisfactory adhesion to the matrix material or reaction with it.

The compositions of polymer nanocomposites based on ultra-high molecular weight polyethylene (UHMWPE) with a filler, which were used as layered silicates, subjected to preliminary mechanical activation, were experimentally studied. The modes of this processing are selected based on the required dispersion of the filler. This was followed by the mechanochemical synthesis of powder composite mixtures, during which, in the mechanochemical synthesis apparatus, which is an MPF-1 planetary ball mill, during the low-temperature process (at 20 ° C and processing time from 10 to 60 min) the powders of the filler and the polymer matrix are processed. A high-energy planetary activator was used to prepare powder composite mixtures. Thus, powder composite mixtures of a polymer matrix and a filler with a different ratio of their mass parts were prepared.

When developing polymer nanocomposites, an important factor is the strength of the adhesive contact of the polymer matrix with a reinforcing filler. The structural strength of the composite, mechanical and tribological characteristics depend on it. Interfacial adhesion is created by the adhesion forces between the surfaces of the composite components.

The adhesion strength in the studied polymer matrix composites was controlled by choosing the modes of mechanochemical processing.

Experimental studies of the obtained materials showed the high efficiency of the proposed method for producing compositions of polymer nanocomposites in the claimed ranges of component values. The results of determining the properties of materials are given in table 1.

Thus, when using the proposed method to obtain a composite polymer material and the actual composite polymer material, higher tribological characteristics, indicators of the mechanical strength of the finished material, elasticity, and breaking stress during bending were achieved than in the prototype.

The possibility of industrial applicability of the proposed method and composite polymer material are confirmed by the following implementation examples.

Example. To study the mechanical and tribotechnical characteristics in laboratory conditions, experimental samples were made by hot pressing of powder composite mixtures. The resulting samples were tested.

Test procedure

Studies of wear resistance and coefficient of sliding friction according to the “rod-disk” scheme are carried out on a Tribometer, CSM Instr. (Switzerland). As a counterbody, a polished steel ball made of 100Cgb steel is used (analogue of ShKh15 steel, hardness 1550 HV, Young's modulus 220 GPa, density 3.0-3.2 g / cm ³ ).

Test conditions

- counterbody - polished ball with a diameter of 3 mm;

- counterbody material: 100Cgb steel (analogue ШХ15);

- normal load - 1N;

- the radius of the wear ring is 9-11 mm;

- linear speed - 20 cm / s;

- the specified test duration is 5000 revolutions.

The diameter of the wear spot of the counterbody — the stationary ball and the width of the wear groove on the rotating sample were determined after testing under visual observation with an MBS-10 and AXIOVERT CA25 microscope (Karl Zeiss, Germany). Depth of the groove of wear was determined on an optical profilometer WYKO NT 1100, VEECO, USA. Measurements of the depth and width of the grooves were carried out in 4-6 diametrically and orthogonally opposite areas and averaged.

Test results were processed using the InstrtumX for Tribometer computer program, CSM Instr. For comparison, nanocomposites with bronze powder were made under the same conditions. The dependence of the coefficient of friction on the filler content is shown in Fig.3. The dependence has the form of a curve with a minimum at a content of montmorillonite of 30 wt.%. The dependence of wear on the content of the filler, as can be seen from Figure 4, also has a curve with a minimum, and rather low (two times lower than that of the matrix material) wear is observed for samples with a filler content of 10-50 wt.%. At higher fill values, wear increases dramatically. The maximum wear spot was obtained when testing an unfilled sample. With an increase in the filler concentration, the antiwear resistance of polymer matrix composites increases (Table 1). The most uniform friction mode (see Figure 5) is observed for a composite containing 30 wt.%, Which is probably optimal for use as an antifriction material.

Table 1 Sample and counterbody wear values Test Counterbody Sample Coefficient of friction (r.p.) Ball wear × 10 ^-6 mm ³ / Nm The maximum depth / width of the groove of wear, microns Wear of the sample × 10 ^-6 mm ³ / Nm Elementary Max. Finite UHMWPE before machining " 3/300 120 0.15 0.22 0.17 UHMWPE after machining ~ 3.2 / 320 135 0.17 0.24 0.15 UHMWPE-Clay (10 wt.%) - 2/250 70 0.15 0.17 0.14 UHMWPE-Clay (20 wt.%) - 2.2 / 240 78 0.13 0.25 0.15 UHMWPE-Clay (30 wt.%) - 1.6 / 300 70 0.12 0.17 0.13 UHMWPE-Clay (50 wt.%) - 2/220 59 0.05 0.17 0.17 UHMWPE-Clay (90 wt.%). - 5/260 190 0.12 0.24 0.21 UHMWPE-Bronze Powder (30 wt.%) ~ 2.5 / 250 75 0.25 0.25 0.16 UHMWPE-Bronze Powder (60 wt.%) * 4/220 122 0.23 0.26 0.16

Studies of the mechanical properties of PMC with different concentrations of filler are carried out according to standard methods. The following characteristics are determined during mechanical tensile tests: elastic modulus E _p , tensile strength σ _P , and elongation ε _p , yield strength σ _T. The results of the study of the mechanical characteristics of the PMC are presented in table 2 and Fig.6-9. For this series of tests, powder composite mixtures were prepared in a globular planetary activator.

As follows from Fig.6-9, with an increase in the concentration of layered silicate to 70 wt.% The characteristics of E _p and σ _T increase by 4.0 and 1.5 times, respectively, σ _P decreases by 0.8 times (in comparison with the sample machined UHMWPE) and 4.3, 1.5 and 0.7 times, respectively, compared with the sample of the original UHMWPE. The ductility of the composites is reduced by 2 times (almost in proportion to the concentration of the filler) to 60 wt.% Clay, while maintaining at a fairly high level (270%) (Fig.7).

table 2 Mechanical characteristics of nanocomposites Sample Module E, MPa Yield strength σ _T , MPa Strength σ _P , MPa Relative elongation ε _P ,% UHMWPE preparation The content of layered silicate (clay), wt.% prior to mechanical activation 0 270 ± 35 17.4 ± 0.5 35.9 ± 2.1 520 ± 20 after mechanical activation 0 285 ± 20 17.2 ± 0.6 33.3 ± 4.0 555 ± 50 3 450 ± 35 18.5 ± 0.4 28.6 ± 5.3 580 ± 60 10 460 ± 20 18.8 ± 0.3 30.4 ± 4.7 490 ± 70 twenty 505 ± 60 20 ± 0.4 28.0 ± 3.9 480 ± 40 thirty 610 ± 60 21.5 ± 0.5 34.0 ± 4.0 500 ± 35 40 770 ± 65 21.7 ± 1.1 28.5 ± 4.1 410 ± b0 fifty 855 ± 50 22.2 ± 0.7 23.4 ± 3.0 320 ± 90 60 1140 ± 90 25.5 ± 0.7 23.5 ± 2.0 270 ± 130 70 1160 ± 130 25, b ± 2.9 25.6 ± 2.9 6 ± 2

As starting materials, UHMWPE GUR powder manufactured by Ticona Gmbh (Germany) was used. The molecular weight of UHMWPE was 3-6 · 10 ⁶ , the temperature of the onset of melting was 152 ° С, the layered silicate Na + - montmorillillite, from the Taganskoye deposit (Kazakhstan). Comparison samples were prepared with bronze powder of the BOD brand according to TU 8-08-09-7-85. The Cu content in powder bronze was 82.8 wt.%, Sn content was 16.5 wt.%, Fe content was 0.39 wt.%, And the lubricant content was about 0.3 wt.%.

Composite material was prepared by joint mechanical activation of UHMWPE powders and layered silicate or bronze using the MPF-1 planetary ball mill.

Experimental studies have shown that in the proposed method and obtained using its composite nanomaterial, high tribological characteristics, indicators of the mechanical strength of the finished material and elasticity are provided.

Claims (2)

1. A method of manufacturing a polymer nanocomposite material with antifriction properties, comprising mechanically activating a powdered filler, mixing the mechanically activated powdered filler and a powdered polymer binder - polyethylene and then molding the mass by compression, characterized in that ultra-high molecular weight polyethylene is used as the polyethylene, layered silicate is used as the filler, its mechanical activation is carried out in a ball mill in high speed, ix - together with mechanical activation in a high energy mill for 10-60 minutes, with the following ratio of ingredients, wt.%:
layered silicate 1-70 ultra high molecular weight polyethylene rest. 2. Polymer nanocomposite material with antifriction properties obtained by the method according to claim 1.

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