CN113980457A

CN113980457A - High-strength self-lubricating polyurethane piston sealing body and preparation method thereof

Info

Publication number: CN113980457A
Application number: CN202111441877.0A
Authority: CN
Inventors: 陈波; 朱志峰; 袁松
Original assignee: Jiangsu XCMG Construction Machinery Institute Co Ltd
Current assignee: Jiangsu XCMG Construction Machinery Institute Co Ltd
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2022-01-28

Abstract

The invention relates to the field of polymer materials, and relates to a high-strength self-lubricating polyurethane piston sealing body and a preparation method thereof. In particular, the invention relates to a composition useful for preparing a piston seal, a piston seal prepared from the composition, and a method of preparing the piston seal. The piston sealing body can be used as a concrete piston sealing body for concrete pumping equipment.

Description

High-strength self-lubricating polyurethane piston sealing body and preparation method thereof

Technical Field

The invention relates to the field of polymer materials, in particular to a composition for preparing a piston sealing body, a piston sealing body prepared from the composition and a method for preparing the piston sealing body. The piston sealing body can be used as a concrete piston sealing body for concrete pumping equipment.

Background

The piston is a key core part for concrete pumping equipment (such as a pump truck, a trailer pump and a vehicle-mounted pump), and plays a role in sealing a cavity and pushing concrete in the conveying process of the concrete. Because the conveyed concrete medium is hard, the components are complex, the pumping pressure is high, and the sealing performance requirement is high, the piston is required to have good mechanical strength and wear resistance. The piston used at present has short service life, frequent replacement and high operation cost.

The existing piston sealing body mainly comprises two materials, namely rubber material and polyurethane material. The rubber piston is prepared by taking nitrile rubber as a main body, adding a reinforcing agent, an anti-aging agent, a vulcanizing agent and the like, mixing and hot-pressing. The Chinese patent application CN201310234970.3 takes nitrile rubber as a main material to prepare the piston for the concrete pump truck, the main raw materials comprise the nitrile rubber, ethyl acetate, polyisocyanate and the like, and although a fiber reinforced material is added in the preparation process, the strength is low, the hardness is low, the highest hardness is 85A, the highest tensile strength is 36MPa, and the market demand cannot be met.

US patent US10415556B2 relates to a portable pumping mechanism for pumping of building materials or water, US patent application US2010/0264635a1 relates to a concrete pump truck structure, neither of which relates to a method for preparing piston materials. German patent application DE102005008242A relates to a process for the preparation of foamed polyurethane materials, but the tensile strength is low, about 2MPa, and is unsuitable for polyurethane materials for piston heads.

Disclosure of Invention

The invention aims to provide a high-strength self-lubricating polyurethane piston, which solves the problems of low strength and high abrasion of the existing polyurethane piston. The filler which is specially treated is added into the polymer system, so that the strength and the wear resistance of the piston are improved, the service life is prolonged, and the replacement frequency is reduced.

In one aspect, the present application provides a composition for preparing a piston seal, comprising the following components in parts by weight: 100 parts of polyurethane prepolymer, 10-20 parts of chain extender, 5-10 parts of surface silanized ultrahigh molecular weight polyethylene powder, 1-1.5 parts of antioxidant, 1-2 parts of surface silanized aluminum oxide powder and 1-3 parts of molybdenum disulfide or sodium-modified polytetrafluoroethylene powder.

The prepolymer is a substance formed by primarily polymerizing the monomers, and can be used in occasions where the monomers are difficult to be completely polymerized into the polymer at one time or the polymer is prevented from generating cavities and cracks easily in processing and forming. The invention uses polyurethane prepolymer as the main material for preparing the piston sealing body.

Polyurethanes are known by their full name as polyurethanes, and are a generic name for polymers containing a certain amount of carbamate groups in the molecule. Polyurethanes can be prepared by the interaction of mono-or poly-organic isocyanic acids, such as Toluene Diisocyanate (TDI) or diphenylmethane diisocyanate (MDI), with polyol compounds, such as polyether polyols or polyester polyols, to form polymers having a backbone containing a plurality of repeating carbamate groups. The polyurethane prepolymer is a reactive semi-finished product obtained by controlling a certain proportion of reaction between polybasic organic isocyanic acid and polyalcohol.

In certain embodiments, the polyurethane prepolymer is polyether.

In certain embodiments, the polyurethane prepolymer is selected from one or both of LF M2050, LF M2032 types.

In certain embodiments, the polyurethane prepolymer has one or more of the following characteristics:

a free MDI content of less than 0.1 wt%, for example 0.01 wt% to 0.02 wt%, 0.02 wt% to 0.03 wt%, 0.03 wt% to 0.04 wt%, 0.04 wt% to 0.05 wt%, 0.05 wt% to 0.06 wt%, 0.06 wt% to 0.07 wt%, 0.07 wt% to 0.08 wt%, or 0.08 wt% to 0.09 wt%;

the isocyanate group (-NCO) content is 3.0% to 5.0%, for example, 3.0% to 3.5%, 3.5% to 4.0%, 4.0% to 4.5%, or 4.5% to 5.0%;

the viscosity is 120 to 500cps, such as 120 to 150cps, 150 to 200cps, 200 to 300cps, 300 to 400cps or 400 to 500 cps.

In the invention, the chain extender refers to a substance which can react with functional groups on a linear polymer chain to expand the molecular chain and increase the molecular weight, and is commonly used for improving the mechanical property and the process property of products such as polyurethane, polyester and the like. In certain embodiments, the chain extender used is an alcohol chain extender, such as an aromatic alcohol chain extender, for example, 1, 4-bis (2-hydroxyethoxy) benzene (HQEE). In certain embodiments, the chain extender used is an amine chain extender, such as a diamine chain extender, for example, 3 '-dichloro-4, 4' -diaminodiphenylmethane.

According to the invention, fillers such as ultra-high molecular weight polyethylene powder and aluminum oxide powder which are subjected to special modification treatment are added into the polyurethane matrix to improve the mechanical strength of polyurethane, and molybdenum disulfide or polytetrafluoroethylene which is subjected to special treatment is added into the piston to serve as self-lubricating particles, so that the friction coefficient is reduced.

In some embodiments, the particle size of the ultra-high molecular weight polyethylene powder used in the present invention is 30 to 50 μm, such as 30 to 35 μm, 35 to 40 μm, 40 to 45 μm, or 45 to 50 μm.

In some embodiments, the ultra-high molecular weight polyethylene powder used in the present invention has a molecular weight (e.g., viscosity average molecular weight) of 400 to 500 ten thousand, such as 400 to 450 ten thousand or 450 to 500 ten thousand.

In some embodiments, the alumina powder used in the present invention has a particle size of 3000 to 5000 mesh, such as 3000 to 4000 mesh or 4000 to 5000 mesh.

In certain embodiments, the antioxidant used in the present invention is a hindered phenolic antioxidant, such as for example, anti-1010.

In certain embodiments, the sodium-modified polytetrafluoroethylene powder is a sodium naphthalene treated polytetrafluoroethylene powder.

In certain embodiments, the sodium-modified polytetrafluoroethylene powder has a particle size of 3 to 20 μm, such as 3 to 5 μm, 5 to 10 μm, 10 to 15 μm, or 15 to 20 μm.

In certain embodiments, the composition includes, by weight, 10 to 11, 11 to 12, 12 to 13, 13 to 14, 14 to 15, 15 to 16, 16 to 17, 17 to 18, 18 to 19, or 19 to 20 parts of a chain extender.

In some embodiments, the composition comprises 5 to 6, 6 to 7, 7 to 8, 8 to 9, or 9 to 10 parts by weight of the surface silanized ultrahigh molecular weight polyethylene powder.

In certain embodiments, the composition comprises, by weight, 1 to 1.2, 1.2 to 1.3, 1.3 to 1.4, or 1.4 to 1.5 parts of an antioxidant.

In some embodiments, the composition comprises 1 to 1.2, 1.2 to 1.5, or 1.5 to 2 parts by weight of surface silanized alumina powder.

In certain embodiments, the composition comprises, in parts by weight, 1 to 2 or 2 to 3 parts of molybdenum disulfide or sodium-modified polytetrafluoroethylene powder.

The surface silanized ultrahigh molecular weight polyethylene powder used in the invention can be prepared by a method comprising the following steps:

step 1, carrying out oxidation treatment on ultra-high molecular weight polyethylene powder;

and 2, reacting the oxidized ultrahigh molecular weight polyethylene powder with a silane coupling agent.

The oxidation treatment of step 1 may be carried out in a solution containing potassium permanganate and nitric acid. In certain embodiments, the solution is a mixed solution of a saturated aqueous potassium permanganate solution and an aqueous nitric acid solution (e.g., 50% to 60% strength aqueous nitric acid). In certain embodiments, the oxidation treatment comprises the steps of: putting the ultra-high molecular weight polyethylene powder into a solution (such as a mixed solution of a saturated potassium permanganate aqueous solution and 50% nitric acid) containing potassium permanganate and nitric acid, heating (such as heating to 80-90 ℃) and stirring (such as stirring for 30-40 min), filtering to obtain powder, repeatedly washing with deionized water, filtering, and drying.

In step 2, the silylation reaction may use common silane coupling agents, such as silane coupling agent KH540, silane coupling agent KH550, silane coupling agent KH560, and silane coupling agent KH 570. In certain embodiments, the silane coupling agent used is the silane coupling agent KH 550. The weight of the silane coupling agent used may be 0.1% to 1% (e.g., 0.3% or 0.6%) of the weight of the ultrahigh molecular weight polyethylene powder.

The silylation reaction can be carried out under stirring (for example, at 1500 to 2000rpm) and heating (for example, at 70 to 80 ℃). In certain embodiments, the silylation treatment is performed in a high speed mixer.

In certain embodiments, the step of silylating comprises: adding the oxidized ultra-high molecular weight polyethylene powder into a high-speed mixer, adjusting the rotating speed to 1500rpm, adjusting the temperature to 70 ℃, and dropwise adding a silane coupling agent KH550 accounting for 0.3 percent or 0.6 percent of the weight of the powder for coupling treatment.

In the present invention, the sodium naphthalene treatment may comprise the steps of: and adding polytetrafluoroethylene powder into the sodium naphthalene treatment liquid, completely immersing, stirring for 10-15 min, filtering, and washing with tetrahydrofuran and deionized water for multiple times until no smell of the sodium naphthalene treatment liquid exists. In certain embodiments, the sodium naphthalene treatment further comprises: and (3) putting the sodium-modified polytetrafluoroethylene powder into an oven for drying (for example, drying at 100-110 ℃ for 100-150 hours), and grinding and dispersing.

In the present invention, the sodium naphthalene treatment solution is a solution in which sodium and naphthalene in equal amounts are dissolved or complexed in an active ether such as tetrahydrofuran.

In certain embodiments, the sodium naphthalene treatment fluid is prepared by: weighing naphthalene under the protection of nitrogen atmosphere, putting the naphthalene into active ether (such as tetrahydrofuran), adding sodium after the naphthalene is completely dissolved, and fully stirring to dissolve the sodium to obtain the sodium naphthalene treatment solution. In certain embodiments, the naphthalene has a weight of 120 to 150g (e.g., 128 g). In certain embodiments, the weight of sodium is 20 to 25g (e.g., 23 g). In certain embodiments, the active ether (e.g., tetrahydrofuran) is in a volume of 1L.

The surface silanized alumina powder used in the present invention can be prepared by a method comprising the steps of: the alumina powder is reacted with the silane coupling agent under stirring (for example, at 2000 to 3000rpm) and heating (for example, at 70 to 80 ℃). In certain embodiments, the steps are performed in a high speed mixer. The silylation reaction may use a common silane coupling agent, such as silane coupling agent KH540, silane coupling agent KH550, silane coupling agent KH560, silane coupling agent KH 570. In certain embodiments, the silane coupling agent used is the silane coupling agent KH 550. The weight of the silane coupling agent used may be 1% to 5%, for example 2%, of the weight of the alumina powder.

In certain embodiments, the steps comprise: putting the alumina powder into a high-speed mixer, adjusting the rotating speed to 2000rpm and the temperature to 70 ℃, and dropwise adding a coupling agent KH550 accounting for 2 percent of the weight of the powder for coupling treatment.

In one aspect, the present application provides the use of the composition of any of the above for preparing a piston seal. In certain embodiments, the piston seal is a concrete piston seal.

In one aspect, the present application provides a piston seal cast from the composition of any of the above. In certain embodiments, the piston seal is a concrete piston seal.

The present application also provides a method of making the piston seal of the present invention comprising casting using the composition of any of the above.

In certain embodiments, the method comprises the steps of:

a) respectively weighing polyurethane prepolymer, chain extender, surface silanized ultra-high molecular weight polyethylene powder, molybdenum disulfide or sodium-modified polytetrafluoroethylene powder, surface silanized aluminum oxide powder and antioxidant in parts by weight;

b) adding a polyurethane prepolymer, surface silanized ultrahigh molecular weight polyethylene powder, molybdenum disulfide or sodium-modified polytetrafluoroethylene powder and surface silanized alumina powder into a casting machine A tank, uniformly mixing, controlling the temperature to be 80-100 ℃ (such as 90 ℃), and stirring at a medium-low speed of 650-950 rpm (such as 700 rpm);

c) adding a chain extender into a B tank of a casting machine, controlling the temperature to be 110-120 ℃ (for example 115 ℃), adding an antioxidant after the chain extender is completely melted, and stirring at a high speed of 1500-2500 rpm (for example 1600 rpm);

d) cleaning a mold cavity, spraying a release agent in the mold, and preheating in an oven at 110-130 ℃ (for example, 120 ℃) for later use;

e) mixing the liquid in the tank A and the liquid in the tank B according to the control proportion of a casting machine, vacuumizing, keeping the temperature at 100-120 ℃, stirring at the rotating speed of 2000-3500 rpm, and casting into a mold;

f) placing the die in an oven at 100-120 ℃, heating for 16-20 h, taking out and demoulding;

g) and machining the demolded blank to obtain the piston sealing body.

In certain embodiments, the surface silanized ultra high molecular weight polyethylene powder, sodium-modified polytetrafluoroethylene powder, and/or surface silanized alumina powder treatment is prepared as described above.

The piston sealing body can be used as a high-strength self-lubricating piston sealing body, has high mechanical strength, excellent wear resistance and small friction coefficient, and can greatly prolong the service life of the piston. In certain embodiments, the piston seal has one or more of the following features:

the tensile strength is more than or equal to 60 MPa;

the elongation at break is more than or equal to 550 percent;

the tearing strength is more than or equal to 115 kN/m;

the Shore hardness is 96-98 HA;

akron abrasion is less than or equal to 0.025cm³；

The service life is more than 550h (the service life is improved by more than 50 percent compared with that of a pure polyurethane concrete piston).

The performance of the piston seal can be tested using methods commonly used in the art. Exemplary detection criteria are as follows:

performance parameter	Reference standard or test method
		Shore Hardness (HA)	GB/T 531.1
Tensile Strength (MPa)	GB/T 528
		Elongation at Break (%)	GB/T 528
Tear Strength (kN/m)	GB/T 529
		Akron abrasion (cm)³)	GB/T 1689

Further, the present application also provides a piston comprising the piston seal body of the present invention. In certain embodiments, the piston is a concrete piston.

Further, the present application also provides a delivery cylinder comprising the piston seal or piston of the present invention.

Further, the present application also provides a concrete pumping apparatus (e.g., such as a pump truck, a trailer pump, a truck pump) comprising a piston seal, piston, or delivery cylinder of the present invention.

Fig. 1 and 2 show the structure of the concrete piston sealing body of the invention by way of example. Fig. 1 is a diagrammatic sectional view and fig. 2 is a schematic partial sectional view of fig. 1.

The reference numerals in the figures denote:

1-included angle between inner ring of concrete piston lip and horizontal plane, 2-included angle between concrete piston lip and horizontal plane, 3-included angle between outer inclined plane of concrete piston lip and vertical direction, 4-friction surface of concrete piston side, 5-lubricating grease storage tank of concrete piston, 6-schematic diagram of ultra-high molecular weight polyethylene powder and 7-schematic diagram of alumina powder.

In certain embodiments, the concrete piston seal body of the present invention has the following major dimensions:

the included angle between the lip inner ring and the horizontal plane is 40-45 degrees;

the included angle between the lip and the horizontal plane is 3-10 degrees;

the included angle between the outer inclined plane of the lip mouth and the vertical direction is 15-25 degrees;

the width of the side friction surface is 10-15 mm;

the lubricating grease storage groove is 3-5 mm deep.

The piston sealing body is provided with the special oil storage groove, so that a better lubricating effect can be achieved.

Advantageous effects of the invention

The piston seal of the present invention has one or more of the following benefits:

1. the piston sealing body has the advantages of simple production process, low cost and stable quality;

2. the piston sealing body adopts a special filler treatment process, so that the ultra-high molecular weight polyethylene powder, the polytetrafluoroethylene powder and the alumina powder can be tightly combined with a polyurethane matrix and are uniformly dispersed;

3. the enhanced antifriction particles of the piston sealing body are uniformly distributed, so that the wear resistance can be improved;

4. the piston sealing body has excellent mechanical property, and meets the concrete pumping working condition under the high pressure condition;

5. the piston sealing body can realize self-lubrication at the sealing lip, the contact surface with the cylinder barrel, the contact surface with concrete and other parts, and reduce the friction coefficient and the abrasion loss;

6. the self-lubricating particles in the piston sealing body are uniformly distributed, and the self-lubricating effect can be continuously realized on a new friction surface.

Drawings

FIG. 1 is a schematic cross-sectional view of a piston seal body of the present invention, and FIG. 2 is a schematic partial cross-sectional view of FIG. 1, wherein the reference numerals indicate:

1-included angle between inner ring of piston lip and horizontal plane, 2-included angle between piston lip and horizontal plane, 3-included angle between outer inclined plane of piston lip and vertical direction, 4-friction surface of piston side, 5-storage tank of piston lubricating grease, 6-schematic diagram of ultra-high molecular weight polyethylene powder, 7-schematic diagram of polytetrafluoroethylene powder and 8-schematic diagram of alumina powder.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Example 1

(1) Adding 2500g of ultra-high molecular weight polyethylene powder into a mixed solution of a saturated potassium permanganate solution and 50% nitric acid, heating to 80 ℃, stirring for 30min, filtering to obtain powder, and repeatedly cleaning and filtering with deionized water. Drying, adding into a high-speed mixer, adjusting the rotation speed to 1500rpm, adjusting the temperature to 70 ℃, and dropwise adding 7.5 g of coupling agent KH550 for coupling treatment for later use;

(2) 750g of polytetrafluoroethylene powder is put into the sodium naphthalene solution and stirred after being completely immersed. Repeatedly washing with tetrahydrofuran, and filtering; drying in a drying oven for 150h, and grinding and dispersing for later use;

(3) adding 250g of alumina powder into a high-speed mixer, adjusting the rotating speed to 2000rpm, adjusting the temperature to 70 ℃, and dropwise adding 5g of coupling agent KH550 for coupling treatment for later use;

(4) adding 25000g of prepolymer into a tank A of a casting machine, controlling the temperature at 90 ℃, uniformly mixing the surface-treated ultrahigh molecular weight polyethylene powder, polytetrafluoroethylene powder and alumina powder into the prepolymer, and stirring at low speed of 700 rpm;

(5) adding 3750g of chain extender into a B tank of the casting machine, controlling the temperature at 115 ℃, adding 250g of antioxidant after the chain extender is completely melted, and stirring at a high speed of 1600 rpm;

(6) cleaning a mold cavity, uniformly spraying a release agent in the mold, and preheating in a 120 ℃ oven for later use;

(7) mixing the liquid in the tank A and the liquid in the tank B, vacuumizing, keeping the temperature at 120 ℃, stirring at a high speed of 2500rpm, and pouring into a mold cavity;

(8) placing the die in a 120 ℃ oven for 16h, taking out and demoulding;

(9) and machining the demolded product blank to obtain the high-strength self-lubricating polyurethane piston.

Example 2

(1) 1250g of ultra-high molecular weight polyethylene powder is put into a mixed solution of saturated potassium permanganate solution and 50 percent nitric acid, heated to 80 ℃, stirred for 30min, filtered to obtain powder, and then repeatedly washed and filtered by deionized water. Drying, adding into a high-speed mixer, adjusting the rotation speed to 1500rpm, adjusting the temperature to 70 ℃, and dropwise adding 7.5 g of coupling agent KH550 for coupling treatment for later use;

(2) 500g of polytetrafluoroethylene powder is put into the sodium naphthalene solution and stirred after the polytetrafluoroethylene powder is completely immersed. Repeatedly washing with tetrahydrofuran, and filtering; drying in a drying oven for 150h, and grinding and dispersing for later use;

(8) placing the die in a 120 ℃ oven for 16h, taking out and demoulding;

Comparative example 1

(1) 25000g of prepolymer is added into a tank A of a casting machine, the temperature is controlled at 90 ℃, and the mixture is stirred at low speed of 700 rpm;

(2) adding 3750g of chain extender into a B tank of the casting machine, controlling the temperature at 115 ℃, and stirring at a high speed of 1600rpm after the chain extender is completely melted;

(3) cleaning a mold cavity, uniformly spraying a release agent in the mold, and preheating in a 120 ℃ oven for later use;

(4) mixing the liquid in the tank A and the liquid in the tank B, vacuumizing, keeping the temperature at 120 ℃, stirring at a high speed of 2500rpm, and pouring into a mold cavity;

(5) placing the die in a 120 ℃ oven for 16h, taking out and demoulding;

(6) and machining the demolded product blank to obtain the high-strength self-lubricating polyurethane piston.

The mechanical properties, wear resistance and service time of the concrete piston sealing bodies prepared in the examples 1 and 2 and the comparative example are tested, and the results are shown in the following table 1:

TABLE 1 Performance test results of concrete pistons prepared according to examples and comparative examples of the present invention

Performance parameter	Reference standard	Example 1	Example 2	Comparative example 1
					Shore Hardness (HA)	GB/T 531.1	97	98	93
Tensile Strength (MPa)	GB/T 528	62	61	50
					Elongation at Break (%)	GB/T 528	570	556	450
Tear Strength (kN/m)	GB/T529	118	115	102
					Akron abrasion (cm)³)	GB/T 1689	0.022	0.025	0.045
Service life (h)	/	580	555	370

While specific embodiments of the invention have been described in detail, those skilled in the art will understand that: various modifications and changes in detail can be made in light of the overall teachings of the disclosure, and such changes are intended to be within the scope of the present invention. The full scope of the invention is given by the appended claims and any equivalents thereof.

Claims

1. The composition for preparing the piston sealing body comprises the following components in parts by weight: 100 parts of polyurethane prepolymer, 10-20 parts of chain extender, 5-10 parts of surface silanized ultrahigh molecular weight polyethylene powder, 1-1.5 parts of antioxidant, 1-2 parts of surface silanized aluminum oxide powder and 1-3 parts of molybdenum disulfide or sodium-modified polytetrafluoroethylene powder.

2. The composition of claim 1, the polyurethane prepolymer is polyether;

preferably, the polyurethane prepolymer is selected from one or two of LF M2050 models and LF M2032 models;

preferably, the polyurethane prepolymer has one or more of the following characteristics:

(1) the free MDI content is less than 0.1 wt%,

(2) the content of isocyanate group (-NCO) is 3.0 percent to 5.0 percent,

(3) the viscosity is 120 to 500 cps.

3. The composition of claim 1 or 2, the surface silanized ultra high molecular weight polyethylene powder being prepared by a process comprising the steps of:

step 2, reacting the oxidized ultrahigh molecular weight polyethylene powder with a silane coupling agent;

preferably, the oxidation treatment of step 1 is carried out in a solution containing potassium permanganate and nitric acid;

preferably, the solution is a mixed solution of a saturated aqueous potassium permanganate solution and an aqueous nitric acid solution (for example, a 50-60% concentration aqueous nitric acid solution);

preferably, step 1 comprises: putting the ultra-high molecular weight polyethylene powder into a solution containing potassium permanganate and nitric acid, heating and stirring, filtering to obtain powder, repeatedly cleaning with deionized water, filtering, and drying.

Preferably, the silane coupling agent is selected from: a silane coupling agent KH540, a silane coupling agent KH550, a silane coupling agent KH560, and a silane coupling agent KH 570;

preferably, the weight of the silane coupling agent is 0.1-1% of the weight of the ultra-high molecular weight polyethylene powder.

4. The composition of any of claims 1-3, the sodium-modified polytetrafluoroethylene powder is a sodium naphthalene treated polytetrafluoroethylene powder;

preferably, the sodium naphthalene treatment comprises the following steps: adding polytetrafluoroethylene powder into the sodium naphthalene treatment liquid, completely immersing, stirring for 10-15 min, filtering, and washing with tetrahydrofuran and deionized water for multiple times until no smell of the sodium naphthalene treatment liquid exists;

preferably, the sodium naphthalene treatment further comprises: and (3) putting the sodium-modified polytetrafluoroethylene powder into an oven for drying, and then grinding and dispersing.

5. The composition of any one of claims 1-4, the surface silanized alumina powder prepared by a process comprising the steps of: under the conditions of stirring and heating, reacting the alumina powder with a silane coupling agent;

preferably, the weight of the silane coupling agent is 1 to 5 percent of the weight of the alumina powder.

6. The composition of any one of claims 1-5, having one or more of the following characteristics:

(1) the chain extender is an alcohol chain extender or an amine chain extender, such as an aromatic alcohol chain extender or a diamine chain extender, such as 1, 4-bis (2-hydroxyethoxy) benzene or 3,3 '-dichloro-4, 4' -diaminodiphenylmethane;

(2) the particle size of the ultra-high molecular weight polyethylene powder is 30-50 mu m;

(3) the molecular weight of the ultra-high molecular weight polyethylene powder is 400-500 ten thousand.

(4) The particle size of the alumina powder is 3000-5000 meshes;

(5) the antioxidant is a hindered phenolic antioxidant, such as anti-1010;

(6) the sodium-modified polytetrafluoroethylene powder has a particle size of 3-20 μm.

7. Use of a composition according to any one of claims 1 to 6 for the preparation of a piston seal;

preferably, the piston sealing body is a concrete piston sealing body.

8. A piston seal cast from the composition of any of claims 1-7;

preferably, the piston sealing body is a concrete piston sealing body;

preferably, the piston seal has one or more of the following features:

the tensile strength is more than or equal to 60 MPa;

the elongation at break is more than or equal to 550 percent;

the tearing strength is more than or equal to 115 kN/m;

the Shore hardness is 96-98 HA;

akron abrasion is less than or equal to 0.025cm³；

The service life is more than 550 h.

9. A method of making a piston seal comprising casting using the composition of any of claims 1-6;

preferably, the method comprises the steps of:

b) adding a polyurethane prepolymer, surface silanized ultrahigh molecular weight polyethylene powder, molybdenum disulfide or sodium polytetrafluoroethylene powder and surface silanized alumina powder into a casting machine A tank, uniformly mixing, controlling the temperature to be 80-100 ℃, and stirring at a low speed of 650-950 rpm;

c) adding a chain extender into a tank B of the casting machine, controlling the temperature to be 110-120 ℃, adding an antioxidant after the chain extender is completely melted, and stirring at a high speed of 1500-2500 rpm;

d) cleaning a mold cavity, spraying a release agent in the mold, and preheating in an oven at 110-130 ℃ for later use;

g) machining the demolded blank to obtain the piston sealing body;

preferably, the surface silanized ultra high molecular weight polyethylene powder, the sodium-modified polytetrafluoroethylene powder and/or the surface silanized alumina powder are prepared according to the method as defined in claim 3, 4 and/or 5.

10. A piston comprising the piston seal body of claim 8;

preferably, the piston is a concrete piston.

11. A delivery cylinder comprising the piston seal of claim 8 or the piston of claim 10.

12. A concrete pumping apparatus (such as a pump truck, trailer pump, truck pump, for example) comprising a piston seal of claim 8, a piston of claim 10 or a delivery cylinder of claim 11.