RU2762570C1 - Method for applying a protective coating of supermolecular polyethylene to rubber - Google Patents

Abstract

FIELD: protective coatings.

SUBSTANCE: invention can be used for the manufacture of rubber products. The method for applying the protective coating involves applying a fabric made of ultra-high molecular weight polyethylene to the surface of the rubber. The fabric is applied during vulcanization to pre-vulcanized rubber, followed by the continuation of the vulcanization process until complete vulcanization.

EFFECT: increase in the hardness, wear resistance and resistance to aggressive environments of rubber products, as well as reduction in the coefficient of friction on their surface.

1 cl, 2 tbl

Description

The invention relates to the field of development of rubber products and can be used to impart increased hardness to rubber, wear resistance, resistance to aggressive media and reduce the coefficient of friction.

The known method of plasma chemical modification (PCM) for creating rubbers with improved tribological characteristics (1. Surikov V.I., Nikolaev I.V., Polonyankin D.A., Rogachev E.A., Tselykh E.P., Surikov V. I. Structure, composition and tribotechnical properties of a tantalum coating on rubber / Dynamics of systems, mechanisms and machines. - Omsk. 2016. No. 2. P. 232-237), which describes a method of applying a refractory metal to rubber - tantalum with different time intervals. With a spraying duration of 34 minutes. abrasion is reduced 8.5 times compared to the original sample. The disadvantages of tantalum coatings include the loss of elasticity of the modified surface. In work (2. Rogachev A.V. Tribotechnical properties of composite coatings deposited by vacuum-plasma methods / Friction and Wear, 2008. V. 29. No. 3. P. 285-292) by the PCM method, a coating based on polytetrafluoroethylene (PTFE ) and polyurethane (PU) in various proportions. It is shown that rubbers with binary polymer-polymer coatings applied to their surface, which are a PU matrix with PTFE particles introduced into its volume, have the highest tribotechnical characteristics. The disadvantage of this technical solution is the complexity of applying a protective layer. In work (3. Abdrashitov E.F., Tarasenko V.A., Tikhomirov L.A., Ponomarev A.N. Friction and wear of plasma-chemically modified elastomers / Friction and wear. - Republic of Belarus, Gomel. 2001. V. 22 No. 2. P. 190) rubber products (RTI) are processed in a glow discharge plasma in a gaseous medium of perfluoroorganic compounds. Under the action of active components of the plasma on the surface of the rubber goods, an antifriction polymer fluorocarbon film is deposited at a rate of 0.5 to 1-3 μm / h. In work (4. Tikhomirov LA Kinetics of plasma deposition of fluorocarbon films of polytetrafluoroethylene / Chemistry of high energies. - M .: 1983. T. 17. No. 4. P. 345) to increase wear resistance, an attempt was made to increase the thickness of the fluoropolymer coating by applying adhesive - an active composition prepared on the basis of a solution of SKF-26 rubber with the addition of molybdenum disulfide in the process of friction. However, additional thickening, as shown by experiments, does not lead to an increase in wear resistance. The disadvantage of the plasma-chemical modification method is the complexity of the coating process, as well as the need to use special machine devices.

Known surface modification of samples from nitrile rubbers with a composition based on polyamide PA-6 and MoS2 (5. Tikhomirov L.A., Tarasenko V.A., Kostina T.Yu., Dorofeeva L.V. Effect of molybdenum disulfide on the tribotechnical characteristics of polyamide coatings on nitrile rubber / Rubber and rubber. - M .: 1914. No. 3. S. 26-28.). Experiments on surface modification were carried out on IRP-1078-NTA rubbers (based on a mixture of SKN-18 and SKN-26 nitrile rubbers). In a 10% solution of PA-6 in formic acid, MoS ₂ powder was added in an amount of 30% by weight of the polymer. Samples in the form of rubber disks with a diameter of 36 mm and a thickness of 2 mm were kept in the specified mixture at a temperature of 58-60 ° C for 20 minutes with continuous stirring. After drying, the samples were treated with a stream of hot air at a temperature of 240-250 ° C. It was shown in (5) that the introduction of molybdenum disulfide into the composition of the polyamide coating leads to an increase in wear resistance by a factor of 4-5. The disadvantage of manufacturing coatings using technology (5) is the complexity of the technological process of obtaining a coating. This invention is taken as an analogue.

The closest technical solution is (6. Sokolova M.D., Shadrinov N.V., Dyakonov A.A. Method of applying a protective film of ultra-high molecular weight polyethylene to rubber // RF Patent No. 2641816, bull. No. 3 dated 01.22.2018) , which describes a method of applying a protective coating of ultra-high molecular weight polyethylene to rubber in the form of a powder. The disadvantage of this technical solution can be attributed to the fact that UHMWPE is applied to the rubber surface in powder form during the manufacture of rubber goods, which in itself is a difficult technological problem, and also makes it difficult to control the uniformity of distribution and the thickness of the application of the protective layer. The unevenness of the applied protective coating can affect the decrease and increase in the spread of indicators of the technical properties of the coated rubber.

Disclosure of invention

The problem to be solved by the claimed invention is to increase the wear resistance of rubber products by applying a protective coating of fabric UHMWPE to the rubber surface.

The technical result achieved with the implementation of the invention consists in obtaining coated rubber products having high abrasion resistance.

Essential features that characterize the invention.

Restrictive: A protective coating made of wear-resistant polymer material is applied to the rubber surface. The proposed method involves the use of preliminary scorching of the rubber mixture to squeeze out excess rubber mixture (flash) before applying a protective coating of UHMWPE. If UHMWPE is applied to the surface of a rubber compound without preliminary scorching, then UHMWPE can be displaced (squeezed out) along with the flash, which can cause the formation of uncovered zones.

Distinctive: In the process of vulcanization, UHMWPE in the form of a fabric is applied to the surface of pre-vulcanized rubber. At the same time, under the influence of high temperature and pressure, UHMWPE passes into a highly elastic state (melting process) and upon cooling (process of transition to a solid state) forms a strong connection with rubber by physically engaging macromolecules. The mesh structure of the UHMWPE fabric helps to improve the physical weave with the rubber.

As a result of the application of UHMWPE fabric using the presented method, a thin monolithic coating is formed on the rubber surface, which performs a protective function. Thickness may vary depending on the weave density of the fabric.

Implementation of the invention

The method of applying a protective coating to the rubber surface is carried out as follows: First, preliminary scorching of the raw rubber compound is performed. For this, the raw rubber mixture is placed in a mold and vulcanized at the vulcanization temperature specified in the technical specifications of the rubber mixture used for 1/10 - 1/8 (depending on the type of rubber and the rheological properties of the rubber mixture) of the total time required for vulcanization of that or other rubber. During scorching, the flash is squeezed out and the sample is given a certain shape. Then, the vulcanization process is temporarily suspended and UHMWPE fabric is applied to the scorched rubber sample. After that, the vulcanization process continues until the rubber is completely vulcanized. For complete vulcanization, the duration of vulcanization indicated in the technical specifications of the rubber compound used is taken. Due to the fact that the melting temperature of various brands of UHMWPE (125-135 ° C) is lower than the vulcanization temperature of rubber (140-160 ° C), the UHMWPE fabric melts and forms a uniform layer on the rubber surface.

To demonstrate the effectiveness of the proposed method, samples of elastomeric matrices based on butadiene rubber (SKD-Ti) and a mixed composition of butadiene and butadiene-styrene rubbers (SKD-Ti / DSSK), covered with a protective layer of UHMWPE fabric, were made. The formulation of rubber compounds is presented in table. one.

Table 1. Formulation of rubber compounds for coating from UHMWPE fabric

No. Ingredient Mass parts per 100 pbw rubber one 2 one SKD-Ti 100.0 40.0 2 DSSK - 60.0 3 TU N330 50.0 4 DBS 5.0 5 ZnO 5.0 6 Stearic acid 2.0 7 S 2.0 eight Sulfenamide C 0.7

The rubber mixture was mixed on laboratory rollers Cm350 ° 150/150 (China) for 30 minutes. Samples for research were vulcanized in a hydraulic press 100-400 2E (Russia) at a temperature of 155 ° C for 20 minutes.

The study of physical and mechanical indicators was carried out in accordance with GOST 270-75 on a UTS testing machine (Germany). Abrasion resistance of rubbers was assessed by the method of determining abrasion resistance in accordance with GOST 23509-79 on a friction machine AR-40 (Russia). Shore A hardness is determined according to GOST 263-75.

Table 2. Properties of rubbers coated with UHMWPE

No. Samples Indicators f _p , MPa f ₁₀₀ , MPa ε _p ,% ΔV, cm ³ H, cu one SKD-Ti ref. 17.7 1.9 627 0.0091 53 2 SKD-Ti + DSSK ref. 20.3 1.9 665 0.0116 53 3 SKD-Ti with UHMWPE coating 5.2 4.2 206 0.0024 76 4 SKD-Ti + DSSK coated with UHMWPE 5.9 4.5 186 0.0041 78

f _p , MPa - conditional tensile strength; f ₁₀₀ , MPa - conditional stress at 100% elongation; ε _p ,% - elongation at break; ΔV, cm ³ - volumetric wear; H, cu - Shore A hardness.

Table 2 shows the results of studies of rubber samples covered with UHMWPE fabric. Compared with the original rubbers, the samples of rubbers with a protective coating made of UHMWPE have lower elongation at break and tensile strength, but at the same time they have higher indices (up to 2.3 times) modulus at 100% elongation. The volumetric wear during abrasion in the SKD-Ti and SKD-Ti / DSSK specimens decreases by 73% and 65%, respectively, which indicates a significant increase in wear resistance. The hardness of the samples increases by about 30-32%.

Claims (1)

A method of applying a protective coating of ultra-high-molecular-weight polyethylene to a rubber surface, characterized in that ultra-high-molecular-weight polyethylene is applied to the rubber surface in the form of a fabric coating during rubber vulcanization, while the application of ultra-high-molecular-weight polyethylene to the rubber surface is performed by applying a fabric of ultra-high molecular weight polyethylene on pre-vulcanized rubber with the subsequent continuation of the vulcanization process until its complete vulcanization.