Ultrahigh molecular weight polyethylene material as well as preparation method and application thereof

Abstract

The invention belongs to the field of ultra-high molecular weight polyethylene materials, and particularly discloses an ultra-high molecular weight polyethylene material as well as a preparation method and application thereof. According to the method disclosed by the invention, the long-carbon-chain alkyl siloxane is used for carrying out surface modification on the ceramic microbeads and carrying out cross-linking modification on the UHMWPE, and cross-linking modification and filler modification of the UHMWPE are realized at the same time, so that the material has high thermal deformation temperature, wear resistance and hardness.

Description

Technical Field

[0001] The invention belongs to the field of ultra-high molecular weight polyethylene materials, and specifically relates to an ultra-high molecular weight polyethylene material and a preparation method and application thereof. Background Art

[0002] The viscosity average molecular weight of ordinary polyethylene is generally within 300,000. Ultra-high molecular weight polyethylene (UHMWPE) is a linear structure polyethylene with a viscosity average molecular weight of more than 1.5 million. The ultra-high molecular weight gives UHMWPE extraordinary material properties. Among them, UHMWPE's wear resistance, impact resistance, corrosion resistance, and low temperature resistance are the highest among all polymers. In addition, the market supply of UHMWPE is sufficient and the price is cheap.

[0003] Laboratory test results confirm that the friction coefficient of UHMWPE is 0.07, the friction coefficient of polytetrafluoroethylene is 0.1, the friction coefficient of nylon 66 is 0.15, and the friction coefficient of stainless steel is 0.44. It can be seen that the wear resistance of UHMWPE is better than that of known polymers and metal materials. Most importantly, because UHMWPE has the ability to self-lubricate, it can work in the form of sliding or rotating without lubricating oil. Therefore, the most common application of UHMWPE is to replace wear-resistant steel to make bearing sleeves and wear-resistant linings. For example, the working conditions of mining machinery are extremely harsh, and water, slag, and sand and gravel often enter the wear-resistant steel bearings to cause equipment damage. According to statistics, for every 1 million tons of standard coal produced, 15,000 wear-resistant steel standard bearings are consumed. If UHMWPE is used to make bearings, the number of bearings consumed can be reduced to 100-200, which can save a lot of costs for coal enterprises. However, UHMWPE bearings are currently only used in low- and medium-speed machines because UHMWPE has a low hardness (Shore hardness 70) and a low heat deformation temperature (80°C). In high-speed bearings, the operating temperature of the bearings will reach 70-90°C. At 70-90°C, the wear of UHMWPE parts will increase sharply due to surface softening. When the bearing clearance is enlarged, the frequency of equipment failures will increase rapidly, making it impossible to use UHMWPE parts in high-speed bearings.

[0004] Therefore, it is extremely important to improve the hardness, wear resistance and heat deformation temperature of UHMWPE. In the polymer material industry, the heat deformation temperature of polymers is generally increased by cross-linking modification, and the bulk and surface hardness of polymers are increased by inorganic fillers. The process of silane cross-linking modified polyethylene is mature and widely used. However, the method of silane cross-linking modified ultra-high molecular weight polyethylene UHMWPE is still being explored in the industry. One of the reasons is that UHMWPE has an extremely high molecular weight and a very high melt viscosity, and it cannot be processed by ordinary extrusion processes, which makes the commonly used silane cross-linked polyethylene formula and process difficult to apply to the modification of UHMWPE. Many practitioners in this industry have carried out cross-linking modification and filler modification on UHMWPE, but failed to obtain the expected performance. Researchers have found that although the common peroxide crosslinking method, silane crosslinking method, and radiation crosslinking method can crosslink UHMWPE (irradiation method is effective for surface crosslinking modification of UHMWPE, but bulk crosslinking is more difficult), the crosslinking degree range has a very large impact on the overall performance of UHMWPE, probably due to the special molecular chain structure of UHMWPE, including heat deformation temperature, melting point, crystallinity, elastic modulus, tensile strength, wear resistance and other key material indicators, all of which are optimal within the crosslinking degree range of 50%-65%. When the crosslinking degree of UHMWPE is higher than 70%, the melting point, elastic modulus and wear resistance of UHMWPE will drop rapidly, and may even be lower than that of uncrosslinked modified UHMWPE. When the crosslinking degree of UHMWPE is lower than 45%, the performance indicators of UHMWPE are not significantly improved. This data is obtained from experiments, and the mechanism of generation is still unclear. Peroxide modification in the prior art usually produces UHMWPE modified materials with a crosslinking degree greater than 80%, and with other existing formulations, the crosslinking degree of UHMWPE is not easy to control within the range of 50% to 65%. This may be the reason why no significant progress has been made in crosslinking modification of UHMWPE to improve properties such as heat deformation temperature.

[0005] The method of modifying UHMWPE with inorganic fillers to increase its hardness has been deeply studied in the industry. From the existing data, it can be seen that in the slider wear test, when the proportion of wear-resistant fillers added is small, as the proportion of fillers increases, the wear amount of UHMWPE decreases significantly, indicating that its wear resistance improves. The reason is that the appropriate amount of inorganic fillers plays the role of rigid support points in UHMWPE, preventing the embedding and grinding of sand particles in the wear test, and improving the wear resistance of the material. When the filler ratio is greater than 20%, the wear amount of UHMWPE increases instead. The reason is that the inorganic filler and UHMWPE are not compatible. When the content is greater than 20%, the filler destroys the structural continuity of UHMWPE, the molecular chain distance increases, and the wear resistance decreases instead. Therefore, in the prior art, simply modifying UHMWPE with inorganic fillers does not improve its hardness and wear resistance to a great extent. Summary of the invention

[0006] In view of the above-mentioned problems in the prior art involving the difficulty in controlling the crosslinking degree of UHMWPE materials within 50-65% and the low hardness, wear resistance and heat deformation temperature, the present invention will provide an ultra-high molecular weight polyethylene material and a preparation method and application thereof.

[0007] To achieve the above purpose, the following technical solutions are specifically included:

[0008] A method for preparing an ultra-high molecular weight polyethylene material comprises the following steps:

[0009] (1) mixing long carbon chain alkyl siloxane and tert-amyl hydroperoxide uniformly to obtain a first mixture;

[0010] (2) subjecting the first mixture to a surface modification reaction with ceramic microbeads under stirring to obtain a second mixture;

[0011] (3) uniformly mixing the second mixture with ultra-high molecular weight polyethylene to obtain a third mixture;

[0012] (4) The third mixture is subjected to melt blending and extrusion, and then subjected to hydrolysis and cross-linking reaction to obtain an ultra-high molecular weight polyethylene material.

[0013] In the method of the present invention, the mixture of long carbon chain alkyl siloxane and tert-amyl hydroperoxide is firstly mixed with ceramic microbeads to achieve surface modification of ceramic microbeads by long carbon chain alkyl siloxane, which can greatly improve the compatibility of ceramic microbeads and ultra-high molecular weight polyethylene, increase the filling amount of ceramic microbeads, and comprehensively improve the hardness and wear resistance of the material; then the obtained mixture is mixed with ultra-high molecular weight polyethylene, and during melt blending and extrusion, the tert-amyl hydroperoxide initiator initiates the grafting reaction between ultra-high molecular weight polyethylene and long carbon chain alkyl siloxane, so that the long carbon chain alkyl siloxane is grafted on the molecular chain of ultra-high molecular weight polyethylene, and finally, the grafted long carbon chain alkyl siloxanes are hydrolyzed and cross-linked in water to achieve limited cross-linking modification of ultra-high molecular weight polyethylene, control the cross-linking degree of ultra-high molecular weight polyethylene, and improve the heat deformation temperature of the material. The method of the present invention simultaneously realizes cross-linking modification and filler modification of UHMWPE, so that the material has high heat deformation temperature, wear resistance and hardness.

[0014] Preferably, the long carbon chain alkyl siloxane includes dodecyltrimethoxysilane, hexadecyltrimethoxysilane or octadecyltrimethoxysilane.

[0015] The use of the above-mentioned long carbon chain alkyl siloxane is not only beneficial to modifying the ceramic microbeads and improving the compatibility of the ceramic microbeads with the matrix, but also can, in combination with the tert-amyl hydroperoxide initiator, allow the UHMWPE to undergo limited crosslinking and control its crosslinking degree within a suitable range, thereby achieving the purpose of improving the thermal deformation temperature, wear resistance and hardness of the material.

[0016] Preferably, the surface modification reaction time is 10-20 min.

[0017] Preferably, the viscosity average molecular weight of the ultra-high molecular weight polyethylene is 3 million to 5 million.

[0018] Preferably, the mass ratio of the ultra-high molecular weight polyethylene to the long carbon chain alkyl siloxane is 100:(3-4.5).

[0019] Preferably, the mass ratio of the ultra-high molecular weight polyethylene to tert-amyl hydroperoxide is 100:(0.03-0.05).

[0020] Preferably, the mass ratio of the ultra-high molecular weight polyethylene to the ceramic microbeads is 100:(30-45).

[0021] Preferably, the average particle size of the ceramic microbeads is 5-15 μm.

[0022] Preferably, the temperature of the melt blending extrusion is 200-250°C.

[0023] Preferably, the temperature of the hydrolysis and cross-linking reaction is 90-100° C., and the time of the hydrolysis and cross-linking reaction is 12-60 hours.

[0024] The invention provides an ultra-high molecular weight polyethylene material prepared by the method for preparing the ultra-high molecular weight polyethylene material.

[0025] Preferably, the cross-linking degree of the ultra-high molecular weight polyethylene material is 50%-70%.

[0026] The ultra-high molecular weight polyethylene material obtained by the present invention has a suitable degree of crosslinking, and can effectively improve the mechanical properties, wear resistance and heat resistance of the material.

[0027] Preferably, the heat deformation temperature of the ultra-high molecular weight polyethylene material is 95-105°C.

[0028] Preferably, the melting point of the ultra-high molecular weight polyethylene material is 134-137°C.

[0029] Preferably, the ultra-high molecular weight polyethylene material has a Shore hardness of 90-105 HD.

[0030] The present invention also provides an application of the ultra-high molecular weight polyethylene material in the preparation of bearings and sleeves. The ultra-high molecular weight polyethylene material of the present invention has high heat deformation temperature, wear resistance and hardness, and is very suitable for use in the preparation of bearings and sleeves of equipment, and can reduce the loss rate of bearings and sleeves, thereby achieving cost reduction and gain.

[0031] Compared with the prior art, the present invention has the following beneficial effects: the method of the present invention uses long carbon chain alkyl siloxane to perform surface modification on ceramic microbeads and cross-link modification on UHMWPE, and simultaneously realizes cross-link modification and filler modification of UHMWPE, so that the material has high heat deformation temperature, wear resistance and hardness. Compared with unmodified UHMWPE, the heat deformation temperature of the ultra-high molecular weight polyethylene material of the present invention is increased by more than 10°C, and the Shore hardness is increased by more than 30HD, which can increase the use temperature of UHMWPE, expand the application scenarios of UHMWPE, and have good economic benefits. DETAILED DESCRIPTION

[0032] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention will be further described below through specific examples. The test methods used in the examples and / or comparative examples are conventional methods unless otherwise specified; the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0033] UHMWPE: GUR 5113, viscosity average molecular weight 3.7 million, Celanese;

[0034] Ceramic micro beads: average particle size is 10μm, from Shanghai Gerunya Nanomaterials;

[0035] Hexadecyltrimethoxysilane: Degussa, 9116;

[0036] Tert-amyl hydroperoxide: Nouryon, TAHP-W85;

[0037] Vinyltrimethoxysilane: Dow Corning, 171;

[0038] Dicumyl peroxide: Nouryon, DCP;

[0039] Production equipment:

[0040] Mixer: Stepless speed regulating sealed mixer: SACMI;

[0041] Plunger machine: Pipe and rod plunger machine, Kaide.

[0042] Examples 1-9

[0043] A method for preparing an ultra-high molecular weight polyethylene material comprises the following steps:

[0044] (1) according to the formula in Table 1, long carbon chain alkyl siloxane and tert-amyl hydroperoxide are uniformly mixed in a mixer to obtain a first mixture;

[0045] (2) mixing the first mixture and the ceramic microbeads in a mixer at room temperature and low speed for 15-20 minutes to achieve surface modification treatment, thereby obtaining a second mixture;

[0046] (3) the second mixture and the ultra-high molecular weight polyethylene are uniformly mixed in a mixer to obtain a third mixture; the discharge temperatures of the first mixture, the second mixture and the third mixture are less than 80° C., which can be lower than the safe storage temperature of tert-amyl hydroperoxide, thereby avoiding premature consumption of peroxide;

[0047] (4) The third mixture is put into a plunger machine for melt blending at 200-250° C., pushed and extruded into rods or tubes, and then treated with hot water at 95° C. for 48 hours to obtain an ultra-high molecular weight polyethylene material.

[0048] Comparative Examples 1-7

[0049] A method for preparing an ultra-high molecular weight polyethylene material comprises the following steps:

[0050] (1) According to the formula in Table 2, long carbon chain alkyl siloxane or vinyl trimethoxy silane, tert-amyl hydroperoxide or diisopropylbenzene peroxide are uniformly mixed in a mixer to obtain a first mixture;

[0051] (2) mixing the first mixture and the ceramic microbeads in a mixer at room temperature and low speed for 15-20 minutes to achieve surface modification treatment, thereby obtaining a second mixture;

[0052] (3) the second mixture and the ultra-high molecular weight polyethylene are uniformly mixed in a mixer to obtain a third mixture; the discharge temperatures of the first mixture, the second mixture and the third mixture are less than 80° C., which can be lower than the safe storage temperature of tert-amyl hydroperoxide, thereby avoiding premature consumption of peroxide;

[0053] (4) The third mixture is put into a plunger machine for melt blending at 200-250° C., pushed and extruded into rods or tubes, and then treated with hot water at 95° C. for 48 hours to obtain an ultra-high molecular weight polyethylene material.

[0054] Comparative Example 8

[0055] A method for preparing an ultra-high molecular weight polyethylene material comprises the following steps:

[0056] (1) According to the formula in Table 2, dicumyl peroxide and ceramic microbeads are uniformly mixed in a mixer at a low speed to obtain a first mixture;

[0057] (3) uniformly mixing the first mixture and the ultra-high molecular weight polyethylene in a mixer to obtain a second mixture;

[0058] (4) The second mixture is fed into a plunger machine for melt blending at 200-250° C., pushed and extruded into rods or tubes, and then treated with hot water at 95° C. for 48 hours to obtain an ultra-high molecular weight polyethylene material.

[0059] Table 1 (by weight)

[0060]

[0061] Table 2

[0062]

[0063] The ultra-high molecular weight polyethylene materials obtained in the above examples and comparative examples were subjected to performance tests in a conventional manner, and the specific test standards are as follows:

[0064] (1) Yield strength (MPa): GB / T 1040;

[0065] (2) Elastic modulus (MPa): GB / T 1040;

[0066] (3) Elongation at break (%): GB / T 1040;

[0067] (4) Melting point (℃): GB / T 19466;

[0068] (5) Heat deformation temperature (℃): GB / T 1643;

[0069] (6) Shore hardness (HD): GB / T 3398.2;

[0070] (7) Crosslinking degree (%): GB / T 18474;

[0071] (8) Wear rate (%): GB / T 5478.

[0072] The test results are shown in Table 3.

[0073] Table 3

[0074]

[0075] It can be seen from the above examples 1-5 that the yield strength of the ultra-high molecular weight polyethylene material obtained after modification of the present invention is 34-37MPa, the elastic modulus is 850-975MPa, the elongation at break is 65%-140%, the melting point is 134-137°C, the heat deformation temperature is 95-105°C, the Shore hardness is 90-105HD, the cross-linking degree is 50%-70%, and the wear rate is 0.8%-1.2%. Compared with the unmodified ultra-high molecular weight polyethylene, the yield strength, elastic modulus, melting point, heat deformation temperature, hardness, and cross-linking degree of the ultra-high molecular weight polyethylene material obtained by the present invention are significantly increased, and the wear rate and elongation are significantly decreased. Compared with the unmodified UHMWPE, the heat deformation temperature of the ultra-high molecular weight polyethylene material of the present invention is increased by more than 10°C, and the Shore hardness is increased by more than 30HD, which can increase the use temperature of UHMWPE, expand the application scenarios of UHMWPE, and have good economic benefits.

[0076] In Examples 1-3, the long carbon chain alkyl siloxanes are hexadecyltrimethoxysilane, dodecyltrimethoxysilane, and octadecyltrimethoxysilane, respectively. Compared with unmodified UHMWPE, hexadecyltrimethoxysilane, dodecyltrimethoxysilane, and octadecyltrimethoxysilane can improve the yield strength, elastic modulus, melting point, heat deformation temperature, and hardness of ultra-high molecular weight polyethylene materials, reduce the wear rate and elongation, and control the crosslinking degree at 50%-70%. The three alkyl groups with different carbon atom numbers have a similar degree of improvement on material performance. Among them, when hexadecyltrimethoxysilane is used, the comprehensive effect of improving material performance is better.

[0077] In Example 1, Example 4, Example 5, and Comparative Example 1, the weight portions of tert-amyl hydroperoxide initiator are 0.04, 0.03, 0.05, and 0.02, respectively. As the content of the initiator increases, the yield strength, elastic modulus, melting point, heat deformation temperature, and crosslinking degree gradually increase, the wear rate and elongation gradually decrease, and the hardness first increases, then remains basically unchanged, and then slightly decreases. It can be seen that the amount of initiator used has a greater effect on the crosslinking modification. When the mass ratio of UHMWPE to tert-amyl hydroperoxide is selected to be 100: (0.03-0.05), a suitable crosslinking degree can be obtained, and the purpose of improving the heat deformation temperature and wear resistance of the material can be achieved.

[0078] In Example 1, the weight portions of long carbon chain alkyl siloxane and tert-amyl hydroperoxide are 4 parts and 0.04 parts respectively. The long carbon chain alkyl siloxane and tert-amyl hydroperoxide in Example 1 are used in suitable amounts, and the crosslinking degree can be controlled at 50%-70%, thereby improving the yield strength, elastic modulus, melting point, heat deformation temperature, hardness and reducing the abrasion rate of the material. In Comparative Example 2, the weight portions of long carbon chain alkyl siloxane and tert-amyl hydroperoxide are 5 parts and 0.05 parts respectively. The long carbon chain alkyl siloxane and tert-amyl hydroperoxide are used in too much amounts, thereby causing the crosslinking degree of the material to be too high, thereby reducing the yield strength, elastic modulus, melting point, heat deformation temperature, hardness and improving the abrasion rate of the material. Therefore, in the system of the present invention, when the mass ratio of UHMWPE to tert-amyl hydroperoxide is 100:(0.03-0.05), and the mass ratio of UHMWPE to long carbon chain alkyl siloxane is 100:(3-4.5), the crosslinking degree of the material is appropriate, and the purpose of improving the heat deformation temperature and wear resistance of the material can be achieved.

[0079] The weight of the ceramic microbeads in Example 1 is 40 parts, and the weight of the ceramic microbeads in Comparative Examples 3-4 are 20 parts and 50 parts respectively. Comparative analysis of the performance of the materials of the embodiment and Comparative Examples 3-4 shows that too low and too high an addition amount of ceramic microbeads will reduce the yield strength, elastic modulus, elongation, heat deformation temperature, hardness and increase the wear rate. Therefore, in the system of the present invention, when the mass ratio of UHMWPE to ceramic microbeads is 100:(30-45), the purpose of improving the heat deformation temperature and wear resistance of the material can be achieved.

[0080] In Example 1, the organosiloxane and the initiator are respectively long carbon chain alkyl siloxane and tert-amyl hydroperoxide, in Comparative Examples 5-6, the organosiloxane and the initiator are respectively vinyl trimethoxy silane and diisopropylbenzene peroxide, and the amount of the organosiloxane and the initiator in Comparative Example 6 is reduced. It can be seen that compared with Example 1, the organosiloxane and the initiator in Comparative Example 7 are respectively vinyl trimethoxy silane and tert-amyl hydroperoxide, and there is no long carbon chain alkyl siloxane and tert-amyl hydroperoxide in Comparative Example 8, but there is diisopropylbenzene peroxide. Comparative analysis of Example 1 and Comparative Examples 6-8 shows that conventional organosiloxane and initiator, or long carbon chain alkyl siloxane or tert-amyl hydroperoxide alone, will lead to excessive crosslinking of the material, and the heat deformation temperature and wear resistance of the material cannot be effectively improved. Only by adopting the scheme of compounding long carbon chain alkyl siloxane and tert-amyl hydroperoxide can UHMWPE be effectively modified to achieve the purpose of significantly improving the heat deformation temperature and wear resistance of the material.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing an ultra-high molecular weight polyethylene material, characterized in that: The steps include: (1) mixing long carbon chain alkyl siloxane and tert-amyl hydroperoxide uniformly to obtain a first mixture; (2) subjecting the first mixture to a surface modification reaction with ceramic microbeads under stirring to obtain a second mixture; (3) uniformly mixing the second mixture with ultra-high molecular weight polyethylene to obtain a third mixture; (4) The third mixture is subjected to melt blending and extrusion, and then subjected to hydrolysis and cross-linking reaction to obtain an ultra-high molecular weight polyethylene material.

2. The method for preparing the ultra-high molecular weight polyethylene material according to claim 1, characterized in that: The long carbon chain alkyl siloxane includes at least one of dodecyltrimethoxysilane, hexadecyltrimethoxysilane and octadecyltrimethoxysilane.

3. The method for preparing the ultra-high molecular weight polyethylene material according to claim 1, characterized in that: The mass ratio of the ultra-high molecular weight polyethylene to the long carbon chain alkyl siloxane is 100:(3-4.5).

4. The method for preparing the ultra-high molecular weight polyethylene material according to claim 1, characterized in that: The mass ratio of the ultra-high molecular weight polyethylene to tert-amyl hydroperoxide is 100:(0.03-0.05).

5. The method for preparing the ultra-high molecular weight polyethylene material according to claim 1, characterized in that: The mass ratio of the ultra-high molecular weight polyethylene to the ceramic microbeads is 100:(30-45).

6. The method for preparing the ultra-high molecular weight polyethylene material according to claim 1, characterized in that: The temperature of the melt blending extrusion is 200-250°C.

7. The method for preparing the ultra-high molecular weight polyethylene material according to claim 1, characterized in that: The temperature of the hydrolysis and cross-linking reaction is 90-100° C., and the time of the hydrolysis and cross-linking reaction is 12-60 hours.

8. An ultra-high molecular weight polyethylene material obtained by the method for preparing an ultra-high molecular weight polyethylene material according to any one of claims 1 to 7.

9. The ultra-high molecular weight polyethylene material according to claim 8, characterized in that: Include at least one of the following: The crosslinking degree of the ultra-high molecular weight polyethylene material is 50%-70%; The heat deformation temperature of the ultra-high molecular weight polyethylene material is 95-105°C; The melting point of the ultra-high molecular weight polyethylene material is 134-137°C; The Shore hardness of the ultra-high molecular weight polyethylene material is 90-105HD.

10. Use of the ultra-high molecular weight polyethylene material according to claim 8 or 9 in the preparation of bearings and sleeves.

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