Preparation method of nylon-based self-lubricating wear-resistant engineering plastic

Abstract

The present application belongs to the functional polymer-based nanocomposite preparation technology, and particularly relates to a preparation of nylon-based self-lubricating wear-resistant engineering plastics and performance testing thereof. The preparation method specifically comprises the following steps: a trace amount of nano-copper coated by a surface organic compound is added in a high-molecular-weight nylon 6 anion polymerization process by using an in-situ polymerization method, and is cross-linked and solidified by diisocyanate to prepare high-strength engineering plastics with self-lubricating wear-resistant functions. The anion in-situ polymerization realizes uniform dispersion of the nano-copper particles in the polymer matrix, and significantly improves the friction and wear resistance of the engineering plastics without affecting the high impact resistance. Compared with the prior art, the preparation method is simple, the nano-copper addition amount is extremely small, and the self-lubricating wear-resistant capacity of the engineering plastics under various working conditions is improved while the high strength of the engineering plastics is maintained.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer-based nanocomposite material preparation technology, specifically relating to a method for preparing a nylon-based engineering plastic with self-lubricating and anti-wear properties. Background Technology

[0002] Cast nylon 6, prepared by anionic ring-opening polymerization of caprolactam and crosslinking with diisocyanate, exhibits superior stability and overall performance, leading to its wide range of applications. For example, in the wind power sector, critical mechanical components of wind turbine generators often operate under harsh environmental conditions, demanding not only high mechanical properties but also enhanced friction reduction and wear resistance in various components, particularly the power machinery. Oguzkan et al. prepared thermoplastic nylon 6 / GO nanocomposites via in-situ polymerization. With 1 wt% GO addition, the material's friction coefficient decreased by 66%, and wear was reduced by 70% (Journal of Materials Science, 2023, 58, 10318-10339). Zhang W et al. modified nylon 6 with nickel-shell microcapsules (NMS) and injection-molded bearings. With 10 wt% NMS addition, the material's friction coefficient decreased from 0.45 to 0.1 (Polymer Composites, 2022, 43, 7074-7085). Randhawa et al. found that h-BN filler can improve the tribological properties of nylon 6. Compared with pure nylon 6, 2 wt% h-BN reinforced nylon 6 composite material reduced the coefficient of friction by nearly 10-15% and the wear rate by 8-10% (e-Polymers, 2020, 20(1):733-745.). Xu Q et al. used copper oxide as the copper source and prepared thermoplastic nylon 6 / copper nanocomposite material by in-situ polymerization. The prepared sample showed good anti-wear and friction reduction properties. When 0.7 wt% CuO was added, the coefficient of friction of the material could be reduced from 1.01 to 0.49 (Journal of the Iranian Chemical Society, 2014, 11(6):1717-1721.). Although the above studies have improved the tribological properties of nylon 6 to a certain extent, their high filler content often leads to increased costs. Therefore, finding fillers that can effectively improve performance while maintaining low content (≤0.2%) remains a key challenge in current research. Summary of the Invention

[0003] The purpose of this invention is to overcome the deficiencies of existing technologies and provide a method for preparing nylon-based engineering plastics with self-lubricating and anti-wear properties. This method involves adding a trace amount of nano-copper (≤0.2wt%) during the synthesis of nylon 6 engineering plastic, followed by crosslinking with diisocyanate. This allows the engineering plastic to achieve friction reduction and anti-wear effects under various working conditions, namely oil lubrication (46# anti-wear hydraulic oil), water lubrication, and dry friction (no water, grease, or other lubricating fluid is present at the friction interface), while maintaining its high mechanical properties.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for preparing a nylon-based self-lubricating anti-wear engineering plastic, comprising the following steps:

[0006] 1) Raw material processing: Add caprolactam monomer to the reaction vessel, heat to 110~150℃, maintain constant temperature under normal pressure until caprolactam monomer is in a molten state, continuously stir and evacuate the vacuum, gradually increase the vacuum degree until the pressure inside the reaction vessel reaches -0.07~-0.09 MPa, and then maintain constant temperature and pressure for 20~60 min;

[0007] 2) Polymerization reaction: Maintain a temperature of 110~150℃ and stirring. Release the system vacuum, add sodium hydroxide catalyst to the reaction vessel, continue to evacuate the reaction system, and gradually increase the vacuum degree until the pressure inside the reaction vessel reaches -0.07~-0.09 MPa. Maintain constant temperature and pressure for 10~30 min, then stop evacuating the vacuum and depressurize the reaction vessel. Add nano copper to the reaction vessel, continue to evacuate the reaction vessel, and gradually increase the vacuum degree until the pressure inside the reaction vessel reaches -0.07~-0.09 MPa. Maintain constant temperature and pressure for 15~45 min.

[0008] 3) Crosslinking reaction: Maintain a temperature of 110~150℃ and stirring, release the system vacuum, add the initiator 2,6-toluene diisocyanate (TDI) into the reaction vessel, quickly pour the obtained solution into a preheated mold, and keep it in an oven at 140~160℃ for 1~2 hours to obtain nylon-based self-lubricating anti-wear engineering plastic.

[0009] Specifically, in step 2), the amount of sodium hydroxide catalyst added can be 1-10% of the mass of caprolactam monomer.

[0010] Furthermore, in step 2), the amount of nano-copper added can be 0.05-0.15% of the mass of caprolactam monomer.

[0011] Specifically, in step 3), the amount of initiator toluene diisocyanate added can be 0.5-5% of the mass of caprolactam monomer.

[0012] Furthermore, the nano-copper described in step 2) is an oil-dispersible nano-copper modified with C1-C20 carbon chain compounds or with carbon chain compounds containing heteroatoms (including sulfur, oxygen, nitrogen, phosphorus, etc.). It has a near-spherical structure, uniform particle size ranging from 5 to 50 nm, and good dispersibility. This nano-copper not only possesses excellent antioxidant properties but also exhibits good dispersibility in organic compounds.

[0013] The present invention also provides a nylon-based self-lubricating and wear-resistant engineering plastic prepared by the above preparation method.

[0014] The purpose of this invention is to provide a method for preparing a nylon-based self-lubricating anti-wear engineering plastic with low filler content and good tribological properties under various working conditions. Compared with the prior art, the main innovations and beneficial effects of this invention are as follows:

[0015] This invention uses nano-sized copper to achieve a large number of nanoparticles in a unit mass of additive, thus exhibiting excellent friction reduction and wear resistance even with low content addition.

[0016] This invention incorporates nano-copper into anionic in-situ polymerization, which enables uniform dispersion of nano-copper in the polymer matrix. This allows thermosetting nylon 6 materials to maintain the high strength of engineering plastics while exhibiting good tribological behavior under various lubrication conditions. Attached Figure Description

[0017] Figure 1 X-ray diffraction (XRD) curves of the nylon-based self-lubricating anti-wear engineering plastic prepared in Comparative Example 1;

[0018] Figure 2 Energy scattering X-ray spectrum (EDS) of the nylon-based self-lubricating anti-wear engineering plastic prepared in Example 1.

[0019] Figure 3 The friction coefficient data of the nylon-based self-lubricating anti-wear engineering plastics prepared in Examples 1, 2 and Comparative Example 1 in different media (oil medium, water medium, dry medium);

[0020] Figure 4 The volumetric wear data of the nylon-based self-lubricating anti-wear engineering plastics prepared in Examples 1, 2 and Comparative Example 1 in different media (oil medium, water medium and dry medium). Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0022] The nano-copper selected in the examples is DN Cu-1 type nano-copper provided by Henan Provincial Nanomaterials Engineering Technology Center. This nano-copper is an oil-dispersible nano-copper modified with a sulfur-containing carbon chain compound. This invention includes, but is not limited to, this type of nano-copper.

[0023] Example 1

[0024] A method for preparing a nylon-based self-lubricating anti-wear engineering plastic, comprising the following steps:

[0025] (1) Under normal pressure, add 450 g of caprolactam monomer to the reaction vessel, heat to 140°C, and keep the temperature constant under normal pressure until the caprolactam monomer is in a molten state (about 40 min).

[0026] (2) Maintain 140℃, turn on the stirrer to mix the materials evenly, and start vacuuming while stirring until the pressure inside the reaction vessel reaches -0.09 MPa. Maintain constant temperature and pressure for 40 min.

[0027] (3) Maintain the temperature and stirring conditions at 140℃, stop the vacuuming and release the system vacuum, maintain the 140℃ condition, add 1 g of catalyst sodium hydroxide into the reaction vessel, start the vacuuming until the pressure inside the reaction vessel reaches -0.09MPa, and maintain it for 15 min;

[0028] (4) Stop vacuuming and release the system vacuum. Maintain the temperature at 140°C. Add 3.21 g (0.1 wt%) of nano copper to the reaction vessel and start vacuuming until the pressure inside the reaction vessel reaches -0.09 MPa. Maintain this temperature for 40 min.

[0029] (5) Maintain the temperature and stirring conditions at 140°C, stop the vacuuming and release the system vacuum, maintain the temperature at 140°C, and add 1.35 g of initiator toluene diisocyanate (TDI) to the reaction vessel.

[0030] (6) Quickly pour the prepared solution into a preheated mold and keep it in a 160°C oven for 2 hours to obtain nylon-based self-lubricating anti-wear engineering plastic.

[0031] Example 2

[0032] A method for preparing a nylon-based self-lubricating anti-wear engineering plastic, comprising the following steps:

[0033] (1) Under normal pressure, add 450 g of caprolactam to the reaction vessel, heat to 140°C, and keep the temperature constant under normal pressure until the caprolactam monomer is in a molten state (about 40 min).

[0034] (2) Maintain 140℃, turn on the stirrer to mix the materials evenly, and start vacuuming while stirring until the pressure inside the reaction vessel reaches -0.09 MPa. Maintain constant temperature and pressure for 40 min.

[0035] (3) Maintain the temperature and stirring conditions at 140℃, stop the vacuuming and release the system vacuum, maintain the 140℃ condition, add 1 g of catalyst sodium hydroxide into the reaction vessel, start the vacuuming until the pressure inside the reaction vessel reaches -0.09MPa, and maintain it for 15 min;

[0036] (4) Stop vacuuming and release the system vacuum. Maintain the temperature at 140°C. Add 1.605 g (0.05 wt%) of nano copper to the reaction vessel and start vacuuming until the pressure inside the reaction vessel reaches -0.09 MPa. Maintain this temperature for 40 min.

[0037] (5) Maintain the temperature and stirring conditions at 140°C, stop the vacuuming and release the system vacuum, maintain the temperature at 140°C, and add 1.35 g of initiator toluene diisocyanate (TDI) to the reaction vessel.

[0038] (6) Quickly pour the prepared solution into a preheated mold and keep it in a 160°C oven for 2 hours to obtain nylon-based self-lubricating anti-wear engineering plastic.

[0039] Comparative Example 1

[0040] A method for preparing nylon engineering plastic, the difference between this comparative example and the embodiment is that nano-copper is not added, and it specifically includes the following steps:

[0041] (1) Under normal pressure, add 450 g of caprolactam to the reaction vessel, heat to 140°C, and keep the temperature constant under normal pressure until the caprolactam monomer is in a molten state (about 40 min).

[0042] (2) Maintain 140℃, turn on the stirrer to mix the materials evenly, and start vacuuming while stirring until the pressure inside the reaction vessel reaches -0.09 MPa. Maintain constant temperature and pressure for 40 min.

[0043] (3) Maintain the temperature and stirring conditions at 140℃, stop the vacuuming and release the system vacuum, maintain the 140℃ condition, add 1 g of catalyst sodium hydroxide into the reaction vessel, start the vacuuming until the pressure inside the reaction vessel reaches -0.09MPa, and maintain it for 15 min;

[0044] (4) Stop evacuating the vacuum and release the system vacuum. Maintain the temperature at 140°C and add 1.35 g of initiator toluene diisocyanate (TDI) to the reaction vessel.

[0045] (5) Quickly pour the prepared solution into a preheated mold and keep it in a 160°C oven for 2 hours to obtain nylon engineering plastic.

[0046] Figure 1 The X-ray diffraction (XRD) curves of the nylon engineering plastic prepared in Comparative Example 1 are shown. The results in the figure confirm that the prepared material is nylon 6.

[0047] The present invention performs energy scattering X-ray spectroscopy tests on the nylon-based self-lubricating anti-wear engineering plastics prepared in the above embodiments, and the results are as follows: Figure 2 As shown in the figure, the results indicate that nano-copper can be uniformly dispersed in the nylon 6 matrix. This uniform dispersion of nano-copper in the nylon 6 matrix helps improve the overall performance of the material, ensuring that the composite material achieves its maximum performance advantage in practical applications.

[0048] Furthermore, this invention conducts friction experiments on the nylon-based self-lubricating anti-wear engineering plastics prepared in the above embodiments under different media (oil medium, water medium, and dry medium; oil medium refers to oil-lubricated 46# anti-wear hydraulic oil, and dry medium refers to the absence of water, grease, or other lubricants at the friction interface) to test its coefficient of friction and volumetric wear. The results are as follows: Figure 3 and Figure 4 As shown in the figure, the friction coefficients of the material in Example 1 (with an addition of 0.1 wt% nano-copper) under three friction conditions (oil medium, water medium, and dry medium) were 0.03, 0.06, and 0.07, respectively, and the volumetric wear was 9.23 × 10⁻⁶. 6 μm 3 3.71×10 6 μm 3 12.05×10 6 μm 3 The values ​​were all lower than those of the material in Comparative Example 1 (without added nano-copper), decreasing by 67%, 54%, 53% and 32%, 65%, 88%, respectively.

[0049] The above results indicate that nano-copper can significantly improve the friction reduction performance and wear resistance of materials under various friction conditions.

[0050] The above embodiments are the preferred embodiments of the technical solution claimed in this invention, and are not intended to limit the invention in any specific way. Based on the embodiments described above, those skilled in the art can modify the relevant technical parameters to obtain the parameter values ​​of the technical solution claimed in this invention. Therefore, this invention does not provide overly repetitive embodiments with corresponding parameter variations.

Claims

1. A process for the preparation of a nylon based self-lubricating wear resistant engineering plastic, characterized in that, It comprises the following steps: 1) heating caprolactam monomer to 110-150℃, keeping constant temperature under normal pressure until caprolactam monomer is in molten state, vacuumizing under continuous stirring until pressure reaches -0.07 to -0.09 MPa, then keeping constant temperature and pressure for 20-60 min; 2) keeping temperature at 110-150℃ and stirring state, releasing vacuum of the system, adding catalyst sodium hydroxide, continuing vacuumizing of the reaction system until pressure reaches -0.07 to -0.09 MPa, keeping constant temperature and pressure for 10-30 min, then stopping vacuumizing and releasing pressure, adding nano-copper, continuing vacuumizing until pressure reaches -0.07 to -0.09 MPa, keeping constant temperature and pressure for 15-45 min; 3) keeping temperature at 110-150℃ and stirring state, releasing vacuum of the system, adding initiator 2,6-toluene diisocyanate, pouring the prepared solution into a mold, keeping in an oven at 140-160℃ for 1-2 h, thus obtaining nylon-based self-lubricating wear-resistant engineering plastic; In step 2), the amount of nano-copper added is 0.05-0.15% of the mass of caprolactam monomer. In step 2), the nano-copper is oil-dispersible nano-copper modified by a C1-C20 carbon chain compound or a carbon chain compound containing heteroatoms, and the particle size is 5-50 nm; the heteroatoms include sulfur, oxygen, nitrogen and phosphorus.

2. A process for the preparation of nylon based self-lubricating anti-friction engineering plastics as claimed in claim 1 wherein, In step 2), the amount of catalyst sodium hydroxide added is 1-10% of the mass of caprolactam monomer.

3. A process for the preparation of nylon based self-lubricating anti-friction engineering plastics as claimed in claim 1 wherein, In step 3), the amount of initiator toluene diisocyanate added is 0.5-5% of the mass of caprolactam monomer.

4. The nylon-based self-lubricating wear-resistant engineering plastic prepared by the preparation method of any one of claims 1-3.

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