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

Abstract

The invention belongs to a preparation technology of a functional polymer-based nano composite material, and particularly relates to preparation and performance testing of nylon-based self-lubricating anti-wear engineering plastic. The preparation method specifically comprises the following steps: adding a trace amount of nano-copper coated with an organic compound on the surface in the anionic polymerization process of high molecular weight nylon 6 by adopting an in-situ polymerization method, and carrying out crosslinking curing through diisocyanate to prepare the high-strength engineering plastic with the self-lubricating and anti-wear functions. The nano-copper particles are uniformly dispersed in a polymer matrix through anion in-situ polymerization, and the friction and wear resistance of the engineering plastic are remarkably improved on the premise that the strong impact resistance of the engineering plastic is not influenced. Compared with the prior art, the preparation method is simple, the addition amount of the nano-copper is extremely small, and the anti-friction and anti-wear capacity of the engineering plastic under various working conditions is improved under the condition that the high strength of the engineering plastic is maintained.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of functional polymer-based nanocomposite materials, and in particular relates to a method for preparing nylon-based engineering plastics with self-lubricating and anti-wear properties. Background Art

[0002] Cast nylon 6 prepared by anionic ring-opening polymerization of caprolactam and cross-linking with diisocyanate has the characteristics of strong stability and better performance in all aspects, and is widely used. For example, in the field of wind power, important mechanical components in wind turbines often need to be in harsh working conditions. Not only do they have high requirements for mechanical properties, but they also put forward higher requirements for the anti-friction and anti-wear capabilities of various accessories, especially the power machinery parts. Oguzkan et al. prepared thermoplastic nylon 6 / GO nanocomposites by in-situ polymerization. When the addition amount of GO was 1 wt%, the friction coefficient of the material decreased by 66% and the wear decreased by 70% (Journal of Materials Science, 2023, 58, 10318-10339). Zhang W et al. modified nylon 6 with nickel shell microcapsules (NMS) and prepared bearings by injection molding. When 10wt% of NMS was added, the friction coefficient of the material 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, the friction coefficient of 2 wt% h-BN reinforced nylon 6 composite material was reduced by nearly 10~15%, and the wear rate was reduced by 8~10% (e-Polymers, 2020, 20(1):733-745.). Xu Q et al. selected copper oxide as the copper source and prepared thermoplastic nylon 6 / copper nanocomposites by in-situ polymerization. The prepared samples showed good anti-wear and friction reduction properties. When 0.7 wt% CuO was added, the friction coefficient 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 filling content often leads to increased costs. Therefore, finding a filler that can effectively improve the performance while maintaining a low content (≤0.2%) is still a key difficulty in current research. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a method for preparing nylon-based engineering plastics with self-lubricating and anti-wear properties. The method adds a trace amount of nano copper (less than or equal to 0.2wt%) during the synthesis of nylon 6 engineering plastics, and after cross-linking with diisocyanate, the engineering plastics can achieve friction reduction and anti-wear effects under three conditions, namely oil lubrication (46# anti-wear hydraulic oil), water lubrication, and dry friction (no water, grease or other lubricating fluid exists between the friction interfaces), while maintaining its high mechanical properties.

[0004] To achieve the above object, the present invention adopts the following technical solution: A method for preparing nylon-based self-lubricating and wear-resistant engineering plastics comprises the following steps: 1) Raw material processing: Add caprolactam monomer into a reaction vessel, heat to 110~150℃, maintain constant temperature under normal pressure until the caprolactam monomer is in a molten state, evacuate under continuous stirring, gradually increase the vacuum degree until the pressure in the reaction vessel reaches -0.07~-0.09 MPa, and then maintain constant temperature and pressure for 20~60 min; 2) Polymerization reaction: Maintain the temperature and stirring conditions at 110-150°C, release the system vacuum, add the catalyst sodium hydroxide into the reaction vessel, continue to evacuate the reaction system, gradually increase the vacuum degree until the pressure in the reaction vessel reaches -0.07-0.09 MPa, maintain constant temperature and pressure for 10-30 min, then stop evacuating and release the pressure of the reaction vessel, add nano copper into the reaction vessel, continue to evacuate the reaction vessel, gradually increase the vacuum degree until the pressure in the reaction vessel reaches -0.07-0.09 MPa, and maintain constant temperature and pressure for 15-45 min; 3) Cross-linking reaction: Maintain the temperature and stirring conditions at 110-150°C, release the system vacuum, add the initiator 2,6-toluene diisocyanate (TDI) into the reaction vessel, quickly pour the prepared solution into the preheated mold, and keep it in an oven at 140-160°C for 1-2 hours to obtain the nylon-based self-lubricating and wear-resistant engineering plastic.

[0005] Specifically, in step 2), the amount of sodium hydroxide added as a catalyst may be 1-10% of the mass of the caprolactam monomer.

[0006] Furthermore, in step 2), the amount of nano copper added may be 0.05-0.15% of the mass of the caprolactam monomer.

[0007] Specifically, in step 3), the added amount of the initiator toluene diisocyanate can be 0.5-5% of the mass of the caprolactam monomer.

[0008] Furthermore, in step 2), the nano copper is oil-dispersible nano copper modified with carbon chain compounds of C1 to C20 or carbon chain compounds containing heteroatoms (heteroatoms include sulfur, oxygen, nitrogen, phosphorus, etc.), having a quasi-spherical structure, uniform particle size, a size range of 5 to 50 nm, and good dispersibility. The nano copper not only has excellent antioxidant properties, but also exhibits good dispersibility in organic compounds.

[0009] The present invention also provides nylon-based self-lubricating and wear-resistant engineering plastics prepared by the above preparation method.

[0010] The purpose of the present invention is to provide a method for preparing a nylon-based self-lubricating and 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 the method of the present invention are as follows: The present invention adopts nano-grade copper to achieve a huge number of nano-particles in a unit mass of additives, and achieves good friction reduction and anti-wear functions at low addition content; The present invention adopts the method of adding nano copper in anionic in-situ polymerization to achieve uniform dispersion of nano copper in a polymer matrix, so that the thermosetting nylon 6 material can exhibit good tribological behavior in various lubrication conditions while maintaining the high strength of engineering plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The X-ray diffraction (XRD) curve of the nylon-based self-lubricating and anti-wear engineering plastic prepared in Comparative Example 1; Figure 2 Energy dispersive X-ray spectrometer (EDS) of the nylon-based self-lubricating and anti-wear engineering plastic prepared in Example 1; Figure 3 The friction coefficient data of the nylon-based self-lubricating and anti-wear engineering plastics prepared in Example 1, Example 2 and Comparative Example 1 in different media (oil medium, water medium, dry medium); Figure 4 The volume wear data of the nylon-based self-lubricating and wear-resistant engineering plastics prepared in Example 1, Example 2 and Comparative Example 1 in different media (oil medium, water medium, dry medium). DETAILED DESCRIPTION

[0012] The technical solution of the present invention is further described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto.

[0013] The nano copper used in the embodiment is DN Cu-1 nano copper provided by Henan Nanomaterial Engineering Technology Center, which is oil-dispersible nano copper modified by a carbon chain compound containing sulfur. The present invention includes but is not limited to this type of nano copper.

[0014] Example 1 A method for preparing nylon-based self-lubricating and wear-resistant engineering plastics comprises the following steps: (1) Under normal pressure, add 450 g of caprolactam monomer into a reaction vessel, raise the temperature to 140°C, and maintain the constant temperature under normal pressure until the caprolactam monomer is in a molten state (about 40 min); (2) Maintaining the temperature at 140°C, start stirring to ensure uniform mixing of the materials, and start vacuuming while continuing to stir until the pressure in the reaction vessel reaches -0.09 MPa, and maintain constant temperature and pressure for 40 min; (3) Continue to maintain the temperature of 140°C and the stirring state, stop vacuuming and release the system vacuum, maintain the temperature of 140°C, add 1 g of catalyst sodium hydroxide into the reaction vessel, start vacuuming until the pressure in the reaction vessel reaches -0.09 MPa, and maintain for 15 min; (4) Stop vacuuming and release the system vacuum, maintain the temperature at 140°C, add 3.21 g (0.1 wt%) of nano-copper into the reaction vessel and start vacuuming until the pressure in the reaction vessel reaches -0.09 MPa, and maintain this for 40 min; (5) While maintaining the temperature at 140°C and stirring, stop evacuating and release the system vacuum, maintain the temperature at 140°C, and add 1.35 g of initiator toluene diisocyanate (TDI) into the reaction vessel; (6) The prepared solution was quickly poured into a preheated mold and kept in an oven at 160°C for 2 h to obtain a nylon-based self-lubricating and anti-wear engineering plastic.

[0015] Example 2 A method for preparing nylon-based self-lubricating and wear-resistant engineering plastics comprises the following steps: (1) Under normal pressure, add 450 g of caprolactam into the reaction vessel, raise the temperature to 140°C, and maintain the constant temperature under normal pressure until the caprolactam monomer is in a molten state (about 40 min); (2) Maintaining the temperature at 140°C, start stirring to ensure uniform mixing of the materials, and start vacuuming while continuing to stir until the pressure in the reaction vessel reaches -0.09 MPa, and maintain constant temperature and pressure for 40 min; (3) Continue to maintain the temperature of 140°C and the stirring state, stop vacuuming and release the system vacuum, maintain the temperature of 140°C, add 1 g of catalyst sodium hydroxide into the reaction vessel, start vacuuming until the pressure in the reaction vessel reaches -0.09 MPa, and maintain for 15 min; (4) Stop vacuuming and release the system vacuum, maintain the temperature at 140°C, add 1.605 g (0.05 wt%) of nano-copper into the reaction vessel, and start vacuuming until the pressure in the reaction vessel reaches -0.09 MPa, and maintain this for 40 min; (5) While maintaining the temperature at 140°C and stirring, stop evacuating and release the system vacuum, maintain the temperature at 140°C, and add 1.35 g of initiator toluene diisocyanate (TDI) into the reaction vessel; (6) The prepared solution was quickly poured into a preheated mold and kept in an oven at 160°C for 2 h to obtain a nylon-based self-lubricating and anti-wear engineering plastic.

[0016] Comparative Example 1 A method for preparing nylon engineering plastics, the difference between this comparative example and the embodiment is that no nano copper is added, and the method specifically comprises the following steps: (1) Under normal pressure, add 450 g of caprolactam into the reaction vessel, raise the temperature to 140°C, and maintain the constant temperature under normal pressure until the caprolactam monomer is in a molten state (about 40 min); (2) Maintaining the temperature at 140°C, start stirring to ensure uniform mixing of the materials, and start vacuuming while continuing to stir until the pressure in the reaction vessel reaches -0.09 MPa, and maintain constant temperature and pressure for 40 min; (3) Continue to maintain the temperature of 140°C and the stirring state, stop vacuuming and release the system vacuum, maintain the temperature of 140°C, add 1 g of catalyst sodium hydroxide into the reaction vessel, start vacuuming until the pressure in the reaction vessel reaches -0.09 MPa, and maintain for 15 min; (4) Stop evacuating the system, release the system vacuum, maintain the temperature at 140°C, and add 1.35 g of initiator toluene diisocyanate (TDI) into the reaction vessel; (5) The prepared solution was quickly poured into a preheated mold and kept in an oven at 160°C for 2 h to obtain nylon engineering plastics.

[0017] Figure 1 The X-ray diffraction (XRD) curve of the nylon engineering plastic prepared in Comparative Example 1 is given. The results in the figure confirm that the prepared material is nylon 6.

[0018] The present invention conducts energy dispersive X-ray spectroscopy test on the nylon-based self-lubricating and anti-wear engineering plastics prepared in the above examples. The results are as follows: Figure 2 The results in the figure show that nano copper can be evenly dispersed in the nylon 6 matrix material. In the nylon 6 matrix material, the uniform dispersion of nano copper helps to improve the overall performance of the material and ensure that the performance of the composite material in practical applications is maximized.

[0019] In addition, the present invention conducts friction experiments on the nylon-based self-lubricating anti-wear engineering plastics prepared in the above embodiments in different media (oil medium, water medium, dry medium, oil medium refers to oil-lubricated 46# anti-wear hydraulic oil, dry medium refers to the absence of water, grease or other lubricating fluids between the friction interfaces), and tests the friction coefficient and volume wear amount. The results are as follows: Figure 3 and Figure 4 As shown in the figure, the friction coefficients of the material in Example 1 (the addition amount of nano copper is 0.1 wt%) under three friction conditions (oil medium, water medium, dry medium) are 0.03, 0.06, and 0.07 respectively, and the volume wear loss is 9.23×10 6 μm 3 , 3.71×10 6 μm 3 , 12.05×10 6 μm 3 , all decreased compared with the material of Comparative Example 1 (without adding nano copper), which decreased by 67%, 54%, 53% and 32%, 65%, 88% respectively.

[0020] The above results show that nano-copper can significantly improve the friction reduction and anti-wear capabilities of materials under various friction conditions.

[0021] The above embodiments are the best embodiments of the technical solutions claimed by the present invention, and are not specific limitations of the present invention. Based on the embodiments of the present invention, those skilled in the art can obtain the various parameter values ​​of the technical solutions claimed by the present invention by modifying the relevant technical parameters, so the present invention no longer provides overly repeated corresponding parameter change embodiments.

Claims

1. A method for preparing nylon-based self-lubricating and wear-resistant engineering plastics, characterized in that: The steps include: 1) Heat the caprolactam monomer to 110-150°C, maintain constant temperature under normal pressure until the caprolactam monomer is in a molten state, evacuate under continuous stirring until the pressure reaches -0.07-0.09 MPa, and then maintain constant temperature and pressure for 20-60 min; 2) Maintain the temperature and stirring conditions at 110-150°C, release the system vacuum, add the catalyst sodium hydroxide, continue to evacuate the reaction system until the pressure reaches -0.07-0.09 MPa, maintain constant temperature and pressure for 10-30 min, then stop evacuating and release the pressure, add nano-copper, continue to evacuate the system until the pressure reaches -0.07-0.09 MPa, and maintain constant temperature and pressure for 15-45 min; 3) Continue to maintain the temperature condition of 110~150℃ and the stirring state, release the system vacuum, add the initiator 2,6-toluene diisocyanate, pour the prepared solution into the mold, and keep it in an oven at 140~160℃ for 1~2 hours to obtain the nylon-based self-lubricating and anti-wear engineering plastic.

2. The method for preparing the nylon-based self-lubricating and wear-resistant engineering plastic according to claim 1, characterized in that: In step 2), the amount of sodium hydroxide added as a catalyst is 1-10% of the mass of the caprolactam monomer.

3. The method for preparing the nylon-based self-lubricating and wear-resistant engineering plastic according to claim 1, characterized in that: In step 2), the amount of nano copper added is 0.05-0.15% of the mass of the caprolactam monomer.

4. The method for preparing the nylon-based self-lubricating and wear-resistant engineering plastic according to claim 1, characterized in that: In step 3), the amount of initiator toluene diisocyanate added is 0.5-5% of the mass of the caprolactam monomer.

5. The method for preparing the nylon-based self-lubricating and wear-resistant engineering plastic according to claim 1, characterized in that: 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 (heteroatoms include sulfur, oxygen, nitrogen, and phosphorus), and has a particle size of 5-50 nm.

6. Nylon-based self-lubricating and anti-wear engineering plastics prepared by the preparation method according to any one of claims 1 to 5.

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