CN106317872A - Polyimide-based self-lubricating composite material applicable to oil lubrication working conditions and preparation method thereof - Google Patents

Abstract

The invention discloses a polyimide-based self-lubricating composite material suitable for oil lubrication working conditions. The components contained in the composite material and the volume percentage of each component are: polyimide 69-94% , glass fiber 5~30%, zinc sulfide 1~7%. The invention also discloses a preparation method of the composite material. The composite material of the invention has high mechanical properties, and exhibits extremely low friction coefficient and wear rate under boundary and mixed lubrication conditions.

Description

A polyimide-based self-lubricating composite material suitable for oil lubrication conditions and its preparation preparation method

technical field

The invention relates to a glass fiber and zinc sulfide composite modified polyimide-based self-lubricating composite material and a preparation method thereof, belonging to the field of self-lubricating composite materials. The composite material can be applied to sliding bearings, thrust bearings and bushings in the fields of automobile engines and the like.

Background technique

With the rapid development of the automotive industry, high-end equipment and other fields, the service conditions of related mechanical motion mechanisms are becoming more and more harsh. Complex working conditions such as frequent start and stop of machinery, high speed, and heavy loads lead to mixed lubrication or even boundary lubrication in the motion mechanisms. Occurs frequently, and poses new challenges to the reliability and service life of traditional mechanical parts. Due to its low density, high specific strength, designable performance, self-lubrication, good corrosion resistance and other excellent properties, polymer composite materials are increasingly used in high-tech industrial fields. Using the optimally designed polymer composite material-metal friction pair to replace the metal-metal friction pair can effectively prevent the seizure of the moving mechanism, which provides a new idea for the design of the mechanical mechanism friction pair. As a superior engineering plastic, polyimide has excellent mechanical properties, outstanding thermal stability, radiation resistance and other properties, and has been widely used in automobiles, aviation, aerospace, transportation and other fields. However, due to the low load-carrying capacity and poor friction and wear properties of pure polyimide materials, it is difficult to meet the use requirements under certain harsh conditions, and it needs to be modified and functionalized according to specific use conditions.

The currently developed polyimide self-lubricating composite materials are mainly used under dry friction conditions, and there are few self-lubricating composite materials developed for harsh oil lubrication conditions. The existing relevant patents in China include: 200510027062.2-a method for preparing a sliding bearing made of nano-Al ₂ O ₃ /polyimide friction composite material, 200810042468.1-a method for preparing a sliding bearing using a polyimide composite material, 201110369472.0-a Polyimide self-lubricating compound. These materials mainly use micron and nanometer fillers to modify polyimide, which are used as sliding bearing materials under dry friction conditions.

Combined with the service conditions of oil-lubricated sliding bearings, thrust bearings, bearing bushes and other components in the automotive engine and other fields, through reasonable material design and formula control, even under harsh oil-lubricated conditions, the polyimide matrix can still be effectively improved. It promotes the composite material to form a boundary reaction film with excellent lubricating properties on the metal pair surface, thereby improving the friction, wear performance and reliability of the material.

Contents of the invention

The object of the present invention is to provide a polyimide-based self-lubricating composite material suitable for oil lubrication conditions and a preparation method thereof. The material has good anti-wear and anti-friction properties, excellent service stability and long service life under severe oil lubrication conditions.

The present invention is realized by following measures:

According to the material structure design and performance optimization, the invention improves the bearing capacity and anti-wear performance of the composite material by adding reinforced phase glass fibers in the polyimide matrix, and improves the formation speed and lubrication of the boundary reaction film on the metal pair surface by adding zinc sulfide particles. The performance makes it quickly form a stable boundary reaction film with superior performance on the contact surface. During use, the composite material ensures the long-term effectiveness and stability of the lubricating system through the synergistic effect with the oil lubricating medium. Polyimide is selected as the polymer matrix, glass fiber as the reinforcing phase, and zinc sulfide particles as the functional filler.

A polyimide-based self-lubricating composite material suitable for oil-lubricated working conditions is characterized in that the components contained in the composite material and the volume percentages of each component are: polyimide 69-94%, Glass fiber 5~30%, zinc sulfide 1~7%.

The polyimide is thermoplastic polyimide powder with a particle size of 45-75 μm.

The glass fiber is chopped glass fiber, the diameter of a single filament is 5-30 μm, and the length is 50-300 μm.

The particle size of the zinc sulfide is 20-300nm.

The preparation method of the polyimide-based self-lubricating composite material as described above is characterized in that the specific steps are: polyimide, glass fiber and zinc sulfide are stirred for preliminary dry mixing, and the fully mixed raw materials are extruded by twin-screws The machine is used for high-temperature melting and kneading and extruded; the extruded material that is melted and kneaded uniformly is injection-molded by the injection machine.

The heating temperature of the first zone of the twin-screw extruder is 385-390°C, the heating temperature of the second zone is 395-405°C, the heating temperature of the third zone is 410-415°C, and the screw speed is 150-250r/min.

The temperature of the injection mold of the injection machine is 210-230°C, the temperature of the injection cylinder is 390-415°C, and the injection pressure is 160-180MPa.

The present invention comprehensively considers the efficacy of different components and the synergistic effect between the components in the material structure and performance design. The material of the invention is composed of a polymer matrix, a reinforcing phase and a functional filler. The polyimide matrix selected in the present invention has excellent mechanical properties, outstanding thermal stability, radiation resistance and corrosion resistance; the selected glass fiber has strong heat resistance, good corrosion resistance, high mechanical strength, wear resistance Good sex and other characteristics. In the state of boundary and mixed lubrication, the glass fiber improves the wear resistance of the polyimide matrix, while the zinc sulfide promotes the tribochemical reaction during the friction process, forming a boundary reaction film with excellent lubricating performance on the metal pair surface, reducing the wear resistance of the moving parts. Friction and wear significantly prolong the service life of moving parts and improve system reliability.

Description of drawings

Fig. 1 is a graph showing the variation of friction coefficient with time of the self-lubricating composite material of the present invention.

Fig. 2 is the average coefficient of friction of the self-lubricating composite material of the present invention.

Fig. 3 is the average wear rate of the self-lubricating composite material of the present invention.

detailed description

The present invention is further illustrated below by specific examples, but the present examples are not intended to limit the present invention, and all similar methods and similar changes thereof that adopt the present invention should be included in the protection scope of the present invention.

Example 1

A polyimide-based self-lubricating composite material suitable for oil-lubricated working conditions has a composition volume percentage of: polyimide: 85%, glass fiber 10%, and zinc sulfide 5%. First, the polyimide and glass fiber raw materials were dried in a blast oven at 150°C for 3 hours, and the zinc sulfide was dried at 100°C for 3 hours. The above volume fraction raw materials are placed in a high-speed mixer for preliminary dry mixing. The fully mixed raw materials are melted and mixed at high temperature by a twin-screw extruder. The extruder adopts three-stage heating, and the heating temperature from the inlet to the outlet The heating temperature of the first zone is 385~390°C, the heating temperature of the second zone is 395~405°C, the heating temperature of the third zone is 410~415°C, and the screw speed is 200r/min. The melted and kneaded uniform extruded material is injection molded by an injection machine, the temperature of the injection mold of the injection machine is 220°C, the temperature of the injection cylinder is 405°C, and the injection pressure is 170MPa.

Example 2

The volume percentage of a polyimide-based self-lubricating composite material suitable for oil lubrication conditions is: polyimide 70%, glass fiber 23%, and zinc sulfide 7%. First, the polyimide and glass fiber raw materials were dried in a blast oven at 150°C for 3 hours, and the zinc sulfide was dried at 100°C for 3 hours. The above volume fraction raw materials are placed in a high-speed mixer for preliminary dry mixing. The fully mixed raw materials are melted and mixed at high temperature by a twin-screw extruder. The extruder adopts three-stage heating, and the heating temperature from the inlet to the outlet The heating temperature of the first zone is 385~390°C, the heating temperature of the second zone is 395~405°C, the heating temperature of the third zone is 410~415°C, and the screw speed is 180r/min. The melted and kneaded uniform extruded material is injection molded by an injection machine, the temperature of the injection mold of the injection machine is 230°C, the temperature of the injection cylinder is 410°C, and the injection pressure is 180MPa.

Example 3

The volume percentage of a polyimide-based self-lubricating composite material suitable for oil lubrication conditions is: polyimide 90%, glass fiber 8%, and zinc sulfide 2%. First, the polyimide and glass fiber raw materials were dried in a blast oven at 150°C for 3 hours, and the zinc sulfide was dried at 100°C for 3 hours. The above volume fraction raw materials are placed in a high-speed mixer for preliminary dry mixing. The fully mixed raw materials are melted and mixed at high temperature by a twin-screw extruder. The extruder adopts three-stage heating, and the heating temperature from the inlet to the outlet The heating temperature of the first zone is 385~390°C, the heating temperature of the second zone is 395~405°C, the heating temperature of the third zone is 410~415°C, and the screw speed is 220r/min. The melted and kneaded uniform extruded material is injection molded by an injection machine, the temperature of the injection mold of the injection machine is 200°C, the temperature of the injection barrel is 400°C, and the injection pressure is 170MPa.

Comparative example 1

The volume percentage of the components of the self-lubricating composite material is adjusted to be: polyimide 100%. The material preparation process is the same as in Example 1.

Example 4

The sample in embodiment 1 and comparative example 1 is processed into the sample block of 50mm * 10mm * 4mm; The sample block of embodiment 1 and comparative example 1 is respectively carried out at least three times of immersion on the ring-block friction and wear testing machine. Friction and wear performance analysis under oil conditions. The test conditions are: the pair is a GCr15 bearing steel test ring, the initial surface roughness is Ra0.1~0.2μm, the lubricating medium is Mobil synthetic base oil PAO4, the friction radius is 30mm, the test load is 400N, and the sliding speed is 0.05m/s and 0.05m/s respectively. 0.2m/s, friction and wear test time is 180min.

Among them, when the sliding speed is 0.05m/s, the friction coefficient of Example 1 is 0.066, and the wear rate is 4.31×10 ^{- 7} mm ³ /Nm. Compared with the friction and wear performance of Comparative Example 1 under the same conditions, the friction coefficient decreased by 20%, and the wear rate decreased by 60%; when the sliding speed was 0.2m/s, the friction coefficient of Example 1 was 0.023, and the wear rate was 9.3×10 ^-8 mm ³ /Nm, compared with the comparative example under the same conditions 1 friction and wear performance, the friction coefficient is reduced by 72%, and the wear rate is reduced by 85%.

The present invention comprehensively considers the efficacy of different components and the synergistic effect between the components in the material structure and performance design. The invention improves the mechanical properties and wear resistance of the polyimide by adding glass fiber as a reinforcing phase. In the state of boundary and mixed lubrication, zinc sulfide promotes the tribochemical reaction in the friction process, forms a boundary reaction film with excellent lubricating performance on the surface of the metal pair, reduces the friction and wear of moving parts, significantly prolongs the service life of moving parts, and improves the system performance. reliability. The polyimide composite material of the present invention can be applied to sliding bearings, thrust bearings and bearing bushes in the fields of automobile engines and the like, and the preparation process is simple. Compared with traditional polyimide composite materials, it shows better performance Reliability and longer service life.

Claims (7)

1. A polyimide-based self-lubricating composite material suitable for oil lubrication conditions, characterized in that the components contained in the composite material and the volume percentage of each component are: polyimide 69~94 %, glass fiber 5~30%, zinc sulfide 1~7%. 2. The self-lubricating composite material according to claim 1, characterized in that the polyimide is thermoplastic polyimide powder with a particle size of 45-75 μm. 3. The self-lubricating composite material according to claim 1, wherein the glass fiber is chopped glass fiber, the diameter of the single filament is 5-30 μm, and the length is 50-300 μm. 4. The self-lubricating composite material according to claim 1, characterized in that the particle size of the zinc sulfide is 20-300nm. 5. the preparation method of polyimide-based self-lubricating composite material as described in any one in claim 1 to 4, it is characterized in that concrete steps are: polyimide, glass fiber and zinc sulfide are stirred and carry out preliminary dry method Mixing, the fully mixed raw materials are melted and kneaded at high temperature by a twin-screw extruder and extruded; the extruded material that is melted and kneaded uniformly is injection molded by an injection machine. 6. The preparation method according to claim 5, wherein the heating temperature of the first zone of the twin-screw extruder is 385~390°C, the heating temperature of the second zone is 395~405°C, and the heating temperature of the third zone is 410~390°C. 415°C, the screw speed is 150-250r/min. 7. The preparation method according to claim 5, characterized in that the temperature of the injection mold of the injection machine is 210-230°C, the temperature of the injection barrel is 390-415°C, and the injection pressure is 160-180MPa.