Super-strong, high-wear-resistant and creep-resistant nylon composite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of engineering plastics, in particular to a super-strong, high-wear-resistant and creep-resistant nylon composite material as well as a preparation method and application thereof. The nylon composite material is prepared from the following components in parts by weight: 80 to 100 parts of PA46 resin, 15 to 20 parts of carbon fiber, 8 to 10 parts of polytetrafluoroethylene, 0.1 to 0.3 part of nucleating agent and 0.2 to 0.8 part of processing aid. The preparation method comprises the following steps: preparing the PTFE and part of the PA46 resin into master batches, and carrying out melt blending granulation on the master batches, the residual resin, the nucleating agent, the processing aid and the carbon fibers. The invention further provides an automobile transmission shaft anti-attrition gasket made of the material. The composite material has ultrahigh strength, rigidity, extremely low friction coefficient and excellent creep resistance, the hub nut tightening torque attenuation rate is smaller than 20% after the prepared gasket is under the surface pressure exceeding 100 MPa and 500,000 times of load cycles, and the problems of torque attenuation and abnormal sound of a traditional gasket are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of engineering plastics, in particular to a nylon composite material with super strength, high wear resistance and creep resistance, and a preparation method and application thereof. BACKGROUND

[0002] As the core component of vehicle power transmission, the reliability and durability of the automobile transmission shaft directly determine the performance and safety of the whole vehicle. In the transmission shaft system, although the wear-reducing gasket is a small component, it bears the key functions of reducing friction loss, transmitting pretightening force, preventing connection loosening and abnormal sound, and its performance has a crucial influence on the long-term stable operation of the transmission system.

[0003] At present, the wear-reducing gaskets widely used in this field are mostly traditional metal gaskets (such as steel gaskets supplemented with surface coatings). Such gaskets can still meet the use requirements under normal working conditions, but when facing extreme working conditions such as high surface pressure exceeding 100 MPa, long-term alternating load and harsh environmental temperature, their inherent defects are exposed. Specifically, the surface coating will quickly fail due to extremely high specific pressure and fretting wear, leading to a sharp increase in the friction coefficient, aggravating wear and possibly producing abnormal sound; more seriously, the metal matrix is prone to fatigue cracking under high stress, which will directly cause the pretightening force (i.e. tightening torque) of the hub nut to decay, which may cause abnormal sound of the transmission system, or even lead to loosening of the transmission shaft connection, bringing serious safety hazards.

[0004] With the rapid development of the automobile industry towards lightweight, long service life, high reliability and high quietness, the market has put forward more stringent requirements for key components. Polymer-based composite materials are considered as an ideal solution to replace traditional metal gaskets due to their lightweight, corrosion resistance, strong designability and excellent potential for friction reduction and noise reduction. Among them, polyamide (PA) material, especially PA46, has become the preferred matrix material for developing a new generation of high-performance wear-reducing gaskets due to its excellent mechanical strength, heat resistance and processing performance.

[0005] However, pure PA or unmodified PA material still has obvious deficiencies when dealing with the above extreme working conditions: firstly, its friction coefficient is not stable enough, and its wear resistance needs to be further improved; secondly, and more importantly, it has poor creep resistance. Under the long-term high pretightening force of the hub nut, the PA gasket will undergo continuous plastic deformation (creep), resulting in a decrease in pretightening force and inability to ensure the long-term stability of the torque, which greatly limits its application in key connection parts.

[0006] Therefore, there is an urgent need in the art for a brand new composite material solution that must be able to comprehensively solve the technical contradiction of high strength, high wear resistance and high creep resistance, so as to manufacture high-performance and long-life polymer wear-reducing gaskets that can meet the extreme working condition requirements of modern automobile transmission shafts. SUMMARY

[0007] In view of the problems existing in the prior art, the present application provides a nylon composite material with ultrahigh strength, high wear resistance and excellent creep resistance, which can be used for preparing automobile transmission shaft wear-reducing gaskets.

[0008] To achieve this object, the present application adopts the following technical solutions:

[0009] The first aspect of the present application provides an ultrahigh-strength, high-wear-resistant and creep-resistant nylon composite material, which comprises the following components in parts by weight:

[0010] PA46 resin 80~100 parts;

[0011] Carbon fiber 15~20 parts;

[0012] Polytetrafluoroethylene 8~10 parts;

[0013] Nucleating agent 0.1~0.3 parts;

[0014] Processing aid 0.2~0.8 parts.

[0015] In some embodiments of the present application, the carbon fiber is a short-cut carbon fiber surface-modified by a silane coupling agent.

[0016] In some embodiments of the present application, the polytetrafluoroethylene is a suspension polymerized PTFE powder.

[0017] In some embodiments of the present application, the particle size of the polytetrafluoroethylene is 5~10 μm.

[0018] In some embodiments of the present application, the nucleating agent is selected from one or more of silica, talc or montmorillonite.

[0019] In some embodiments of the present application, the processing aid comprises an antioxidant heat-resistant agent and a processing lubricant.

[0020] The second aspect of the present application provides a preparation method of the above-mentioned ultrahigh-strength, high-wear-resistant and creep-resistant nylon composite material, comprising the following steps:

[0021] 1) polytetrafluoroethylene and part of PA46 resin are added to a twin-screw extruder, melt blended, extruded and granulated to obtain PA46 / PTFE masterbatch;

[0022] 2) mixing PA46 / PTFE masterbatch, the rest of PA46 resin, nucleating agent and processing aid evenly, then adding carbon fiber into the twin-screw extruder, melt blending, extruding and granulating, thus obtaining the super-strong, high-wear-resistant and creep-resistant nylon composite material.

[0023] In some embodiments of the present application, the PA46 resin used in step 1) and step 2) needs to be dried before use.

[0024] In some embodiments of the present application, in step 1), the mass ratio of PA46 resin to polytetrafluoroethylene is 65-75:35-25.

[0025] In some embodiments of the present application, in step 2), the PA46 / PTFE masterbatch, the rest of PA46 resin, nucleating agent and processing aid are added from the main feeding port of the twin-screw extruder.

[0026] In some embodiments of the present application, in step 2), the carbon fiber is added from the side feeding port of the twin-screw extruder.

[0027] In some embodiments of the present application, the melt blending in step 1) and step 2) is carried out in a twin-screw extruder with a screw length-diameter ratio L / D≥40:1 and a processing temperature range of 280-305℃.

[0028] In some embodiments of the present application, the mixing in step 2) is carried out by using a high-speed mixer at 500-800 rpm for 120-180 s.

[0029] In some embodiments of the present application, a vacuum degree of-0.07 MPa or more is maintained during the melt blending process of step 2) to remove volatile substances.

[0030] The third aspect of the present application provides a wear-reducing gasket for automobile transmission shaft, which is made of the super-strong, high-wear-resistant and creep-resistant nylon composite material.

[0031] The wear-reducing gasket is prepared by injection molding, and under the working condition of surface pressure exceeding 100 MPa, the hub nut tightening torque attenuation rate of the connecting part thereof is less than 20% after 500,000 load cycles.

[0032] The fourth aspect of the present application provides a preparation method of the wear-reducing gasket for automobile transmission shaft, which comprises the following steps:

[0033] S1, precision injection molding: the nylon composite material granules are put into an injection molding machine, and injection molding is carried out under the condition that the mold temperature is 130-150℃, thus obtaining a gasket blank;

[0034] S2, annealing treatment: the gasket blank is placed in an environment of 150-160 DEG C for 30-60 minutes, and then slowly cooled to room temperature, to obtain.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] 1. The nylon composite material provided by the present application, through the multi-scale synergistic effect of carbon fiber and PTFE, the carbon fiber acts as a reinforcing framework, greatly improving the bending strength, modulus and creep resistance of PA46 nylon material; PTFE as a solid lubricant forms a transfer film on the friction interface, giving the material extremely low and stable friction coefficient (as low as 0.065-0.067) and excellent wear resistance; the material system maintains a tensile strength retention rate of more than 91% after heat aging at 160 DEG C for 16 days, and the hardness does not change, showing excellent long-term thermal stability, enough to cope with the high temperature environment generated by the transmission system during operation.

[0037] 2. The present application effectively solves the industry problems of uneven dispersion of PTFE and easy breaking of carbon fiber through the optimized two-step mixing process (first prepare PTFE master batch) and side feeding technology, ensuring uniform distribution of fillers and fiber aspect ratio, finally making the high-filled composite material still have good fluidity and injection molding processability.

[0038] 3. The nylon composite material provided by the present application, the high content of carbon fiber enhances the ability of the matrix to resist plastic deformation, combined with high mold temperature injection and annealing process to optimize the material crystalline structure and internal stress, so that the gasket made of it has very small creep under long-term high pressure. Bench test shows that after 500,000 load cycles, the tightening torque attenuation rate of the hub nut can be less than 20%, even without decay in normal and low temperature environments. DETAILED DESCRIPTION

[0039] The super-strong, high-wear-resistant and creep-resistant nylon composite material and its preparation method and application are described in detail below.

[0040] The inventors of the present application, in solving the high wear resistance, creep resistance and long service life requirements of automobile transmission shaft gaskets under extreme working conditions, abandoned the conventional approach of simply increasing the content of the base resin or the amount of a single reinforcing component, and adopted a multi-scale synergistic reinforcement and internal lubrication composite material design strategy. By introducing short carbon fibers as reinforcing framework and polytetrafluoroethylene (PTFE) as solid lubricant into high temperature nylon PA46 resin, and supplemented by nucleating agent to optimize crystallization, compared with single use of high proportion of reinforcing fibers or lubricants, the material is endowed with extremely low and stable friction coefficient and excellent creep resistance while achieving super mechanical properties. This composite system combines two-step mixing and high mold temperature injection-molding annealing process, so that the PA46 composite material reduces the excessive dependence on a single component while achieving better molding processability, dimensional stability and SMT temperature resistance, thereby successfully preparing high-performance wear-reducing gaskets that meet the stringent requirements of automobile transmission systems. On this basis, the present application is completed.

[0041] The first aspect of the present application provides a super-strong, high wear-resistant and creep-resistant nylon composite material, comprising the following components in parts by weight:

[0042] PA46 resin 80~100 parts;

[0043] Carbon fiber 15~20 parts;

[0044] Polytetrafluoroethylene 8~10 parts;

[0045] Nucleating agent 0.1~0.3 parts;

[0046] Processing aid 0.2~0.8 parts.

[0047] The PA46 resin as the base, with a weight fraction of 80~100 parts, provides excellent heat resistance, mechanical strength and processing formability. The data of the examples show that the use of PA46 resin in this preferred range is the basis for obtaining a nylon composite material with high bending strength and high bending modulus.

[0048] The carbon fiber acts as a reinforcing framework, effectively bearing the load by its high modulus, and is the core of the material to obtain super-stiffness and anti-creep performance. The polytetrafluoroethylene (PTFE) acts as a solid lubricant, and can form a stable transfer film on the friction surface through fibrillation during the friction process, thereby giving the composite material an extremely low friction coefficient and excellent self-lubricating wear resistance. It is found that there is a multi-scale synergistic effect between carbon fiber and PTFE: the carbon fiber macroscopically reinforces the matrix, inhibiting the excessive extrusion and destruction of the PTFE layer; and the lubricating effect of PTFE reduces the friction heat and abrasion of carbon fiber, and the two achieve a perfect combination of high strength and low friction. According to the data in Table 1, when the content of carbon fiber is 18-20 parts and the content of PTFE is 9-10 parts, the synergistic effect is best, and the composite material can maintain high bending strength (>130 MPa) while the friction coefficient can be stabilized at an extremely low level of 0.065-0.067.

[0049] In some embodiments of the present application, the carbon fiber is a short carbon fiber surface-modified by a silane coupling agent. Preferably, the silane coupling agent is KH-550. Preferably, the surface modification comprises the following steps: dipping the short carbon fiber in an ethanol solution of silane coupling agent for 20-40 minutes, and then drying at 120°C for 2 hours. Specifically, the concentration of silane coupling agent in the ethanol solution of silane coupling agent is 1wt%-3wt%. In some embodiments of the present application, the length of the short carbon fiber is 150-300μm, which can be 150-200μm, 200-250μm, 250-300μm, and the diameter is 6-8μm, which can be 6-6.5μm, 6.5-7μm, 7-7.5μm, 7.5-8μm. The short carbon fiber of this specification has the strongest interfacial bonding force with the PA46 matrix after pretreatment, which can effectively transfer stress and maintain sufficient aspect ratio during processing to maximize the reinforcing effect, while avoiding the decrease in reinforcing efficiency caused by too short length or the uneven dispersion and processing difficulty caused by too long length.

[0050] In some embodiments of the present application, the polytetrafluoroethylene is a suspension polymerization PTFE powder, which has a fibrillation tendency and can form a stable transfer film during the friction process. In some embodiments of the present application, the particle size of the polytetrafluoroethylene is 5-10μm, which can be 5-6μm, 6-7μm, 7-8μm, 8-9μm, 9-10μm.

[0051] In some embodiments of the present application, the nucleating agent is selected from one or more of silica, talcum powder or montmorillonite, preferably silica, which can effectively promote heterogeneous nucleation of PA46 resin during cooling process, forming a more fine and uniform crystal structure. This not only increases the crystallinity of the material, thereby improving the heat distortion temperature and short-term heat resistance, but more importantly significantly improves the dimensional stability of the product, reducing the warping deformation caused by uneven crystallization shrinkage, which is crucial for the preparation of high-precision gasket components.

[0052] In some embodiments of the present application, the processing aid includes an antioxidant heat-resistant agent and a processing lubricant. The weight fraction of the antioxidant heat-resistant agent is 0.1-0.5 parts, and the weight fraction of the processing lubricant is 0.1-0.3 parts. Preferably, the antioxidant heat-resistant agent is selected from phenolic antioxidants and / or phosphite antioxidants, and copper salt stabilizers. Further preferably, the phenolic antioxidant is selected from tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester or β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid n-octadecanol ester; and the copper salt stabilizer is a complex of cuprous iodide and potassium iodide. This system can synergistically inhibit the thermal oxidation of PA46 during high-temperature processing and use. As shown in Table 2, after 160°C heat aging for 16 days, the tensile strength retention rate is still over 91%, and the hardness remains unchanged, proving that this antioxidant heat-resistant system has excellent long-term stability.

[0053] In some embodiments of the present application, the processing lubricant is selected from one or more of stearic acid lubricants, siloxane-based lubricants, and amide-based lubricants. Preferably, the stearic acid lubricant is calcium stearate.

[0054] The second aspect of the present application provides a preparation method of the above-mentioned super-strong, high-wear-resistant and creep-resistant nylon composite material, comprising the following steps:

[0055] 1) Polytetrafluoroethylene and part of PA46 resin are added to a twin-screw extruder, melt blended, extruded and granulated to obtain PA46 / PTFE masterbatch;

[0056] 2) The PA46 / PTFE masterbatch, the remaining PA46 resin, the nucleating agent, the antioxidant heat-resistant agent and the processing lubricant are uniformly mixed, and then added to a twin-screw extruder together with carbon fibers, melt blended, extruded and granulated to obtain the super-strong, high-wear-resistant and creep-resistant nylon composite material.

[0057] In some embodiments of the present application, the PA46 resin used in step 1) and step 2) needs to be dried before use. The drying process includes the following steps: placing the PA46 resin in a dehumidifying dryer and drying at 105-115°C for 4-6 hours to reduce the water content to below 0.05%, which is a key step to prevent hydrolytic degradation and performance deterioration caused by molecular weight reduction during high-temperature processing.

[0058] Step 1) first melt blending to prepare PA46 / PTFE masterbatch aims to solve the problem of uneven mixing of PTFE and PA46 due to differences in density and polarity. In some embodiments of the present application, in step 1), the mass ratio of the PA46 resin to polytetrafluoroethylene is 65-75:35-25, preferably 70:30.

[0059] In some embodiments of the present application, in step 2), the PA46 / PTFE masterbatch, the remaining PA46 resin, the nucleating agent and the processing aid are added from the main feeding port of the twin-screw extruder; and the carbon fibers are added from the side feeding port of the twin-screw extruder. This feeding method can effectively prevent excessive breakage of carbon fibers and maintain the aspect ratio, maximizing the reinforcing effect. The high flexural modulus (all higher than 5600 MPa) of Examples 1-3 proves the effective maintenance of fiber length by this method.

[0060] In some embodiments of the present application, the melt blending in step 1) and step 2) is carried out in a twin-screw extruder with a screw length-diameter ratio L / D≥40:1 and a processing temperature range of 280-305°C.

[0061] Preferably, in step 1), the processing temperature of the twin-screw extruder is set as follows: from the feeding port to the die head, the temperature gradient is set as follows: feeding section 280°C → compression section 285, 290°C → homogenization section 295°C → die head 290°C; the screw rotation speed is 250-300 rpm to provide high shear for dispersing PTFE. Preferably, the vacuum degree during the melt blending process of step 1) is -0.06 ~-0.08 MPa to completely remove volatile matter and water vapor.

[0062] Preferably, in step 2), the processing temperature of the twin-screw extruder is set as follows: feeding section 285°C → compression section 290, 295°C → melting section 300°C → die head 295°C. The temperature is slightly higher than the first stage, aiming to ensure the fluidity of the high-viscosity melt. The screw rotation speed is 300-350 rpm. Preferably, a vacuum degree of -0.07 MPa or higher is maintained during the melt blending process of step 2) to remove volatile matter.

[0063] In some embodiments of the present application, the mixing in step 2) is mixing at 500-800 rpm for 120-180 s, preferably mixing at 600-700 rpm for 140-160 s, using a high-speed mixer.

[0064] The third aspect of the present application provides a wear-reducing gasket for automobile drive shafts, which is made of the super-strong, high-wear-resistant and creep-resistant nylon composite material.

[0065] The wear-reducing gasket is made by injection molding, and under the working condition of a surface pressure exceeding 100 MPa, the torque attenuation rate of the hub nut tightening at the connecting part of the gasket is less than 20% after 500,000 load cycles, thus fundamentally solving the safety hazard of torque attenuation of traditional metal gaskets.

[0066] The fourth aspect of the present application provides a preparation method of the wear-reducing gasket for automobile drive shafts, comprising the following steps:

[0067] S1, precision injection molding: the nylon composite material pellets are put into an injection molding machine, and injection molding is performed under the condition that the mold temperature is 130-150 DEG C, to obtain a gasket blank;

[0068] S2, annealing treatment: the gasket blank is placed in an environment at 150-160 DEG C for 30-60 minutes, and then slowly cooled to room temperature.

[0069] The precision injection molding step is the key to obtaining a drive shaft gasket product with stable size and low internal stress. During injection molding, the mold temperature is strictly controlled at 130-150 DEG C. This high mold temperature condition provides sufficient movement ability for the PA46 molecular chain, so that it can be regularly arranged to form a more perfect and stable crystal structure, which not only directly improves the crystallinity, rigidity and heat distortion temperature of the product, but also significantly reduces the internal stress and molding warping, and improves the dimensional stability. Subsequently, the obtained gasket blank is subjected to annealing treatment at 150-160 DEG C for 30-60 minutes. This annealing process can further eliminate the frozen internal stress in the injection molding process, and on the other hand, can promote the crystal structure to be perfect and stable, further improving the dimensional stability and creep resistance.

[0070] The injection molding machine is selected to be a full-electric or electric-hydraulic injection molding machine. The clamping force is selected according to the size of the product and the number of cavities. The injection molding machine is equipped with a dehumidifying and drying hopper to prevent the nylon composite material pellets from reabsorbing moisture before processing.

[0071] Preferably, the temperature of the barrel adopts a distribution of high in the rear and low in the front: 285-290℃ in the rear section (to prevent the "bridge" phenomenon of the material at the feeding port and ensure smooth feeding), 295-300℃ in the middle section (to ensure that the material is sufficiently melted and mixed, i.e. fully plasticized), and 300-305℃ in the front section (to homogenize the melt and ensure the uniformity of its composition and temperature).

[0072] Preferably, the temperature of the nozzle is 300℃.

[0073] Preferably, a medium-high speed injection is adopted during injection, with a speed of 50-150 mm / s, preferably 80-120 mm / s, which helps to avoid the temperature of the melt front from dropping too fast, thereby ensuring the smoothness of the surface quality of the product, while preventing uneven fiber orientation caused by too slow flow rate.

[0074] Preferably, multi-stage packing is adopted, with the first stage packing pressure being 80%-90% of the maximum injection pressure, to compensate for the space in the mold cavity due to the shrinkage of the melt caused by cooling, and the subsequent packing pressure gradually decreasing to continue to compensate for the shrinkage while avoiding excessive internal stress.

[0075] Preferably, the total packing time is 15-30 seconds, which can be 15-20 seconds, 20-25 seconds, or 25-30 seconds. The total packing time is determined according to the wall thickness of the product, and is usually 15-30 seconds to compensate for shrinkage, with the gate freezing as the end criterion.

[0076] Preferably, the back pressure is set to 0.5-1.0 MPa, which can be 0.5-0.8 MPa or 0.8-1.0 MPa. During plasticization, the melt is compacted by back pressure, which helps to remove gas in the melt and reduce internal bubbles of the product.

[0077] Preferably, the cooling method of the annealing treatment is slow cooling to room temperature with the furnace, which can prevent new stress from being generated due to too fast cooling.

[0078] The specific embodiments of the present application are further described in detail below with reference to the preferred embodiments. When numerical ranges are given in the embodiments, it should be understood that, unless otherwise specified by the present application, each numerical range has two endpoints and any number between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art. In addition to the specific methods, devices, materials used in the embodiments, any method, device and material of the prior art similar or equivalent to those described in the embodiments of the present application can also be used to implement the present application, as long as they are within the scope of the present application.

[0079] The raw materials and related parameters used in the following examples and comparative examples are as follows:

[0080] PA46 resin: weight average molecular weight about 40,000, melt index (295℃ / 1.05kg) 200~300 g / 10min, relative viscosity 2.8~3.2.

[0081] Carbon fiber: length 150~300μm, diameter 6~8μm, short-cut carbon fiber.

[0082] Glass fiber: length 150~300μm, diameter 6~8μm, glass fiber; pretreatment method is to immerse in 2wt% KH-550 silane coupling agent ethanol solution for 30 minutes, and then dry at 120℃ for 2 hours, ready for use.

[0083] Polytetrafluoroethylene (PTFE): suspension polymerization powder, particle size 5~10μm.

[0084] Nucleating agent: nano-silicon dioxide.

[0085] Antioxidant heat-resistant agent: mixture of antioxidant 1010 and cuprous iodide / potassium iodide complex (mass ratio 1:1).

[0086] Processing lubricant: calcium stearate.

[0087] Example 1

[0088] A super-strong, high-wear-resistant, anti-creep nylon composite material, comprising the following components by weight fraction: PA46 resin 100 parts; carbon fiber 15 parts; PTFE 8 parts; nucleating agent 0.2 parts, antioxidant heat-resistant agent 0.3 parts, processing lubricant 0.2 parts.

[0089] The preparation method of the above-mentioned super-strong, high-wear-resistant, anti-creep nylon composite material, comprising the following steps:

[0090] (1) Raw material pretreatment: PA46 resin is vacuum dried at 110℃ for 5 hours to make the water content <0.05%. Short-cut carbon fiber is immersed in 2wt% KH-550 coupling agent ethanol solution for 30 minutes, and then dried at 120℃ for 2 hours to obtain carbon fiber.

[0091] (2) Masterbatch preparation: 18.67 parts of PA46 resin and 8 parts of PTFE powder (weight fraction ratio 70:30) are melt blended in a twin-screw extruder, process parameters: temperature gradient feeding section 280℃ → compression section 285, 290℃ → homogenization section 295℃ → die 290℃, screw speed 250~300 rpm, vacuum degree -0.06~-0.08 MPa, granulation to obtain PA46 / PTFE masterbatch.

[0092] (3) Final composite granulation: the remaining PA46 resin, PA46 / PTFE masterbatch, nucleating agent, antioxidant heat-resistant agent, and processing lubricant are premixed by a high-speed mixer (600 rpm, 150 s) according to the above weight ratio, and then added into a twin-screw extruder from the main feeding port. The pretreated carbon fiber is added from the side feeding port. The process parameters are: feeding section 285°C → compression section 290, 295°C → melting section 300°C → die head 295°C, screw speed 300-350 rpm, vacuum degree maintained above -0.07 MPa. After melting and blending, the material is extruded, cooled, and granulated to obtain a nylon composite material.

[0093] The prepared composite nylon material pellets are molded into standard test bars and automobile transmission shaft wear pads on a precision injection molding machine.

[0094] The injection molding process parameters are: barrel temperature rear / middle / front section: 285-290°C / 295-300°C / 300-305°C; mold temperature: 140°C; injection speed: 100 mm / s; three-stage pressure holding is adopted, the first stage pressure holding pressure is 85% of the maximum injection pressure, and the pressure holding time is 5 seconds; the second stage pressure is reduced to 70% of the first stage, and the pressure holding time is 10 seconds; the third stage pressure is reduced to 50% of the first stage, and the pressure holding time is 10 seconds. The total pressure holding time is 25 seconds; back pressure: 0.8 MPa.

[0095] Annealing treatment parameters: the injection molded pad blank is placed in a 155°C air oven for 45 minutes, and then cooled to room temperature with the oven.

[0096] Example 2

[0097] A super-strong, high-wear-resistant, and creep-resistant nylon composite material, comprising the following components in weight parts: PA46 resin 80 parts; carbon fiber 15 parts; PTFE 8 parts; nucleating agent 0.1 part, antioxidant heat-resistant agent 0.1 part, and processing lubricant 0.1 part.

[0098] The preparation method of the above super-strong, high-wear-resistant, and creep-resistant nylon composite material, and the preparation process of the standard test bar and the automobile transmission shaft wear pad are the same as those of Example 1.

[0099] Example 3

[0100] A super-strong, high-wear-resistant, and creep-resistant nylon composite material, comprising the following components in weight parts: PA46 resin 100 parts; carbon fiber 20 parts; PTFE 10 parts; nucleating agent 0.3 parts, antioxidant heat-resistant agent 0.5 parts, and processing lubricant 0.3 parts.

[0101] The preparation method of the above super-strong, high-wear-resistant, and creep-resistant nylon composite material, and the preparation process of the standard test bar and the automobile transmission shaft wear pad are the same as those of Example 1.

[0102] Example 4

[0103] A super-strong, high-wear-resistant, creep-resistant nylon composite material, comprising the following components in parts by weight: PA46 resin 100 parts; carbon fiber 20 parts; PTFE 10 parts; nucleating agent 0.3 parts, antioxidant heat-resistant agent 0.5 parts, processing lubricant 0.3 parts, wherein the antioxidant heat-resistant agent is a mixture of antioxidant 168 and cuprous iodide / potassium iodide complex (in a mass ratio of 1:1), and the processing lubricant is ethylene bis-stearamide (EBS).

[0104] The preparation method of the above-mentioned super-strong, high-wear-resistant, creep-resistant nylon composite material, standard test sample and automobile transmission shaft wear-resistant gasket preparation process are the same as those of Example 1.

[0105] Comparative Example 1

[0106] A nylon composite material, comprising the following components in parts by weight: PA46 resin 60 parts; carbon fiber 15 parts; PTFE 8 parts; nucleating agent 0.1 parts, antioxidant heat-resistant agent 0.1 parts, processing lubricant 0.1 parts.

[0107] The preparation method of the above-mentioned nylon composite material, standard test sample and automobile transmission shaft wear-resistant gasket preparation process are the same as those of Example 1.

[0108] Comparative Example 2

[0109] A nylon composite material, comprising the following components in parts by weight: PA46 resin 120 parts; carbon fiber 15 parts; PTFE 8 parts; nucleating agent 0.1 parts, antioxidant heat-resistant agent 0.1 parts, processing lubricant 0.1 parts.

[0110] The preparation method of the above-mentioned nylon composite material, standard test sample and automobile transmission shaft wear-resistant gasket preparation process are the same as those of Example 1.

[0111] Comparative Example 3

[0112] Except that PTFE is not added, the rest is the same as Example 2.

[0113] Comparative Example 4

[0114] Except that carbon fiber is not added, the rest is the same as Example 2.

[0115] Comparative Example 5

[0116] Except that the same weight fraction of glass fiber is used instead of carbon fiber, the rest is the same as Example 2.

[0117] The preparation method of the above-mentioned nylon composite material, standard test sample and automobile transmission shaft wear-resistant gasket preparation process are the same as those of Example 1.

[0118] The component distribution ratio of each of the above examples and comparative examples is shown in Table 1 below.

[0119] Table 1 Component distribution ratio of each of the examples and comparative examples

[0120]

[0121] The composite nylon material pellets prepared in the above Examples 1-4 and Comparative Examples 1-5 were molded into standard test bars and automobile drive shaft wear pads on a precision injection molding machine. The injection molding process parameters were: barrel temperature rear / middle / front section: 288℃ / 298℃ / 303℃; mold temperature: 140℃; injection speed: 100 mm / s; three-stage pressure maintaining was used; annealing treatment parameters: the molded pad blank was placed in a 155℃ air oven for 45 minutes, and then cooled to room temperature with the oven.

[0122] Performance test method:

[0123] Bending strength and bending modulus: tested according to ISO 178 standard.

[0124] Friction coefficient: tested on a ring block friction and wear testing machine according to ASTM G99 standard.

[0125] Bench friction life test: simulate the actual working condition of automobile drive shaft connection, and perform cyclic loading test at 23℃, 150℃ and -70℃ respectively under the condition of surface pressure of 120 MPa, and record the intact state of the pad and the attenuation rate of the hub nut tightening torque after 500,000 times of load cycle.

[0126] Bending strength, bending modulus, friction coefficient and bench friction life test were tested in triplicate, and the average value was taken, and the test results are shown in Table 2.

[0127] Table 2 Test results of bending strength, bending modulus, friction coefficient and bench friction life test

[0128]

[0129] From the detection data corresponding to the samples obtained from the above examples and comparative examples, it can be seen that the examples 1-4 of the present application all exhibit excellent comprehensive performance, the bending strength is higher than 132 MPa, the bending modulus is higher than 5400 MPa, and the friction coefficient is not higher than 0.067. The bench test results show that after 500,000 times of load cycle at 150℃ high temperature, the torque decay rate is only 15%, which fully proves that the composite material system of the present application has excellent and stable anti-creep and torque retention ability at high temperature and high pressure. This shows that within the range of the required formula of the present application, the ideal effect satisfying the harsh use requirements can be obtained.

[0130] Comparative Example 1 (PA46 resin too little) due to insufficient matrix strength and poor interfacial bonding, leading to a sharp deterioration of mechanical properties and friction properties, and cracking failure in advance in the bench test at room temperature. Comparative Example 2 (PA46 resin too much) due to insufficient relative content of carbon fibers and lubricating components, its stiffness and creep resistance are significantly decreased, especially the torque decay rate exceeds 35% at 150°C high temperature.

[0131] Comparative Example 3 (without PTFE) the friction coefficient is relatively high, indicating the key role of PTFE in providing friction-reducing lubrication, reducing friction heat and ensuring torque stability. Comparative Example 4 (without carbon fiber) although the initial flexural modulus is acceptable, but due to lack of fiber reinforced skeleton, the creep resistance is very poor, and serious creep occurs at room temperature under high load, which leads to premature failure and cannot maintain the necessary pre-tightening force.

[0132] After using glass fiber instead of carbon fiber in Comparative Example 5, the flexural modulus and creep resistance at various temperatures of the material are significantly decreased, which proves that carbon fiber plays an important role in achieving super strength and creep resistance.

[0133] The standard test bars prepared in Example 1 were subjected to heat aging performance test, and the samples were placed in a 160°C air oven, and the tensile strength (ISO 527) and hardness (Shore D) were tested at predetermined intervals. The test results are shown in Table 3 below.

[0134] Table 3 Heat aging performance test results of standard test bars prepared in Example 1

[0135]

[0136] The nylon composite prepared in Example 1 exhibits excellent long-term thermal stability at 160°C. After 384 hours (16 days) of long-term heat aging, the mechanical properties (tensile strength) decay rate is very low (<10%), and the hardness does not change at all, which fully meets the stringent requirements of the automotive transmission system on the long-term reliability of the material in high temperature environment.

[0137] The above examples are only illustrative of the principles and effects of the present application, and are not intended to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

1. A high-strength, highly wear-resistant, and creep-resistant nylon composite material, characterized in that, Includes the following components by weight: 80-100 parts of PA46 resin; 15-20 parts carbon fiber; 8-10 parts of polytetrafluoroethylene; Nucleating agent 0.1~0.3 parts; Processing aids: 0.2-0.8 parts.

2. The ultra-strong, highly wear-resistant, and creep-resistant nylon composite material as described in claim 1, characterized in that, Includes one or more of the following characteristics: (1) The carbon fiber is a short-cut carbon fiber that has been surface-modified with a silane coupling agent; (2) The polytetrafluoroethylene is a suspension polymerized PTFE powder; (3) The particle size of the polytetrafluoroethylene is 5~10μm; (4) The nucleating agent is selected from one or more of silica, talc or montmorillonite; (5) The processing aids include antioxidants and heat-resistant agents and processing lubricants.

3. The ultra-strong, highly wear-resistant, and creep-resistant nylon composite material as described in claim 2, characterized in that, Includes one or more of the following characteristics: (1a) The silane coupling agent is KH-550; (1b) The length of the short-cut carbon fiber is 150~300μm and the diameter is 6~8μm; (4a) The nucleating agent is silicon dioxide; (5a) The antioxidant and heat-resistant agent is selected from phenolic antioxidants and / or phosphite antioxidants, as well as copper salt stabilizers; (5b) The processing lubricant is selected from one or more of stearic acid lubricants, siloxane lubricants, and amide lubricants.

4. The ultra-strong, highly wear-resistant, and creep-resistant nylon composite material as described in claim 3, characterized in that, Includes one or more of the following characteristics: (5a1) The phenolic antioxidant is selected from pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] or octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; (5a2) The copper salt stabilizer is a complex of cuprous iodide and potassium iodide; (5b1) The stearic acid lubricant is calcium stearate.

5. A method for preparing a high-strength, high-wear-resistant, and creep-resistant nylon composite material as described in any one of claims 1 to 4, characterized in that, Includes the following steps: 1) Add polytetrafluoroethylene and part of PA46 resin to a twin-screw extruder, melt blend, extrude and granulate to obtain PA46 / PTFE masterbatch; 2) Mix PA46 / PTFE masterbatch, the remaining PA46 resin, nucleating agent and processing aid evenly, and then add it together with carbon fiber into a twin-screw extruder for melt blending, extrusion granulation, and thus obtain a super-strong, highly wear-resistant and creep-resistant nylon composite material.

6. The method for preparing the ultra-strong, high-wear-resistant, and creep-resistant nylon composite material as described in claim 5, characterized in that, Includes one or more of the following technical features: (a) The PA46 resin used in steps 1) and 2) needs to be dried before use; (b) In step 1), the mass ratio of the added PA46 resin to polytetrafluoroethylene is 65~75:35~25; (c) The PA46 / PTFE masterbatch, the remaining PA46 resin, the nucleating agent and the processing aids described in step 2) are added from the main feed port of the twin-screw extruder; (d) The carbon fiber described in step 2) is fed from the side feed port of the twin-screw extruder; (e) The melt blending described in steps 1) and 2) is carried out in a twin-screw extruder with a screw length-to-diameter ratio L / D ≥ 40:1 and a processing temperature range of 280~305℃; (f) The mixing in step 2) is performed using a high-speed mixer at 500-800 rpm for 120-180 s; (g) During the melt blending process in step 2), maintain a vacuum of -0.07 MPa or higher to remove volatiles.

7. A friction-reducing shim for automotive drive shafts, characterized in that, Made from the ultra-strong, highly wear-resistant, and creep-resistant nylon composite material as described in any one of claims 1 to 4.

8. The anti-friction shim for automotive drive shafts as described in claim 7, characterized in that, The friction-reducing gasket is manufactured by injection molding, and under working conditions with a surface pressure exceeding 100MPa, after 500,000 load cycles, the torque attenuation rate of the wheel hub nut at the connection part where it is located is less than 20%.

9. A method for preparing a friction-reducing shim for an automotive driveshaft as described in claim 7 or 8, characterized in that, Includes the following steps: S1. Precision injection molding: The nylon composite material granules are put into an injection molding machine and injection molded at a mold temperature of 130~150℃ to obtain a gasket blank. S2. Annealing treatment: The gasket blank is placed in an environment of 150~160℃ for 30~60 minutes and then slowly cooled to room temperature to obtain the gasket.

10. The preparation method according to claim 9, characterized in that, The precision injection molding step also includes one or more of the following technical features: (a) The barrel temperature of the injection molding machine adopts a distribution of high temperature at the front and low temperature at the back: 285-290℃ in the back section, 295-300℃ in the middle section, and 300-305℃ in the front section; (b) The injection speed is 50~150 mm / s; (c) Multi-stage pressure holding is adopted, with the first stage pressure holding pressure being 80%-90% of the maximum injection pressure; (d) The total holding time is 15-30 seconds; (e) Back pressure is set to 0.5-1.0 MPa.

Images