A polyamide material and preparation method thereof

Abstract

A wear-resistant and antistatic polyamide material comprises the following components: 100 parts of polyamide; 10-50 parts of surface-treated stainless steel fibers; 0-5 parts of lubricant; and 0-5 parts of antioxidant. The surface-treated stainless steel fibers are stainless steel fibers with micropores on their surfaces obtained by acid and electrochemical surface etching. The microporous structure formed by the surface etching of the stainless steel fibers enhances the bonding force between the resin and the fibers, thereby improving the mechanical strength and wear resistance of the material and exhibiting good antistatic properties.

Description

Technical Field

[0001] The invention relates to the field of polymers, and in particular to a wear-resistant and antistatic polyamide material. Background Art

[0002] Polyamide has good comprehensive properties, including excellent mechanical properties, heat resistance, chemical resistance and self-lubrication, and is therefore widely used in automobiles, electrical equipment, mechanical parts, rail transportation, textiles and other fields. However, when polyamide is used in parts such as gears and bearings, it has the problem of poor wear resistance. In the prior art, polyamide usually needs to be modified to improve wear resistance. CN201210040331.9 reports the addition of fillers such as aluminum nitride, aluminum oxide, and silicon nitride as heat-conducting and wear-resistant fillers. However, this technology results in a large filler loading in the polyamide, a high filler density, and a high density of the composite material. In addition, inorganic fillers such as aluminum nitride, aluminum oxide, and silicon nitride cause the impact strength of the composite material to be significantly reduced. CN201410387072.6 reports the addition of polysiloxane resin as a wear-resistant agent, which is beneficial to reducing the friction coefficient of polyamide, but the effect of reducing friction loss is not obvious. CN201611227099.4 reports improving the wear resistance of composite materials through the synergistic effect of modified hexagonal boron nitride microplates and silicon carbide capsules. However, this solution involves a complex preparation process, and the wear-resistant filler reduces the composite's impact strength. While the addition of POE improves the material's impact resistance, it also reduces the overall strength of the composite. Furthermore, due to the high volume resistivity of polyamide, it is prone to static electricity when rubbed against other insulating components, posing a fire or explosion hazard. These issues limit the wider application of polyamide.

[0003] To improve the wear resistance and antistatic properties of polyamide, stainless steel fiber is used as a reinforcing filler. It not only improves the stiffness, hardness, heat resistance, and wear resistance of polyamide, but also imparts special antistatic properties. However, stainless steel fiber has poor compatibility with polymers, resulting in low strength and modulus, and poor toughness, for polyamide filled with stainless steel fiber. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention adopts the following solutions:

[0005] In one aspect, the present invention provides a polyamide material comprising the following raw materials in parts by weight:

[0006] 100 parts of polyamide;

[0007] 8-50 parts of surface-treated stainless steel fibers;

[0008] 0-5 parts of lubricant;

[0009] 0-5 parts of antioxidant;

[0010] The surface-treated stainless steel fiber is a stainless steel fiber with micropores on the surface obtained by acid and electrochemical surface etching. Preferably, the amount of the surface-treated stainless steel fiber is 10-30 parts.

[0011] Furthermore, the polyamide material of the present invention further comprises 2-15 parts of vinylidene chloride-acrylate-glycidyl methacrylate terpolymer, preferably 3-8 parts.

[0012] The mass ratio of glycidyl methacrylate, methyl acrylate and vinylidene chloride in the terpolymer is 2-10:2-10:80-96.

[0013] The weight average molecular weight of the terpolymer is 70,000-80,000.

[0014] In the present invention, the polyamide is one or a mixture of the following polyamides: PA6, PA66, PA612, PA610, PA1010, PA1012, PA11, PA12, PA1212, PA6T, and PA6I.

[0015] In the present invention, the lubricant is selected from one or more of ethylene acrylic acid copolymer and stearate.

[0016] In the present invention, the antioxidant is selected from one or more of hindered phenols, phosphites, and phosphites.

[0017] In the present invention, the preparation method of the surface-treated stainless steel fiber comprises the following steps:

[0018] (1) Grind the stainless steel fiber with sandpaper, soak it in a solvent to remove impurities on the surface, wash it, and dry it for later use;

[0019] (2) etching the stainless steel fiber treated in step (1) in acid, and then cleaning and drying the treated stainless steel fiber for later use after etching;

[0020] (3) The stainless steel fiber treated in step (2) is used as an anode and the platinum electrode is used as a cathode, and they are immersed in an electrolyte and energized for electrochemical treatment. After the treatment, the stainless steel fiber is cleaned and dried.

[0021] Preferably, the stainless steel fiber in step (1) is made of 304 stainless steel or 312 stainless steel, preferably 304 stainless steel, has a diameter of 10-20 μm, preferably 10-15 μm, and a length of 3-10 mm, preferably 5-10 mm.

[0022] Preferably, the mesh size of the sandpaper in step (1) is 10-200 meshes, and the solvent is one of 25% by mass formic acid, 50% by mass ethanol, and 5% by mass sodium hydroxide, preferably 25% by mass formic acid and 5% by mass sodium hydroxide.

[0023] Preferably, the acid in step (2) is selected from one or more of hydrofluoric acid, acetic acid, and hydrochloric acid, preferably hydrofluoric acid and hydrochloric acid.

[0024] Preferably, the etching time in step (2) is 1-10 hours, preferably 3-8 hours.

[0025] Preferably, the electrolyte in step (3) is perchloric acid and ethylene glycol, and the mass ratio of perchloric acid to ethylene glycol is 5-20:80-95.

[0026] Preferably, the voltage applied in step (3) is 36-48V, and the etching time is 30s-180s.

[0027] Preferably, the cleaning liquid in the cleaning step in steps (1), (2) and (3) is water; the drying temperature is 50-180°C, preferably 100-150°C; and the drying time is 1-10h, preferably 1-5h.

[0028] In the present invention, the preparation method of the vinylidene chloride-acrylate-glycidyl methacrylate terpolymer comprises the following steps:

[0029] First, add a dispersant aqueous solution to a reactor, followed by monomers glycidyl methacrylate, methyl acrylate, vinylidene chloride, and an initiator. The reactor is closed, nitrogen is introduced to remove air, and the temperature is raised for polymerization. After polymerization is complete, the material is discharged, washed, and dried to obtain a vinylidene chloride-acrylate-glycidyl methacrylate terpolymer.

[0030] Preferably, the dispersant is selected from one or more of hydroxypropyl methylcellulose, hydroxyethyl cellulose, and polyvinyl alcohol;

[0031] The mass fraction of the dispersant in the dispersant aqueous solution is 0.1-10%.

[0032] Preferably, the initiator is selected from one or more of benzoyl peroxide, cumene hydroperoxide, and tert-butyl benzoyl peroxide;

[0033] Preferably, the mass ratio of glycidyl methacrylate, methyl acrylate and vinylidene chloride is 2-10:2-10:80-96, and the amount of the initiator is 0.5%-1% of the mass of the monomers.

[0034] Preferably, the reaction temperature of the polymerization reaction is 50-100° C., the reaction pressure is 1-3 MPa, and the reaction time is 6-10 h.

[0035] Preferably, the washing liquid in the washing step is one or both of water and ethanol, the drying temperature is 40-70° C., and the drying time is 12-48 hours.

[0036] On the other hand, the present invention also provides a method for preparing a polyamide material, the method comprising the following steps:

[0037] The weighed components except the surface-treated stainless steel fibers are mixed uniformly in an internal mixer, the mixed materials are placed in the main feeding hopper of a twin-screw extruder, the surface-treated stainless steel fibers are added from the side feeding hopper, melt-extruded, granulated, and dried.

[0038] Preferably, the mixing time is 10-40 min, the mixer speed is 100-500 rpm, and the mixing temperature is 40-100°C.

[0039] Preferably, the extrusion temperature is 240-260° C., the screw speed is 100-300 r / min, the drying temperature is 60-100° C., and the drying time is 12-24 h.

[0040] The present invention has the following beneficial effects compared to the prior art:

[0041] (1) The present invention forms a microporous structure by etching the surface of stainless steel fiber, thereby improving the bonding strength between the resin and the fiber. Since stainless steel fiber has excellent electrical conductivity, the stainless steel fiber filling material has good antistatic effect and a volume resistivity of 10 6 -10 12 Ω*cm.

[0042] (2) A vinylidene chloride-acrylate-glycidyl methacrylate terpolymer is further added, wherein the acrylate segment can form a complex with the iron ions on the surface of the stainless steel fiber, thereby having good adhesion to the stainless steel fiber, and the glycidyl methacrylate segment can react with the amino group in the polyamide, thereby improving the compatibility and bonding between the resin and the fiber, making the stainless steel fiber easier to disperse in the resin matrix, and improving the mechanical properties and electrical conductivity of the material. This polyamide material can be used for workshop equipment parts with explosion-proof requirements, such as track parts, gears, etc. DETAILED DESCRIPTION

[0043] The raw materials used in the embodiments and comparative examples are as follows:

[0044]

[0045] Performance testing is carried out in accordance with the following standards

[0046]

[0047]

[0048] Preparation Example 1 (vinylidene chloride-acrylate-glycidyl methacrylate VDC-MA-GMA-1):

[0049] To a 10L autoclave, first add 2L of a premixed 0.22% aqueous solution of hydroxypropyl methylcellulose. Then, add 97.0g of glycidyl methacrylate, 137.0g of methyl acrylate, 1445.0g of vinylidene chloride monomer, and 15.9g of benzoyl peroxide (initiator). Close the autoclave, purge with nitrogen, and adjust the pressure to 3MPa. Then, turn on the circulating water tank and raise the temperature to 95°C. Stirring is initiated at 400r / min for polymerization for 6h. After completion, cool the autoclave with circulating water until the temperature drops below 40°C. Stop stirring, let the autoclave stand for 10 minutes, and then vent, unload, and discharge the product. The collected product is washed five times with deionized water and ethanol, then centrifuged for dehydration and dried in a 60°C oven for 24h.

[0050] Preparation Example 2 (vinylidene chloride-acrylate-glycidyl methacrylate VDC-MA-GMA-2):

[0051] To a 10L autoclave, add 2L of a premixed 0.22% aqueous solution of hydroxyethyl cellulose. Then, add 30.2g of glycidyl methacrylate, 30.2g of methyl acrylate, 1445.0g of vinylidene chloride monomer, and 14.5g of cumene hydroperoxide. Close the autoclave, purge air with nitrogen, and adjust the pressure to 1MPa. Then, turn on the circulating water tank and raise the temperature to 55°C. Start stirring and polymerize at 400 rpm for 10 hours. After completion, cool the autoclave with circulating water until the temperature drops below 40°C. Stop stirring, let the autoclave stand for 10 minutes, and then vent, unload, and discharge the product. The collected product is washed five times with deionized water and ethanol, then centrifuged for dehydration. Then, dry in a 60°C oven for 24 hours before use.

[0052] Preparation Example 3 (surface-etched stainless steel fiber):

[0053] 1) A 304 stainless steel fiber with a diameter of 12 μm and a length of 6 mm was polished with 80-mesh dry sandpaper for 10 min and soaked in 25% formic acid for 2 h to remove oil stains and impurities on the fiber surface. The fiber was then washed with deionized water five times and dried in a vacuum oven at 100°C for 1 h.

[0054] 2) The stainless steel fiber was placed in a 45% hydrofluoric acid solution for preliminary etching for 5 h, then taken out and washed with deionized water 5 times, and dried in a vacuum oven at 100° C. for 1 h.

[0055] 3) The stainless steel fiber was electrochemically treated in a mixed electrolyte solution of 10% by mass perchloric acid and 90% by mass ethylene glycol. The platinum electrode was connected to the negative pole of the power supply to be protected, and the stainless steel fiber was connected to the positive pole of the power supply to be etched. The power supply voltage was 45 V and the etching time was 30 s.

[0056] Example 1

[0057] Preparation of composite materials: polyamide PA6, antioxidant 1010 and 168. Lubricant AC-540A is premixed in an internal mixer, and the premix is ​​melt-blended and extruded with surface-etched stainless steel fibers through a twin-screw extruder. The premix enters the extruder from the main feed port, and the stainless steel fibers enter the extruder from the side feed port. The extrusion temperature is 250°C and the screw speed is 200 r / min.

[0058] Example 2

[0059] Preparation of composite materials: polyamide PA6, vinylidene chloride-acrylate-methacrylate glycidyl ester-1, antioxidant 1010 and 168. Lubricant AC-540A is premixed in an internal mixer, and the premix is ​​melt-blended and extruded with stainless steel fiber through a twin-screw extruder, wherein the premix enters the extruder from the main feed port and the stainless steel fiber enters the extruder from the side feed port. The extrusion temperature is 240°C and the screw speed is 200 r / min.

[0060] Examples 3-5

[0061] Preparation of composite materials: polyamide PA6, vinylidene chloride-acrylate-methacrylate glycidyl ester-1, antioxidant 1010 and 168. Lubricant AC-540A is premixed in an internal mixer, and the premix is ​​melt-blended and extruded with surface-etched stainless steel fibers through a twin-screw extruder. The premix enters the extruder from the main feed port, and the stainless steel fibers enter the extruder from the side feed port. The extrusion temperature is 250°C and the screw speed is 300 r / min.

[0062] Example 6

[0063] Preparation of composite materials: polyamide PA6, vinylidene chloride-acrylate-glycidyl methacrylate-2, antioxidant 1010 and 168. Lubricant AC-540A was premixed in an internal mixer, and the premix was melt-blended and extruded with surface-etched stainless steel fibers through a twin-screw extruder. The premix entered the extruder from the main feed port, and the stainless steel fibers entered the extruder from the side feed port. The extrusion temperature was 260°C and the screw speed was 100 r / min.

[0064] Comparative Example 1

[0065] The difference from Example 1 is that the surface-etched stainless steel fiber is not added, and the other components and process parameters are the same as those in Example 1.

[0066] Comparative Example 2

[0067] The difference from Example 1 is that the surface-etched stainless steel fibers are replaced with an equal amount of stainless steel fibers, and the remaining components and process parameters are the same as those in Example 1.

[0068] Comparative Example 3

[0069] The difference from Comparative Example 1 is that the surface-etched stainless steel fibers are replaced with an equal amount of stainless steel fibers, and the remaining components and process parameters are the same as those in Example 1.

[0070] The dosage of each component is shown in the table below:

[0071]

[0072]

[0073] As shown in the table, by comparing Example 1 and Comparative Example 1, it can be seen that the addition of surface-etched stainless steel fibers can improve the tensile strength and tensile modulus of the material, reduce the amount of wear and volume resistivity, improve the wear resistance of the material, and give the material antistatic properties. By comparing Example 1 and Comparative Example 2, it can be seen that the stainless steel fibers are electrochemically treated and the bonding strength with the matrix resin is enhanced, thereby improving the tensile properties and wear resistance of the material. By comparing Example 1 and Comparative Example 1, it can be seen that when stainless steel fibers are not included in the system, the addition of vinylidene chloride-acrylate-glycidyl methacrylate does not improve the performance of the material. As shown in Examples 2-6, the addition of vinylidene chloride-acrylate-glycidyl methacrylate is beneficial to the dispersion of stainless steel fibers in the matrix resin, improves the bonding strength with the resin, thereby further improving the tensile properties and wear resistance of the material and reducing the volume resistivity of the material.

[0074] The above experimental examples are merely illustrative examples and are not intended to limit the embodiments. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all embodiments here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A polyamide material, characterized in that: Contains the following raw materials in parts by weight: 100 parts of polyamide; 8-50 parts of surface-treated stainless steel fibers; 0-5 parts of lubricant; 0-5 parts of antioxidant; The surface-treated stainless steel fiber is a stainless steel fiber with micropores on the surface obtained by acid and electrochemical surface etching. The polyamide material also contains 2-15 parts of vinylidene chloride-acrylate-glycidyl methacrylate terpolymer.

2. The polyamide material according to claim 1, characterized in that The polyamide material further comprises 3-8 parts of a vinylidene chloride-acrylate-glycidyl methacrylate terpolymer.

3. The polyamide material according to claim 2, characterized in that The preparation method of the vinylidene chloride-acrylate-glycidyl methacrylate terpolymer comprises the following steps: The dispersant aqueous solution is first added into the reactor, and then monomers glycidyl methacrylate, methyl acrylate, vinylidene chloride and initiator are added; the reactor is closed, nitrogen is passed through to exclude air, and the temperature is increased for polymerization; after the polymerization is completed, the material is discharged, washed and dried to obtain the vinylidene chloride-acrylate-glycidyl methacrylate terpolymer.

4. The polyamide material according to claim 3, characterized in that The dispersant is selected from one or more of hydroxypropyl methylcellulose, hydroxyethyl cellulose, and polyvinyl alcohol; and / or the initiator is selected from one or more of benzoyl peroxide, cumene hydroperoxide, and tert-butyl benzoyl peroxide.

5. The polyamide material according to claim 3 or 4, characterized in that The mass ratio of glycidyl methacrylate, methyl acrylate and vinylidene chloride is 2-10:2-10:80-96, and the amount of initiator used is 0.5%-1% of the monomer mass; and / or, the reaction temperature of the polymerization reaction is 50-100°C, the reaction pressure is 1-3 MPa, and the reaction time is 6-10 hours.

6. The polyamide material according to any one of claims 1 to 3, characterized in that The polyamide is selected from one or more of PA6, PA66, PA612, PA610, PA1010, PA1012, PA11, PA12, PA1212, PA6T, and PA6I; and / or the lubricant is selected from one or more of ethylene acrylic acid copolymers and stearates; and / or the antioxidant is selected from one or more of hindered phenols, phosphites, and phosphites.

7. The polyamide material according to any one of claims 1 to 3, characterized in that The preparation method of the surface-treated stainless steel fiber comprises the following steps: (1) Grind the stainless steel fiber with sandpaper, soak it in a solvent to remove impurities on the surface, wash it, and dry it for later use; (2) etching the stainless steel fiber treated in step (1) in acid, and then cleaning and drying the treated stainless steel fiber for later use after etching; (3) The stainless steel fiber treated in step (2) is used as an anode and the platinum electrode is used as a cathode, and they are immersed in an electrolyte and energized for electrochemical treatment. After the treatment, the stainless steel fiber is cleaned and dried.

8. The polyamide material according to claim 7, characterized in that In the step (1), the stainless steel fiber is made of 304 stainless steel or 312 stainless steel, the diameter of the stainless steel fiber is 10-20 μm, and the length of the stainless steel fiber is 3-10 mm; and / or, the solvent in the step (1) is one or more of formic acid, ethanol, and sodium hydroxide.

9. The polyamide material according to claim 7, characterized in that In the step (2), the acid is selected from one or more of hydrofluoric acid, acetic acid, and hydrochloric acid; and / or, the etching time in the step (2) is 1-10 hours; and / or, the electrolyte in the step (3) is perchloric acid and ethylene glycol, and the mass ratio of perchloric acid to ethylene glycol is 5-20:80-95; and / or, the voltage of the power supply in the step (3) is 36-48V, and the etching time is 30s-180s.

10. The method for preparing a polyamide material according to any one of claims 1 to 9, wherein: The method comprises the following steps: The weighed components except the surface-treated stainless steel fibers are mixed uniformly in an internal mixer, the mixed materials are placed in the main feeding hopper of a twin-screw extruder, the surface-treated stainless steel fibers are added from the side feeding hopper, melt-extruded, granulated, and dried.

Images