Preparation method of wear-resistant polyethylene composite plastic

Abstract

The invention discloses a preparation method of wear-resistant polyethylene composite plastic, and relates to the field of polyethylene composite plastic. Dopamine hydrochloride is subjected to autoxidation polymerization under the weak alkaline condition of a Tris buffer solution to generate a polydopamine coating, catechol groups and amino functional groups of the polydopamine coating and hydroxyl groups on the surface of the silicon carbide fiber form hydrogen bonds, carboxymethyl chitosan and the polydopamine coating are subjected to Michael addition and electrostatic bonding, and the interface bonding strength is improved; maleic anhydride groups of the maleic anhydride grafted polyethylene and hydroxyl groups on the surfaces of the silicon carbide nanoparticles are subjected to esterification reaction in a molten state to generate covalent ester bonds, and meanwhile, polyethylene chain segments of the maleic anhydride grafted polyethylene are entangled with a polyethylene matrix, so that the tensile strength and the elongation at break are improved; the cross-linking density of acetal bonds is controlled by forming gradient heat treatment, so that the surface layer is highly cross-linked, and the wear resistance is improved.

Description

Technical Field

[0001] The invention relates to the field of polyethylene composite plastics, in particular to a preparation method of wear-resistant polyethylene composite plastics. Background Art

[0002] Polyethylene (PE), a general-purpose plastic, is widely used in packaging, medical, and industrial applications due to its excellent chemical stability, processing properties, and low cost. However, the insufficient wear resistance and mechanical strength of conventional PE limit its application in high-end applications. To improve the wear resistance and mechanical properties of PE, existing technologies typically employ the addition of inorganic nanofillers (such as silicon carbide and silica) or fiber reinforcement.

[0003] Publication No. CN118374038B discloses a preparation method and application of a wear-resistant polyethylene composite plastic, belonging to the technical field of plastic molded products. In the wear-resistant polyethylene composite plastic, adding polyvinyl pyrrolidone and water-soluble carboxymethyl chitosan in a coating manner can improve the hot-pressing, bonding, and thermosetting sealing properties of the gloves; adding silicon carbide fibers can resist tearing; adding silicon carbide to the silicon carbide fibers by coating can improve wear resistance; and adding palm oil can improve the homogeneity and smoothness of the mixed film blowing, making the plastic film blowing quality more uniform. However, the following problems still exist: silicon carbide nanoparticles and fibers are prone to agglomeration due to their high specific surface area. In particular, agglomeration may be exacerbated by solvent evaporation during the drying process, resulting in stress concentration within the composite material, which in turn reduces the overall toughness and wear resistance of the material. Although the three-layer film structure increases the number of uses, insufficient interlayer bonding strength during heat sealing and cutting may lead to delamination. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a wear-resistant polyethylene composite plastic to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing a wear-resistant polyethylene composite plastic, comprising the following preparation steps: (1) Immersing silicon carbide fiber in a Tris buffer solution with a pH value of 8.0-9.0, wherein the Tris buffer solution contains 1.0%-1.5% dopamine hydrochloride by mass, and stirring the mixture at 35°C-45°C for 20-28 hours to obtain a primary modified silicon carbide fiber with a polydopamine coating on the surface; mixing the primary modified silicon carbide fiber with a carboxymethyl chitosan aqueous solution with a mass fraction of 4%-6% in a mass ratio of 1:5-8, reacting the mixture at 50°C-70°C for 1.5-2.5 hours, filtering and drying the mixture to obtain a secondary modified silicon carbide fiber with a carboxymethyl chitosan coating on the surface; (2) Silicon carbide nanoparticles with a particle size of 200 nm to 500 nm, maleic anhydride grafted polyethylene and p-toluenesulfonic acid catalyst are mixed in a mass ratio of 1:4-6:0.04-0.06, added to a twin-screw extruder for melt blending, extruded into granules and then crushed into composite particles with a particle size of 50 μm to 100 μm; (3) Mixing the polyethylene particles, the composite particles obtained in step (2), and the secondary modified silicon carbide fibers obtained in step (1), adding epoxy soybean oil, and mixing in a high-speed mixer under nitrogen protection for 10-20 minutes to obtain a mixture; adding the mixture to a film blowing machine to blow a film into a cylindrical film with a thickness of 0.05 mm to 0.15 mm; (4) Immersing the tubular film in a polyvinyl alcohol aqueous solution having a mass fraction of 4% to 6%, wherein the pH value of the polyvinyl alcohol aqueous solution is adjusted to 3.5 to 5.0 with hydrochloric acid, and the polyvinyl alcohol aqueous solution contains 0.8% to 1.2% of glutaraldehyde, and the immersion time is 30 to 60 seconds; after taking out, heat-treating the film at 75°C to 85°C for 8 to 12 minutes and at 95°C to 105°C for 5 to 8 minutes, and then repeating the above-mentioned immersion-heat treatment process 2 to 3 times to obtain a polyethylene composite plastic.

[0006] Furthermore, the stirring speed in step (1) is 200 rpm-300 rpm.

[0007] Furthermore, the drying in step (1) is carried out in a vacuum drying oven with a vacuum degree of -0.08 MPa-0.1 MPa, a drying temperature of 55°C-65°C, and a drying time of 3-5 hours.

[0008] Furthermore, in step (1), the diameter of the silicon carbide fiber is 0.5 μm-2 μm and the length is less than 0.3 mm.

[0009] Furthermore, the temperatures of the twin-screw extruder in step (2) are as follows: zone 1 165°C-175°C, zone 2 170°C-180°C, zone 3 175°C-185°C, zone 4 180°C-190°C, zone 5 185°C-195°C, the screw aspect ratio is 40-45:1, and the screw speed is 100rpm-150rpm.

[0010] Furthermore, in step (3), the rotation speed of the high-speed mixer is 500 rpm-800 rpm.

[0011] Furthermore, the polyethylene particles in step (3) have a particle size of 50 μm-300 μm and are selected from a mixture of one or more of low-density polyethylene, high-density polyethylene, and linear polyethylene.

[0012] Furthermore, the molecular weight of the epoxidized soybean oil in step (3) is 900-1100.

[0013] Furthermore, in step (3), the melting temperature of the film blowing machine is 180°C-200°C, and the die head temperature is 195°C-205°C.

[0014] Furthermore, the mass ratio of the polyethylene particles in step (3), the composite particles obtained in step (2), the secondary modified silicon carbide fibers obtained in step (1), and the epoxidized soybean oil is 100:(10-20):(5-10):(2-4).

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. In the present invention, dopamine hydrochloride undergoes self-oxidative polymerization under the weak alkaline conditions of Tris buffer (tris(hydroxymethyl)aminomethane) buffer to form a polydopamine coating on the surface of the silicon carbide fiber. The catechol groups and amino functional groups of the polydopamine coating form hydrogen bonds with the hydroxyl groups on the surface of the silicon carbide fiber. Carboxymethyl chitosan undergoes Michael addition with the catechol groups of the polydopamine coating through the amino groups. At the same time, the carboxylate groups of the carboxymethyl chitosan electrostatically bond with the amino groups of the polydopamine coating, thereby improving the interfacial bonding strength and effectively improving the stress transfer efficiency between the silicon carbide fiber and the polyethylene matrix.

[0016] 2. The maleic anhydride groups of the maleic anhydride grafted polyethylene undergo esterification reaction with the hydroxyl groups on the surface of the silicon carbide nanoparticles in the molten state to form covalent ester bonds. At the same time, the polyethylene chain segments of the maleic anhydride grafted polyethylene are entangled with the polyethylene matrix, which improves the dispersion uniformity of the silicon carbide nanoparticles and thus improves the tensile strength of the material.

[0017] 3. The hydroxyl groups of polyvinyl alcohol and the aldehyde groups of glutaraldehyde react under the acidic conditions of the impregnation solution to form acetal bonds, forming a three-dimensional network structure; the cross-linking density of the acetal bonds is controlled by forming a gradient heat treatment of 75℃-95℃, so that the surface layer is highly cross-linked to improve wear resistance, and the inner layer is lowly cross-linked to maintain flexibility. DETAILED DESCRIPTION

[0018] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0019] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0020] The test methods for various indicators of the materials obtained in the following embodiments and comparative examples are as follows: The tensile performance test is based on GB / T1040.3-2006, using a universal material testing machine, cutting the sample into a dumbbell shape (Type I), the tensile speed is 50 mm / min, and the tensile strength (MPa) and elongation at break (%) are recorded. The wear resistance test is based on ASTMD4060-2019, using a Taber wear tester, using an H-18 grinding wheel, a load of 1 kg, 1000 cycles, and weighing the sample wear mass loss (mg). The surface friction coefficient test is based on GB / T10006-2021, using a friction coefficient meter, a slider weight of 200 g, a sliding speed of 100 mm / min, and recording the dynamic friction coefficient. Example 1

[0021] (1) A silicon carbide fiber with a diameter of 0.5 μm and a length of less than 0.3 mm was immersed in a Tris buffer solution with a pH value of 8.0, wherein the Tris buffer solution contained 1.0% dopamine hydrochloride by mass, and the mixture was stirred at 35°C for 20 hours at a stirring speed of 200 rpm to obtain a primary modified silicon carbide fiber with a polydopamine coating on the surface; the primary modified silicon carbide fiber was mixed with a 4% carboxymethyl chitosan aqueous solution at a mass ratio of 1:5, reacted at 50°C for 1.5 hours, filtered and dried to obtain a secondary modified silicon carbide fiber with a carboxymethyl chitosan coating on the surface; the drying was carried out in a vacuum drying oven with a vacuum degree of -0.08 MPa, a drying temperature of 55°C, and a drying time of 3 hours.

[0022] (2) Silicon carbide nanoparticles with a particle size of 200 nm, maleic anhydride grafted polyethylene and p-toluenesulfonic acid catalyst were mixed in a mass ratio of 1:4:0.04, added to a twin-screw extruder for melt blending, extruded and granulated, and then crushed into composite particles with a particle size of 50 μm; the temperatures of the twin-screw extruder were: 165°C in zone 1, 170°C in zone 2, 175°C in zone 3, 180°C in zone 4, and 185°C in zone 5, the screw aspect ratio was 40:1, and the screw speed was 100 rpm.

[0023] (3) Mix the polyethylene particles, the composite particles obtained in step (2), and the secondary modified silicon carbide fiber obtained in step (1), add epoxy soybean oil, and mix in a high-speed mixer at 500 rpm for 10 minutes under nitrogen protection to obtain a mixture; add the mixture to a film blowing machine to blow a film into a cylindrical film with a thickness of 0.05 mm; the polyethylene particles have a particle size of 50 μm and are low-density polyethylene. The molecular weight of the epoxy soybean oil is 900. The melt temperature of the film blowing machine is 180°C, and the die head temperature is 195°C. The mass ratio of the polyethylene particles, the composite particles obtained in step (2), the secondary modified silicon carbide fiber obtained in step (1), and the epoxy soybean oil is 100:10:5:2.

[0024] (4) Immerse the tubular film in a 4% by mass aqueous solution of polyvinyl alcohol, wherein the pH value of the polyvinyl alcohol aqueous solution is adjusted to 3.5 with hydrochloric acid, and the polyvinyl alcohol aqueous solution contains 0.8% by mass glutaraldehyde, and the immersion time is 30 seconds; after taking out, heat-treat the film at 75°C for 8 minutes and at 95°C for 5 minutes, and then repeat the above immersion-heat treatment process twice to obtain a polyethylene composite plastic. Example 2

[0025] (1) A silicon carbide fiber with a diameter of 1.25 μm and a length of less than 0.2 mm was immersed in a Tris buffer solution with a pH value of 8.5, wherein the Tris buffer solution contained 1.25% dopamine hydrochloride by mass, and the mixture was stirred at 40°C for 24 hours at a stirring speed of 250 rpm to obtain a primary modified silicon carbide fiber with a polydopamine coating on the surface; the primary modified silicon carbide fiber was mixed with a 5% carboxymethyl chitosan aqueous solution at a mass ratio of 1:6.5, reacted at 60°C for 2 hours, filtered and dried to obtain a secondary modified silicon carbide fiber with a carboxymethyl chitosan coating on the surface; the drying was carried out in a vacuum drying oven with a vacuum degree of -0.09 MPa, a drying temperature of 60°C, and a drying time of 4 hours.

[0026] (2) Silicon carbide nanoparticles with a particle size of 350 nm, maleic anhydride grafted polyethylene and p-toluenesulfonic acid catalyst were mixed in a mass ratio of 1:5:0.05, added to a twin-screw extruder for melt blending, extruded and granulated, and then crushed into composite particles with a particle size of 75 μm; the temperatures of the twin-screw extruder were: 170°C in zone 1, 175°C in zone 2, 180°C in zone 3, 185°C in zone 4, and 190°C in zone 5, the screw aspect ratio was 42:1, and the screw speed was 125 rpm.

[0027] (3) The polyethylene particles, the composite particles obtained in step (2), and the secondary modified silicon carbide fiber obtained in step (1) are mixed, epoxy soybean oil is added, and the mixture is mixed at a speed of 650 rpm in a high-speed mixer under nitrogen protection for 15 minutes to obtain a mixture; the mixture is added to a film blowing machine and blown into a cylindrical film with a thickness of 0.1 mm; the polyethylene particles have a particle size of 175 μm and are low-density polyethylene. The molecular weight of the epoxy soybean oil is 1000. The melt temperature of the film blowing machine is 190°C, and the die head temperature is 200°C. The mass ratio of the polyethylene particles, the composite particles obtained in step (2), the secondary modified silicon carbide fiber obtained in step (1), and the epoxy soybean oil is 100:15:7.5:3.

[0028] (4) Immersing the tubular film in a 5% by mass aqueous solution of polyvinyl alcohol, wherein the pH value of the polyvinyl alcohol aqueous solution is adjusted to 4.25 with hydrochloric acid, and the polyvinyl alcohol aqueous solution contains 1.0% by mass glutaraldehyde, and the immersion time is 45 seconds; after taking out, heat-treating the film at 80°C for 10 minutes and at 100°C for 6.5 minutes, and then repeating the above-mentioned immersion-heat treatment process twice to obtain a polyethylene composite plastic. Example 3

[0029] (1) A silicon carbide fiber with a diameter of 2 μm and a length of less than 0.1 mm was immersed in a Tris buffer solution with a pH value of 9.0, wherein the Tris buffer solution contained 1.5% dopamine hydrochloride by mass, and the mixture was stirred at 45°C for 28 hours at a stirring speed of 300 rpm to obtain a primary modified silicon carbide fiber with a polydopamine coating on the surface; the primary modified silicon carbide fiber was mixed with a 6% carboxymethyl chitosan aqueous solution at a mass ratio of 1:8, reacted at 70°C for 2.5 hours, filtered and dried to obtain a secondary modified silicon carbide fiber with a carboxymethyl chitosan coating on the surface; the drying was carried out in a vacuum drying oven with a vacuum degree of -0.1 MPa, a drying temperature of 65°C, and a drying time of 5 hours.

[0030] (2) Silicon carbide nanoparticles with a particle size of 500 nm, maleic anhydride grafted polyethylene and p-toluenesulfonic acid catalyst were mixed in a mass ratio of 1:6:0.06, added to a twin-screw extruder for melt blending, extruded and granulated, and then crushed into composite particles with a particle size of 100 μm; the temperatures of the twin-screw extruder were: 175°C in zone 1, 180°C in zone 2, 185°C in zone 3, 190°C in zone 4, and 195°C in zone 5, the screw aspect ratio was 45:1, and the screw speed was 150 rpm.

[0031] (3) Mix the polyethylene particles, the composite particles obtained in step (2), and the secondary modified silicon carbide fiber obtained in step (1), add epoxy soybean oil, and mix in a high-speed mixer at 800 rpm for 20 minutes under nitrogen protection to obtain a mixture; add the mixture to a film blowing machine and blow it into a cylindrical film with a thickness of 0.15 mm; the polyethylene particles have a particle size of 300 μm and are low-density polyethylene. The molecular weight of the epoxy soybean oil is 1100. The melt temperature of the film blowing machine is 200°C, and the die head temperature is 205°C. The mass ratio of the polyethylene particles, the composite particles obtained in step (2), the secondary modified silicon carbide fiber obtained in step (1), and the epoxy soybean oil is 100:20:10:4.

[0032] (4) Immerse the tubular film in a 6% by mass aqueous solution of polyvinyl alcohol, wherein the pH value of the polyvinyl alcohol aqueous solution is adjusted to 5.0 with hydrochloric acid, and the polyvinyl alcohol aqueous solution contains 1.2% by mass glutaraldehyde, and the immersion time is 60 seconds; after taking out, heat-treat the film at 85°C for 12 minutes and at 105°C for 8 minutes, and then repeat the above immersion-heat treatment process 3 times to obtain a polyethylene composite plastic.

[0033] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that dopamine hydrochloride is not added to modify the silicon carbide fiber.

[0034] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that no carboxymethyl chitosan aqueous solution is added to modify the silicon carbide fiber.

[0035] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that no maleic anhydride-grafted polyethylene is added.

[0036] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that the second heat treatment is omitted (ie, the heat treatment at 95° C. for 5 minutes is omitted).

[0037] Table 1 below shows the performance analysis results of the samples prepared in the examples of the present invention and the comparative examples.

[0038] Table 1

[0039] From the experimental data of the embodiments and comparative examples, it can be found that dopamine hydrochloride in the present invention undergoes self-oxidative polymerization under the weak alkaline conditions of Tris buffer to form a polydopamine coating on the surface of the silicon carbide fiber, and the catechol group and amino functional group of the polydopamine coating form hydrogen bonds with the hydroxyl groups on the surface of the silicon carbide fiber; carboxymethyl chitosan undergoes Michael addition with the catechol group of the polydopamine coating through the amino group, and at the same time, the carboxylate group of the carboxymethyl chitosan is electrostatically bonded with the amino group of the polydopamine coating, thereby improving the interfacial bonding strength, and the maleic anhydride group of the maleic anhydride grafted polyethylene undergoes esterification reaction with the hydroxyl groups on the surface of the silicon carbide nanoparticles in a molten state to form a covalent ester bond, and at the same time, the polyethylene chain segments of the maleic anhydride grafted polyethylene are entangled with the polyethylene matrix, thereby improving the dispersion uniformity of the silicon carbide nanoparticles, and further improving the tensile strength and elongation at break; by forming a gradient heat treatment to control the crosslinking density of the acetal bond, the surface layer is highly crosslinked, and the wear resistance is effectively improved.

[0040] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed therein. Any reference in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for preparing a wear-resistant polyethylene composite plastic, characterized in that: The method comprises the following preparation steps: (1) Immersing silicon carbide fiber in a Tris buffer solution with a pH value of 8.0-9.0, wherein the Tris buffer solution contains 1.0%-1.5% dopamine hydrochloride by mass, and stirring the mixture at 35°C-45°C for 20-28 hours to obtain a primary modified silicon carbide fiber with a polydopamine coating on the surface; mixing the primary modified silicon carbide fiber with a carboxymethyl chitosan aqueous solution with a mass fraction of 4%-6% in a mass ratio of 1:5-8, reacting the mixture at 50°C-70°C for 1.5-2.5 hours, filtering and drying the mixture to obtain a secondary modified silicon carbide fiber with a carboxymethyl chitosan coating on the surface; (2) Silicon carbide nanoparticles with a particle size of 200 nm to 500 nm, maleic anhydride grafted polyethylene and p-toluenesulfonic acid catalyst are mixed in a mass ratio of 1:4-6:0.04-0.06, added to a twin-screw extruder for melt blending, extruded into granules and then crushed into composite particles with a particle size of 50 μm to 100 μm; (3) Mixing the polyethylene particles, the composite particles obtained in step (2), and the secondary modified silicon carbide fibers obtained in step (1), adding epoxy soybean oil, and mixing in a high-speed mixer under nitrogen protection for 10-20 minutes to obtain a mixture; adding the mixture to a film blowing machine to blow a film into a cylindrical film with a thickness of 0.05 mm to 0.15 mm; (4) Immersing the tubular film in a polyvinyl alcohol aqueous solution having a mass fraction of 4% to 6%, wherein the pH value of the polyvinyl alcohol aqueous solution is adjusted to 3.5 to 5.0 with hydrochloric acid, and the polyvinyl alcohol aqueous solution contains 0.8% to 1.2% of glutaraldehyde, and the immersion time is 30 to 60 seconds; after taking out, heat-treating the film at 75°C to 85°C for 8 to 12 minutes and at 95°C to 105°C for 5 to 8 minutes, and then repeating the above-mentioned immersion-heat treatment process 2 to 3 times to obtain a polyethylene composite plastic.

2. The method for preparing a wear-resistant polyethylene composite plastic according to claim 1, characterized in that: The stirring speed in step (1) is 200 rpm-300 rpm.

3. The method for preparing a wear-resistant polyethylene composite plastic according to claim 1, characterized in that: The drying in step (1) is carried out in a vacuum drying oven with a vacuum degree of -0.08MPa-0.1MPa, a drying temperature of 55°C-65°C, and a drying time of 3-5 hours.

4. The method for preparing a wear-resistant polyethylene composite plastic according to claim 1, characterized in that: In step (1), the diameter of the silicon carbide fiber is 0.5 μm-2 μm and the length is less than 0.3 mm.

5. The method for preparing a wear-resistant polyethylene composite plastic according to claim 1, characterized in that: The temperatures of the twin-screw extruder in step (2) are as follows: zone 1 165°C-175°C, zone 2 170°C-180°C, zone 3 175°C-185°C, zone 4 180°C-190°C, zone 5 185°C-195°C, the screw aspect ratio is 40-45:1, and the screw speed is 100rpm-150rpm.

6. The method for preparing a wear-resistant polyethylene composite plastic according to claim 1, characterized in that: In step (3), the rotation speed of the high-speed mixer is 500 rpm-800 rpm.

7. The method for preparing a wear-resistant polyethylene composite plastic according to claim 1, characterized in that: The polyethylene particles in step (3) have a particle size of 50 μm to 300 μm and are selected from a mixture of one or more of low-density polyethylene, high-density polyethylene, and linear polyethylene.

8. The method for preparing a wear-resistant polyethylene composite plastic according to claim 1, characterized in that: The molecular weight of the epoxidized soybean oil in step (3) is 900-1100.

9. The method for preparing a wear-resistant polyethylene composite plastic according to claim 1, characterized in that: In step (3), the melting temperature of the film blowing machine is 180°C-200°C, and the die head temperature is 195°C-205°C.

10. The method for preparing a wear-resistant polyethylene composite plastic according to claim 1, characterized in that: The mass ratio of the polyethylene particles in step (3), the composite particles obtained in step (2), the secondary modified silicon carbide fibers obtained in step (1), and the epoxidized soybean oil is 100:(10-20):(5-10):(2-4).

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