Ultra-high molecular weight polyethylene composite film as well as preparation method and application thereof

Abstract

The invention relates to the technical field of functional polymer membrane materials, in particular to an ultra-high molecular weight polyethylene composite membrane and a preparation method and application thereof.The preparation method comprises the following steps that S1, 85-99.9 parts by weight of ultra-high molecular weight polyethylene mixed liquid and 0.1-15 parts by weight of surface modified graphene are preheated and blended in an organic solvent, and a gel solution is obtained; s2, preheating the gel solution obtained in the step S1, keeping for a period of time, and extruding to form a composite material film; and S3, cooling and soaking the composite material film obtained in S2, washing with an organic solvent, and drying to obtain the ultra-high molecular weight polyethylene composite film. The surface modified graphene is used in the ultra-high molecular weight polyethylene for enhancement, and compared with traditional ultra-high molecular weight polyethylene, the mechanical property of the ultra-high molecular weight polyethylene is remarkably improved, and the barrier property of the ultra-high molecular weight polyethylene is enhanced.

Description

Technical Field

[0001] This invention relates to the field of functional polymer membrane materials technology, specifically providing an ultra-high molecular weight polyethylene composite membrane, its preparation method, and its application. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) is a high-performance polymer with excellent abrasion resistance, chemical corrosion resistance, high impact strength, and self-lubricating properties, widely used in engineering plastics, medical implants, and bulletproof materials. However, traditional UHMWPE membranes have high mechanical strength but low porosity, limiting their separation efficiency and restricting their application in high-end separation membranes and specialty packaging. In seawater desalination, traditional polyethylene membranes experience aging and fouling during use, leading to a significant decrease in water flux output and requiring regular maintenance and replacement, which increases operating costs to some extent.

[0003] Graphene, as a two-dimensional nanomaterial, has extremely high specific surface area and strength (theoretical strength of about 130 GPa), which can effectively transfer stress and suppress matrix deformation. However, direct graphene filling can easily lead to embrittlement of UHMWPE films, and the stacking of pure graphene nanosheets will reduce the mass transfer efficiency of UHMWPE films.

[0004] Therefore, there is an urgent need to develop a UHMWPE composite membrane for seawater desalination that can improve water flux, stability and mechanical strength while maintaining its lightweight properties. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide an ultra-high molecular weight polyethylene composite film, its preparation method and application, in order to solve the above-mentioned problems.

[0006] In a first aspect, the present invention provides a method for preparing an ultra-high molecular weight polyethylene composite film, comprising the following steps: S1. 85-99.9 parts by weight of ultra-high molecular weight polyethylene mixture and 0.1-15 parts by weight of surface-modified graphene are preheated and mixed in an organic solvent to obtain a gel solution. S2. Preheat the gel solution obtained in S1, maintain it for a period of time, and then extrude it into a composite material film. S3. Cool and soak the composite material membrane obtained in S2, wash it with an organic solvent and dry it to obtain an ultra-high molecular weight polyethylene composite membrane.

[0007] This invention utilizes surface-modified graphene to reinforce ultra-high molecular weight polyethylene (UHMWPE), thereby improving the strength of UHMWPE and suppressing matrix deformation caused by pressure in seawater desalination membranes. Furthermore, the use of surface-modified graphene increases the water flux of the UHMWPE composite membrane, thus improving seawater desalination efficiency.

[0008] In step S1, the ultra-high molecular weight polyethylene mixture is composed of ultra-high molecular weight polyethylene and an antioxidant. This invention adds an antioxidant to ultra-high molecular weight polyethylene, which can slow down the aging of the ultra-high molecular weight polyethylene composite film and improve its stability.

[0009] Preferably, the weight-average molecular weight of the ultra-high molecular weight polyethylene is ≥1600000 g / mol. For example, 1700000 g / mol, 1800000 g / mol, 1900000 g / mol, 2000000 g / mol, 2100000 g / mol, 2200000 g / mol, 2300000 g / mol, 2400000 g / mol, or 2500000 g / mol, etc.

[0010] Preferably, the antioxidant is 0.5 to 1.5 parts by weight relative to 100 parts by weight of the ultra-high molecular weight polyethylene; for example, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1.0 parts by weight, 1.1 parts by weight, 1.2 parts by weight, 1.3 parts by weight, 1.4 parts by weight, or 1.5 parts by weight. In this invention, if the amount of antioxidant used is less than 0.5 parts by weight, the desired effect will not be achieved; if it is more than 1.5 parts by weight, it will not only waste resources but also have no significant effect on performance improvement.

[0011] Preferably, the antioxidant is a phenolic antioxidant, specifically selected from one or more of the following: β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), 2,6-di-tert-butyl-4-methylphenol, and 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-triazine-2,4,6-(1H,3H,5H)trione.

[0012] In step S1, the surface-modified graphene is obtained by modifying the surface of graphene with a surface modifier. The specific modification method adopts existing methods (such as patent CN102923694A), which will not be described in detail here.

[0013] Preferably, the graphene is graphene oxide or aminated graphene, with a specific surface area ≥ 500 m² / g.

[0014] Preferably, the surface modifier is 0.05 to 5.0 parts by weight relative to 100 parts by weight of graphene; for example, 0.05 parts by weight, 0.1 parts by weight, 0.5 parts by weight, 0.8 parts by weight, 1.0 parts by weight, 1.5 parts by weight, 2.0 parts by weight, 2.5 parts by weight, 3.0 parts by weight, 3.5 parts by weight, 4.0 parts by weight, 4.5 parts by weight, or 5.0 parts by weight. In this invention, if the amount of modifier used is less than 0.05 parts by weight, the desired effect will not be achieved; if it is more than 5 parts by weight, it will not only waste resources but also have no significant effect on performance improvement.

[0015] Preferably, the surface modifier is one or more of a coupling agent or a compatibilizer.

[0016] The coupling agent is selected from one or more of silane coupling agents (such as KH-550, KH-560) and titanate coupling agents (such as NDZ-105).

[0017] The compatibilizer is selected from one or more of polyethylene-g-maleic anhydride, sodium dodecylbenzenesulfonate, and styrene-ethylene / butene-styrene triblock copolymer.

[0018] In step S1, the ultra-high molecular weight polyethylene mixture and the surface-modified graphene are preheated in an organic solvent at a temperature of 100-180 °C. For example, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, or 180 °C. The purpose of preheating in step S1 is to ensure that the ultra-high molecular weight polyethylene mixture and the surface-modified graphene are mixed more thoroughly and uniformly. Mixing below 100 °C results in poor uniformity of the mixture, while excessively high temperatures promote the volatilization of antioxidants, accelerate self-oxidative degradation, and waste energy.

[0019] In step S2, the preheating temperature of the gel solution is 120~200℃. For example, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, or 200℃. The extrusion temperature of the composite film is 150~250℃. For example, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, or 250℃. Preheating the gel solution before extrusion in step S2 of this invention can improve the uniformity of the solution, reduce the viscosity of the solution, and improve the stability of extrusion. Simultaneously, preheating can eliminate dissolved gases, preventing air bubbles from being squeezed into the fibers and causing stress defects.

[0020] In step S3, the immersion solution for the composite material membrane is deionized water.

[0021] The organic solvent used for washing is one or more of straight-chain or branched-chain alkane solvents and cycloalkane solvents. For example, it can be one or more of n-hexane, n-heptane, cyclohexane, and isodecane.

[0022] Secondly, the present invention provides an ultra-high molecular weight polyethylene composite film, which is prepared by the above method.

[0023] Thirdly, the present invention provides a seawater desalination membrane prepared using the above-mentioned ultra-high molecular weight polyethylene composite membrane.

[0024] The beneficial effects of this invention are that it uses surface-modified graphene to reinforce ultra-high molecular weight polyethylene, which significantly improves its mechanical properties and enhances its barrier properties compared to traditional ultra-high molecular weight polyethylene. Detailed Implementation

[0025] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0026] Example 1 This invention provides a method for preparing an ultra-high molecular weight polyethylene (UHMWPE) composite membrane, comprising the following steps: 0.5 parts by weight of surface-modified graphene (pore size 10 nm, containing 0.05 parts by weight of polyethylene-g-maleic anhydride) and 99.5 parts by weight of an UHMWPE mixture (containing 1.0 part by weight of 2,6-di-tert-butyl-4-methylphenol and 0.5 parts by weight of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)) with a molecular weight of 1,800,000 g / mol) are blended in an organic solvent (paraffin oil). The blending preheating temperature is 160 °C, and a gel solution is obtained after blending. The gel solution is then preheated to 180 °C and held for 30 min before extrusion at 180 °C. The extruded product is cooled to 25 °C in deionized water, immersed in n-hexane for 24 h, and dried to obtain an UHMWPE composite membrane. This composite membrane is used in the field of seawater desalination.

[0027] Example 2 Unlike Example 1, 0.1 parts by weight of surface-modified graphene (pore size 10 nm, containing 1.0 parts by weight of styrene-ethylene / butene-styrene triblock and 0.5 parts by weight of polyethylene-g-maleic anhydride) and 99.9 parts by weight of ultra-high molecular weight polyethylene (containing 0.5 parts by weight of 2,6-di-tert-butyl-4-methylphenol, 0.5 parts by weight of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl alcohol ester and 0.5 parts by weight of 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-triazine-2,4,6-(1H,3H,5H)trione) with a molecular weight of 1,800,000 g / mol were blended in an organic solvent (paraffin oil) at a blending preheating temperature of 170°C.

[0028] Example 3 Unlike Example 1, 1.0 parts by weight of porous graphene (pore size 10 nm, containing 2.0 parts by weight of polyethylene-g-maleic anhydride and 1.0 parts by weight of KH-550) and 99.0 parts by weight of ultra-high molecular weight polyethylene (containing 1.0 parts by weight of 2,6-di-tert-butyl-4-methylphenol and 0.5 parts by weight of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl alcohol ester) with a molecular weight of 1,800,000 g / mol were blended in an organic solvent (paraffin oil). The blending preheating temperature was 165°C, the gel solution preheating temperature was 175°C, and the mixture was maintained for 25 min before extrusion.

[0029] Example 4 Unlike Example 1, 5.0 parts by weight of porous graphene (pore size 10 nm, containing 2.0 parts by weight of styrene-ethylene / butene-styrene triblock copolymer) and 95.0 parts by weight of ultra-high molecular weight polyethylene (containing 1.0 part by weight of 2,6-di-tert-butyl-4-methylphenol and 0.5 parts by weight of 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-triazine-2,4,6-(1H,3H,5H)trione) with a molecular weight of 1,800,000 g / mol were blended in an organic solvent (paraffin oil). The blending preheating temperature was 155°C, the gel solution preheating temperature was 170°C, and the mixture was maintained for 20 min before extrusion.

[0030] Example 5 Unlike Example 1, 2.0 parts by weight of porous graphene (pore size 10 nm, containing 2.0 parts by weight of KH-560 and 1 part by weight of sodium dodecylbenzenesulfonate) and 98.0 parts by weight of ultra-high molecular weight polyethylene (containing 1.0 part by weight of 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-triazine-2,4,6-(1H,3H,5H)trione) with a molecular weight of 1,800,000 g / mol were blended in an organic solvent (paraffin oil). The blending preheating temperature was 155°C, the gel solution preheating temperature was 170°C, and the mixture was maintained for 20 min before extrusion.

[0031] Example 6 Unlike Example 1, 3.0 parts by weight of porous graphene (pore size 10 nm, containing 2.0 parts by weight of NDZ-105 and 1 part by weight of KH-550) and 97.0 parts by weight of ultra-high molecular weight polyethylene (containing 1.0 part by weight of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and 0.5 parts by weight of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) with a molecular weight of 1,800,000 g / mol) were blended in an organic solvent (paraffin oil). The blending preheating temperature was 155°C, the gel solution preheating temperature was 170°C, and the mixture was maintained for 20 min before extrusion.

[0032] Comparative Example 1 Unlike Example 1, only a mixture of ultra-high molecular weight polyethylene with a molecular weight of 1,800,000 g / mol containing 1.0 parts by weight of 2,6-di-tert-butyl-4-methylphenol was used as raw material.

[0033] Comparative Example 2 Unlike Comparative Example 1, 1.0 parts by weight of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and 0.5 parts by weight of 2,6-di-tert-butyl-4-methylphenol were used as antioxidants.

[0034] Comparative Example 3 Unlike Example 1, 20.0 parts by weight of surface-modified graphene (pore size 10 nm, containing 1.0 parts by weight of ethylene-acrylic acid copolymer) was blended with 80.0 parts by weight of ultra-high molecular weight polyethylene mixture with a molecular weight of 1,800,000 g / mol.

[0035] Comparative Example 4 Unlike Example 1, 0.05 parts by weight of surface-modified graphene (pore size 10 nm, containing 0.5 parts by weight of tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenyl bisphosphonate) was blended with 99.95 parts by weight of a mixture of ultra-high molecular weight polyethylene with a molecular weight of 1,400,000 g / mol.

[0036] Testing standards: Salt rejection test: According to ASTM D4194, 3.5 parts by weight of NaCl solution was prepared to simulate seawater, and the test was carried out at 25°C and operating pressure of 5.5 MPa.

[0037] Water flux test: The volume of water permeating the membrane per unit time is measured according to ASTM D4194 at 25°C and constant pressure.

[0038] Tensile modulus test: According to ASTM D882, a nano tensile tester was used to test the composite film with a thickness ≤1 mm in advance at 23±2℃ and 50±5% RH.

[0039] Long-term stability testing: Accelerated aging tests were conducted according to ASTM D6908, involving 500 hours of salt solution immersion. After aging, the aged composite membrane was subjected to the initial baseline test three times, and the salt rejection rate data were compared with that of the composite membrane before aging. The results are detailed in Table 1. Similarly, the water flux of the aged composite membrane was tested, and the changes were compared with those of the composite membrane before aging. The changes are detailed in Table 1.

[0040] The relevant data for the above embodiments and comparative examples are detailed in Table 1.

[0041] Table 1 Analysis of the data in Table 1 shows that, taking Examples 1-6 as examples, the salt rejection rate of the ultra-high molecular weight polyethylene composite membrane of the present invention is >99.7%, the water flux is 25~68 L / (m²·h·MPa), and the tensile modulus is 1530~3270 MPa. Comparison with the data of the composite membrane before aging shows that the salt rejection rate after aging is >99.1%, and the water flux after aging is 23~62 L / (m²·h·MPa).

[0042] Compared to the existing ultra-high molecular weight polyethylene membrane in Comparative Example 1, the ultra-high molecular weight polyethylene composite membranes prepared in Examples 1-2 of this invention have higher salt rejection rate, water flux and tensile modulus.

[0043] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing an ultra-high molecular weight polyethylene composite film, characterized in that, Includes the following steps: S1. 85-99.9 parts by weight of ultra-high molecular weight polyethylene mixture and 0.1-15 parts by weight of surface-modified graphene are preheated and mixed in an organic solvent to obtain a gel solution. S2. Preheat the gel solution obtained in S1, maintain it for a period of time, and then extrude it into a composite material film. S3. Cool and soak the composite material membrane obtained in S2, wash it with an organic solvent and dry it to obtain an ultra-high molecular weight polyethylene composite membrane.

2. The preparation method according to claim 1, characterized in that, In step S1, the ultra-high molecular weight polyethylene mixture is composed of ultra-high molecular weight polyethylene and an antioxidant. Preferably, the weight-average molecular weight of the ultra-high molecular weight polyethylene is ≥1600000 g / mol; Preferably, the antioxidant is 0.5 to 1.5 parts by weight relative to 100 parts by weight of the ultra-high molecular weight polyethylene; Preferably, the antioxidant is a phenolic antioxidant selected from one or more of the following: β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), 2,6-di-tert-butyl-4-methylphenol, and 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-triazine-2,4,6-(1H,3H,5H)trione.

3. The preparation method according to claim 1, characterized in that, In step S1, the surface-modified graphene is obtained by modifying the surface of graphene using a surface modifier. Preferably, the graphene is graphene oxide or aminated graphene, with a specific surface area ≥ 500 m² / g; Preferably, the surface modifier is 0.05 to 5.0 parts by weight relative to 100 parts by weight of the graphene; Preferably, the surface modifier is one or more of a coupling agent or a compatibilizer.

4. The preparation method according to claim 3, characterized in that, The coupling agent is selected from one or more of silane coupling agents and titanate coupling agents; the compatibilizer is selected from one or more of polyethylene-g-maleic anhydride, sodium dodecylbenzenesulfonate, and styrene-ethylene / butene-styrene triblock copolymer.

5. The preparation method according to claim 1, characterized in that, In step S1, the ultra-high molecular weight polyethylene mixture and the surface-modified graphene are preheated in an organic solvent at a temperature of 100~180 ℃.

6. The preparation method according to claim 1, characterized in that, In step S2, the preheating temperature of the gel solution is 120~200 ℃.

7. The preparation method according to claim 1, characterized in that, In step S2, the extrusion temperature of the composite film is 150~250 ℃.

8. The preparation method according to claim 1, characterized in that, In step S3, the immersion solution for the composite membrane is deionized water; the organic solvent for washing is one or more of straight-chain or branched-chain alkane solvents and cycloalkane solvents.

9. A composite film of ultra-high molecular weight polyethylene, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. A seawater desalination membrane prepared using the ultra-high molecular weight polyethylene composite membrane as described in claim 9.

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