Surface modified ultra-high molecular weight polyethylene fiber, preparation method thereof and application of surface modified ultra-high molecular weight polyethylene fiber in ultra-high performance concrete

Abstract

The invention discloses a surface-modified ultra-high molecular weight polyethylene fiber and a preparation method and application thereof in ultra-high performance concrete.The preparation method of the surface-modified ultra-high molecular weight polyethylene fiber comprises the following steps that 1, the UHMWPE fiber is soaked in alkali liquor, then stirring reaction is conducted under a certain temperature condition, cleaning is conducted after the reaction is finished, and the surface-modified ultra-high molecular weight polyethylene fiber is obtained; and drying to obtain the UHMWPE fiber subjected to'alkali liquor etching '. And (2) mixing the UHMWPE fiber subjected to'alkali liquor etching 'with deionized water, adding calcium salt and silicate to obtain a mixed solution, then carrying out stirring reaction under a certain temperature condition, and after the reaction is finished, rinsing and drying to obtain the surface modified UHMWPE fiber. The surface modified UHMWPE fiber prepared by the invention has strong hydrophilicity and good compatibility with a cement-based material, and can be used for preparing a UHPC material with excellent mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-high performance concrete, and in particular relates to a surface-modified ultra-high molecular weight polyethylene fiber, a preparation method thereof, and an application thereof in ultra-high performance concrete. Background Art

[0002] Steel fiber is a primary component of ultra-high-performance concrete (UHPC). Its high elastic modulus (nearly 200 GPa) acts as a bridge within the concrete, inhibiting the propagation of internal microcracks and thereby improving the material's tensile strength and flexural toughness. However, long-term exposure to extreme environments rich in chloride ions (such as the ocean and areas where de-icing salt is used) can cause the ions to slowly penetrate and trigger localized electrochemical reactions, penetrating the passive film on the steel fiber surface and accelerating pitting corrosion, which in turn undermines the structural integrity of the UHPC and reduces its service life. Therefore, replacing steel fibers with corrosion-resistant, high-tenacity fibers in the production of UHPC has become a key approach to preventing corrosion damage.

[0003] Ultra-high molecular weight polyethylene (UHMWPE) fibers are high-performance polymer materials with exceptional wear and fatigue resistance, corrosion resistance, and weathering resistance. Their density parameters are among the lowest among known fiber systems, while exhibiting excellent strength and elastic modulus (70-170 GPa). Together with carbon fibers and aromatic polyamide fibers, they constitute three major advanced fiber systems and are widely used in various industrial fields. However, UHMWPE's microstructure is characterized by significant crystallization and molecular orientation, with methylene segments exhibiting a highly ordered linear arrangement. This unique molecular topology results in low-roughness interface characteristics on the material's surface. The lack of active functional groups in the molecular chain significantly reduces surface free energy, resulting in significant chemical inertness and prominent hydrophobic properties. This interfacial characteristic leads to poor compatibility of fibers in inorganic cementitious materials. Increasing the dosage will significantly affect the fluidity of cement-based materials. In addition, the interfacial bonding strength between the fibers and the inorganic cementitious matrix is ​​insufficient, making it impossible to achieve the intrinsic mechanical properties of the material in cement-based composites. This interfacial compatibility problem directly restricts its practical application in UHPC.

[0004] Commonly used UHMWPE surface modification methods include plasma modification, irradiation grafting modification, chemical reagent modification, corona discharge modification, and coating modification. Other methods include alkali treatment and nanoparticle filling. To further improve the interfacial bonding between the matrix material and the fiber reinforcement material, two or more modification methods can be combined to synergistically modify the fiber on the basis of a single modification treatment. However, compared with the existing modification methods, how to solve the problem of low interfacial compatibility and adhesion between UHMWPE fibers and the cement matrix in UHPC without damaging its own mechanical properties remains a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] Purpose of the invention: In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a surface-modified ultra-high molecular weight polyethylene fiber, a preparation method thereof, and an application in ultra-high performance concrete. The surface-modified UHMWPE fiber prepared by the present invention has strong hydrophilicity and good compatibility with cement-based materials, and can be used to prepare UHPC materials with excellent mechanical properties.

[0006] Technical solution: In order to achieve the above-mentioned purpose of the invention, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a surface-modified ultra-high molecular weight polyethylene fiber, comprising the following steps:

[0008] (1) UHMWPE fiber is immersed in alkali solution, and then stirred and reacted under certain temperature conditions. After the reaction is completed, it is washed and dried to obtain UHMWPE fiber after "alkali solution etching". The fiber surface is rich in hydroxyl and carboxyl groups;

[0009] (2) The UHMWPE fiber after "alkali etching" is mixed with deionized water, and calcium salt and silicate are added to obtain a mixed solution, which is then stirred and reacted under certain temperature conditions. After the reaction is completed, it is rinsed and dried to obtain the surface-modified ultra-high molecular weight polyethylene fiber, that is, the UHMWPE fiber after "seed attachment", with a large number of calcium silicate seed particles attached to the surface.

[0010] In the above preparation method:

[0011] In the first step, the fiber surface modification method of "alkaline solution etching" is adopted. By controlling the influencing factors such as the type of alkali solution, reaction temperature and dissolution time, the alkali solution dissolution sites are shaped on the surface of the UHMWPE fiber, reducing the carbonyl groups on the fiber surface while introducing polar groups such as hydroxyl and carboxyl groups. By improving the surface roughness and polar sites of the fiber, the compatibility and adhesion of the fiber in UHPC are improved.

[0012] In the second step, the fiber surface treatment process of "seed attachment" is adopted. Calcium silicate seed particles are evenly attached to the fiber surface through the sol-gel method, further increasing the reaction sites on the fiber surface. The hydration of the seed crystals on the fiber surface is used to complex the cement matrix interface in UHPC, promote mechanical interlocking and chemical bonding between the interfaces, and improve the interfacial bonding performance of the fiber.

[0013] As a specific implementation scheme, in step (1), the UHMWPE fiber has a length of 3-12 mm and an aspect ratio of 200-450; the alkali in the alkali solution is selected from NaOH or KOH; and the concentration of the alkali solution is 6-10 mol / L.

[0014] As a specific implementation scheme, in step (1), the stirring reaction temperature is 20-45°C and the time is 2-10 minutes; the cleaning is ultrasonic cleaning using ethanol; and the drying is carried out at 40-50°C for 30-60 minutes.

[0015] As a specific embodiment, in step (2), the calcium salt is selected from CaCl2 or Ca(NO3)2; the silicate is selected from Na2SiO3 or K2SiO3; the Ca in the mixed solution is selected from 2+ and SiO3 2- The molar ratio of the ions is in the range of 1:1 to 1:2.

[0016] As a specific implementation scheme, in step (2), the UHMWPE fiber after "alkali solution etching" is mixed with deionized water according to a solid-liquid mass ratio of 1:1500~1:2000; the calcium salt and silicate are added in the form of solution, first adding the calcium salt solution, and then gradually adding the silicate solution dropwise, the concentration of the calcium salt solution is 0.5-1.2 mol / L, and the concentration of the silicate solution is 0.5-1.2 mol / L; in the mixed solution, Ca 2+ The concentration of ions is 0.08-0.24 mol / L, SiO3 2- The concentration of ions is 0.08-0.24 mol / L.

[0017] As a specific implementation scheme, in step (2), the stirring reaction temperature is 30-60°C, the time is 2-6 h, and the rotation speed is 40-75 r / min; the rinsing is ethanol rinsing; and the drying is carried out at 30-45°C for 30-60 min.

[0018] In a second aspect, the present invention provides a surface-modified ultra-high molecular weight polyethylene fiber, which is prepared by the above-mentioned preparation method.

[0019] In a third aspect, the present invention provides an application of the surface-modified ultra-high molecular weight polyethylene fiber in the preparation of ultra-high performance concrete.

[0020] In a fourth aspect, the present invention provides an ultra-high performance concrete, which is mainly made of the above-mentioned surface-modified ultra-high molecular weight polyethylene fiber.

[0021] As a specific embodiment, the ultra-high performance coagulation comprises the following components:

[0022] PO425 cement 1000-1200 kg / m 3 ;

[0023] Silica fume 140-170 kg / m 3 ;

[0024] Quartz sand 1100-1250 kg / m 3 ;

[0025] The surface-modified ultra-high molecular weight polyethylene fiber of claim 7 25-45 kg / m 3 ;

[0026] Polycarboxylic acid high efficiency solid water reducer 8-15 kg / m 3 ;

[0027] Water 190-250 kg / m 3 .

[0028] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0029] 1. The UHMWPE fibers modified by the combined “alkaline etching-seed attachment” process have strong hydrophilicity and good compatibility with cement-based materials. They are easy to disperse during the co-mixing process with the UHPC slurry. Increasing the dosage does not significantly reduce the fluidity of the UHPC slurry, thereby ensuring the volume dosage of the fiber in the UHPC and the workability and pumpability of the fiber-reinforced UHPC.

[0030] 2. The surface of the UHMWPE fiber modified by the combined "alkaline etching-seed attachment" process is rich in reactive sites. Especially in cement-based materials, the hydration of the calcium silicate seeds attached to the surface can complex the cement substrate interface in UHPC, promote mechanical interlocking and chemical bonding between the interfaces, enhance the interfacial bonding performance of the fibers, and give full play to the high strength and high elastic modulus characteristics of UHMWPE fibers. Even if all steel fibers are replaced, UHPC materials with excellent mechanical properties can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the flow chart of the surface modification technology of UHMWPE fiber (cross section);

[0032] Figure 2 The micromorphology of UHMWPE fibers in UHPC matrix before and after modification, where (a) is the fiber before modification and (b) is the fiber after modification. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0034] Example 1

[0035] 1. Select a 12 mm long UHMWPE fiber with an aspect ratio of 450 and immerse it in a 10 mol / L NaOH or KOH solution at 45°C with stirring for 10 minutes. After the reaction, ultrasonically clean it with ethanol and dry it at 50°C for 60 minutes to obtain an alkaline-etched UHMWPE fiber with a rich surface area of ​​hydroxyl and carboxyl groups.

[0036] 2. Mix the fiber after "alkali etching" with deionized water at a solid-liquid mass ratio of 1:1500, add 1.2 mol / L CaCl2 solution, and then gradually add 1.2 mol / L Na2SiO3 solution to obtain a mixed solution to ensure that Ca 2+ and SiO3 2- The molar ratio of ions is 1:1. In the mixed solution, Ca 2+ The concentration of ions is 0.24 mol / L, SiO3 2- The ion concentration was 0.24 mol / L. The reaction was stirred continuously at 60°C and 75 r / min for 6 hours. After the reaction, the fibers were rinsed with ethanol and dried at 45°C for 60 minutes to obtain UHMWPE fibers with a large number of calcium silicate seed particles attached to their surfaces.

[0037] 3. According to PO425 cement 1000-1200 kg / m 3 , silica fume 160 kg / m 3 , 20-40 mesh quartz sand 1250 kg / m 3 , modified UHMWPE fiber 45 kg / m 3 , polycarboxylic acid high efficiency solid water reducing agent 12 kg / m 3 , water 250 kg / m 3 By mixing the mixture in the right proportion, a UHPC material with a slump expansion of 850 mm, a compressive strength of 140 MPa after 28 days of curing at room temperature, and a flexural strength of 25 MPa can be obtained.

[0038] Example 2

[0039] 1. Select 8 mm long UHMWPE fibers with an aspect ratio of 300 and immerse them in 8 mol / L NaOH or KOH solution at 30°C with stirring for 5 minutes. After the reaction, ultrasonically clean the fibers with ethanol and dry them at 40°C for 30 minutes to obtain alkaline-etched UHMWPE fibers with a rich surface area of ​​hydroxyl and carboxyl groups.

[0040] 2. Mix the fiber after "alkali etching" with deionized water at a solid-liquid mass ratio of 1:2000, add 1.0 mol / L CaCl2 solution, and then gradually add 1.0 mol / L Na2SiO3 solution to obtain a mixed solution to ensure that Ca 2+ and SiO3 2- The molar ratio of ions is 1:1. In the mixed solution, Ca 2+ The concentration of ions is 0.08 mol / L, SiO3 2- The ion concentration was 0.08 mol / L, and the reaction was stirred continuously at 50°C and 60 r / min for 3 hours. After the reaction, the fibers were rinsed with ethanol and dried at 40°C for 30 minutes to obtain UHMWPE fibers with a large number of calcium silicate seed particles attached to the surface.

[0041] 3. According to PO425 cement 1050 kg / m 3 , silica fume 160 kg / m 3 , 40-70 mesh quartz sand 1250 kg / m 3 , modified UHMWPE fiber 30 kg / m 3 , polycarboxylic acid high efficiency solid water reducing agent 12 kg / m 3 , water, 210 kg / m 3 By mixing the mixture in the right proportion, a UHPC material with a slump expansion of 950 mm, a compressive strength of 150 MPa after 28 days of curing at room temperature, and a flexural strength of 35 MPa can be obtained.

[0042] Example 3

[0043] 1. Select a 3 mm long UHMWPE fiber with an aspect ratio of 200 and immerse it in a 6 mol / L KOH solution at 20°C with stirring for 2 minutes. After the reaction, ultrasonically clean the fiber with ethanol and dry it at 50°C for 60 minutes to obtain an alkaline-etched UHMWPE fiber with a rich surface area of ​​hydroxyl and carboxyl groups.

[0044] 2. Mix the fiber after "alkali etching" with deionized water at a solid-liquid mass ratio of 1:1800, add 0.5 mol / L Ca(NO3)2 solution, and then gradually add 0.5 mol / L K2SiO3 solution to obtain a mixed solution to ensure that Ca 2+ and SiO3 2- The molar ratio of ions is 1:2. In the mixed solution, Ca 2+ The concentration of ions is 0.10 mol / L, SiO3 2- The ion concentration was 0.20 mol / L, and the reaction was stirred continuously at 60°C and 75 r / min for 6 hours. After the reaction, the fibers were rinsed with ethanol and dried at 45°C for 60 minutes to obtain UHMWPE fibers with a large number of calcium silicate seed particles attached to the surface.

[0045] 3. According to PO425 cement 1200 kg / m 3 , silica fume 170 kg / m 3 , 40-70 mesh quartz sand 1100 kg / m 3 , modified UHMWPE fiber 25 kg / m 3 , polycarboxylic acid high efficiency solid water reducing agent 15 kg / m 3 , water 200 kg / m 3 By mixing the mixture in the right proportion, a UHPC material with a slump expansion of 950 mm, a compressive strength of 135 MPa after 28 days of curing at room temperature, and a flexural strength of 25 MPa can be obtained.

[0046] Comparative Example 1

[0047] The method is basically the same as Example 1, except that unsurface-modified UHMWPE fibers are used, and finally a UHPC material with a slump expansion of 800 mm, a compressive strength of 105 MPa after 28 days of room temperature curing, and a flexural strength of 13 MPa is obtained.

[0048] Comparative Example 2

[0049] The method is basically the same as Example 1, except that the UHMWPE fiber is only subjected to the alkali solution etching modification in step 1, and the "seed attachment" modification in step 2 is not performed. Finally, a UHPC material with a slump expansion of 950 mm, a compressive strength of 110 MPa after 28 days of room temperature curing, and a flexural strength of 15 MPa is obtained.

[0050] Comparative Example 3

[0051] The method is basically the same as Example 1, except that the UHMWPE fiber is only subjected to the "seed attachment" modification in step 2, and the alkali solution etching modification in step 1 is not performed. Finally, a UHPC material with a slump expansion of 800 mm, a compressive strength of 125 MPa after 28 days of room temperature curing, and a flexural strength of 16 MPa is obtained.

[0052] The above describes the implementation of the present invention in detail with reference to specific embodiments. However, the present invention is not limited to the above implementation. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A method for preparing surface-modified ultra-high molecular weight polyethylene fiber, characterized in that: The following steps are involved: (1) Soaking the UHMWPE fiber in alkali solution, then stirring and reacting it under certain temperature conditions, washing and drying it after the reaction is completed to obtain the UHMWPE fiber after "alkali solution etching"; (2) The UHMWPE fiber after "alkali solution etching" is mixed with deionized water, and calcium salt and silicate are added to obtain a mixed solution, which is then stirred and reacted under certain temperature conditions. After the reaction is completed, the fiber is rinsed and dried to obtain the surface-modified ultra-high molecular weight polyethylene fiber.

2. The method for preparing surface-modified ultra-high molecular weight polyethylene fiber according to claim 1, wherein: In step (1), the UHMWPE fiber has a length of 3-12 mm and an aspect ratio of 200-450; the alkali in the alkali solution is selected from NaOH or KOH; and the concentration of the alkali solution is 6-10 mol / L.

3. The method for preparing surface-modified ultra-high molecular weight polyethylene fiber according to claim 1, wherein: In step (1), the stirring reaction temperature is 20-45°C and the time is 2-10 min; the cleaning is performed by ultrasonic cleaning with ethanol; The drying step is to dry the mixture at 40-50° C. for 30-60 min.

4. The method for preparing surface-modified ultra-high molecular weight polyethylene fiber according to claim 1, wherein: In step (2), the calcium salt is selected from CaCl2 or Ca(NO3)2; the silicate is selected from Na2SiO3 or K2SiO3; the Ca 2+ and SiO3 2- The molar ratio of the ions is in the range of 1:1 to 1:

2.

5. The method for preparing surface-modified ultra-high molecular weight polyethylene fiber according to claim 1, wherein: In step (2), the UHMWPE fiber after "alkali etching" is mixed with deionized water according to a solid-liquid mass ratio of 1:1500~1:2000; the calcium salt and silicate are added in the form of solution, first adding the calcium salt solution, and then gradually adding the silicate solution dropwise, the concentration of the calcium salt solution is 0.5-1.2 mol / L, and the concentration of the silicate solution is 0.5-1.2 mol / L; in the mixed solution, Ca 2+ The concentration of ions is 0.08-0.24 mol / L, SiO3 2- The concentration of ions is 0.08-0.24 mol / L.

6. The method for preparing surface-modified ultra-high molecular weight polyethylene fiber according to claim 1, wherein: In step (2), the stirring reaction temperature is 30-60°C, the time is 2-6 h, and the rotation speed is 40-75 r / min; the rinsing is performed by ethanol; and the drying is performed at 30-45°C for 30-60 min.

7. A surface-modified ultra-high molecular weight polyethylene fiber, characterized in that: The surface-modified ultra-high molecular weight polyethylene fiber is prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the surface-modified ultra-high molecular weight polyethylene fiber according to claim 7 in the preparation of ultra-high performance concrete.

9. An ultra-high performance concrete, characterized in that: The ultra-high performance concrete is mainly made of the surface-modified ultra-high molecular weight polyethylene fiber described in claim 7.

10. The ultra-high performance concrete according to claim 9, characterized in that The ultra-high performance coagulation comprises the following components: PO425 cement 1000-1200 kg / m 3 ; Silica fume 140-170 kg / m 3 ; Quartz sand 1100-1250 kg / m 3 ; Surface modified ultra-high molecular weight polyethylene fiber 25-45 kg / m 3 ; Polycarboxylic acid high efficiency solid water reducer 8-15 kg / m 3 ; Water 190-250 kg / m 3 .

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