Cellulose-based polymer reinforcing additive, method for preparing same, and use thereof

Abstract

The application discloses a cellulose-based geopolymer reinforcing additive and a preparation method and application thereof, and relates to the field of building materials, which comprises nanocellulose and layered double hydroxide grown in situ on the nanocellulose. The cellulose-based geopolymer reinforcing additive loads the layered double hydroxide on the nanocellulose in the form of in-situ growth to form a cellulose-layered double hydroxide nanocomposite, on the one hand, the agglomeration of the layered double hydroxide is inhibited by loading the layered double hydroxide on the nanocellulose, and on the other hand, the compatibility of the nanocellulose and the geopolymer matrix is optimized. It is accidentally found that the layered double hydroxide in the cellulose-based geopolymer reinforcing additive has excellent epitaxial growth characteristics compared with the layered double hydroxide existing alone, and when applied to a geopolymer gel material, the compressive strength, the bending strength and the elastic modulus of the geopolymer gel material are improved.

Description

Technical Field

[0001] This invention relates to the field of building materials, and in particular to a cellulose-based polymer reinforcing additive, its preparation method, and its application. Background Technology

[0002] Geopolymers are a new type of low-carbon cementitious material produced by the reaction of alkali-activated aluminosilicate raw materials (such as fly ash, slag, metakaolin, etc.). Due to their low energy consumption during preparation, low carbon dioxide emissions, high mechanical strength, and excellent high-temperature and corrosion resistance, they are considered a potential alternative to ordinary silicate cement (OPC) and have broad application prospects in the field of green building materials.

[0003] Because the reaction products of geopolymers are mainly amorphous (semi-)crystalline NASH or CASH gels, these gel phases have low intrinsic elastic moduli (18~25 GPa), making geopolymers prone to excessive deformation under load. Macroscopically, the elastic modulus of geopolymers is generally 20%~30% lower than that of ordinary silicate cement. This performance limitation restricts the application of geopolymers in tall or long-span structural engineering. Currently, geopolymer reinforcement methods include adding high intrinsic modulus micro / nano fillers as reinforcing phases to directly increase the elastic modulus of the geopolymer, and adding polymer resins to construct a three-dimensional network as a reinforcing skeleton to improve the toughness and compressive and flexural strength of the geopolymer.

[0004] However, the addition of micro and nano fillers has the problem of easy agglomeration leading to uneven dispersion. Furthermore, the poor compatibility between polymer resins, as organic materials, and geopolymer matrices, which are mainly aluminosilicate gels, makes it easy for microcracks to be induced at stress concentration points in the agglomerated micro and nano fillers, or for stress to be difficult to be effectively transferred at weak points in the interface between the reinforcing skeleton and the matrix. This results in the expansion and aggravation of microcracks in the geopolymer under load, or the failure of the reinforcing phase before the matrix, leading to structural failure. Summary of the Invention

[0005] In view of the shortcomings of the above-mentioned related technologies, the present invention provides a cellulose-based polymer reinforcing additive, its preparation method and application.

[0006] In a first aspect, the cellulose-based polymer reinforcing additive provided by the present invention adopts the following technical solution:

[0007] A cellulose-based polymer reinforcing additive comprising nanocellulose and a layered double hydroxide grown in situ on the nanocellulose.

[0008] Preferably, the in-situ growth is carried out by one or more of the following methods: hydrothermal method, ambient temperature co-precipitation method, urea hydrolysis hydrothermal method, and ion exchange method.

[0009] Preferably, the weight ratio of the nanocellulose to the layered double hydroxide is 10:2~4.

[0010] Preferably, the weight ratio of the nanocellulose to the layered double hydroxide is 10:2.8.

[0011] Preferably, the nanocellulose includes one or more of cellulose nanocrystals, oxidized modified cellulose nanocrystals, cellulose nanofibers, and oxidized modified cellulose nanofibers.

[0012] Preferably, the general chemical formula of the layered double hydroxide is: [A 2+ (1-x) B 3+ x (OH)2] x+ [C n- ] x / n ·mH2O, wherein: A includes one or more of magnesium, zinc, calcium, and nickel; B includes one or more of aluminum, iron, and chromium; C n- It includes one or more of carbonate ions, chloride ions and nitrate ions, with x ranging from 0.2 to 0.33 and m ranging from 0.2 to 0.7.

[0013] Preferably, A is magnesium, B is aluminum, and C is aluminum. n- It is a carbonate ion.

[0014] Secondly, the preparation method of the cellulose-based polymer reinforcing additive provided by the present invention adopts the following technical solution:

[0015] A method for preparing a cellulose-based polymer reinforcing additive includes the following steps:

[0016] Preparation of cellulose nanofiber suspension: cellulose nanofibers were mixed with deionized water and homogenized.

[0017] Preparation of layered double hydroxide precursor solution: Dissolve divalent and trivalent metal salts in deionized water;

[0018] In-situ growth of layered double hydroxides: A layered double hydroxide precursor solution and an alkaline solution were simultaneously added dropwise to a cellulose nanofiber suspension. During the addition, the pH of the system was controlled at 10.00±0.05, the system temperature at 15~25 ℃, and the stirring speed at 1000~2000 rpm. After the addition was completed, the system was aged at 65~75 ℃ for 4~6 h. The filter cake was obtained by vacuum filtration, and the filter cake was washed and dried to obtain the cellulose macropolymer reinforcing additive.

[0019] Preferably, the molar ratio of divalent metal ions to trivalent metal ions in the layered double hydroxide precursor solution is 2~4:1.

[0020] Preferably, the molar ratio of divalent metal ions to trivalent metal ions in the layered double hydroxide precursor solution is 3:1.

[0021] Preferably, the concentration of cellulose nanofibers in the cellulose nanofiber suspension is 0.45 wt.%~0.55 wt.%; and the molar concentration of divalent metal ions in the layered double hydroxide precursor solution is 0.08~0.1 mol / L.

[0022] Preferably, the solute in the alkaline solution comprises sodium hydroxide and sodium carbonate in a weight ratio of 10:5~7, wherein the concentration of sodium hydroxide is 45-55 g / L.

[0023] Thirdly, the present invention provides the application of a cellulose-based polymer reinforcing additive in the preparation of geopolymer gel materials.

[0024] The application of a cellulose-based polymer reinforcing additive in the preparation of geopolymer gel materials, wherein the geopolymer gel materials comprise 0.1 wt.% to 0.5 wt.% of the cellulose-based polymer reinforcing additive.

[0025] Preferably, the geopolymer gel material comprises 0.2 wt.% of cellulose-based geopolymer reinforcing additives.

[0026] Preferably, the geopolymer gel material is made of the following components in parts by weight: 0.1 to 0.5 parts of cellulose-based geopolymer reinforcing additive, 80 to 120 parts of aluminosilicate precursor, and 3 to 6 parts of alkaline activator; the water-gel ratio is 0.35 to 0.37.

[0027] Preferably, the aluminosilicate precursor includes one or more of fly ash, blast furnace slag, metakaolin, silica fume, and steel slag.

[0028] In summary, the present invention has at least one of the following beneficial technical effects:

[0029] 1. The cellulose-based macropolymer reinforcing additive of the present invention loads layered double hydroxides onto cellulose nanofibers through in-situ growth. On the one hand, this inhibits the aggregation of layered double hydroxides and improves their uniformity on the cellulose nanofibers; on the other hand, it optimizes the compatibility between the cellulose nanofibers and the macropolymer matrix. Furthermore, it was unexpectedly discovered that the layered double hydroxide seed crystals in the cellulose-based macropolymer reinforcing additive exhibit superior epitaxial growth characteristics compared to isolated layered double hydroxides, serving as both seed crystals and reinforcing phases while facilitating the expansion of the reinforcing phase.

[0030] 2. When the cellulose-based polymer reinforcing additive of the present invention is applied to geopolymer gel materials, on the one hand, the unique aspect ratio of cellulose nanofibers is beneficial for bridging microcracks; on the other hand, in addition to the high intrinsic modulus of the layered double hydroxide itself, which can serve as a reinforcing phase, the layered double hydroxide enhances the compatibility between cellulose nanofibers and the geopolymer gel material matrix. It can also act as a seed crystal in the subsequent hydration process to improve the hydration effect of the geopolymer gel material, thereby achieving the extension and expansion of the reinforcing phase in the matrix. Under the combined effect, the compressive strength, flexural strength and elastic modulus of the geopolymer gel material are improved. Attached Figure Description

[0031] Figure 1 This is a comparison of the X-ray diffraction patterns of cellulose nanofibers, layered double hydroxides, and the cellulose base polymer reinforcing additive of Example 1.

[0032] Figure 2 This is a comparison diagram of the infrared spectra of cellulose nanofibers, layered double hydroxides, and the cellulose macropolymer reinforcing additive of Example 1;

[0033] Figure 3 The thermogravimetric curves of cellulose nanofibers, layered double hydroxides, and the cellulose macropolymer reinforcing additive of Example 1 are compared.

[0034] Figure 4 This is a comparison of differential thermogravimetric curves of cellulose nanofibers, layered double hydroxides, and the cellulose macropolymer reinforcing additive of Example 1.

[0035] Figure 5 This is a scanning electron microscope image of cellulose nanofibers;

[0036] Figure 6 This is a scanning electron microscope image of layered double hydroxides;

[0037] Figure 7 This is a scanning electron microscope image of the cellulose base polymer reinforcing additive from Example 1;

[0038] Figure 8These are the results of energy dispersive spectroscopy analysis of layered double hydroxides;

[0039] Figure 9 The results are from the energy dispersive spectroscopy analysis of the cellulose-based polymer reinforcing additive in Example 1.

[0040] Figure 10 This is a transmission electron microscope image of cellulose nanofibers;

[0041] Figure 11 This is a transmission electron microscope image of layered double hydroxides;

[0042] Figure 12 This is a transmission electron microscope image of the cellulose base polymer reinforcing additive from Example 1;

[0043] Figure 13 This is a comparison of the X-ray diffraction patterns of CNF@LDH-0d, CNF@LDH-1d, and CNF@LDH-3d cellulose base polymer reinforcing additive samples.

[0044] Figure 14 This is a comparison of the infrared spectra of CNF@LDH-0d, CNF@LDH-1d, and CNF@LDH-3d cellulose base polymer reinforcing additive samples.

[0045] Figure 15 This is a comparison of the thermogravimetric curves of CNF@LDH-0d, CNF@LDH-1d, and CNF@LDH-3d cellulose base polymer reinforcing additive samples;

[0046] Figure 16 This is a comparison of the differential thermogravimetric curves of CNF@LDH-0d, CNF@LDH-1d, and CNF@LDH-3d cellulose base polymer reinforcing additive samples.

[0047] Figure 17 This is a high-resolution transmission electron microscope image of a CNF@LDH-0d cellulose base polymer reinforcing additive sample.

[0048] Figure 18 This is a high-resolution transmission electron microscope image of a CNF@LDH-3d cellulose base polymer reinforcing additive sample.

[0049] Figure 19 These are the energy dispersive spectroscopy (EDS) results of CNF@LDH-0d cellulose-based polymer-reinforced additive samples.

[0050] Figure 20 These are the energy dispersive spectroscopy (EDS) results of CNF@LDH-3d cellulose-based polymer-reinforced additive samples.

[0051] Figure 21This is a scanning electron microscope image of a layered double hydroxide sample of LDH-3d;

[0052] Figure 22 This is a comparison of the X-ray diffraction patterns of LDH-0d and LDH-3d layered double hydroxide samples;

[0053] Figure 23 This is a comparison of the heat flow-time curves during the hydration process of the geopolymer gel materials in Application Example 2 and Comparative Examples 1-4;

[0054] Figure 24 This is a comparison chart of the cumulative heat-time curves during the hydration process of the geopolymer gel materials in Application Example 2 and Comparative Examples 1-4;

[0055] Figure 25 The thermogravimetric curves of the geopolymer gel materials in Application Example 2 and Comparative Examples 1-4 are shown in comparison.

[0056] Figure 26 The differential thermogravimetric curves of the geopolymer gel materials in Application Example 2 and Comparative Examples 1-4 are shown in comparison.

[0057] Figure 27 This is a comparison diagram of the X-ray diffraction patterns of the geopolymer gel materials in Application Example 2 and Comparative Examples 1-4;

[0058] Figure 28 This is a comparison of the infrared spectra of the geopolymer gel materials in Application Example 2 and Comparative Examples 1-4;

[0059] Figure 29 This is a scanning electron microscope image of the geopolymer gel material in Comparative Example 1;

[0060] Figure 30 This is a scanning electron microscope image of the geopolymer gel material of Comparative Example 4 with a scale bar of 10 μm;

[0061] Figure 31 This is a scanning electron microscope image of the geopolymer gel material of Comparative Example 4 with a scale bar of 2 μm;

[0062] Figure 32 This is a scanning electron microscope image of the geopolymer gel material in Application Example 2 with a scale bar of 10 μm;

[0063] Figure 33 This is a scanning electron microscope image of the geopolymer gel material in Application Example 2 with a scale bar of 2 μm;

[0064] Figure 34 The diagram shows a comparison of the compressive strength of the geopolymer cementitious materials used in Examples 1-3 and Comparative Examples 1-4.

[0065] Figure 35The graphs show a comparison of the flexural strength of the geopolymer cementitious materials used in Examples 1-3 and Comparative Examples 1-4. Detailed Implementation

[0066] The present invention will be further described in detail below with reference to the embodiments. The following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the following embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the methods used are conventional methods known in the art, and the consumables and reagents used are commercially available. Unless otherwise stated, the technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be applied to the present invention. The raw materials used in the embodiments and comparative examples are all commercially available.

[0067] Example 1

[0068] Example 1 of the present invention provides a cellulose-based polymer reinforcing additive, which is prepared by the following steps:

[0069] Preparation of cellulose nanofiber suspension: 16.67 g of cellulose nanofiber (CNF) hydrogel (purchased from SappiNetherlands Services BV, catalog number BH-22-1077-05, solid content 3 wt.%) was homogenized with 83.33 g of deionized water to obtain 100 g of uniformly dispersed cellulose nanofiber suspension (CNF dry weight 0.5 g). The cellulose nanofiber suspension was then transferred to a three-necked flask equipped with a stirrer, temperature control device, and pH monitoring device.

[0070] Preparation of layered double hydroxide precursor solution: 5.13 g of magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) and 2.25 g of aluminum nitrate nonahydrate (Al(NO3)3·9H2O) were dissolved in 200 mL of deionized water to obtain a solution containing Mg... 2+ The concentration was 0.09 mol / L and Al 3+ A layered double hydroxide precursor solution with a concentration of 0.03 mol / L;

[0071] Preparation of alkaline solution: Dissolve 10.00 g of sodium hydroxide (NaOH) and 6.36 g of sodium carbonate (Na2CO3) in 200 mL of deionized water to obtain an alkaline solution.

[0072] In-situ growth of layered double hydroxides (LDH): A peristaltic pump was used to simultaneously add a LDH precursor solution and an alkaline solution to a cellulose nanofiber suspension. During the addition, the mixture was stirred at 1500 rpm, and the system temperature was controlled at 20℃. The initial drop rate of the LDH precursor solution was 2.5 mL / min, and the initial drop rate of the alkaline solution was 0.5 mL / min. The pH of the system was controlled to 10.00±0.05 by controlling the drop rate of the alkaline solution, so that the LDH could be uniformly nucleated and grown on the surface of the cellulose nanofibers. After the addition was completed, the system temperature was controlled at 70℃, and the mixture was aged for 5 hours to allow the LDH to form seed crystals on the surface of the cellulose nanofibers. After the reaction was completed, the system was vacuum filtered, and the filter cake was repeatedly washed with deionized water and anhydrous ethanol until nitrate ions were removed. Finally, the washed filter cake was dried in an oven at 60℃ for 4 hours to obtain a cellulose macropolymer reinforcing additive.

[0073] Example 2

[0074] Example 2 of this invention provides a cellulose-based polymer reinforcing additive. The difference between Example 2 and Example 1 is that the concentration of cellulose nanofibers in the cellulose nanofiber suspension of Example 2 is 0.45 wt.%; the concentration of Mg in the layered double hydroxide precursor solution is... 2+ Concentration of 0.1 mol / L, Al 3+ The concentration is 0.033 mol / L.

[0075] Example 3

[0076] Example 3 of this invention provides a cellulose-based polymer reinforcing additive. The difference between Example 3 and Example 1 is that the concentration of cellulose nanofibers in the cellulose nanofiber suspension of Example 3 is 0.55 wt.%; the concentration of Mg in the layered double hydroxide precursor solution is... 2+ Concentration of 0.08 mol / L, Al 3+ The concentration is 0.027 mol / L.

[0077] Application Example 1

[0078] Application Example 1 of this invention provides a geopolymer cementitious material, which is prepared by the following method:

[0079] 50 parts by weight of blast furnace slag and 50 parts by weight of fly ash were dry-mixed as an aluminosilicate precursor. 0.1 parts by weight of the cellulose-based geopolymer reinforcing additive from Example 1 were pre-dispersed in a portion of the mixing water. 4 parts by weight of alkali activator (Na2O, modulus 2.0) were mixed with a portion of the mixing water to prepare an alkali activator solution. The above materials were then mixed together and added to a mixer, controlling the water-cement ratio at 0.36. The mixture was slowly stirred for 1 minute and then rapidly stirred for 3 minutes. The freshly mixed slurry was poured into a mold and vibrated for 20 seconds to obtain a sample. The sample was cured in an environmental chamber at 20 °C and relative humidity (RH) ≥ 95% for 24 hours, and then cured for an additional 28 days in the same environmental chamber to obtain the geopolymer cementitious material.

[0080] Application Example 2

[0081] Application Example 2 of the present invention provides a geopolymer cementitious material. The difference between Application Example 2 and Application Example 1 is that the amount of cellulose geopolymer reinforcing additive used in Example 1 during the preparation process of Application Example 2 is 0.2 parts by weight.

[0082] Application Example 3

[0083] Application Example 3 of the present invention provides a geopolymer cementitious material. The difference between Application Example 3 and Application Example 1 is that the amount of cellulose geopolymer reinforcing additive used in Example 1 during the preparation process of Application Example 3 is 0.5 parts by weight.

[0084] Comparative Example 1

[0085] Comparative Example 1 of the present invention provides a geopolymer cementitious material. The difference between Comparative Example 1 and Application Example 1 is that Comparative Example 1 does not add the cellulose-based geopolymer reinforcing additive of Example 1 during the preparation process.

[0086] Comparative Example 2

[0087] Comparative Example 2 of the present invention provides a geopolymer cementitious material. The difference between Comparative Example 2 and Application Example 1 is that an equal amount of cellulose nanofibers are used to replace the cellulose geopolymer reinforcing additive in Example 1 during the preparation process of Comparative Example 2. The cellulose nanofibers are obtained by drying cellulose nanofiber hydrogel.

[0088] Comparative Example 3

[0089] Comparative Example 3 of this invention provides a geopolymer cementitious material. The difference between Comparative Example 3 and Application Example 1 is that in the preparation process of Comparative Example 3, 2 parts by weight of layered double hydroxides are used to replace 0.2 parts by weight of the cellulose-based geopolymer reinforcing additive in Example 1. The preparation steps of the layered double hydroxides are as follows: a peristaltic pump is used to simultaneously add the layered double hydroxide precursor solution and the alkaline solution from the preparation process of Example 1. During the addition, the mixture is stirred at 1500 rpm, the system temperature is controlled at 20 °C, the dropping rate of the layered double hydroxide precursor solution is 2.5 mL / min, and the initial dropping rate of the alkaline solution is 0.5 mL / min. The pH of the system is controlled to be 10.00 ± 0.05 by controlling the dropping rate of the alkaline solution, so that the layered double hydroxides can nucleate and grow uniformly. After the addition is complete, the system temperature is controlled at 70 °C. The mixture was aged at ℃ for 5 hours. After the reaction was completed, the system was vacuum filtered, and the filter cake was taken. It was repeatedly washed with deionized water and anhydrous ethanol until nitrate ions were removed. Finally, the washed filter cake was dried in an oven at 60 ℃ for 4 hours and then thoroughly ground to obtain layered double hydroxide.

[0090] Comparative Example 4

[0091] Comparative Example 4 of the present invention provides a geopolymer cementitious material. The difference between Comparative Example 4 and Application Example 1 is that 0.144 parts by weight of cellulose nanofibers and 0.056 parts by weight of layered double hydroxides are used to replace the cellulose-based geopolymer reinforcing additives in Example 1 during the preparation process of Comparative Example 4.

[0092] Testing and Inspection

[0093] (1) X-ray diffraction was performed on cellulose nanofibers (CNF), layered double hydroxides (LDH), and the cellulose matrix polymer reinforcing additive (CNF@LDH) of Example 1. The comparison of the X-ray diffraction patterns is shown in the figure below. Figure 1 As shown; infrared spectroscopy tests were performed, and the comparison of the infrared spectra obtained is shown in the figure below. Figure 2 As shown; thermal analysis was performed, and the thermogravimetric curves were compared as follows. Figure 3 As shown in the figure, the differential thermogravimetric curves are compared as follows. Figure 4 The scanning electron microscope (SEM) images of cellulose nanofibers, layered double hydroxides, and the cellulose matrix polymer reinforcing additive from Example 1 are shown below. Figures 5-7 As shown, the elemental composition and content of the layered double hydroxides were analyzed using energy dispersive spectroscopy (EDS), and the results are as follows: Figure 8 As shown, the elemental types and contents of the cellulose-based polymer reinforcing additive in Example 1 were analyzed using energy dispersive spectroscopy (EDS), and the results are as follows: Figure 9 The transmission electron microscopy (TEM) images of cellulose nanofibers, layered double hydroxides, and the cellulose-based polymer reinforcing additive from Example 1 are shown below. Figures 10-12 As shown.

[0094] (2) The cellulose-based polymer reinforcing additive from Example 1 was subjected to an alkaline-activated simulated pore solution immersion experiment to simulate the stability and epitaxial growth capability of the cellulose-based polymer reinforcing additive in the alkaline environment of the geopolymer gel material. The alkaline-activated simulated pore solution immersion experiment steps are as follows: 100 g of blast furnace slag (GBFS) powder was accurately weighed and mixed with 54 g of a 9.55 wt.% sodium hydroxide solution (4% equivalent Na2O), and the mixture was mechanically stirred and homogenized at 1500 rpm for 5 minutes to obtain a slurry. Subsequently, the slurry was placed on a shaker and continuously shaken for 12 hours to accelerate the dissolution of the slag powder and the formation of hydration products. After the reaction, the slurry was filtered, and the resulting supernatant was centrifuged at 20000 ×g for 45 minutes, then filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane to completely remove colloidal particles, finally obtaining a clear alkali-activated simulated pore solution. 0.1 g of the cellulose-based polymer reinforcing additive (CNF@LDH-0d) from Example 1 was placed in 50 mL of the alkali-activated simulated pore solution and stirred at 300 rpm for 1 day at a constant temperature of 20°C. The mixture was then removed, washed with deionized water, and dried to obtain sample (CNF@LDH-1d). After stirring for 3 days, the mixture was removed, washed with deionized water, and dried to obtain sample (CNF@LDH-3d). 0.1 g of the layered double hydroxide (LDH-0d) from Comparative Example 3 was placed in 50 mL of the alkali-activated simulated pore solution and stirred at 300 rpm for 1 day at a constant temperature of 20°C. After stirring at low speed for 3 days at rpm, the sample was taken out, washed with deionized water and dried to obtain the sample (LDH-3d) as a control.

[0095] X-ray diffraction was performed on cellulose matrix polymer reinforcing additive samples of CNF@LDH-0d, CNF@LDH-1d, and CNF@LDH-3d, and the comparison of the X-ray diffraction patterns is shown in the figure below. Figure 13 As shown; infrared spectroscopy tests were performed, and the comparison of the infrared spectra obtained is shown in the figure below. Figure 14 As shown; thermal analysis was performed, and the thermogravimetric curves were compared as follows. Figure 15 As shown in the figure, the differential thermogravimetric curves are compared as follows. Figure 16 As shown; high-resolution transmission electron microscopy images of CNF@LDH-0d and CNF@LDH-3d cellulose base polymer reinforcing additive samples, as shown in the figures below. Figure 17 and Figure 18 As shown, and combined with energy dispersive spectroscopy analysis of element types and contents, as follows: Figure 19 and Figure 20 As shown; the weight of the LDH-3d layered double hydroxide sample was 0.1023 g, and the scanning electron microscope image is shown below. Figure 21As shown; X-ray diffraction was performed on layered double hydroxide samples of LDH-0d and LDH-3d, and the comparison of the X-ray diffraction patterns is shown in the figure. Figure 22 As shown.

[0096] (3) The heat flow and accumulated heat during the hydration process of the geopolymer gel materials in Application Example 2 and Comparative Examples 1-4 were detected by isothermal calorimetry, and heat flow-time curve comparison diagrams were obtained, as shown in the figure. Figure 23 As shown, a comparison graph of cumulative heat-time curves is obtained, as follows. Figure 24 As shown; thermal analysis was performed, and the thermogravimetric curves were compared as follows. Figure 25 As shown, the differential thermogravimetric curves comparison diagram is obtained as follows: Figure 26 As shown; X-ray diffraction was performed, and the comparison diagram of the obtained X-ray diffraction patterns is shown below. Figure 27 As shown; infrared spectroscopy tests were performed, and the comparison of the infrared spectra obtained is shown in the figure below. Figure 28 As shown; Scanning electron microscopy (SEM) images of the geopolymer gel material in Comparative Example 1, the results are as follows. Figure 29 As shown, the scanning electron microscope image of the geopolymer gel material in Comparative Example 4 is as follows. Figure 30 and Figure 31 As shown, the scanning electron microscope image of the geopolymer gel material in Application Example 2 is as follows. Figure 32 and Figure 33 As shown. Figures 23-33 In the examples, the geopolymer gel material of Application Example 2 is labeled CNF@LDH02, the geopolymer gel material of Comparative Example 1 is labeled REF, the geopolymer gel material of Comparative Example 2 is labeled CNF02, the geopolymer gel material of Comparative Example 3 is labeled LDH20, and the geopolymer gel material of Comparative Example 4 is labeled CNF&LDH02.

[0097] (4) The compressive and flexural strengths of the geopolymer cementitious materials used in Examples 1-3 and Comparative Examples 1-4 were tested, and the compressive strength comparison charts are shown below. Figure 34 As shown in the figure, the comparison chart of flexural strength is as follows. Figure 35 As shown, Figure 34 and Figure 35 In this study, the geopolymer gel material of Application Example 1 was labeled CNF@LDH01, the geopolymer gel material of Application Example 2 was labeled CNF@LDH02, the geopolymer gel material of Application Example 1 was labeled CNF@LDH05, the geopolymer gel material of Comparative Example 1 was labeled REF, the geopolymer gel material of Comparative Example 2 was labeled CNF02, the geopolymer gel material of Comparative Example 3 was labeled LDH20, and the geopolymer gel material of Comparative Example 4 was labeled CNF&LDH02. The elastic modulus of the geopolymer gel materials of Application Examples 1-3 and Comparative Examples 1-4 was measured, and the percentage increase in elastic modulus of the geopolymer gel materials of Application Examples 1-3 and Comparative Examples 2-4 compared to the geopolymer gel material of Comparative Example 1 was calculated. The results are shown in Table 1 below.

[0098] Table 1:

[0099]

[0100] Results Analysis

[0101] The present invention will be described in detail below with reference to the experimental results provided in the test and detection section.

[0102] Reference Figure 1 The cellulose nanofibers and cellulose matrix polymer reinforcing additives both exhibit broad diffraction peaks at 14.9° and 22.6°, corresponding to the (110) and (200) crystal planes of cellulose Iβ (PDF#00-056-1718), respectively, which is an inherent structural characteristic of cellulose. The characteristic diffraction peaks of the layered double hydroxides and cellulose matrix polymer reinforcing additives are consistent with those of Mg6Al2(OH). 16 The CO3·4H2O hydrotalcite standard card (PDF#51-1525) is in perfect agreement. Calculations showed that the most representative (003) interplanar spacing values ​​for the layered double hydroxide and the cellulose-based polymer-reinforced additive are 0.774 nm and 0.768 nm, respectively. Compared to the pure layered double hydroxide, the XRD diffraction peak intensity of the cellulose-based polymer-reinforced additive is weakened, indicating a slight decrease in the crystallite size of its layered double hydroxide, but a significant enhancement in its dispersibility within the cellulose-based polymer-reinforced additive.

[0103] Reference Figure 2 The cellulose-based polymer reinforcing additive exhibits an overlap of characteristic bands between cellulose nanofibers and layered double hydroxides in the spectrum. (1352 cm⁻¹) -1 The peak at that location originates from carbonate ions. v The superposition of 3 asymmetric stretching vibration and CH2 bending vibration, and 400~800 cm -1 The region corresponds to the lattice vibration of M–O (M = Mg / Al) in the layered double hydroxide. The C6 primary alcohol C–O stretching vibration peak (originally located at 1018 cm⁻¹ in cellulose nanofibers) is also present. -1 ) 32 cm -1 The redshift indicates that covalent M–O–C bonds have formed between the layered double hydroxide metal ions and the hydroxyl groups of the cellulose nanofibers. Furthermore, at 620 cm⁻¹... -1 A new weak peak appeared, which can be attributed to the Al–O–C vibration. This confirms that chemical bonds are formed between the cellulose nanofibers and the layered double hydroxides in the cellulose base polymer reinforcing additive, rather than a simple physical mixture.

[0104] Reference Figure 3 and Figure 4The total weight loss rates of the cellulose-based polymer reinforcing additive, layered double hydroxide, and cellulose nanofibers at 600 °C were 68.7%, 43.3%, and 78.6%, respectively. Differential thermogravimetric curves showed the superposition of characteristic degradation peaks at 180 °C (dehydration of layered double hydroxide), 350 °C (depolymerization of cellulose nanofibers), and 380 °C (dehydroxylation and carbonate decomposition of layered double hydroxide), confirming successful hybridization and the absence of a new phase formation. The loading fraction of layered double hydroxide in the cellulose-based polymer reinforcing additive was quantitatively calculated using the following formula (…). w LDH ): .in, L CNF@LDH , L LDH and L CNF The values, in order, represent the total weight loss of cellulose macropolymer reinforcing additives, layered double hydroxides, and cellulose nanofibers at 600 °C. The calculated values ​​are... w LDH The value was 28.0%, confirming that the layered double hydroxides in the cellulose-based polymer reinforcing additive effectively adhered to the cellulose nanofibers without altering their inherent degradation pathway, thus verifying the successful synthesis of the cellulose-based polymer reinforcing additive.

[0105] Reference Figure 5 The diameter of cellulose nanofibers is approximately 5–60 nm, and the length is approximately 2–10 μm; (Refer to...) Figure 6 The layered double hydroxides exhibit a typical petal-like lamellar morphology with an average size of approximately 200 nm, but show obvious lamellar stacking and aggregation; (Refer to...) Figure 7 In the cellulose-based polymer reinforcing additive, 200 nm layered double hydroxide nanosheets are uniformly anchored as "leaf" units on the "branch" framework of cellulose nanofibers, forming a spatially ordered composite structure.

[0106] Reference Figure 8 and Figure 9 Energy dispersive spectroscopy analysis showed that the atomic ratio of magnesium to aluminum in the cellulose-based polymer reinforcing additive was approximately 3:1. This ratio is consistent with the atomic ratio of magnesium to aluminum in the layered double hydroxide, verifying the integrity of the layered double hydroxide crystals in the cellulose-based polymer reinforcing additive.

[0107] Reference Figure 10 The surface of cellulose nanofibers is smooth. (Refer to...) Figure 11 The layered double hydroxide particles exhibit a leaf-like morphology and a size of approximately 200 nm, compared to... Figure 6 The observations are consistent. (Refer to...) Figure 12In the cellulose base polymer reinforcing additive, layered double hydroxide leaf-like crystals are attached to the surface of cellulose nanofibers, and the results observed by transmission electron microscopy are consistent with those observed by scanning electron microscopy.

[0108] Reference Figure 13 Characteristic peaks of cellulose nanofibers and layered double hydroxides were present in all samples. The peak intensity of layered double hydroxides increased significantly with the extension of soaking time, but no new phase appeared, indicating that the layered double hydroxide seeds on the cellulose nanofibers continued to grow.

[0109] Reference Figure 14 3660 cm -1 The Mg-OH vibrational peak (originating from the hydroxyl groups exposed on the defective layered double hydroxide crystal plane) appears in CNF@LDH-0d and CNF@LDH-1d, with the latter showing a higher peak intensity due to the increased exposure of Mg-OH groups. This phenomenon is attributed to the partial dissolution of the layered double hydroxide in an alkaline environment (Al). 3+ Preferential dissolution), resulting in undissolved Mg 2+ Magnesium is enriched at crystal plane edges. These magnesium-rich crystals may lower the nucleation energy barrier and provide templates for the formation of new phases, thereby promoting Mg in solution. 2+ / Al 3+ Ions and OH - / CO3 2- Reprecipitation. 3660 cm⁻¹ in CNF@LDH-3d. -1 The disappearance of the peak indicates enhanced lattice integrity and reduced defects. Meanwhile, the 1350–1380 cm⁻¹ peak... -1 CO3 2- of v 3. Enhancement of vibrational peaks (from layered double hydroxides) and 1050 cm⁻¹ -1 The weakening of the CO peak (originating from cellulose nanofibers) further confirms the increased loading of layered double hydroxides. Furthermore, the 400–800 cm⁻¹ peak in CNF@LDH-1d... -1 The shift and superposition of the metal-oxygen vibration peaks in the region indicate that the layered double hydroxides are undergoing a continuous dissolution-recrystallization process. In contrast, the peak intensity of CNF@LDH-3d in this region is significantly enhanced, but no peak shift occurs, which further proves the growth of layered double hydroxide seeds in cellulose nanofibers in the cellulose matrix polymer reinforcing additive.

[0110] Reference Figures 15-20 , Figure 15 and Figure 16 The overall trend of the curve and Figure 3 and Figure 4The consistency of the cellulose-based polymer reinforcing additive indicates that the composition and structure of the cellulose-based polymer reinforcing additive did not change during growth in the alkaline-activated simulated pore solution. Furthermore, the peak intensities at 180 ℃ and 380 ℃ increased with increasing soaking time, while the peak at 350 ℃ significantly decreased. This trend suggests that the proportion of layered double hydroxides in the cellulose-based polymer reinforcing additive continuously increases with increasing soaking time. Figure 17 The clear lattice corresponding to the (015) and (110) crystal planes of the layered double hydroxide seed crystals, with spacings of 0.231 nm and 0.197 nm respectively, confirms that the layered double hydroxides nucleate and form seed crystals on cellulose nanofibers. Figure 18 The results show lattice spacings of 0.153 nm and 0.231 nm, corresponding to the (113) and (015) crystal planes, respectively. This indicates that the layered double hydroxide crystals are maturing, suggesting a reduction in interlayer defects and a more uniform distribution of interlayer anions. From a quantitative perspective, Figure 15-16 The total weight loss rates of CNF@LDH-0d, CNF@LDH-1d, and CNF@LDH-3d cellulose-based polymer reinforcing additive samples at 600 °C were 68.7%, 67.6%, and 60.0%, respectively. The calculated loading rates of layered double hydroxide seeds were 28%, 31.2%, and 52.7%, respectively, further verifying the epitaxial growth of layered double hydroxide seeds in the cellulose-based polymer reinforcing additive, with a growth rate of 88.2% within three days. Figure 19 and Figure 20 The ratio of magnesium to aluminum atoms was approximately 3:1, and the total proportion of both magnesium and aluminum increased after soaking in the alkaline-activated simulated pore solution for three days, consistent with the above analysis and calculation results.

[0111] Reference Figure 21 and Figure 22X-ray diffraction comparison showed that LDH-3d and LDH-0d had the same composition, and the scanning electron microscopy image of LDH-3d also showed the same composition as LDH-0d, both being aggregated plate-like particles. The weighing results showed that the weight of the layered double hydroxide sample of LDH-3d was 0.1023 grams, and the growth rate over three days was only 2.3%, with only a small amount of epitaxial growth. The present invention describes a cellulose-based polymer reinforcing additive prepared by in-situ growth of layered double hydroxides onto cellulose nanofibers to form seed crystals. This method is beneficial for improving the efficiency of epitaxial growth of layered double hydroxides in alkaline-activated simulated pore liquid. The reasons are as follows: First, the cellulose-based polymer reinforcing additive utilizes the high specific surface area and abundant surface functional groups of cellulose nanofibers to effectively disperse the layered double hydroxides and prevent their aggregation. Second, chemical bonding, such as MOC covalent bonds, enhances interfacial bonding, lowers the nucleation energy barrier of the layered double hydroxides, and promotes heterogeneous nucleation. Third, in an alkaline environment, the layered double hydroxide seed crystals attached to the cellulose-based polymer reinforcing additive act as templates to guide the dissolution and recrystallization process, accelerating the epitaxial growth of the layered double hydroxides and thus improving growth efficiency.

[0112] Reference Figure 23 and Figure 24 Compared to Comparative Example 1, Comparative Examples 2 and 3 both enhanced the initial dissolution peak, while shifting the second and third peaks to the left and increasing their intensity. Comparative Example 4 enhanced all three peaks compared to Comparative Example 1. However, Application Example 2 showed superior performance compared to Comparative Examples 2-4, with its third peak exhibiting greater width and height. Over 24 hours, the heat release of Application Example 2 was 14.0 J / g higher than Comparative Example 1 and 4.4 J / g higher than Comparative Example 4. This is attributed to the fact that in Application Example 2, the layered double hydroxides in the cellulose-based polymer reinforcing additive were uniformly dispersed on the cellulose nanofibers, maximizing the specific surface area of ​​the layered double hydroxides and generating far more nucleation sites than the aggregated layered double hydroxides, significantly reducing the energy barrier for hydration nucleation. In contrast, the layered double hydroxides and cellulose nanofibers used in Comparative Example 4, in a physically mixed state, provided limited surface area and nucleation sites.

[0113] Reference Figure 25 and Figure 26 The sample in Example 2 was used Figure 26 An exothermic shoulder peak appeared at 170 °C, which corresponds to the dewatering process of layered double hydroxides. Figure 25 The mass loss between 280 and 400 °C mainly originates from the dehydroxylation reaction between the layers of the layered double hydroxide, which... Figure 26 A distinct exothermic peak is observed at 365 °C. This assumes the chemical formula of the layered double hydroxide is ideally [Mg6Al2(OH)]. 16CO3·4H2O was used to quantitatively analyze the content of layered double hydroxides by attributing the mass loss in the 280-400 °C range entirely to the interlayer dihydroxylation of the layered double hydroxides. In Example 2, compared to Comparative Example 1, the content of layered double hydroxides increased by 4.27 wt%, a much higher increase than in Comparative Examples 2-4. Figure 21 and Figure 22 The displayed results are consistent.

[0114] Reference Figure 27 The characteristic peak at 11.5° corresponds to the (003) crystal plane of the layered double hydroxide. In Comparative Example 3, the addition of layered double hydroxide significantly enhanced the diffraction peak intensity of the layered double hydroxide in the geopolymer gel material compared to Comparative Example 1, acting as a crystal seed. In Comparative Example 2, the effect of adding cellulose nanofibers alone on the characteristic peak of the layered double hydroxide was negligible compared to Comparative Example 1. Furthermore, the diffraction peak intensity of the layered double hydroxide in the geopolymer gel material of Comparative Example 4 was almost identical to that of Comparative Example 3, indicating that adding cellulose nanofibers and layered double hydroxide through physical mixing in Comparative Example 4 had almost no additional gain on increasing the diffraction peak intensity of the crystal seed. In Application Example 2, the diffraction peak intensity of the (003) crystal plane was significantly higher than that of Comparative Examples 1-4. The results show that the cellulose-based geopolymer reinforcing additive added in Application Example 2, which uses the in-situ growth of layered double hydroxide on cellulose nanofibers to form crystal seeds, is beneficial to promoting the formation of layered double hydroxide in the geopolymer gel material.

[0115] Reference Figure 28 3200~3700 cm -1 The broad absorption band within this range is related to the stretching vibrations of OH bonds in hydration products, and its intensity can quantitatively reflect the content of hydration products. (1410 cm⁻¹) -1 The peak at that point belongs to CO3 in layered double hydroxides. 2- of v 3. Asymmetric stretching vibration, 870 cm -1 and 855 cm -1 The double peaks come from CO3 2- Out-of-plane bending vibrations. In Application Example 2, the introduction of cellulose-based polymer reinforcing additives significantly enhanced the 1410 cm⁻¹ structure. -1 870 cm -1 and 855 cm -1 The peak intensity at the point indicates that Application Example 2 has a significant effect on promoting the formation of the layered double hydroxide crystal phase in the geopolymer gel material compared to Comparative Examples 1-4.

[0116] Reference Figure 29 The geopolymer cementitious material in Comparative Example 1 exhibited a dense matrix, but with visible and obvious microcracks; (Refer to...) Figure 30 and Figure 31 In Comparative Example 4, layered double hydroxides and cellulose nanofibers were clearly observed in the geopolymer gel material, but there was a lack of interfacial bonding between them; they were merely in a physical mixed state. Figure 32 and Figure 33 In this process, cellulose nanofibers are deeply embedded in the matrix of the geopolymer gel material, while maintaining the crack bridging function. A large number of layered double hydroxides are uniformly anchored on the surface of the cellulose nanofibers in a leaf-like configuration. Around the cellulose nanofiber skeleton, hexagonal plate-like layered double hydroxide crystals with a size of about 2 μm grow. This morphological evolution is related to the spatial location of nucleation sites and the difference in local chemical environment during the crystallization process. It is highly consistent with the growth behavior of layered double hydroxides observed in alkaline simulated pore solutions and is consistent with the aforementioned characterization results.

[0117] Reference Figure 34 and Figure 35As shown in Table 1, the compressive strength, flexural strength, and elastic modulus of the geopolymer gel materials in Application Examples 1-3 are generally higher than those in Comparative Examples 1-4. This is because Application Examples 1-3 incorporate cellulose-based macropolymer reinforcing additives that chemically hybridize cellulose nanofibers and layered double hydroxides. On one hand, the unique aspect ratio of cellulose nanofibers facilitates bridging microcracks, and the in-situ growth of layered double hydroxide seeds on the cellulose nanofibers promotes uniform dispersion and epitaxial growth during hydration. On the other hand, besides the high intrinsic modulus of the layered double hydroxides themselves serving as a reinforcing phase, the layered double hydroxides enhance the compatibility between cellulose nanofibers and the geopolymer gel matrix. Furthermore, they act as seeds in the subsequent hydration process, improving the hydration effect of the geopolymer gel material and significantly increasing the content of the reinforcing phase in the matrix. These combined effects improve the compressive strength, flexural strength, and elastic modulus of the geopolymer gel material. Furthermore, in the geopolymer gel materials of Examples 1-3, as the amount of cellulose-based macropolymer reinforcing additive increased, the compressive strength, flexural strength, and elastic modulus of the geopolymer gel materials of Examples 1-3 first increased and then decreased. The analysis is as follows: the cellulose-based macropolymer reinforcing additive can achieve uniform dispersion in the geopolymer, forming a multi-scale reinforcing network, and providing efficient heterogeneous nucleation sites, significantly accelerating the hydration reaction and promoting the formation of high-modulus layered double hydroxide crystals, effectively sharing the load, and improving the strength and stiffness of the material, showing a trend of increasing compressive strength, flexural strength, and elastic modulus. However, with the increase of the dosage, the viscosity of the slurry also increases, the workability deteriorates, and more air bubbles and macroscopic defects are introduced during the molding process, increasing the overall porosity. At this time, the negative effects of increasing the dosage outweigh the reinforcing effect, resulting in a downward trend in macroscopic properties such as compressive strength, flexural strength, and elastic modulus.

[0118] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A cellulose-based polymer reinforcing additive, characterized by: The nanocellulose and the layered double hydroxide grown in situ on the nanocellulose; the weight ratio of the nanocellulose to the layered double hydroxide is 10:2-4.

2. A cellulosic-based polymer reinforcing additive according to claim 1, characterized in that: The nanocellulose includes one or more of cellulose nanocrystals, oxidized cellulose nanocrystals, cellulose nanofibrils, and oxidized cellulose nanofibrils.

3. A cellulosic-based polymer reinforcing additive according to claim 1, characterized in that: The general chemical formula of the layered double hydroxide is: [A 2+ (1-x) B 3+ x (OH)2] x+ [C n- ] x / n ·mH2O, wherein: A includes one or more of magnesium, zinc, calcium, and nickel, B includes one or more of aluminum, iron, and chromium, C n- includes one or more of carbonate ions, chloride ions, and nitrate ions, x ranges from 0.2 to 0.33, and m ranges from 0.2 to 0.

7.

4. A process for the preparation of a cellulose-based polymer reinforcing additive, characterized by: The method includes the following steps: Cellulose nanofibril suspension preparation: mixing cellulose nanofibrils with deionized water and performing homogenization treatment; Layered double hydroxide precursor solution preparation: mixing divalent metal salt and trivalent metal salt with deionized water and dissolving; Layered double hydroxide in-situ growth: simultaneously adding the layered double hydroxide precursor solution and the alkaline solution to the cellulose nanofibril suspension, controlling the pH of the system to be 10.00±0.05, the temperature of the system to be 15-25 ℃, and the stirring speed to be 1000-2000 rpm during the adding process, after the adding process, controlling the temperature of the system to be 65-75 ℃ for aging for 4-6 h, vacuum filtration to obtain the filter cake, and washing and drying the filter cake to obtain the cellulose-based geopolymer reinforcing additive; The weight ratio of the nanocellulose to the layered double hydroxide is 10:2-4.

5. A process for the preparation of a cellulosic-based polymeric reinforcement additive according to claim 4, characterized in that: The molar ratio of divalent metal ions to trivalent metal ions in the layered double hydroxide precursor solution is 2-4:

1.

6. A process for the preparation of a cellulosic-based polymeric reinforcement additive according to claim 5, characterized in that: The concentration of cellulose nanofibrils in the cellulose nanofibril suspension is 0.45 wt.%-0.55 wt.%, and the molar concentration of divalent metal ions in the layered double hydroxide precursor solution is 0.08-0.1 mol / L.

7. A process for the preparation of a cellulosic-based polymeric reinforcement additive according to claim 4, characterized in that: The solute of the alkaline solution includes sodium hydroxide and sodium carbonate in a weight ratio of 10:5-7, wherein the concentration of the sodium hydroxide is 45-55 g / L.

8. Use of a cellulose-based polymer reinforcing additive according to any one of claims 1 to 3 for the preparation of a geopolymer gel material, characterized in that: The geopolymer gel material includes 0.1 wt.%-0.5 wt.% of the cellulose-based geopolymer reinforcing additive.

9. Use of a cellulose-based polymer reinforcing additive according to claim 8 for the preparation of a geopolymer gel material, characterized in that: The geopolymer gel material is made of components including the following weight parts: cellulose-based geopolymer reinforcing additive 0.1-0.5 parts, aluminosilicate precursor 80-120 parts, and alkaline activator 3-6 parts. The water-binder ratio is 0.35-0.37.

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