Wide temperature threshold modified shear thickening fluid and method of making same

Abstract

The application discloses a kind of wide temperature threshold modified shear thickening fluid and preparation method thereof.The shear thickening fluid is composed of carboxylated silica nanoparticles, polyethylene glycol 200-600, polyacrylic acid and anhydrous calcium chloride, wherein the mass of carboxylated silica nanoparticles accounts for 40-42% of the total mass of polyethylene glycol 200-600 and carboxylated silica nanoparticles, the mass ratio of polyacrylic acid to carboxylated silica nanoparticles is 0.3:1, and the mass ratio of calcium chloride to carboxylated silica nanoparticles is 0.1:1.The application expands the application range of shear thickening fluid from below 25℃ to below 35℃ based on the traditional silica / polyethylene glycol shear thickening fluid system, and ensures that the shear thickening performance is not weakened at a temperature higher than room temperature.

Description

Technical Field

[0001] This invention belongs to the field of intelligent protective materials and relates to a wide temperature threshold modified shear thickening liquid and its preparation method. Background Technology

[0002] Shear thickening fluid (STF) is a field-responsive smart fluid material. It has a constant viscosity and certain fluidity when at rest, but it can quickly change from a liquid to a solid-like state when subjected to force. It has been widely used in damping, polishing, sports equipment, and protective composite materials.

[0003] Traditional shear-thickening fluids achieve their thickening effect macroscopically by forming particle clusters through hydrogen bonding between dispersed phase particles and the dispersion at a certain shear rate, resulting in a solid-like thickening effect. Currently, the most widely studied shear-thickening fluid system is the silica / polyethylene glycol system. Researchers have explored the effects of different influencing factors on the rheological properties of shear-thickening fluids by changing the type, size, aspect ratio, content, and type of dispersed phase particles. Some studies have also found that modifying the dispersed phase particles can improve the dispersion and thickening properties of shear-thickening fluids. For example, Liu et al. modified SiO2 with PVP K30, resulting in a shear-thickening fluid with a critical shear rate that decreased by about 16 times and a maximum viscosity that increased by about 7 times, from 3 Pa·s to 25 Pa·s, significantly enhancing the shear thickening effect (Liu M, Chen Q, Wang S, et al. PVP immobilized SiO2 nanospheres for high-performance shear thickening fluid[J]. Journal of Nanoparticle Research, 2017, 19, 234.); Yu et al. modified the surface of nano-silica with KH570, titanate, and stearic acid, finding that the modification could effectively inhibit the aggregation of nano-silica and increase its maximum particle concentration in polyethylene glycol. The shear-thickening fluid formed by the modified silica-based fluid exhibited strong shear thickening reversibility and high stability under repeated shear fracture (Yu M, Qiao X, Dong X, et al. Effect of particle modification on the shear thickening behaviors of the suspensions of silica nanoparticles in PEG[J]. Colloid andPolymer Science,2018,296,1767-1776.).K. Talreja et al. modified the surface of spherical silica particles using the hydrophilic silane APTES and the hydrophobic silane MTMS, respectively. The results showed that, compared to unmodified and APTES-modified silica particles, the STF prepared from MTMS-modified silica particles (70 wt%) had a lower peak viscosity and a higher critical shear rate, while the STF prepared from APTES-modified silica particles had the highest peak viscosity (Talreja K, Chauhan I, Ghosh A, et al. Functionalization of silicap particles to tune the impact resistance of shear thickening fluid-treated aramid fabrics[J]. Royal Society of Chemistry Advance, 2017, 7, 49787-49794.). Although surface modification of silica can improve its dispersion performance and peak viscosity, traditional shear thickeners are highly hygroscopic, leading to unstable performance.

[0004] As field-responsive smart materials, the rheological properties of shear thickening fluids are also affected by temperature. Typically, the rheological properties of traditional shear thickening fluids are measured at room temperature. However, common application scenarios involve temperatures above 25°C. When the temperature of traditional shear thickening fluids increases from room temperature, both the degree of thickening and the peak viscosity decrease. This phenomenon limits the application and development of traditional shear thickening fluids. Summary of the Invention

[0005] The purpose of this invention is to provide a wide-temperature-threshold modified shear thickening fluid and its preparation method. The shear thickening fluid of this invention is composed of inorganic nanoparticles, polyacrylic acid, and an organic solvent. It does not weaken its thickening effect at temperatures above room temperature, and its viscosity even increases, exhibiting excellent stability.

[0006] The technical solution for achieving the objective of this invention is as follows:

[0007] The wide-temperature-threshold modified shear thickener is composed of carboxylated silica nanoparticles, polyethylene glycol 200-600, polyacrylic acid, and anhydrous calcium chloride. The mass of the carboxylated silica nanoparticles accounts for 40%-42% of the total mass of polyethylene glycol 200-600 and carboxylated silica nanoparticles. The mass ratio of polyacrylic acid to carboxylated silica nanoparticles is 0.3:1, and the mass ratio of calcium chloride to carboxylated silica nanoparticles is 0.1:1.

[0008] The carboxylated silica nanoparticles of this invention are prepared by conventional methods, specifically: silica nanoparticles are ultrasonically dispersed in ethanol, stirred until uniformly dispersed, then silane coupling agent KH550 is added, and the reaction is continued to be stirred to obtain aminated silica. After drying, ethanol is added, the temperature is raised to 40°C, glutaric anhydride is added, and after the reaction is complete, the silica nanoparticles are dried under vacuum to obtain carboxylated silica nanoparticles.

[0009] Preferably, the mass of the carboxylated silica nanoparticles accounts for 41% of the total mass of polyethylene glycol 200-600 and the carboxylated silica nanoparticles.

[0010] Preferably, the particle size of the carboxylated silica nanoparticles is 12 nm.

[0011] The preparation method of the above-mentioned wide temperature threshold modified shear thickening liquid includes the following steps:

[0012] In a specific ratio, while stirring, polyacrylic acid, carboxylated silica nanoparticles, and anhydrous calcium chloride powder are added sequentially to polyethylene glycol 200-600. The mixture is stirred continuously until homogeneous to obtain a wide-temperature-threshold modified shear thickening liquid.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] (1) The present invention effectively reduces the agglomeration degree of silica particles, increases the content of silica particles in polyethylene glycol 200, and improves the thickening degree;

[0015] (2) In the case of traditional shear thickening liquids, which only have hydrogen bonds and interparticle friction, this invention introduces carboxyl groups and calcium ions, and utilizes hydrophobic and electrostatic forces to effectively expand the application temperature range of shear thickening liquids from below 25°C to below 35°C. Attached Figure Description

[0016] Figure 1 The rheological diagrams of the modified silica-based shear thickener (41%) of Example 1 at different temperatures are shown.

[0017] Figure 2 The rheological diagrams of the modified silica-based shear thickener (37%) of Comparative Example 1 at different temperatures are shown.

[0018] Figure 3 The rheological diagrams of the modified silica-based shear thickener (45%) of Comparative Example 2 at different temperatures are shown.

[0019] Figure 4 The rheological diagrams of the modified silica-based shear thickener of Comparative Example 3 at different temperatures are shown.

[0020] Figure 5This is a physical image of the modified silica-based shear thickening liquid sample from Comparative Example 4. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0022] The carboxylated silica nanoparticles of the present invention are prepared using existing methods and can be prepared through the following steps:

[0023] (1) 10g of 12nm silica nanoparticles and an appropriate amount of ethanol were placed in a three-necked flask, ultrasonically dispersed for 10 minutes, and magnetically stirred at 40℃ (1500rpm) for 2 hours. Then, 10ml of silane coupling agent KH550 was added, and the reaction was continued for 12 hours. After the reaction was completed, the nanoparticles were centrifuged and washed, and then vacuum dried at 60℃ for 12 hours to obtain aminated silica nanoparticles.

[0024] (2) After finely grinding 10g of completely dried aminated silica nanoparticles, pour them into a three-necked flask, mix with an appropriate amount of ethanol and stir magnetically. After heating to 40℃, add 25g of glutaric anhydride and react for 3 hours. Then wash once with 0.1M NaCl solution to remove the glutaric anhydride adhering to the surface of the inorganic particles, wash three times with ethanol, and finally vacuum dry to obtain carboxylated silica nanoparticles.

[0025] Example 1

[0026] The modified shear-thickening liquid was prepared by adding 10g of polyethylene glycol 200 to 600 by mass, with the mass ratio of polyacrylic acid to carboxylated silica nanoparticles being 0.3:1 and the mass ratio of calcium chloride to carboxylated silica nanoparticles being 0.1:1, and then adding 2.13g of polyacrylic acid under low-speed mechanical stirring. After mixing for 30 minutes, 7.1g of carboxylated silica was added in small amounts several times, and finally 0.71g of anhydrous calcium chloride powder was added, also in small amounts several times. The mixture was stirred mechanically for about 8 to 12 hours to obtain the modified shear-thickening liquid.

[0027] Comparative Example 1

[0028] This embodiment is basically the same as Embodiment 1, except that the mass of carboxylated silica nanoparticles accounts for 37% of the total mass of polyethylene glycol 200-600 and carboxylated silica nanoparticles.

[0029] Comparative Example 2

[0030] This comparative example is basically the same as Example 1, except that the mass of carboxylated silica nanoparticles accounts for 45% of the total mass of polyethylene glycol 200-600 and carboxylated silica nanoparticles.

[0031] Comparative Example 3

[0032] This comparative example is basically the same as Example 1, except that anhydrous calcium chloride is not added.

[0033] Comparative Example 4

[0034] This comparative example is basically the same as Example 1, except that polyacrylic acid is not added.

[0035] Figures 1-3 The rheological diagrams of the modified silica-based shear thickeners of Example 1, Comparative Example 1, and Comparative Example 2 at different temperatures are shown. The comparison reveals that the modified silica-based shear thickeners exhibit a double shear phenomenon at high carboxylated silica content. However, only when the mass of carboxylated silica nanoparticles is 200-600 parts polyethylene glycol and 41% of the total mass of carboxylated silica nanoparticles, the initial viscosity of the shear thickeners above 25°C is higher than that at 25°C, showing a trend of first increasing and then decreasing; the viscosity peak at 35°C is higher than that at 25°C, increasing from 726 Pa·s to 1331 Pa·s, an increase of 83%. Comparison of Example 1 and Comparative Examples 3 and 4 shows that the absence of polyacrylic acid leads to the system's inability to disperse further, resulting in a gel-like texture (e.g., ...). Figure 5 As shown in the figure, the absence of anhydrous calcium chloride leads to excessive fluidity and low viscosity in the system, indicating that polyacrylic acid plays a role in providing carboxyl sites and regulating viscosity in the system.

Claims

1. A wide-temperature-threshold modified shear thickener, characterized in that, The nanoparticles are composed of carboxylated silica nanoparticles, polyethylene glycol 200-600, polyacrylic acid, and anhydrous calcium chloride. The carboxylated silica nanoparticles account for 40%-42% of the total mass of polyethylene glycol 200-600 and the total mass of the carboxylated silica nanoparticles. The mass ratio of polyacrylic acid to carboxylated silica nanoparticles is 0.3:1, and the mass ratio of calcium chloride to carboxylated silica nanoparticles is 0.1:

1. The carboxylated silica nanoparticles are prepared by the following method: silica nanoparticles are ultrasonically dispersed in ethanol and stirred until uniformly dispersed. Then, silane coupling agent KH550 is added, and the reaction is continued with stirring to obtain aminated silica. After drying, ethanol is added, the temperature is raised to 40°C, glutaric anhydride is added, and after the reaction is complete, the nanoparticles are vacuum dried to obtain carboxylated silica nanoparticles.

2. The wide temperature threshold modified shear thickener according to claim 1, characterized in that, The mass of carboxylated silica nanoparticles accounts for 41% of the total mass of polyethylene glycol 200-600 and carboxylated silica nanoparticles.

3. The wide temperature threshold modified shear thickener according to claim 1, characterized in that, The particle size of the carboxylated silica nanoparticles is 12 nm.

4. The method for preparing the wide temperature threshold modified shear thickening liquid according to any one of claims 1 to 3, characterized in that, Includes the following steps: In a specific ratio, while stirring, polyacrylic acid, carboxylated silica nanoparticles, and anhydrous calcium chloride powder are added sequentially to polyethylene glycol 200-600. The mixture is stirred continuously until homogeneous to obtain a wide-temperature-threshold modified shear thickening liquid.

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