CN111454488B - Bacterial cellulose-based composite protective material and preparation method thereof - Google Patents

Bacterial cellulose-based composite protective material and preparation method thereof Download PDF

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CN111454488B
CN111454488B CN201910056615.9A CN201910056615A CN111454488B CN 111454488 B CN111454488 B CN 111454488B CN 201910056615 A CN201910056615 A CN 201910056615A CN 111454488 B CN111454488 B CN 111454488B
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dstf
protective material
sio
composite protective
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CN111454488A (en
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杨加志
李锦坤
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Nanjing University of Science and Technology
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L3/00—Compositions of starch, amylose or amylopectin or of their derivatives or degradation products
    • C08L3/02—Starch; Degradation products thereof, e.g. dextrin
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
    • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
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Abstract

The invention discloses a bacterial cellulose-based composite protective material and a preparation method thereof. The method takes fine starch particles as a disperse phase, prepares DSTF by a mechanical stirring and ultrasonic method, and prepares BC/SiO by flocculent bacterial cellulose and TEOS by a hydrothermal synthesis method2Coarse fibers, finally mixing BC/SiO2The coarse fibers are uniformly dispersed in the DSTF to prepare the BC-DSTF composite protective material. The BC-DSTF composite protective material disclosed by the invention has the advantages that the critical shear rate of a DSTF system is reduced by adding the coarse fibers, the force chain network structure is enhanced, the BC-DSTF composite protective material has good shear thickening performance and excellent impact resistance, and can be effectively applied to the field of individual protection.

Description

Bacterial cellulose-based composite protective material and preparation method thereof
Technical Field
The invention relates to a bacterial cellulose-based composite protective material and a preparation method thereof, belonging to the technical field of preparation of personal protective materials.
Background
The shear thickening fluid has a viscosity η with shear rate
Figure BDA0001952697790000011
The Fluid having Shear Thickening properties is called Shear Thickening Fluid (Shear Thickening Fluid). In the field of impact resistance, the fluid has very wide application prospect. The shear thickening liquid has good fluidity when not subjected to external force or when the external force is small, and the viscosity of the shear thickening liquid is high when the shear thickening liquid is subjected to strong external forceThe viscosity will increase rapidly, and some high performance thickeners will even solidify instantaneously, consuming external energy.
At present, according to the particle size of dispersant particles and the shear thickening behavior thereof, shear thickening fluids are divided into two main categories, namely colloid system STF with particle size below micron level, usually with nano-SiO2As a dispersed phase, PEG was prepared as a dispersion medium; another is a non-Brownian particle system with particle size above micron level, which shows strong discontinuous Shear Thickening behavior, hereinafter DSTF (discontinuous Shear Thickening fluid) refers to the Shear Thickening fluid.
The DSTF system has shear thickening performance far superior to that of STF, and when external force is applied to make the shear rate reach a certain value, the viscosity eta of the DSTF system shows large-amplitude transition of several orders of magnitude, and the thickening liquid is instantaneously converted into a solid-like state from a liquid state, so that the impact of the external force can be blocked and even rebounded. When the external force is removed, the thickening liquid can be changed from a solid-like state to a liquid state, the shear thickening behavior is not only discontinuous, but also reversible, and the system rheological behavior conforms to the formula
Figure BDA0001952697790000012
For the preparation and use of DSTF, document 1 reports that DSTF shear-thickening fluids having a maximum thickening viscosity of up to 300Pa · s (Haw M d. hamming, two-fluid viscosity, and "self-filtration" in centralized particulate suspensions [ J ]. Physical review letters,2004,92(18):185506.) are prepared using rigid PMMA particles as the dispersed phase and deionized water as the dispersing medium. Document 2 reports that DSTF shear thickening fluids prepared using corn starch particles as the dispersed phase and deionized water as the dispersing medium have a maximum thickening viscosity of up to 450 Pa-s (Fall A, Bertrand F, Ovarlez G, et al, shear thickening of cornstand subsensions [ J ]. Journal of biotechnology 2012,56(3):575 & 591.).
Disclosure of Invention
The invention aims to provide a bacterial cellulose-based composite protective material and a bacterial cellulose-based composite protective materialA preparation method. In the process of preparing the DSTF system by the method, based on the 'Jamming' mechanism, bacterial cellulose/SiO is added2(BC/SiO2) The coarse fiber is used as a friction agent to prepare the BC-DSTF composite protective material with excellent protective performance.
The technical solution for realizing the invention is as follows:
the preparation method of the bacterial cellulose-based composite protective material comprises the steps of preparing Discontinuous Shear Thickening Fluid (DSTF) by taking fine starch particles as a disperse phase and preparing BC/SiO2Coarse fiber as friction agent, BC/SiO2The BC-DSTF composite protective material is prepared by uniformly dispersing the BC-DSTF in DSTF shear thickening fluid, and specifically comprises the following steps:
step 1, uniformly dispersing starch granules in a dispersion medium under the conditions of mechanical stirring and ultrasonic dispersion to obtain DSTF.
Step 2, gradually soaking flocculent BC in ethanol solution with gradient concentration, removing disordered water on the surface of the BC, homogenizing the BC without disordered water, dispersing the BC into ethanol and acetic acid solution of Tetraethoxysilane (TEOS), stirring the mixture until the mixture is uniformly dispersed, carrying out hydrothermal reaction on the mixed solution, rinsing the mixed solution by using ethanol after the reaction is finished, centrifuging the rinsed solution, and freeze-drying the washed solution to obtain BC/SiO2Coarse fibers;
step 3, mixing BC/SiO2The coarse fibers are uniformly dispersed in the DSTF to obtain the BC-DSTF composite protective material, wherein the BC/SiO is2The mass ratio of the coarse fibers to the DSTF is 1-5: 100.
in step 1, the starch granules are conventionally used starch granules for preparing discontinuous shear thickening fluid in the field, and can be selected from corn starch granules or potato starch granules, and the starch granules are fine grades and have the size of less than 20 microns.
In step 1, the dispersion medium may be water or a CsCl solution, the starch particles may be prevented from settling by using the CsCl solution as the dispersion medium, and the mass fraction of the CsCl solution is preferably 55 wt%.
Preferably, in the step 1, the volume fraction of the starch granules is more than or equal to 34 percent and less than or equal to 45 percent.
Preferably, in step 1, the ethanol solution with gradient concentration can be 20%, 40%, 60%, 80% and 100%, or 10%, 40%, 70% and 100% by using the gradient concentration for dehydration conventionally used in the art.
Preferably, in step 2, in the ethanol and acetic acid solution of tetraethyl orthosilicate (TEOS), the volume fraction of TEOS is 15-20%, and the amount of acetic acid is preferably 0.1N.
Preferably, in the step 2, the dispersing time is 5-10 h.
Preferably, in the step 2, the hydrothermal reaction time is 20-24 hours, and the reaction temperature is 150-180 ℃.
Preferably, in the step 3, the homogenizing speed is 500-700 r/min.
Compared with the prior protective material of a shear thickening system, the invention has the following advantages:
(1) the DSTF prepared by taking fine starch particles as a dispersion phase and taking a CsCl solution as a dispersion medium is taken as a protective material, and the shear thickening effect of the DSTF is far better than that of STF of a colloid system;
(2) the invention is based on the 'Jamming' mechanism in the physics of dry particles, and adds BC/SiO to DSTF2The coarse fiber is used as a friction agent to prepare the BC-DSTF composite protective material, compared with DSTF, the shear thickening effect of BC-DSTF is greatly enhanced, the maximum thickening viscosity can reach 590Pa & s, and the protective performance is better.
Drawings
FIG. 1 is a scanning electron micrograph of dispersed phase particles.
FIG. 2 shows the addition of 1 wt% BC/SiO2BC-DSTF rheological profiles of different volume fractions of coarse fibers.
In FIG. 3, when phi is 40.1%, different BC/SiO are added2BC-DSTF rheological Performance plot of coarse fiber content.
Detailed Description
The present invention will be described in further detail with reference to the following examples and the accompanying drawings.
Example 1
The first step is as follows: 45.0g CsCl was weighed out and dissolved in 55.0g deionized water to prepare a solution55wt% CsCl (aq) as a dispersion medium for DSTF, the dispersion medium having a density of 1.69g/cm3。
The second step is that: 59.0g of fine corn starch was weighed out and the fine corn starch granules were homogeneously dispersed in the dispersion medium prepared in the first step under mechanical stirring and ultrasonic dispersion conditions, the volume fraction Φ of the dispersed phase being 38.5%.
The third step: the flocculent BC is soaked in 20%, 40%, 60%, 80% and 100% ethanol solution step by step, and the surface of the BC is removed with disordered water. Homogenizing BC without disordered water by a homogenizer, and dispersing the BC into an ethanol and acetic acid solution of TEOS, wherein the volume fraction of TEOS is 20%, and the amount of acetic acid is 0.1N. The mixed solution is dispersed strongly for 5h by magnetic stirring, and then the mixture is put into a stainless steel reaction vessel with a polytetrafluoroethylene lining for reaction for 24h at 180 ℃. Rinsing the product with ethanol, centrifuging, and freeze-drying for later use to obtain BC/SiO2Coarse fibers.
The fourth step: scale 1.59gBC/SiO2And uniformly dispersing the coarse fibers in the DSTF prepared in the second step by using a homogenizer at the rotating speed of 700r/min to obtain the BC-DSTF composite protective material.
In this example, the volume fraction of starch granules, Φ, is 38.5%, BC/SiO2The mass ratio of the DSTF to the DSTF is 1: 100. the critical shear rate of the BC-DSTF protective material prepared in this example was tested by MCR302 type rheometer
Figure BDA0001952697790000031
Maximum viscosity η that can be achievedjam＝56.9Pa·s。
Example 2
The procedure is essentially as in example 1, except that the amount of dispersed phase particles added is 63.0g, BC/SiO2The amount of coarse fibres added was 1.63 g.
In this example, the volume fraction of starch granules, Φ, is 40.1%, BC/SiO2The mass ratio of the DSTF to the DSTF is 1: 100. the critical shear rate of the BC-DSTF protective material prepared in this example was tested by MCR302 type rheometer
Figure BDA0001952697790000041
Maximum viscosity η that can be achievedjam＝192Pa·s。
Example 3
This example is essentially the same as example 1, except that the dispersed phase particles are added in an amount of 71.0g, BC/SiO2The amount of coarse fibres added was 1.71 g.
In this example, the volume fraction of starch granules, Φ, 43.0%, BC/SiO2The mass ratio of the DSTF to the DSTF is 1: 100. the critical shear rate of the BC-DSTF protective material prepared in this example was tested by MCR302 type rheometer
Figure BDA0001952697790000042
Maximum viscosity η that can be achievedjam＝590Pa·s。
FIG. 2 shows the addition of 1 wt% BC/SiO2BC-DSTF rheological Performance plots of different volume fractions of coarse fibers from which it can be seen that the volume fraction of dispersed phase particles affects the rheological Performance when the amount of coarse fibers is kept consistent in the system, the greater the volume fraction of the dispersed phase system, the greater the critical shear rate of the BC-DSTF
Figure BDA0001952697790000043
The smaller, and the more pronounced the "Jamming" effect.
Example 4
This example is essentially the same as example 2, except that BC/SiO2The amount of coarse fibres added was 4.89 g.
In this example, the volume fraction of starch granules, Φ, is 40.1%, BC/SiO2The mass ratio of the carbon black to the DSTF is 3: 100. the critical shear rate of the BC-DSTF protective material prepared in this example was tested by MCR302 type rheometer
Figure BDA0001952697790000044
Maximum viscosity η that can be achievedjam＝315Pa·s。
Example 5
This example is essentially the same as example 2, except that BC/SiO2Coarse fiberThe amount of vitamin added was 8.15 g.
In this example, the volume fraction of starch granules, Φ, is 40.1%, BC/SiO2The mass ratio of the DSTF to the DSTF is 5: 100. the critical shear rate of the BC-DSTF protective material prepared in this example was tested by MCR302 type rheometer
Figure BDA0001952697790000045
Maximum viscosity η that can be achievedjam＝472Pa·s。
Example 6
This example is essentially the same as example 1, except that 59g of fine corn starch granules were weighed and dispersed in 59g of deionized water using deionized water as the dispersing medium to give a DSTF system with Φ of 38.5%; adding 1.18gBC/SiO into DSTF system2And (4) roughening the fiber to obtain the BC-DSTF composite protective material.
In this example, the volume fraction of starch granules, Φ, is 38.5%, BC/SiO2The mass ratio of the DSTF to the DSTF is 1: 100. the critical shear rate of the BC-DSTF protective material prepared in this example was tested by MCR302 type rheometer
Figure BDA0001952697790000051
Maximum viscosity η that can be achievedjamThe system stability is poor at 56.9Pa · s, but static blocking is likely to occur, which indicates that the use of cscl (aq) as a dispersion medium is more favorable for the system stability than deionized water, but the kind of the dispersion medium does not affect the critical shear rate and the shear thickening viscosity.
Comparative example
This comparative example is essentially the same as example 2, except that BC/SiO2The amount of coarse fibres added was 11.4 g.
In this example, the volume fraction of starch granules, Φ, is 40.1%, BC/SiO2The mass ratio of the carbon black to the DSTF is 7: 100. through the test of MCR302 type rheometer, the BC-DSTF protective material prepared by the comparative example has static blockage under zero stress, loses the flowing ability and has the initial viscosity eta of the systemjam＝909Pa·s。
FIG. 3 shows that 40.1% of the total amount of phi is addedThe BC-DSTF rheological property graph of the same coarse fiber content shows that when the volume fraction of the dispersed phase in the BC-DSTF is constant, the critical shear rate of the BC-DSTF is increased along with the increase of the coarse fiber content
Figure BDA0001952697790000052
The smaller, and the more pronounced the "Jamming" effect. However, when the amount of the coarse fibers exceeds a certain value, the static plugging density Φ s is decreased due to the increase of friction, and the occurrence of a system-like solid state is caused, so that the amount of the coarse fibers to be added should be controlled within 5%.

Claims (7)

1. The preparation method of the bacterial cellulose-based composite protective material is characterized by comprising the following steps:
step 1, uniformly dispersing starch particles in a dispersion medium under the conditions of mechanical stirring and ultrasonic dispersion to obtain a discontinuous shear thickening fluid DSTF, wherein the dispersion medium is a CsCl solution with the mass fraction of 55wt%, and the volume fraction of the starch particles is more than or equal to 34% and less than or equal to 45%;
step 2, gradually soaking flocculent bacterial cellulose BC in ethanol solution with gradient concentration, removing disordered water on the surface of BC, homogenizing BC without disordered water, dispersing the BC into ethanol and acetic acid solution of tetraethoxysilane TEOS, stirring until the mixture is uniformly dispersed, carrying out hydrothermal reaction on the mixed solution, rinsing with ethanol after the reaction is finished, centrifuging, and freeze-drying to obtain BC/SiO2Coarse fibers;
step 3, mixing BC/SiO2The coarse fibers are uniformly dispersed in the DSTF to obtain the BC-DSTF composite protective material, wherein the BC/SiO is2The mass ratio of the coarse fibers to the DSTF is 1-5: 100.
2. the method according to claim 1, wherein in step 1, the starch granules are selected from corn starch granules or potato starch granules, and the size of the starch granules is less than 20 μm.
3. The method according to claim 1, wherein the ethanol solution of gradient concentration in step 2 is 20%, 40%, 60%, 80% and 100%, or 10%, 40%, 70% and 100%.
4. The preparation method according to claim 1, wherein in the step 2, the volume fraction of TEOS in the ethanol and acetic acid solution of tetraethoxysilane is 15-20%, the amount of acetic acid is 0.1N, and the dispersion time is 5-10 h.
5. The preparation method according to claim 1, wherein in the step 2, the hydrothermal reaction time is 20-24 hours, and the reaction temperature is 150-180 ℃.
6. The method according to claim 1, wherein the homogenization rate in step 2 is 500 to 700 r/min.
7. The bacterial cellulose-based composite protective material prepared by the preparation method according to any one of claims 1 to 6.
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CN113072810B (en) * 2021-03-30 2022-01-11 江南大学 Crosslinked starch reinforced composite shear thickening elastomer
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