阅读说明：本技术 一种复合泡沫材料及其制备方法和应用 (Composite foam material and preparation method and application thereof ) 是由 刘子瑾 于晖 刘熙 吴清华 林江华 唐玉 于 2021-08-13 设计创作，主要内容包括：本发明公开了一种复合泡沫材料及其制备方法和应用。所述复合泡沫材料包括开孔泡沫基体材料与第一碳系填料,所述开孔泡沫基体材料中具有开孔结构的泡孔,所述泡孔的内壁附着有第二碳系填料。本发明实现了碳材料填料网结构的有效构筑,调控碳系填料的空间分布,避免了碳系填料的堆叠,制备出可压缩的导电复合泡沫材料。(The invention discloses a composite foam material and a preparation method and application thereof. The composite foam material comprises an open-cell foam base material and a first carbon-based filler, wherein cells with an open-cell structure are arranged in the open-cell foam base material, and a second carbon-based filler is attached to the inner walls of the cells. The invention realizes the effective construction of the carbon material filler net structure, regulates and controls the spatial distribution of the carbon series filler, avoids the stacking of the carbon series filler and prepares the compressible conductive composite foam material.)

1. A method of making a syntactic foam, characterized by: the method comprises the following steps:

(1) dispersing a first carbon filler in a solvent to obtain a first carbon filler dispersion, and diluting a foam base material with the first carbon filler dispersion to obtain a mixed solution of the foam base material with the solid content of 6.25% or less;

(2) freeze-drying the mixed solution to obtain an open-cell foam base material;

(3) adsorbing a second carbon-based filler into the open-cell foam base material to obtain the composite foam material.

2. A method of making a syntactic foam according to claim 1, wherein:

and (2) adding a vulcanization aid into the foam base material, and stirring to obtain the foam base material added with the vulcanization system.

3. A method of making a syntactic foam according to claim 2, wherein:

the vulcanization auxiliary agent comprises the following components in parts by mass:

0.5-3 parts of sulfur, 0.1-3 parts of zinc oxide, 0.3-5 parts of accelerator zinc N-ethyl-N-phenyl dithiocarbamate, 0.1-1 part of accelerator zinc diethyl dithiocarbamate, 0.5-3 parts of anti-aging agent 2, 6-di-tert-butyl-4-methylphenol, 0.05-1 part of methylene dinaphthalene sodium sulfonate diffusant and 0.01-1 part of potassium hydroxide.

4. A syntactic foam characterized by:

the composite foam material comprises the open-cell foam base material and the first carbon-based filler, wherein the open-cell foam base material is provided with cells with an open-cell structure, and the inner walls of the cells are attached with the second carbon-based filler.

5. A syntactic foam according to claim 4, wherein:

the foam base material comprises at least one or a combination of more of carboxylic styrene-butadiene latex, butyronitrile latex, styrene-butadiene latex, chloroprene latex and polyacrylate emulsion.

6. A syntactic foam according to claim 4, wherein:

the first carbon-based filler includes at least one of graphene, fullerene, activated carbon, acetylene black, carbon nanotube, carbon fiber, and derivatives thereof.

7. A syntactic foam according to claim 4, wherein:

the second carbon-based filler includes at least one of graphene, fullerene, activated carbon, acetylene black, carbon nanotube, carbon fiber, and derivatives thereof.

8. A method of reducing a syntactic foam according to any one of claims 4 to 7, in which:

and carrying out in-situ reduction on the composite foam material to obtain a reduced composite foam material.

9. Use of a syntactic foam according to any one of claims 4 to 7 in a flexible material.

10. A pressure sensor, characterized by: a composite foam material comprising any one of claims 4 to 7.

Technical Field

The invention belongs to the technical field of foam materials, and particularly relates to a composite foam material and a preparation method and application thereof.

Background

Some two-dimensional carbon materials have the characteristics of high conductivity, high aspect ratio, high specific surface area, low density, good flexibility and the like, and are ideal fillers for improving the conductivity of the composite material under the condition of low filler consumption.

However, these carbon materials have a disadvantage in that they are easily stacked, which is disadvantageous for their dispersion in the polymer, and their agglomeration in the polymer leads to the formation of defect spots, which seriously affects the conductive properties of the carbon material/polymer composite.

How to suppress or even avoid stacking of the carbon material in the carbon material/polymer composite material and where the carbon material is distributed in the carbon material/polymer composite material are problems to be discussed.

Disclosure of Invention

The first technical problem to be solved by the invention is as follows:

a method for preparing a syntactic foam is provided.

The second technical problem to be solved by the invention is:

a syntactic foam prepared by the above method is provided.

The third technical problem to be solved by the invention is:

use of the above-described syntactic foam.

The invention also provides a pressure sensor which comprises the composite foam material.

In order to solve the first technical problem, the invention adopts the technical scheme that:

a method of making a syntactic foam, comprising the steps of:

(1) dispersing a first carbon series filler in a solvent to obtain a first carbon series filler dispersion liquid, and diluting a foam base material by using the first carbon series filler dispersion liquid to obtain a mixed dispersion system with the solid content of the foam base material being less than 6.25%;

(2) freeze-drying the mixed solution to obtain an open-cell foam base material;

(3) adsorbing a second carbon-based filler into the open-cell foam base material to obtain the composite foam material.

When the solid content of the foam base material is 6.25% -1%, the foam material with an open-cell structure is obtained.

The composite foam material is prepared by a vacuum freeze drying method. In a water dispersion system, water is crystallized at low temperature to form ice crystals, the generated ice crystals extrude other components in the system, the other components are rearranged and assembled, the components are mutually stacked to form a three-dimensional structure, and the ice sublimes to obtain the three-dimensional porous foam material. The structure and the appearance of the foam material are regulated and controlled by changing the process of a vacuum freeze drying method and the composition of the material.

According to an embodiment of the present invention, the step (1) further comprises adding an auxiliary agent to the foam base material, and stirring to obtain the foam base material with the auxiliary agent system added. In this step, the stirring time was 2 hours, and the ultrasonic treatment was carried out for 10 minutes after the completion of the stirring. The above-mentioned addition of the vulcanization system serves to effect curing crosslinking.

According to an embodiment of the present invention, the step (2) further comprises placing the mixed solution in a container, covering the container with a heat-insulating layer, and allowing the container to stand in a freezer at 0 ℃ or lower, preferably at-18 ℃ for overnight freezing; and (3) taking out the container after complete freezing, quickly placing the container in a pre-refrigerated freeze dryer, and freeze-drying for 48 hours to obtain the open-cell foam matrix material.

According to an embodiment of the present invention, the step (3) further includes immersing the open-cell foam base material in the second aqueous dispersion of carbon-based filler, placing the second aqueous dispersion of carbon-based filler in a vacuum oven, vacuum-defoaming the second aqueous dispersion of carbon-based filler overnight at room temperature, taking the second aqueous dispersion of carbon-based filler out, and vacuum-drying the second aqueous dispersion of carbon-based filler at 50 ℃.

The second carbon-based filler is impregnated into the interior of the cells of the open-cell foam base material through the three-dimensionally connected cell passages of the open-cell foam base material and adsorbed on the inner walls of the cells; wherein the carboxylated open-cell foam base material is capable of interacting with the groups on the surface of the second carbon-based filler.

According to an embodiment of the invention, the auxiliary agent comprises the following components in parts by mass:

0.5-3 parts of sulfur, 0.1-3 parts of zinc oxide, 0.3-5 parts of accelerator zinc N-ethyl-N-phenyl dithiocarbamate, 0.1-1 part of accelerator zinc diethyl dithiocarbamate, 0.5-3 parts of anti-aging agent 2, 6-di-tert-butyl-4-methylphenol, 0.05-1 part of methylene dinaphthalene sodium sulfonate diffusant and 0.01-1 part of potassium hydroxide.

In order to solve the second technical problem, the invention adopts the technical scheme that:

a syntactic foam:

the composite foam material comprises the open-cell foam base material and the first carbon-based filler, wherein the open-cell foam base material is provided with cells with an open-cell structure, and the inner walls of the cells are attached with the second carbon-based filler.

According to an embodiment of the present invention, the above-mentioned foam base material includes at least one or a combination of more of carboxylic styrene-butadiene latex, nitrile-butadiene latex, styrene-butadiene latex, polychloroprene latex and polyacrylate emulsion.

According to an embodiment of the present invention, the first carbon-based filler includes at least one of graphene, fullerene, activated carbon, acetylene black, carbon nanotube, carbon fiber, and a derivative thereof.

According to an embodiment of the present invention, the second carbon-based filler includes at least one of graphene, fullerene, activated carbon, acetylene black, carbon nanotube, carbon fiber, and a derivative thereof.

According to an embodiment of the present invention, the first carbon-based filler dispersion has a concentration of 2 mg/ml.

According to an embodiment of the present invention, the first carbon-based filler dispersion is prepared by dispersing the first carbon-based filler in water, stirring for 2 hours, and then sonicating in an ice-water bath for 10 minutes.

A method for reducing the syntactic foam includes carrying out in-situ reduction on the syntactic foam to obtain a reduced syntactic foam.

According to one embodiment of the present invention, the method for reducing the syntactic foam includes placing a support in a polytetrafluoroethylene liner of a hydrothermal reactor, placing the prepared syntactic foam on the support, placing hydrazine hydrate solution under the support, reacting at 95 ℃ for 3 hours to obtain the reduced syntactic foam, filtering, washing with water, and vacuum drying at 60 ℃ for later use. After the reduction treatment, the brownish yellow colored syntactic foam described above is converted to a black colored reduced syntactic foam described above.

The reduced syntactic foam described above was then cross-linked by vulcanization in a forced air oven. The vulcanization temperature is 110 ℃, and the vulcanization time is t₉₀And obtaining the reduced composite foam material with orderly distributed fillers.

In another aspect, the invention also relates to the use of the above-described syntactic foam in a flexible material.

In yet another aspect of the present invention, there is provided a pressure sensor comprising a syntactic foam as described above.

One of the above technical solutions has at least one of the following advantages or beneficial effects:

(1) converting the closed-cell composite foam material into an open-cell composite foam material by a vacuum freeze-drying method, and attaching carbon fillers to the inner wall of the cells to enhance the conductivity and mechanical property of the composite foam material;

(2) the solid content of the composite foam material is regulated to adjust the cell structure, and the cell size is accurately controlled.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic of the preparation of GSBR and GSBR/GO foams.

FIG. 2(a) a pictorial representation of GSBR/GO foam and (b) a pictorial representation of GSBR/rGO foam.

FIG. 3 is an apparatus graph testing the resistance of GSBR/rGO foams as a function of compression set.

FIG. 4 is a low magnification SEM image of GSBR-50, (b) GSBR-25, (c) GSBR-12.5 and (d) GSBR-6.25 foams.

FIG. 5 is SEM cross-sectional views of GSBR-50, (c, d) GSBR-25, (e, f) GSBR-12.5 and (g, h) GSBR-6.25 foams.

FIG. 6 shows the cell size distribution of GSBR-50, (b) GSBR-25, (c) GSBR-12.5 and (d) GSBR-6.25 foams.

Fig. 7 is an average cell size for GSBR foams of varying solids content.

FIG. 8 SEM images of GSBR/rGO foams (a, b) before and (c, d) after compression.

FIG. 9 Raman spectra of GO, GSBR/GO and GSBR/rGO foams.

FIG. 10 relative rates of change of resistance, σ, for SBR/rGO foams with a maximum strain of (a) 37%, (b) 55%, (c) 78% in that order_νCurve of variation with strain and (d) σ_νPeak-to-peak analysis of (1).

FIG. 11 is a graph of the relative rate of change of resistance of GSBR/rGO foams versus time (inset is a schematic of the compression-recovery process).

Detailed Description

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout.

The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, if there are first, second, third, etc. described only for the purpose of distinguishing technical features, it is not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplicity of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the description of the present invention, it should be noted that unless otherwise explicitly defined, terms such as arrangement, installation, connection and the like should be broadly understood, and those skilled in the art can reasonably determine the specific meanings of the terms in the present invention in combination with the detailed contents of the technical solutions.

In order to explain the technical content, the objects and the effects of the present invention in detail, the following description will be given with reference to the embodiments.

Example 1

The graphene/styrene-butadiene latex composite (GSBR) is prepared by the method for preparing the composite foam material.

(1) Experimental raw materials and reagents:

carboxylated SBR latex (carboxylated styrene-butadiene latex) having a solid content of 50% was produced by Zhejiang morning latex industries, Ltd.

Graphene Oxide (GO), available from Nanjing Xiancheng nanomaterial science and technology Limited.

Deionized (DI) water was produced by a Barnstead Smart 2 pure water purification system (Thermo Scientific).

Sulfur, zinc oxide, NF diffusant (sodium methylene dinaphthalene sulfonate), KOH (potassium hydroxide), accelerator PX (zinc N-ethyl-N-phenyl dithiocarbamate), accelerator ZDC (zinc diethyl dithiocarbamate) and anti-aging agent 264(2, 6-di-tert-butyl-4-methylphenol) are industrial grade auxiliaries.

The NF diffusant (sodium methylene dinaphthalene sulfonate) and KOH (potassium hydroxide) are directly added into the carboxylated SBR latex under the condition of stirring, and other auxiliary agents are ground into the latex by a ball mill for standby.

(2) Preparing GSBR:

adding a vulcanization aid into SBR latex in the following vulcanization formula (100 parts by mass of SBR, 1 part by mass of sulfur, 0.7 part by mass of zinc oxide, 0.35 part by mass of accelerant PX, 0.1 part by mass of accelerant ZDC, 1.0 part by mass of anti-aging agent 264, 0.05 part by mass of NF diffusant and 0.05 part by mass of KOH) while stirring; stirring for 2 hours, and carrying out ultrasonic treatment for 10 minutes to obtain SBR latex added with a vulcanization system, and stirring for later use.

Dispersing GO in water, stirring for 2 hours, and performing ultrasonic treatment in an ice-water bath for 10 minutes to obtain a GO dispersion liquid (2 mg/ml). The SBR latex is diluted by GO dispersion liquids with different volumes, SBR and GO blended (GSBR for short) latex with the solid content of SBR being 50%, 25%, 12.5% and 6.25% are prepared, and the prepared latexes are marked as GSBR-50, GSBR-25, GSBR-12.5 and GSBR-6.25 respectively.

Placing GSBR in a container, coating an insulating layer on the outside, standing in a freezer at-18 ℃, and freezing overnight; taking out after completely freezing, quickly placing in a pre-refrigerated freeze dryer, and freeze-drying for 48 hours to obtain GSBR foam material, wherein the preparation process is shown in figure 1.

(3) Preparing GSBR/GO foam material:

a vacuum-assisted impregnation method is adopted to adsorb GO into a GSBR foam material with an open-cell structure, and the method comprises the following specific steps:

and (3) dipping the GSBR-6.25 foam material into the GO water dispersion, placing the GO in a vacuum oven, carrying out vacuum defoamation overnight at room temperature, taking out the GO, and carrying out vacuum drying at 50 ℃ to obtain the GSBR/GO foam material. GO is soaked into GSBR cells through three-dimensional communicated cell channels of the GSBR and adsorbed on the inner walls of the cells; wherein the content groups of the carboxylated SBR and the GO surface can generate interaction, and the preparation process is shown in a figure 1.

(4) Preparation of GSBR/rGO foam material by in-situ reduction

And (3) carrying out in-situ reduction treatment on the GSBR/GO foam material by adopting hydrazine hydrate to obtain the GSBR/rGO foam material. The method comprises the following specific steps:

placing a support in a polytetrafluoroethylene inner container of a hydrothermal kettle, placing the prepared GSBR/GO foam material on the support, reacting the GSBR/GO foam material with hydrazine hydrate solution at 95 ℃ for 3 hours to obtain the GSBR/rGO foam material, filtering, washing with water, and vacuum drying at 60 ℃ for later use.

As shown in FIG. 2, after the reduction treatment, the brownish yellow GSBR/GO foam transforms into a black GSBR/rGO foam.

Curing and crosslinking the GSBR/rGO foam in a forced air oven. The vulcanization temperature is 110 ℃, and the vulcanization time is t₉₀And obtaining the GSBR/rGO foam material with orderly distributed fillers.

The ordered distribution means that rGO is orderly distributed on the inner wall of the foam cells.

The resistance of the GSBR/rGO foam was tested as a function of compression set, the apparatus of the test being shown in figure 3.

And (3) performance testing:

in the freezing process of preparing the GSBR, ice crystals can be formed in the GSBR, the size of the ice crystals is related to the solid content of the latex, and the size of the ice crystals can be regulated and controlled by changing the solid content, so that foam materials with different cell sizes can be obtained. The structure and morphology of the cells in the GSBR foam was observed using the SEM of fig. 4.

As can be seen from FIG. 4a, the cells in the GSBR-50 foam are oval, which are formed by the extrusion rearrangement of spherical ice crystals. The cells are closely adjacent and randomly distributed.

As shown in FIG. 4b, the cell size of the GSBR-25 foam is significantly larger than that of the GSBR-50 foam, and the number of cells in the GSBR-25 foam per unit area is significantly less than that of the GSBR-50 foam.

The size of the cells in the GSBR-12.5 foam in fig. 4c is further increased compared to the GSBR-25 foam and the number of cells per unit area is reduced.

The solids content of the GSBR latex was further reduced to 6.25% and the cell size of the GSBR-6.25 foam did not increase further than the GSBR-12.5 foam, as shown in FIG. 4 d.

Comparing GSBR-50, GSBR-25, GSBR-12.5 and GSBR-6.25 foams, it can be found that the pores of GSBR-50 and GSBR-25 foams are mostly closed cell structures, while GSBR-6.25 has a distinct open cell structure.

As shown in FIG. 5, the structural morphology of GSBR-50, GSBR-25, GSBR-12.5 and GSBR-6.25 foams was studied by SEM. The process of transition of the GSBR foam from a closed cell structure to an open cell structure was analyzed.

Wherein fig. 5b, fig. 5d, fig. 5f, fig. 5h are partial enlarged views of fig. 5a, fig. 5c, fig. 5e, and fig. 5g in sequence.

FIG. 5a is a cross-sectional view of a GSBR-50 foam showing elliptical cells with a relatively uniform distribution and a closed cell structure.

As can be seen in fig. 5b, some regions of the GSBR-50 foam exhibited cell wall perforation, with adjacent cells communicating, but no apparent three-dimensional communicating cell channels. As indicated by the white arrows, the squeezing between adjacent cells makes the cell walls thinner, which can be as low as 20 μm thick.

As shown in FIG. 5c, the cross-section of the GSBR-25 foam showed irregular round cells with randomly distributed cells.

As shown in fig. 5d, the thickness of the cell walls of the GSBR-25 foam tended to decrease overall (indicated by white arrows) compared to the cell walls of the GSBR-50 foam, and the white circled areas indicated that adjacent cells were interconnected to form locally interconnected channels.

As shown in fig. 5e, the cell size of the GSBR-12.5 foam was further increased.

The small white circle in fig. 5f is the connecting channel between a cell and an adjacent cell, and the large white circle is a large size cell with a size of up to 200 μm, but still having a closed cell structure.

FIG. 5g is a cross-sectional profile of a GSBR-6.25 foam having a large cell size of about 120 μm with a large number of small cells. The inner wall of the cell is a GO-loaded carrier, and the more the cells are, the larger the total surface area of the cells is, and the more GO can be adsorbed.

As shown in fig. 5h, GSBR-6.25 cell walls were thinner, surface roughened, cell bottoms were connected, showing an open cell structure (shown by white circles) compared to GSBR-12.5 foam; the cells are mutually communicated to form a three-dimensional communicated cell channel.

FIG. 6 is a graph of the cell size distribution of the foam:

as shown in FIG. 6a, the GSBR-50 foam has a narrow pore size distribution with over 75% of the cells having a size of 30-40 μm.

The GSBR-25 foam has a broader distribution of cell sizes, mainly in the range of 30-90 μm, compared to GSBR-50 foam, where the proportion of cells with a cell size of about 50 μm is the most and the size of the largest pores can reach 150 μm (fig. 6 b).

For the GSBR-12.5 foam (FIG. 6c), the distribution of cell sizes is further broadened compared to the GSBR-50 foam, and the maximum cell size can reach 280 μm.

For the GSBR-6.25 foam (fig. 6d), the cell size did not continue to increase with increasing water content. The cells in the GSBR-6.25 foam with large size over 150 μm are reduced compared to the GSBR-12.5 foam, and the GSBR-6.25 cell size distribution is narrowed, shifting towards small size.

FIG. 7 is a graph of the average cell size of the foam:

as shown in fig. 7a, the average size of the cells of the GSBR foam increased as the solids content decreased, and the maximum value appeared for the average size of the cells of the GSBR foam when the solids content was 12.5%; when the solid content was 6.25%, a decrease in the average cell size occurred.

The cell density of the GSBR foam is calculated according to formula 5-1, and the cell density of the GSBR foam is reduced and then increased. As can be seen from FIG. 7b, the cell density of the GSBR foam is 1X 10¹¹～6×10¹¹cells/cm³Within the range.

The GSBR-6.25 foam material with an open-cell structure is soaked in GO water dispersion liquid by a vacuum auxiliary soaking method, and then GO adsorbed in the cell is reduced in situ by hydrazine hydrate to obtain the GSBR/rGO foam material. FIG. 8 is a cross-sectional SEM topography of GSBR/rGO foam before and after compression.

FIG. 8a is an SEM image of a cross section of a GSBR foam before compression, wherein cells are oval and have a size of 50-200 μm; the walls of the foam holes are mutually extruded, and the foam holes are obviously deformed; the adjacent cells are mutually communicated (in the direction of white arrows) to form communicated cell channels.

FIG. 8b is an enlarged partial view of FIG. 8a, with black arrows indicating cell walls of GSBR foam having smooth cross sections and no rGO cladding; the white arrows indicate the inner walls of the cells of the GSBR foam, and the surface of the cells is coated with rGO sheets.

The rGO has an obvious fold structure, and the rGO lamella is tightly adsorbed on the inner wall of the cell of the GSBR foam material, which shows that the ordered distribution of the rGO lamella on the inner wall of the cell of the GSBR foam material communicated with each other is successfully realized by adopting a vacuum-assisted impregnation method.

Fig. 8c and 8d are SEM images of the GSBR foam cross section after compression.

As shown in fig. 8c, after compression, the structure of the GSBR foam did not change significantly from that before compression (fig. 8a), indicating that the GSBR foam had a compressible-resilient characteristic;

from fig. 8d it can be seen that rGO lamellae are tightly adsorbed to the inner cell walls of the GSBR foam (indicated by white arrows) with no significant change compared to before the compression treatment. This indicates that rGO can be tightly adsorbed in GSBR foam, which may be related to good flexibility of rGO, capillary action during impregnation and drying, and good interaction of rGO with SBR.

FIG. 9 is Raman spectra of GO, GSBR/GO and GSBR/rGO foams:

as shown in FIG. 9, the Raman spectra of GO, GSBR/GO and GSBR/rGO foams all show obvious D peak and G peak, which are respectively located at 1342cm^-1And 1583cm^-1At, it respectively corresponds to sp³Disordered structural regions and sp of hybridized carbon²Graphitic structural regions of hybrid carbon.

In raman spectroscopy, the intensity ratio of the D and G peaks (ID/IG) is often used to characterize structural defects and the degree of disorder of carbon materials.

The intensity ratio of the D and G peaks (ID/IG) of GO was 0.97, which is consistent with previous experimental results.

The ID/IG of GSBR/GO is 0.72, and after reduction with hydrazine hydrate, the ID/IG of GSBR/rGO is improved to 1.31, which indicates that GO is successfully reduced to rGO in situ.

FIG. 10 is a graph showing the relative rate of change of resistance, σ, for SBR/rGO foams with maximum strain of (a) 37%, (b) 55%, (c) 78% in this order_νCurve of variation with strain and (d) σ_νPeak-to-peak analysis of (1):

as shown in FIG. 10a, in the compression process (maximum compressive strain 37%), σ is increased with the increase of strain_νAnd continuously decreases, and negative values appear. This indicates that the GSBR/rGO foam is continuously resistive during compressionThe reduction, i.e. the improvement of the electrical conductivity of the foam material. In the recovery process, in the process that the compressive strain is reduced from 37% to 20%, the recovery curve is linearly changed and is superposed with the compression curve, which indicates that a linear change interval exists in the compression-recovery process; when the compressive strain is less than 20%, σ_νContinuing to increase, wherein the numerical value of the recovery curve is higher than that of the compression curve of the corresponding strain interval; when it returns, its sigma_νGreater than 0, indicating that the electrical conductivity of the GSBR/rGO foam decreases after compression-recovery treatment.

As shown in FIG. 10b, in the compression process (maximum compressive strain 55%), σ is increased with the increase of strain_νThe values are all below 0, which is similar to the 37% compression process. In the recovery process, σ_νIn the process of 55% to 10%, the recovery curve and the compression curve are basically overlapped, and a linear change interval exists; when the compressive strain is less than 10%, the slope of the recovery curve is greater than that of the compression curve, sigma_νValues are greater than 0 but less than the corresponding value of 37%. As shown in FIG. 10c, when the maximum compression strain is 78%, σ is the compression process_νContinuously decrease, during the recovery process, σ_νContinuously rising; while the whole compression-recovery process, σ_νThe value is less than 0, which shows that the electrical conductivity of the GSBR/rGO foam material is better than the initial electrical conductivity in the process.

It is noted that during the compression-recovery process at 37%, 55% and 78% strain, a region where the recovery curve and the compression curve coincide, and σ is present_νThe linear variation of the value with strain, this region may be referred to as the linear region. The characteristic of the linear region is beneficial to expanding the application of the GSBR/rGO foam material in the fields of pressure sensors and the like.

FIG. 10d is σ for GSBR/rGO foam at maximum strain during compression-recovery (37%, 55%, and 78%)_νAnd (5) carrying out numerical comparison analysis. After compression, σ thereof_νThe values are all less than 0 and decrease progressively in the order of strain 37%, 55% and 78%. This indicates that the compression treatment results in an increase in the electrical conductivity of the GSBR/rGO foam, and that its electrical conductivity increases with increasing compressive strain. This may be due to compressionIn the process, the rGO sheets adsorbed on the inner wall of the GSBR/rGO foam material form a more compact and complete conductive network. Sigma of GSBR/rGO foam after recovery treatment_νThe values are gradually decreased in the order of 37%, 55%, and 78%.

To further study the effect of compression set on the structure of GSBR/rGO foams, the following procedure was designed: the GSBR/rGO foam material is compressed and then rapidly returns to the initial state as shown in the inset in FIG. 11, and the change rule of the resistance of the GSBR/rGO foam material along with time is recorded.

The relative change rate sigma of the resistance is calculated according to the formula 5-1_νTime dependence. Sigma of compressed-recovered GSBR/rGO foam_νThe time course is shown by the line in fig. 11. The change in resistance of the GSBR/rGO foam over time is in three stages; first decrease rapidly, then decrease slowly, and finally gradually return to 0. This indicates that the GSBR/rGO foam is able to revert to the original state.

After the compression-recovery treatment, the resistance of the GSBR/rGO foam material is continuously reduced, and the conductivity of the GSBR/rGO foam material is gradually recovered to the initial state. This is related to the redistribution of rGO sheets within the inner walls of the GSBR/rGO foam. The compression-recovery process destroys the conductive network formed by rGO, which returns to the original state over time.

Sigma of GSBR/rGO foam within the first 5min_νThe value decreases rapidly, and the stage corresponds to the rapid recovery of the cellular structure under large deformation; sigma of GSBR/rGO foam material within 5-100min_νThe value slowly decreases, this stage is related to the process of changing from loose contact to close contact between the adsorbed rGO sheets on the inner walls of the cells; sigma of GSBR/rGO foam material after time is more than 100min_νThe values substantially trend towards 0, indicating that the GSBR/rGO foam has substantially reverted from a large deformation to the initial state. It is noted that variations in the shape and size of the foam material also have an effect on its electrical resistance.

In summary, the change in electrical conductivity of the compression-recovery processed GSBR/rGO foam has a time delay effect.

The thermal stability of the GSBR foam was tested:

thermal stability of GSBR foams was studied using thermogravimetric analysis (TGA). The content of graphene in the GSBR-50, GSBR-25, GSBR-12.5 and GSBR-6.25 foam materials is increased in sequence.

Table 5-1 shows the thermal weight loss parameters for GSBR-50, GSBR-25, GSBR-12.5 and GSBR-6.25 foams.

Initial decomposition temperature T of GSBR-50 foam₅308.1 ℃, the initial decomposition temperatures of the GSBR-25, GSBR-12.5 and GSBR-6.25 foam materials are sequentially increased to 330.2 ℃, 331.9 ℃ and 345.7 ℃, and the amplification degrees are sequentially increased to 22.1 ℃, 23.8 ℃ and 37.6 ℃.

This indicates that the graphene sheet layer plays a physical barrier role in SBR, delaying the degradation process of SBR. At the same time, the fastest decomposition temperature T of the GSBR-50, GSBR-25, GSBR-12.5 and GSBR-6.25 foam materials_maxAnd temperature T at 50% weight loss on heating₅₀Are all sequentially increased, and the fastest decomposition temperature T of the GSBR-6.25 foam material_maxT of GSBR-50 foam_maxThe T of the GSBR-6.25 foam material is improved by 54.5 DEG C₅₀T of GSBR-50 foam₅₀The temperature is increased by 25.6 ℃.

This is also related to the physical barrier effect of the graphene sheets, slowing the degradation process of the GSBR.

TABLE 5-1 thermal weight loss parameters for GSBR-50, GSBR-25, GSBR-12.5 and GSBR-6.25 foams

The above description is only an example of the present invention and is not intended to limit the scope of the present invention, and all equivalent modifications made by the present invention as described in the specification of the present invention or directly or indirectly applied to the related technical fields are included in the scope of the present invention.