CN112375387A

CN112375387A - Stress-buffering silicone rubber foam material and preparation method thereof

Info

Publication number: CN112375387A
Application number: CN202011372771.5A
Authority: CN
Inventors: 唐昶宇; 向亮; 朱晓伟; 温金鹏; 白龙腾; 谭鸿; 陈勇前; 邵虹
Original assignee: General Engineering Research Institute China Academy of Engineering Physics; Chengdu Science and Technology Development Center of CAEP
Current assignee: General Engineering Research Institute China Academy of Engineering Physics; Chengdu Science and Technology Development Center of CAEP
Priority date: 2020-11-30
Filing date: 2020-11-30
Publication date: 2021-02-19
Anticipated expiration: 2040-11-30
Also published as: CN112375387B

Abstract

The invention relates to the field of polymer porous materials, in particular to a stress buffering silicone rubber foam material and a preparation method thereof. The foam material comprises at least two basic structure units, each of which comprises a first cell wall layer and a second cell wall layer which are stacked on each other; the first unit wall layer comprises a plurality of first silicon rubber strip groups which are arranged in parallel at equal intervals; the second unit wall layer comprises a plurality of second silicon rubber strip groups which are arranged in parallel at equal intervals; the included angle between the first silicon rubber strip group and the second silicon rubber strip group is 90 degrees; the first silicon rubber strip group comprises at least one silicon rubber strip, and the second silicon rubber strip group comprises at least one silicon rubber strip; the overlapping ratio of the first silicon rubber strip group and the second silicon rubber strip group is 0.15-0.5. The material has good elastic buckling platform length and good stress fluctuation range, and can be used for stress buffer protection of high-end equipment and precise electronic key components.

Description

Stress-buffering silicone rubber foam material and preparation method thereof

Technical Field

The invention relates to the field of polymer porous materials, in particular to the field of design and preparation of a silicon rubber porous microstructure, and specifically relates to a stress buffering silicon rubber foam material and a preparation method thereof.

Background

The equipment is often exposed to complex environments such as temperature change, vibration and the like in the service section of the whole service life such as storage, transportation, emission and the like. These factors may cause the displacement, loosening or overload damage of the functional components inside the equipment, and bring a serious threat to the reliability and safety of the equipment. The silicon rubber foam material is a porous high-molecular elastomer material taking silicon rubber as base rubber, integrates the characteristics of the silicon rubber and the foam material, has the characteristics of low relative density, large compressible deformation amount, irradiation resistance, thermal-oxidative aging resistance, wide working temperature range (-60 ℃ to 200 ℃) and the like, can be used for damping, vibration reduction and stress buffering, can effectively buffer stress change, and has important application in the fields of national defense equipment and high-end electronics.

The traditional method for manufacturing the silicon rubber porous material mainly prepares the porous foam through chemical foaming (CN 106589959A; CN 104774473A; CN 106589958A) or physical dissolution (CN 106433139A; CN 103130454B; CN 101199867B), and the foaming process and the silica gel curing process are coupled, so that the size distribution of a cell structure is uneven, the uniformity and controllability of the structure and the performance of the silicon rubber porous material are poor due to disordered distribution of cells, a compression curve of the silicon rubber foam almost has no stress platform, and the buffering and energy absorption performance is not ideal.

In recent years, the 3D printing method is adopted to prepare the silicon rubber porous material (CN 105599311A; CN 105818378A; CN 106751906A; adv.Funct.Mater.2014,24, 4905-. At present, a Simple Tetragonal (abbreviated as ST) type microporous structure exists, a porous silicon foam material with the microporous structure is subjected to additive manufacturing in an abab type arrangement mode (the direction a is perpendicular to the direction b), although the porous silicon foam material shows uniform stress distribution in a uniaxial compression state, the width of a stress platform area is short, and the porous silicon foam material cannot well adapt to the corresponding mechanical use environment requirements.

The abab structure, which is widely used in many documents, requires at least 8 layers and has certain requirements on the porosity of the porous material to enable the stress plateau effect of a less obvious foam structure to be observed, while in another aabb structure, which is an extended structure developed by the inventor before, a basic structure comprising 4 layers of silicon rubber line groups is enough to generate the obvious plateau effect, and of course, the basic structure also causes problems, such as that the height of the stress plateau is greatly reduced, the stress fluctuation is extremely serious, and a jagged and extremely unstable stress curve is presented; this structure requires at least two infrastructures, i.e. groups of 8 layers of silicone rubber lines, for application possibilities, which results in printed product thicknesses that are difficult to apply in the context of some ultra-thin applications.

The existing silicone rubber foam material with an abab structure or an aabb structure prepared by 3D printing has large stress fluctuation range, and the printed product has high thickness.

Disclosure of Invention

The invention aims to: aiming at the problem that the stress fluctuation amplitude is large when the existing silicon rubber foam material is bent in the prior art, the silicon rubber foam material for buffering the stress is provided, and has good elastic bending platform length and good stress fluctuation amplitude by arranging an overlapping part between two adjacent silicon rubber strip groups and controlling the overlapping proportion within the range of 0.15-0.5.

In order to achieve the purpose, the invention adopts the technical scheme that:

a stress-buffering silicone rubber foam material comprising at least two basic structural units, each of said basic structural units comprising a first cell wall layer and a second cell wall layer stacked on top of each other;

the first unit wall layer comprises a plurality of first silicon rubber strip groups which are arranged in parallel at equal intervals;

the second unit wall layer comprises a plurality of second silicon rubber strip groups which are arranged in parallel at equal intervals;

the included angle between the first silicon rubber strip group and the second silicon rubber strip group is 90 degrees;

the first silicon rubber strip group comprises at least one silicon rubber strip, and the second silicon rubber strip group comprises at least one silicon rubber strip;

the overlapping ratio of the first silicon rubber strip group and the second silicon rubber strip group is 0.15-0.5;

the overlap ratio is calculated by the following formula;

the unit of the height of the lifting needle is the same as that of the height of the silica gel strip.

The traditional 3D direct-writing printing method adopts high-thixotropy and high-viscosity ink, the overlapping between the first silicon rubber strip group and the second silicon rubber strip group is not controlled, the first silicon rubber strip group and the second silicon rubber strip group form weak connection, layering or mechanical instability can be caused between the first silicon rubber strip group and the second silicon rubber strip group when foams are compressed under stress, and therefore good combination connection between the first silicon rubber strip group and the second silicon rubber strip group is very important. The length of the stress platform interval of the silicon rubber foam material in a uniaxial compression state is more than 25%. The segment of the curve in which the stress-strain slope <1 is defined as the stress plateau. The stress fluctuation amplitude in the stress platform area is quantitatively represented by the stress difference between the peak top and the peak bottom of the maximum stress fluctuation peak in the platform area.

When the overlapping proportion of the first silicon rubber strip group and the second silicon rubber strip group is 0.15-0.5, the stress fluctuation amplitude is greatly reduced to be below 20kPa under the condition that the length of a foam material compressive stress platform interval is ensured to be more than 25%. By arranging the overlapping portion, not only is the stress fluctuation amplitude reduced, but also the overall thickness of the foam material is reduced due to the overlapping arrangement. The preferred overlap ratio is 0.2-0.4. Further preferably, the overlap ratio is 0.25.

As a preferable aspect of the present invention, each of the first silicone rubber strip groups includes two silicone rubber strips stacked in a vertical direction; each second silicon rubber strip group comprises two silicon rubber strips which are stacked in the vertical direction.

Defining the line group at the bottommost layer and the layer parallel to the direction of the line group as a layer, and defining the layer vertical to the direction of the line group as b layer, wherein the scheme is an aabb type scheme.

The inventor researches the structure to find that the effectiveness of the aabb type structure in widening the stress platform interval is realized, the buckling platform of the aabb type structure is reversible when the structure mainly occurs in the silicon rubber line group (aa or bb) which is overlapped by double layers after pressure is applied to the structure in an inclined collapse mode. Meanwhile, the protocell takes 4 layers as a repeating unit, and the flexibility is high, so that compared with an abab type structure, elastic buckling can be easily generated to further generate a stress platform. However, due to the fact that the primitive cell repeating unit is 4 layers, under the 4-layer structure, stress fluctuation in the stress platform is severe and is not suitable for practical application scenes, at least 8 layers of structures are needed to be relatively stable, application possibility of the structure in ultrathin application scenes is limited, and meanwhile, due to the fact that the aabb type structure is easy to elastically buckle, the stress value of the stress platform is relatively reduced.

Experiments have shown that for foam materials of aabb structure with 4 layers printed, the stress fluctuation amplitude is reduced from 112kPa to 25kPa by providing an overlap. For the foam material of the aabb structure with 8 printing layers, the stress fluctuation amplitude is reduced from 23kPa to 14 kPa. That is, for the foam material with aabb structure, the stress fluctuation range of the material can be obviously reduced by arranging the overlapping part.

As a preferable aspect of the present invention, each of the first silicone rubber strip groups includes two silicone rubber strips stacked in a vertical direction; each second silicone rubber strip group comprises a silicone rubber strip.

The above scheme is an aab-type scheme. The aabb type scheme can meet the requirement of stress fluctuation amplitude under the condition of 8 layers, and the printed product is thick and cannot be applied to ultrathin application scenes.

In order to improve a stress platform and make silicone rubber foam thinner, an inventor carries out corresponding design modification on an ordered structure, and on the basis of an aabb structure, mechanical simulation guidance and actual experiment verification are carried out, and a double-layer superposed structure is reserved on a silicone rubber line group in a single direction, and the silicone rubber line group layer is designed in the other direction. Therefore, according to the analysis of the technical principle, the inventor proposes the stress-buffering silicone rubber foam material, wherein the foam material is formed by repeatedly overlapping two or more basic structures, and each basic structure is formed by overlapping and arranging 3 layers of silicone rubber line groups in a mode of aab or abb. Under the prerequisite that keeps silicon rubber strip diameter d of appearing unchangeable, aa in novel silicon rubber ordered porous material structure or bb two-layer height h be close to 2 times of diameter (d), ratio (h/d) between them is greater than the critical buckling flexibility value 1.5 of pore wall, and only need two aab repeating unit (6 layers totally) alright produce comparatively showing and the lower bucking platform effect of volatility under the unipolar compression state, and along with the increase of repeating unit number, the platform buckling effect is more obvious, the platform is more steady. In this scenario, a minimum of 6 layers are printed, corresponding to a thickness of at most less than 1mm, the structure promotes a wide stress plateau (cushioning ability) for foams at very thin thicknesses, whereas abab structures typically require more than 12 layers to be printed to exhibit similar mechanical properties. The surface of the lowermost silicone strip is preferably a plane surface because the contact surface of the lowermost silicone strip with the printing base becomes a plane surface under the self-gravity and the pressure of the upper silicone strip during the printing process.

As a preferable aspect of the present invention, each of the first silicone rubber strip groups includes one silicone rubber strip; each second silicon rubber strip group comprises two silicon rubber strips which are stacked in the vertical direction; one side of the first silica gel strip group, which is far away from the second silica gel strip group, is a plane.

The scheme is the abb scheme. I.e. layer a is below and two b layers are printed above layer a. In this case, the bottom surface of the a-layer is flat due to gravity, which increases the restraint during compression. Under the condition that other parameters are kept the same, the abb arrangement sequence is more stable than the elastic buckling stress platform interval stress value in a uniaxial compression state shown by the aab arrangement sequence, and the fluctuation is lower.

As a preferable scheme of the invention, the stress-buffering silicone rubber foam material comprises two base units, the total thickness is less than or equal to 1mm, and the thickness is more than 0 mm.

The base unit of the stress-damping silicone rubber foam material is compressed to 2, i.e. only 6 layers in total, and the thickness thereof is compressed to 1mm or less while maintaining the mechanical properties of the material. The method is suitable for ultrathin application scenes.

As a preferable scheme of the invention, the arrangement distance between the adjacent first silicon rubber strip groups is 0.01-1.0 mm; the arrangement distance between the adjacent second silicon rubber strip groups is 0.01-1.0 mm.

The interlayer height of each of the cell wall layers is 0.01 to 1mm, more preferably 0.1 to 0.3 mm; the arrangement pitch of the silicon rubber body strip groups arranged in parallel in each unit wall layer is 0.01-3.0mm, and more preferably 0.1-2 mm.

A method for preparing a silicon rubber foam material for buffering stress,

s1, performing 3D printing path planning on the ink to be printed according to the structure of the stress-buffered silicon rubber foam material, and printing the corresponding stress-buffered silicon rubber foam material according to the planned 3D printing path;

s2, after the first cell wall layer is printed, setting the needle lifting height according to the planned overlapping proportion by taking the upper surface of the first cell wall layer as a datum plane;

printing a second cell wall layer, and heating the part of the printed silica gel strip overlapped with the second cell wall layer before printing the silica gel overlapped with the first cell wall layer in the second cell wall layer; heating at 40-70 deg.c;

and S3, heating and curing the printed material after printing is finished, and obtaining the stress-buffering silicone rubber foam material.

The height of each layer of silicon rubber line group is accurately controlled with the precision of 0.01mm, and then the direct contact area of each adjacent two layers of silicon rubber line groups (namely the height of the overlapping part between the two layers of silicon rubber line groups) is regulated, especially the contact area between the adjacent ab layer silicon rubber line groups can be pertinently increased, so that the overlapping degree between the two groups of silicon rubber line groups which are vertical to each other is increased, and the purpose of adjusting the fluctuation of the stress curve in the stress platform area can be effectively achieved through the mode. So as to further reduce the whole thickness and stress fluctuation of the stress platform area.

The overlapping degree is realized by adjusting the height of the lifting pin between two adjacent layers in the 3D printing process, and when the layer to be printed is different from the layer which is printed only (not being a layer or b layer), the height of the lifting pin is controlled to be pressed down to a desired value. When the height h of the overlapping portion is less than 0.6h0, the overlapping portion is too large, resulting in a shortened plateau region length.

Meanwhile, in the process, a local heat source is applied by illumination, the viscosity of the silicone rubber lines in the overlapped area during printing is reduced, the viscosity of the first unit wall layer is reduced by local infrared heating, and the second layer vertically passes through the first unit wall layer, so that structural damage is avoided in the printing process of the porous material with high overlapping degree.

Under the condition that the overlapping proportion is 0.15-0.5, the length of the platform interval can be ensured to be more than 25%, and the good stress fluctuation amplitude is less than 20 KPa.

As a preferable aspect of the present invention, the viscosity of the printing ink is 100-650 pa.s; the ink has a gel time of more than 10min at a temperature of 40-80 ℃.

As a preferable scheme of the invention, when 3D printing is carried out, a 3D printer with a printing needle head with the inner diameter of 0.06-1mm is used, and the printing speed is controlled to be 1-20 mm/s.

The problem that the silicon rubber strips are difficult to extrude when the viscosity of the silicon rubber is too high is solved, the silicon rubber strips are difficult to extrude when the viscosity of the silicon rubber is too low and difficult to form, the printing speed and the filament outlet line width of a silicon rubber ordered porous structure and the viscosity of slurry are indirectly influenced by the inner diameter of a printer needle head, the silicon rubber filament outlet diameter is easy to lead to too wide when the inner diameter is too large, the silicon rubber strips stacked in a lamination mode in each silicon rubber strip group are excessively deformed, the silicon rubber strips collapse and deform in the vertical direction, the interlayer height h of the whole silicon rubber microporous structure is reduced, and therefore the mechanical property of the whole silicon rubber ordered porous material is; the silicon rubber is too slow to be discharged due to the excessively thin inner diameter of the needle head, and the forming and stress strength of the whole silicon rubber material can be caused due to the insufficient consumption of raw materials, so that the silicon rubber with proper viscosity and the proper inner diameter of the needle head are more favorable for ensuring the quality of the silicon rubber ordered porous material. And similarly, the printing speed is controlled in the range, so that the continuity and the uniformity of lines of the printed sample are guaranteed.

As a preferable scheme of the invention, the temperature for heating and curing is 100-150 ℃, and the curing time is 20-120 min. The proper heating temperature and sufficient heating time can ensure that the cross-linking curing reaction of the silicon rubber porous material printing sample is more complete and the curing efficiency is higher.

As a preferable aspect of the present invention, the printing ink contains the following materials in parts by weight:

100 parts of vinyl-terminated silicone oil;

15-20 parts of inorganic nano filler; the inorganic nano filler has a specific surface area of more than 200m²(ii) fumed silica per gram;

3-8 parts of light absorption heat transfer material; the light absorption heat transfer material is carbon black or carbon nano tubes;

0.1-0.3 part of catalyst; the catalyst is a platinum catalyst;

1-5 parts of an inhibitor; the inhibitor is one or more of 1-ethynyl-1-cyclohexanol, 2-methyl-3-butyn-2-ol, propargyl alcohol, 3-butyn-1-ol, 3, 5-dimethyl-1-hexyn-3-ol and 3,7, 11-trimethyldodecyn-3-ol.

1-2 parts of a thixotropic auxiliary agent; the thixotropic auxiliary agent is a resin thixotropic agent.

1-3 parts of hydrogen-containing silicone oil.

Controlling infrared energy by adding the light absorption heat transfer material in parts by weight; the silica gel strip that makes in the printing can fully absorb the infrared ray and convert the heat into, and the temperature risees and makes viscosity reduce to can not lead to the lines crooked because of viscosity is too high when controlling the overlap proportion, can not produce high temperature again because of the power of infrared ray is too high, and it leads to solidifying in advance, and this kind of scheme does benefit to and controls the overlap proportion of lines at the printing in-process. The instantaneous temperature of the material after infrared irradiation is between 40 and 70 ℃.

The amount of inhibitor used is higher than that used in conventional printing inks.

As a preferable aspect of the present invention, the printing ink is prepared by the following method:

mixing the terminal vinyl silicone oil, the inorganic nano-filler, the light absorption heat transfer material, the catalyst and the inhibitor in a formula amount at a speed of 1000-1200r/min by a high-speed dispersion machine at room temperature for 10-15min to obtain a first mixture;

secondly, adding hydrogen-containing silicone oil and a thixotropic auxiliary agent into the first mixture, and mixing the mixture for 10-15min at the speed of 1000-1200r/min by using a high-speed dispersion machine at room temperature to obtain a second mixture;

thirdly, the second mixture is placed into a centrifuge at room temperature, and the printing ink is obtained after centrifugation and deaeration for 8-10min at the speed of 7000-8000 r/min.

The interlayer height of the cell wall layer, the arrangement distance of the silicon rubber strip groups and the diameter of the silicon rubber strip groups in the stress-buffering silicon rubber foam material can be accurately adjusted according to the use requirements, and the deformation characteristics of the silicon rubber ordered porous material are obviously influenced by parameter adjustment, so that a series of silicon rubber ordered porous structures with different stress platform area widths can be obtained, and the use requirements of various fields can be met.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. according to the stress-buffering silicon rubber foam material, when the overlapping proportion of the first silicon rubber strip group and the second silicon rubber strip group is controlled to be 0.15-0.5, the stress fluctuation amplitude is greatly reduced to be below 20Kpa under the condition that the length of a compression stress platform interval of the foam material is more than 25%. By arranging the overlapping portion, not only is the stress fluctuation amplitude reduced, but also the overall thickness of the foam material is reduced due to the overlapping arrangement. The foam material with the configuration of aabb, abb, aab and the like can play a role in reducing the stress fluctuation amplitude.

2. According to the stress-buffering silicone rubber foam material, the overlapping structure is arranged, and the overlapping proportion is controlled, so that three layers of silicone rubber line groups which are sequentially overlapped by aab or abb are a basic structure layer, and two or more basic structure layers are overlapped repeatedly. Compared with the existing abab type silicon rubber microporous structure, the structure has a wider buckling platform section made of the silicon foam material, and can effectively control the stress fluctuation range of the silicon foam material; compared with an aabb type silicon rubber microporous structure designed before, the number of primitive cell layers of the repetitive structure is reduced from 4 to 3, a stress platform effect can be realized under the condition of lower number of layers and thinner thickness, and meanwhile, the strength of the stress platform is higher than that of the aabb structure under the same number of layers, so that the stress platform can be applied to thinner and more limited buffer damping application scenes. In a more preferred embodiment, the stress-damping silicone rubber foam comprises two base units, i.e. a total of 6 silicone strips, with a total thickness of not more than 1 mm.

3. According to the preparation method of the stress buffering silicon rubber material, the second unit wall layer is printed, and the part of the printed silica gel strip overlapped with the second unit wall layer is heated before the silica gel overlapped with the first unit wall layer in the second unit wall layer is printed; heating at 40-70 deg.c; and 3-8 parts by weight of light absorbing and heat transferring material and 3-8 parts by weight of inhibitor are added in the printing ink, and the amount of the inhibitor is increased by increasing the light absorbing and heat transferring material. After the first cell wall layer is finished and the second cell wall layer is printed on the upper side of the first cell wall layer, the part to be overlapped in the first cell wall layer can be locally heated, so that the overlapping proportion between the second cell wall layer and the first cell wall layer is easier to control, the structure is more stable, and the design requirements are better met.

4. According to the preparation method of the stress buffering silicone rubber material, the silicone rubber foam material structure can accurately control the needle lifting height of each layer in the printing process, so that the overlapping degree of the overlapping area between two adjacent layers of silicone rubber line groups is regulated and controlled, and further the stress fluctuation range of the stress platform area of the whole material is regulated and controlled. In the printing preparation process, a light source which moves in parallel with the needle head irradiates on the lower layer of lines to reduce the viscosity of the lower layer of silicon rubber lines, so that the lines with high overlapping height ratio are overlapped on the premise of not damaging the structure.

5. According to the preparation method of the stress-buffering silicone rubber material, the silicone rubber ordered porous structure can be accurately controlled through a 3D printing technology, and the structural length parameter of the silicone rubber ordered porous structure can be flexibly allocated according to the actual application requirements, so that the prepared silicone rubber ordered porous material is ensured to have better buffering and energy-absorbing properties, and simultaneously, the environmental requirements for different mechanics can be met, and the applicable field of the silicone rubber foam material is further widened.

Drawings

Fig. 1 is a schematic spatial structure diagram of a conventional abab-type silicone rubber porous material with 2 base structure layers.

Fig. 2 is a side view of fig. 1.

FIG. 3 is a schematic spatial structure diagram of an aabb type silicone rubber ordered porous material with 2 base structure layers according to the invention; reference number 1-base unit in the figure; 2-silica gel strip layer; 3-a silicone strip group; 4-silica gel strip.

Fig. 4 is a side view of fig. 3.

FIG. 5 is a schematic view showing a connection relationship between a silicone strip in the first wall layer and a silicone strip in the second wall layer;

reference numeral in the figure, 100 — a silicone gel strip in the first cell wall layer; 200-a silicone strip in the second cell wall layer; a-needle lifting height; and b-the silica gel strip layer is high. The overlap ratio was 1- (a/b).

Fig. 6 is a schematic spatial structure diagram of the aab type silicone rubber ordered porous material (aab stacked) with 1 base structure layer according to the invention.

Fig. 7 is a side view of fig. 6.

Fig. 8 is a schematic spatial structure diagram of the aab type silicone rubber ordered porous material (aab stacked) with 2 basic structure layers according to the invention.

Fig. 9 is a side view of fig. 8.

Fig. 10 is a schematic space structure diagram of part of the aab type silicon rubber ordered porous material (abb superposed) with 1 basic structure layer.

Fig. 11 is a side view of fig. 10.

Fig. 12 is a schematic spatial structure diagram of an abb-type silicone rubber ordered porous material (abb superposition) with 2 basic structure layers.

Fig. 13 is a side view of fig. 12.

Fig. 14 is a graph comparing the experimental stress-strain curves of the aab-type (6-layer) structure material of example 1 and the abb-type (6-layer) structure silicone rubber porous material of example 2 in the compression experiment.

Fig. 15 is a graph of the stress-strain curves of the compression experiment of the aab-type (6-layer) structural material of example 1 and the aabb-type (8-layer) spatial structure silicone rubber porous material of example 4.

Fig. 16 is a graph comparing the stress-strain curves of the aab-type (6-layer) structural material of example 1 with the aab-type (6-layer) structural material of comparative example 1.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

The basic structural unit of this embodiment has a configuration aab, the number of printed layers is 6, the overall structure is aabab, the overlap ratio is 0.25, the structure is shown in fig. 6 to 9,

comprising two basic structure units each shown in fig. 6 and 7, an overlapping relationship of the two basic structure units each comprising a first cell wall layer and a second cell wall layer stacked on each other as shown in fig. 8 and 9;

the first silicon rubber strip group consists of two silicon rubber strips, and the second silicon rubber strip group consists of one silicon rubber strip; from bottom to top, an aab structure;

the overlapping ratio of the first silicon rubber strip group and the second silicon rubber strip group is 0.25;

the overlap ratio is calculated by the following formula;

the unit of the height of the lifting needle is the same as that of the height of the silica gel strip. As shown in FIG. 5, the overlap ratio is 1- (a/b).

The stress buffering capacity can be expressed by the work which can be absorbed by the material from the starting point to the end of the stress plateau area in the compression process, and because of different thicknesses of the material, the thicker the material with the same performance is, the stronger the capacity of naturally absorbing energy is. The performance of the materials for absorbing energy is defined by comparison for excluding the thickness factor;

wherein for an abab-type material without a stress plateau region, the work actually absorbed by the material from the start point to the end of the stress plateau is corrected to the work actually absorbed before densification of the material in units of millijoules (mJ).

The preparation method comprises the following steps:

1. preparation of printing ink

Mixing 100 parts of end vinyl silicone oil, 15 parts of fumed silica, 8 parts of light absorption and heat transfer materials, 0.2 part of catalyst and 2.5 parts of inhibitor at room temperature for 10min at the speed of 1000r/min by using a high-speed dispersion machine to obtain a first mixture; the light absorption and heat transfer material is carbon black, and the inhibitor is 1-ethynyl-1-cyclohexanol.

Adding 1 part of hydrogen-containing silicone oil and 2 parts of thixotropic auxiliary agent into the first mixture, and mixing for 15min at room temperature by adopting a high-speed dispersion machine at a speed of 1000r/min to obtain a second mixture;

namely vinyl-terminated silicone oil, inorganic nano filler, light absorption material, catalyst, inhibitor, thixotropic additive and hydrogen-containing silicone oil, the weight ratio of 100: 15: 8: 0.2: 2.5: 1:2.

Thirdly, the second mixture is placed into a centrifuge at room temperature, and the printing ink is obtained after centrifugation and deaeration for 8min at the speed of 8000 r/min.

2. Taking the silicone rubber subjected to centrifugal defoaming as a 3D printing raw material, planning a 3D printing path according to the aabab structure, and printing a corresponding silicone rubber ordered porous material structure according to the planned 3D printing path;

3. in the printing process, the needle heads with different apertures are selected, the printing speed is adjusted, the air pressure applied to the raw materials and the rotating speed extruded by the screw valve are controlled, and the thickness of the printed silicone rubber lines is controlled. Generally, the needle closest to the desired line thickness is selected and the line thickness is set to the desired value by the above parameters. In addition, the layer height of each silicone rubber thread group can be controlled by accurately controlling the needle lifting height at the beginning of the needle head printing of each silicone rubber thread group with the accuracy of 0.01 mm.

4. And in the printing process, controlling the infrared irradiation power to enable the instantaneous temperature of the silicon rubber right below the moving needle head to be 40-70 ℃, and monitoring the temperature by adopting an infrared thermal imager. As the printing proceeds, there is a fluctuation in temperature, but the whole is between 40-70 ℃.

5. After printing is finished, the printed silicon rubber ordered porous material is heated and cured step by step, and the heating and curing are carried out at the temperature of 120-150 ℃ for 1h, so that the silicon rubber ordered porous material with the wide stress platform area is obtained.

Namely, in the embodiment, the composite structure comprises two aab-type basic structure units, 6 groups of silicon rubber line layers are regularly overlapped from bottom to top, the overlapping mode is aabab, and the included angle between the layer a and the line group of the layer b is 90 degrees; the interval of the arrangement lines of each parallel arrangement silicon rubber strip group is 0.6mm, and the layer height of each silicon rubber strip group 2 is 0.2 mm; the cross-sectional diameter d of each silicone rubber strip was 0.23 mm. Through detection, the length of the elastic buckling stress platform interval of the silicon rubber foam material with the aab type silicon rubber ordered porous structure in a uniaxial compression state is 40%.

Example 2

The basic structural unit of this embodiment has a configuration of abb, the number of printed layers is 6 layers, i.e., abbabbab, the overlap ratio is 0.25, the structure is shown in fig. 10 to 13,

selecting nano silicon dioxide as a nano inorganic filler, selecting a carbon nano tube as a light absorption heat transfer material, selecting 2-methyl-3-butyne-2-ol as an inhibitor, and mixing vinyl-terminated silicone oil, the inorganic nano filler, the light absorption material, a catalyst, the inhibitor, a thixotropic additive and hydrogen-containing silicone oil by the weight ratio of 100: 18: 8: 5: 1: the ratio of 1:1 was mixed in the manner of example 1 to obtain a printing material.

Example 3

The basic structural unit of this example had a configuration aabb, the number of printed layers was 4, and the overlap ratio was 0.25.

Selecting nano silicon dioxide as a nano inorganic filler, selecting a carbon nano tube as a light absorption heat transfer material, selecting 2-methyl-3-butyne-2-ol as an inhibitor, and mixing vinyl-terminated silicone oil, the inorganic nano filler, the light absorption material, a catalyst, the inhibitor, a thixotropic additive and hydrogen-containing silicone oil by the weight ratio of 100: 20: 6: 0.2: 2: the ratio of 1:1 was mixed in the manner of example 1 to obtain a printing material.

The silicon rubber strips with the same material and shape as those in example 1 were used to form an aabb type silicon rubber ordered porous material, and 4 silicon rubber strip groups, each of which includes an aabb type base structure, were stacked in an aabb manner. Wherein the diameter of the cross section of each silicone rubber strip is d, and the arrangement line pitch of the silicone rubber strips is the same as that in example 1. It differs from example 1 in that: the two structures are different, and the layer number is different. Through detection, the width of the elastic buckling stress platform interval of the silicon rubber ordered porous material in a uniaxial compression state is 38%.

Example 4

The basic structural unit of this example has a configuration aabb, the number of printed layers is 8, i.e., aabbababb, the overlap ratio is 0.25, and the structure is shown in fig. 3 and 4.

Selecting nano silicon dioxide as a nano inorganic filler, selecting a carbon nano tube as a light absorption heat transfer material, selecting 2-methyl-3-butyne-2-ol as an inhibitor, and mixing vinyl-terminated silicone oil, the inorganic nano filler, the light absorption material, a catalyst, the inhibitor, a thixotropic additive and hydrogen-containing silicone oil by the weight ratio of 100: 18: 8: 0.3: 3: the 2:1 ratio was mixed in the manner of example 1 to obtain a printing stock.

The silicon rubber strips with the same material and shape as those in example 1 were used to form an aabb type silicon rubber ordered porous material, and 4 silicon rubber strip groups, each of which includes an aabb type base structure, were stacked in an aabb manner. Wherein the diameter of the cross section of each silicone rubber strip is d, and the arrangement line pitch of the silicone rubber strips is the same as that in example 1. It differs from example 1 in that: the two structures are different, and the layer number is different. Through detection, the width of the elastic buckling stress platform interval of the silicon rubber ordered porous material in a uniaxial compression state is 42%.

Comparative example 1

The comparative example differs from example 1 in that the overlap ratio is 0.

Comparative example 2

The comparative example differs from example 2 in that the overlap ratio is 0.

Comparative example 3

The comparative example differs from example 3 in that the overlap ratio is 0.

Comparative example 4

The comparative example differs from example 4 in that the overlap ratio is 0.

Comparative example 5

The present comparative example differs from comparative example 4 in that the number of printed layers was 12, i.e., aabbababb.

The present comparative example differs from comparative example 4 in that: the number of layers is 12, contains 3 foundation structures, and through detection, the width of the elastic buckling stress platform interval of the silicon rubber ordered porous material in a uniaxial compression state is 43%.

Comparative example 6

The basic structural unit of this comparative example had a configuration ab, and the number of printed layers was 6.

The same number, material and shape of silicone rubber strips as those in example 1 were used to form an abab-type silicone rubber ordered porous material, and 6 silicone rubber strip groups, each of which contained 3 ab-type base structures, were stacked in abababab. Wherein the diameter of the cross section of each silicone rubber strip is d, and the arrangement pitch of the silicone rubber strips is the same as that in example 1. It differs from example 1 in that: the two structures are different. Through detection, the silicon rubber ordered porous material has no elastic buckling stress platform in a uniaxial compression state.

Comparative example 7

The basic structural unit of this comparative example had a configuration of ab, and the number of printed layers was 8. The silicon rubber ordered porous material comprises 4 base structures, and elastic buckling stress platforms of the silicon rubber ordered porous material in a uniaxial compression state do not exist through detection.

Comparative example 8

The present comparative example differs from comparative example 1 in that: the number of layers is 10, and the silicon rubber ordered porous material comprises 5 base structures, and the width of an elastic buckling stress platform interval of the silicon rubber ordered porous material in a uniaxial compression state is 16%.

The experimental data of examples 1-4 and comparative examples 1-8 are summarized in the following table,

table 1: summary of Experimental data for examples 1-4 and comparative examples 1-8

The comparison results of example 1 and example 2 are shown in FIG. 14, the comparison results of example 1 and example 4 are shown in FIG. 15, the comparison results of example 1 and comparative example 1 are shown in FIG. 16,

as can be seen from the above-mentioned data,

1. the overlapping proportion has the effects of improving the height of the stress platform and reducing the fluctuation range of the stress for the aabb structure and the aab structure, wherein the influence optimization capacity on the aab structure is obviously stronger than that of the aabb structure.

2. abab configuration requires a certain number of layers to have a shorter stress platform; the aabb configuration 4 layer can have a stress platform, but the fluctuation of the platform is severe, and the height of the stress platform is low; the aab structure requires only 6 layers to have a relatively high stress plateau and a long plateau length.

3. There is some difference in the performance of the aab and abb configurations, relative to a lower amplitude of stress fluctuation for the abb configuration. Although the height of the stress platform is slightly lower, the requirement that the length of the elastic buckling platform is more than 25 percent is also met.

4. The control of a certain overlapping proportion can obviously improve the stress buffering capacity of the material.

Test example 1

The aab configuration was analyzed at different overlap ratios, and a 6 layer number of printed layers of foam was tested for performance according to the fabrication method of example 1. Experimental example design and test results are given in the following table:

table 2 shows the influence of the overlap ratio on the range width and stress fluctuation range of the elastic buckling stress platform

From the above data, it can be seen that the overlap ratio has a significant impact on the performance of the silicone rubber foam in the aab basic configuration. Generally speaking, as the overlapping proportion increases, the height of the stress platform increases, and the fluctuation amplitude of the stress decreases and then increases. When the overlapping proportion is 0.15-0.5, the length of the elastic buckling platform is more than 25%, the stress fluctuation amplitude is lower than 20KPa, and when the overlapping proportion is 0.2-0.4, the stress fluctuation amplitude is lower. And the overlap ratio is a relatively better value at 0.25.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A stress-buffering silicone rubber foam material comprising at least two basic structural units, each of said basic structural units comprising a first cell wall layer and a second cell wall layer stacked on top of each other;

the overlap ratio is calculated by the following formula;

2. The stress-absorbing silicone rubber foam material according to claim 1, wherein each of the first silicone rubber strip groups comprises two vertically stacked silicone rubber strips; each second silicon rubber strip group comprises two silicon rubber strips which are stacked in the vertical direction.

3. The stress-absorbing silicone rubber foam material according to claim 1, wherein each of the first silicone rubber strip groups comprises two vertically stacked silicone rubber strips; each second silicone rubber strip group comprises a silicone rubber strip.

4. The stress-absorbing silicone rubber foam material according to claim 1, wherein each of the first silicone rubber strip groups comprises a silicone rubber strip; each second silicon rubber strip group comprises two silicon rubber strips which are stacked in the vertical direction; one side of the first silica gel strip group, which is far away from the second silica gel strip group, is a plane.

5. The stress-cushioned silicone rubber foam of claim 1, comprising two base units, having a total thickness of less than or equal to 1mm and a thickness greater than 0 mm.

6. The stress-buffering silicone rubber foam material according to claim 1, wherein the arrangement pitch between adjacent first silicone rubber strip groups is 0.01 to 1.0 mm; the arrangement distance between the adjacent second silicon rubber strip groups is 0.01-1.0 mm.

7. A method of producing a stress-damping silicone rubber foam material as claimed in any of claims 1 to 6,

s1, planning a 3D printing path according to the structure of the stress-buffering silicone rubber foam material of any one of claims 1-6 to prepare for printing ink, and printing the corresponding stress-buffering silicone rubber foam material according to the planned 3D printing path;

printing a second cell wall layer, and heating the part of the printed silica gel strip overlapped with the second cell wall layer before printing the silica gel overlapped with the first cell wall layer in the second cell wall layer;

8. The method of claim 7, wherein the viscosity of the printing ink is 100-650 Pa.s; the ink has a gel time of more than 10min at a temperature of 40-80 ℃.

9. The method for preparing a stress-buffering silicone rubber foam material according to claim 7, wherein a 3D printer with a printing needle having an inner diameter of 0.06-1mm is used to control the printing rate at 1-20mm/s during 3D printing.

10. The method for producing a stress-damping silicone rubber foam material according to claim 7, wherein the printing ink contains the following components in parts by weight:

100 parts of vinyl-terminated silicone oil;

15-20 parts of inorganic nano filler;

3-8 parts of light absorption heat transfer material;

0.1-0.3 part of catalyst;

1-5 parts of an inhibitor;

1-2 parts of a thixotropic auxiliary agent;

1-3 parts of hydrogen-containing silicone oil.