CN114621495B - Silicone rubber foaming material and preparation method thereof - Google Patents
Silicone rubber foaming material and preparation method thereof Download PDFInfo
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- C08J2383/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
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- C08J2483/14—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers in which at least two but not all the silicon atoms are connected by linkages other than oxygen atoms
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Abstract
The invention relates to a silicone rubber foaming material and a preparation method thereof. The preparation method comprises the following steps: preparing polydimethylsiloxane, boric acid and derivatives thereof and an organic solvent into a polydimethylsiloxane solution, performing polycondensation reaction, and then removing unreacted boric acid and derivatives thereof and the organic solvent to obtain a shear thickening gel; mixing 1 to 10 parts by mass of the shear thickening gel with 100 parts by mass of vinyl-containing silicone rubber, obtaining a silicon rubber base material; mixing silicone rubber base material with 1-20 parts by mass of nano cellulose, 1-10 parts by mass of expansion microsphere mixing 0.01 to 0.5 parts by mass of an organic peroxide crosslinking agent, obtaining silicon rubber compound; the silicone rubber compound is subjected to the pre-forming and the cross-linking foaming are carried out, and obtaining the silicone rubber foaming material. The silicone rubber foaming material prepared by the preparation method has the advantages of high rebound, low compression deformation and the like, and can be better applied to the field of shock absorption and impact resistance.
Description
Technical Field
The invention relates to the technical field of foaming materials, in particular to a silicone rubber foaming material and a preparation method thereof.
Background
Compared with the traditional impact-resistant material, the shear thickening material has excellent damping performance and reversible soft-hard conversion characteristics. In its natural state, a shear thickening material can maintain good flexibility and when impacted, it can harden rapidly against the impact.
The shear thickening materials can be largely classified into shear thickening gels and shear thickening fluids, wherein the shear thickening gels have more excellent structural stability and high and low temperature resistance characteristics. However, since the shear thickening gel has strong cold flow properties, it cannot maintain its original shape in a natural state. Therefore, in the conventional art, a porous material is often used as a skeleton to coat the shear thickening gel to give it a certain shape. Although simple and effective, the adsorption force between the shear thickening gel and the porous material is weak, so that the structural stability of the shear thickening gel is poor.
The silicone rubber and the shear thickening gel have good compatibility, and the blending material of the silicone rubber has good high and low temperature resistance, electrical insulation property, radiation resistance and chemical stability, and has excellent mechanical property and damping property. In addition, the foaming material prepared based on the blending material has the excellent performances of light weight, good recovery, compression resistance and the like, and is an ideal shock absorption and impact resistance material. However, the blend material of the shear thickening gel and the silicone rubber has strong self-adhesion, and the blend material is directly foamed, so that the foam wall is very easy to adhere after being repeatedly compressed in the use process of the obtained foam material, and irreversible deformation is caused.
Disclosure of Invention
Based on this, it is necessary to provide a silicone rubber foam material and a method for producing the same in view of the above-mentioned problems; the silicon rubber foaming material obtained by the preparation method is difficult to adhere when repeatedly compressed foam walls are used, has the advantages of high rebound, low compression deformation and the like, has excellent comprehensive performance, and can be better applied to the fields of shock absorption and shock resistance.
A preparation method of a silicone rubber foaming material, which comprises the following steps:
preparing polydimethylsiloxane, boric acid and derivatives thereof and an organic solvent into a polydimethylsiloxane solution, performing polycondensation reaction, and then removing unreacted boric acid and derivatives thereof and the organic solvent to obtain a shear thickening gel;
mixing 1-10 parts by mass of the shear thickening gel with 100 parts by mass of vinyl-containing silicone rubber to obtain a silicone rubber base material;
mixing the silicone rubber base stock with 1 to 20 parts by mass of nanocellulose, 1 to 10 parts by mass of expanded microspheres and 0.01 to 0.5 part by mass of organic peroxide cross-linking agent to obtain silicone rubber compound; and
and (3) performing preforming, crosslinking and foaming on the silicone rubber compound to obtain the silicone rubber foaming material.
In one embodiment, the vinyl-containing silicone rubber has a mole fraction of vinyl groups of 0.05% to 1%.
In one embodiment, the vinyl-containing silicone rubber is selected from at least one of methyl vinyl hydroxyl silicone rubber, methyl vinyl phenyl silicone rubber, methyl vinyl silicone rubber, and methyl vinyl chloro silicone rubber.
In one embodiment, the polydimethylsiloxane solution comprises 10-15% by mass of polydimethylsiloxane, 0.5-2.5% by mass of boric acid and derivatives thereof, and 82.5-89.5% by mass of organic solvent.
In one embodiment, the polydimethylsiloxane is selected from hydroxyl-terminated polydimethylsiloxanes having a kinematic viscosity of from 65cSt to 100 cSt.
In one embodiment, the nanocellulose is selected from silane coupling agent modified nanocellulose, the nanocellulose has a cross-sectional diameter of 1nm to 300nm and a length of 10 μm to 4000 μm.
In one embodiment, the organic peroxide crosslinking agent is at least one selected from dicumyl peroxide, bis (t-butylperoxyisopropyl) benzene, t-butylcumyl peroxide.
In one embodiment, the temperature of the polycondensation reaction is from 100 ℃ to 140 ℃.
In one embodiment, the cross-linked foaming temperature is 150 ℃ to 200 ℃.
The silicone rubber foaming material obtained by the preparation method.
According to the invention, on one hand, by adopting the expanded microspheres as the foam body, not only can the excellent rebound resilience of the expanded microspheres be utilized to enable the compression deformation of the foam cells in the silicone rubber foaming material to be reversible and improve the resilience of the silicone rubber foaming material, but also the size, the number density and the distribution of the foam cells can be adjusted by changing the content of the expanded microspheres and the foaming temperature and time, so that the foam cells in the silicone rubber foaming material have controllability. On the other hand, the shear thickening gel prepared based on the polydimethylsiloxane, the boric acid and the derivatives thereof and the organic solvent has less impurity residues, higher boron content and more excellent shear thickening property, and is more beneficial to improving the impact resistance of the silicone rubber foaming material. Therefore, the silicon rubber foaming material obtained by the preparation method is difficult to adhere after repeatedly compressing the foam wall in the use process, has the advantages of high rebound, low compression deformation and the like, and can be better applied to the fields of shock absorption and shock resistance.
Meanwhile, the nano cellulose component can provide mechanical strength support for the foam cells, and is favorable for reducing compression deformation of the foam cells, so that the mechanical property of the silicone rubber foaming material can be further improved, and the comprehensive property of the silicone rubber foaming material is more excellent.
Detailed Description
The silicone rubber foaming material and the preparation method thereof provided by the invention are further described below.
The preparation method of the silicone rubber foaming material provided by the invention comprises the following steps:
s1, preparing polydimethylsiloxane, boric acid and derivatives thereof and an organic solvent into a polydimethylsiloxane solution, performing polycondensation reaction, and then removing unreacted boric acid and derivatives thereof and the organic solvent to obtain a shear thickening gel;
s2, mixing 1-10 parts by mass of the shear thickening gel with 100 parts by mass of vinyl-containing silicone rubber to obtain a silicone rubber base material;
s3, mixing the silicone rubber base stock with 1 to 20 parts by mass of nanocellulose, 1 to 10 parts by mass of expanded microspheres and 0.01 to 0.5 part by mass of organic peroxide cross-linking agent to obtain silicone rubber compound; and
and S4, performing preforming, crosslinking and foaming on the silicone rubber compound to obtain the silicone rubber foaming material.
Unlike the traditional solvent-free method for preparing the shear thickening gel, the shear thickening gel prepared by adding the organic solvent based on the polydimethylsiloxane, the boric acid and the derivatives thereof in the step S1 has fewer impurity residues, higher boron content and more excellent shear thickening property, and is more beneficial to improving the shock resistance of the silicone rubber foaming material.
Specifically, in the step of preparing the polydimethylsiloxane, the boric acid and the derivatives thereof and the organic solvent into the polydimethylsiloxane solution, the polydimethylsiloxane, the boric acid and the derivatives thereof and the organic reagent are preferably stirred at a rotation speed of 60rpm-720rpm for 1h-5h at a temperature of 20 ℃ to 60 ℃ to obtain the polydimethylsiloxane solution. Then, the polydimethyl siloxane solution is heated to 100-140 ℃ for polycondensation reaction, and the reaction is carried out for 6-12 h under the stirring speed of 60-480 rpm, thus obtaining the polyborosiloxane solution. Finally, filtering out unreacted boric acid and derivative particles thereof from the polyborosiloxane solution by using a microporous filter membrane, and continuously drying for 6-24 hours at the temperature of 40-80 ℃ and the environmental pressure of-3 MPa to-0.1 MPa to remove the organic solvent in the polyborosiloxane solution, thereby obtaining the shear thickening gel.
Wherein, in the polydimethylsiloxane solution, the mass fraction of the polydimethylsiloxane is 10% -15%, the mass fraction of the boric acid and derivatives thereof is 0.5% -2.5%, and the mass fraction of the organic solvent is 82.5% -89.5%.
In one embodiment, the polydimethylsiloxane is selected from hydroxyl-terminated polydimethylsiloxanes having a kinematic viscosity of 65cSt to 100cSt, preferably from hydroxyl-terminated polydimethylsiloxanes having a kinematic viscosity of 65 cSt.
In one embodiment, the boric acid and its derivatives are selected from at least one of boric acid, triethyl borate, preferably boric acid.
In one embodiment, the organic solvent is at least one selected from toluene and xylene, preferably toluene.
In the step S2, as the shear thickening gel does not participate in the crosslinking of the vinyl-containing silicone rubber, 1 to 10 parts by mass of the shear thickening gel and 100 parts by mass of the vinyl-containing silicone rubber are selected for mixing, the reduction of the crosslinking degree of the silicone rubber caused by the excessive addition of the shear thickening gel can be avoided, the mechanical property of the foaming material is improved, and the preparation cost of the foaming material is effectively reduced.
Specifically, the mole fraction of vinyl in the vinyl-containing silicone rubber is 0.05% -1%; the vinyl-containing silicone rubber is at least one selected from methyl vinyl hydroxyl silicone rubber, methyl vinyl phenyl silicone rubber, methyl vinyl silicone rubber and methyl vinyl chloro silicone rubber, and is preferably methyl vinyl phenyl silicone rubber.
In one embodiment, the shear thickening gel is mixed with the vinyl-containing silicone rubber for 20min to 100min, preferably at a speed of 40rpm to 160rpm under vacuum conditions of 40 ℃ to 80 ℃.
In the step S3, the nanocellulose is added into the silicone rubber base material, so that mechanical strength support can be provided for the foam cells of the silicone rubber foaming material, the compression deformation of the foam cells can be reduced, and the mechanical properties of the silicone rubber foaming material can be further improved.
Specifically, the nanocellulose is selected from silane coupling agent modified nanocellulose, preferably polymethyltriethoxy oxysilane modified nanocellulose; the cross section diameter of the nanocellulose is 1nm-300nm, and the length is 10 mu m-4000 mu m.
Compared with noble metal catalyst, the invention has the advantages of innocuity, environmental protection and low cost when selecting the organic peroxide cross-linking agent. Specifically, the organic peroxide crosslinking agent comprises at least one of dicumyl peroxide, bis (tert-butylperoxyisopropyl) benzene and tert-butylcumyl peroxide.
In one embodiment, the nano cellulose and the organic peroxide cross-linking agent are sequentially added into the silicone rubber base material to be mixed for 20min-100min under the vacuum condition of 40-80 ℃ at the rotating speed of 40-160 rpm, so as to obtain the silicone rubber premix, then the expanded microspheres are added into the silicone rubber premix to be mixed for 10min-30min at the rotating speed of 30-80 rpm under the temperature condition of 30-80 ℃ so as to obtain the silicone rubber compound, and the silicone rubber compound is parked at normal temperature for not less than 24h.
In another embodiment, the nanocellulose, the organic peroxide cross-linking agent and the expansion microsphere are sequentially added into the silicone rubber base material for mixing for 20min to 100min at the rotation speed of 40rpm to 160rpm under the vacuum condition of 40 ℃ to 80 ℃, obtaining the silicone rubber premix, then mixing the silicone rubber premix for 10-30 min at the temperature of 30-80 ℃ and the rotating speed of 30-80 rpm to obtain the silicone rubber compound, and standing the silicone rubber compound for at least 24h at normal temperature.
The expanded microsphere is a thermoplastic hollow polymer microsphere, liquid alkane is filled in the expanded microsphere, when the expanded microsphere is heated at a certain temperature, the thermoplastic shell of the expanded microsphere is softened, and the liquid alkane in the expanded microsphere is heated and gasified, so that the volume of the expanded microsphere is rapidly increased, and cells are formed. Therefore, in the cross-linking foaming process of the step S4, by adopting the expanded microspheres as the foam body, not only the excellent rebound resilience of the expanded microspheres can be utilized to enable the compression deformation of the foam cells in the silicone rubber foaming material to be reversible and improve the resilience of the silicone rubber foaming material, but also the size, the number density and the distribution of the foam cells in the silicone rubber foaming material can be regulated by changing the content of the expanded microspheres and the foaming temperature and time, so that the foam cells in the silicone rubber foaming material have controllability.
Specifically, the cross-linking foaming temperature is 150-200 ℃.
In order to obtain a finished product with a regular shape, the silicone rubber compound can be preformed at 30-60 ℃ and then crosslinked and foamed.
The invention also provides the silicone rubber foaming material obtained by the preparation method.
The silicon rubber foaming material obtained by the preparation method is difficult to adhere after repeatedly compressing the foam wall in the use process, has the advantages of high rebound, low compression deformation and the like, has excellent comprehensive performance, and can be better applied to the fields of shock absorption and impact resistance.
Hereinafter, the silicone rubber foaming material and the preparation method thereof will be further described by the following specific examples.
Example 1
10 parts by mass of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity: 65 cSt), 0.5 parts by mass of dried boric acid, and 89.5 parts by mass of toluene were sequentially added to a sealed vessel, stirred at a rotation speed of 120rpm at 60 ℃ for 120min to obtain a uniform hydroxyl-terminated polydimethylsiloxane solution, and the hydroxyl-terminated polydimethylsiloxane solution was heated to 120 ℃ to perform polycondensation reaction, and reacted for 12h at a stirring speed of 120rpm to obtain a polyborosiloxane solution. Then, the polyborosiloxane solution was filtered out unreacted boric acid particles with a microporous filter membrane having a pore size of 0.44 μm, the filtrate was poured into a glass dish, and dried in a vacuum oven at 80℃and-3 MPa for 24 hours, toluene was removed, to obtain a shear-thickening gel.
100 parts by mass of methyl vinyl silicone rubber (hardness: 40A, molecular weight: 50X 10 4 The molar fraction of g/mol and vinyl is 0.55 percent, and 10 parts by mass of shear thickening gel are sequentially added into a vacuum kneader, and are mixed for 45 minutes at a rotating speed of 120rpm under the vacuum condition of 80 ℃ to obtain the silicone rubber base stock.
3 parts by mass of a polymethyl triethoxysiloxane-treated nanocellulose (having a cross-sectional diameter of 50nm and a length of 40 μm), 0.5 parts by mass of dicumyl peroxide, and 10 parts by mass of expanded microspheres (EXPANCEL 950 DU 80) were sequentially added to a vacuum kneader containing a silicone rubber base, and kneaded at a rotation speed of 120rpm under a vacuum condition at 80℃for 30 minutes to obtain a silicone rubber premix. And adding the silicone rubber premix into a two-roll mill, mixing at a temperature of 30 ℃ and a rotating speed of 40rpm for 30min to obtain a silicone rubber compound, and standing at normal temperature for 24h.
And (3) adding the silicone rubber compound into a molding press, performing at the temperature of 30 ℃, and then performing cross-linking foaming at the high temperature of 150 ℃ to obtain the silicone rubber foaming material.
Example 2
10 parts by mass of a hydroxyl-terminated polydimethylsiloxane (kinematic viscosity: 75 cSt), 0.5 parts by mass of dried boric acid, 89.5 parts by mass of toluene were sequentially added to a sealed vessel, stirred at a rotation speed of 120rpm at 60 ℃ for 120min to obtain a uniform hydroxyl-terminated polydimethylsiloxane solution, and the hydroxyl-terminated polydimethylsiloxane solution was heated to 120 ℃ to perform polycondensation reaction, and reacted for 12h at a stirring speed of 120rpm to obtain a polyborosiloxane solution. Then, the polyborosiloxane solution was filtered out unreacted boric acid particles with a microporous filter membrane having a pore size of 0.44 μm, the filtrate was poured into a glass dish, and dried in a vacuum oven at 80℃and-3 MPa for 24 hours, toluene was removed, to obtain a shear-thickening gel.
Will 100 parts by mass of methyl vinyl silicone rubber (hardness 40A, molecular weight 50X 10 4 The molar fraction of g/mol and vinyl is 0.55 percent, and 10 parts by mass of shear thickening gel are sequentially added into a vacuum kneader, and are mixed for 45 minutes at a rotating speed of 120rpm under the vacuum condition of 80 ℃ to obtain the silicone rubber base stock.
5 parts by mass of nanocellulose (with the cross section diameter of 50nm and the length of 40 mu m) treated by polymethyl triethoxysilane and 0.5 part by mass of dicumyl peroxide are sequentially added into a vacuum kneader containing a silicone rubber base material, and are mixed for 30 minutes at a rotating speed of 120rpm under a vacuum condition at 80 ℃ to obtain the silicone rubber premix. Then 10 parts by mass of expanded microspheres (EXPANCEL 950 DU 80) and silicone rubber premix are added into a two-roll mill, and the mixture is mixed for 30 minutes at a rotating speed of 40rpm under the temperature condition of 30 ℃ to obtain silicone rubber compound, and the silicone rubber compound is parked for 24 hours at normal temperature.
And (3) adding the silicone rubber compound into a molding press, performing at the temperature of 30 ℃, and then performing cross-linking foaming at the high temperature of 150 ℃ to obtain the silicone rubber foaming material.
Example 3
10 parts by mass of a hydroxyl-terminated polydimethylsiloxane (kinematic viscosity: 75 cSt), 0.5 parts by mass of dried boric acid, 89.5 parts by mass of toluene were sequentially added to a sealed vessel, stirred at a rotation speed of 120rpm at 60 ℃ for 120min to obtain a uniform hydroxyl-terminated polydimethylsiloxane solution, and the hydroxyl-terminated polydimethylsiloxane solution was heated to 120 ℃ to perform polycondensation reaction, and reacted for 12h at a stirring speed of 120rpm to obtain a polyborosiloxane solution. Then, the polyborosiloxane solution was filtered out unreacted boric acid particles with a microporous filter membrane having a pore size of 0.44 μm, the filtrate was poured into a glass dish, and dried in a vacuum oven at 80℃and-3 MPa for 24 hours, toluene was removed, to obtain a shear-thickening gel.
100 parts by mass of methyl vinyl silicone rubber (hardness: 40A, molecular weight: 50X 10 4 The g/mol, the mole fraction of vinyl is 0.55 percent, 5 parts by mass of shear thickening gel are sequentially added into a vacuum kneader, and are mixed for 45 minutes at a rotating speed of 120rpm under the vacuum condition of 80 DEG CAnd obtaining the silicon rubber base material.
10 parts by mass of nanocellulose (with a cross section diameter of 50nm and a length of 40 mu m) treated by polymethyl triethoxysilane and 0.5 part by mass of bis (tert-butyl peroxyisopropyl) benzene are sequentially added into a vacuum kneader containing a silicone rubber base material, and are mixed for 30 minutes at a rotating speed of 120rpm under a vacuum condition at 80 ℃ to obtain the silicone rubber premix. Then 5 parts by mass of expanded microspheres (EXPANCEL 950 DU 80) and silicone rubber premix are added into a two-roll mill, and the mixture is mixed for 30 minutes at a rotating speed of 40rpm under the temperature condition of 30 ℃ to obtain silicone rubber compound, and the silicone rubber compound is parked for 24 hours at normal temperature.
And (3) adding the silicone rubber compound into a molding press, performing at the temperature of 30 ℃, and then performing cross-linking foaming at the high temperature of 150 ℃ to obtain the silicone rubber foaming material.
Comparative example 1
Comparative example 1 differs from example 1 in that the shear thickening gel was prepared using a solvent-free process, with no toluene added during the preparation.
Comparative example 2
Comparative example 2 differs from example 2 in that the shear thickening gel was prepared by a solvent-free process, with no toluene added during the preparation.
Comparative example 3
Comparative example 3 is different from example 1 in that nanocellulose is not added to prepare a silicone rubber foam material.
Comparative example 4
Comparative example 4 is different from example 2 in that the silicone rubber foaming material was prepared without adding nanocellulose.
Comparative example 5
Comparative example 5 is different from example 1 in that 10 parts by mass of hollow glass microspheres are used instead of 10 parts by mass of expanded microspheres.
Comparative example 6
Comparative example 6 differs from example 1 in that 20 parts by mass of a shear thickening gel is used.
Comparative example 7
Comparative example 7 is different from example 1 in that the cross-linking foaming is performed using a high temperature of 220 ℃.
The shear thickening gels obtained in examples 1-2 and comparative examples 1-2 were subjected to light transmittance test, and the results are shown in Table 1.
TABLE 1
As is clear from Table 1, the transmittance of example 1 was 89.2%, the transmittance of example 2 was 85.3%, and the transmittance was equivalent to that of the hydroxyl-terminated polydimethylsiloxane (90.1%), and the purity was extremely high. In contrast, comparative examples 1 and 2, because the formulation for preparing the shear-thickening gel was solvent-free, the formulation produced a shear-thickening gel containing a large amount of unreacted boric acid particles, which had a light transmittance as low as 8.1%.
The shear thickening gels obtained in examples 1-2 and comparative examples 1-2 were tested for their rate dependence by a rotameter and showed that: during shearing, the storage modulus of the shear-thickening gels obtained in example 1 and example 2 were each from 10 as the angular frequency increased from 0.01rad/s to 500rad/s 2 MPa is increased to 10 6 MPa, exhibiting excellent shear hardening characteristics; whereas the storage modulus of the shear-thickening gel obtained in comparative example 1 was from 10 2 MPa is increased to 10 5 The storage modulus of the shear-thickening gel obtained in comparative example 2 is only from 10 MPa 3 MPa is increased to 10 5 MPa, which is due to the fact that the formulations of comparative examples 1 and 2 for preparing the shear-thickening gels have no solvent, the viscosity of the system is high, the reaction rate is low, and the products contain a large amount of free boric acid, resulting in poor shear hardening properties of the resulting shear-thickening gels.
The silicone rubber foam materials obtained in examples 1 to 3 and comparative examples 1 to 7 were subjected to performance test, and the results are shown in Table 2, in which the drop impact test: at 2500N impact force, the ratio of the impact force absorbed by the sample to the total impact force is the absorptivity.
TABLE 2
As is clear from Table 2, the silicone rubber foam materials obtained in examples 1 to 3 exhibited high rebound and low compression set characteristics as high as 88% rebound. In comparative example 5, 10 parts by mass of hollow glass beads are used to replace 10 parts by mass of expansion beads, so that the hardness of the foaming material is obviously increased, and the compressibility of the foaming material is deteriorated; comparative example 7 the resulting foamed material was yellowish in color due to the excessively high foaming temperature, and the partially expanded microspheres were broken to cause a small number of holes to appear on the surface of the sample.
The tensile strength of the silicone rubber foaming material obtained in the examples 1-3 is up to 11.43MPa, and the elongation at break is up to 412.6%. In contrast, in comparative examples 3 to 4, since nanocellulose was not added, the density, mechanical properties, hardness, and rebound rate of the silicone rubber foam material obtained in comparative examples 3 to 4 were all reduced as compared with those in examples 1 to 3 to which nanocellulose was added; comparative example 6 since the addition amount of the shear thickening gel was excessive, the tensile strength, hardness and rebound resilience of the silicone rubber foam obtained in comparative example 6 were reduced as compared with example 1.
The silicone rubber foams obtained in examples 1 to 3 were able to absorb up to 89.1% of the impact force at 2500N, exhibited excellent impact resistance, and, during shearing, the storage modulus of the silicone rubber foams obtained in examples 1 and 2 was increased from 10 as the angular frequency increased from 0.01rad/s to 500rad/s 4 MPa is increased to 10 6 The good shear hardening properties are maintained at MPa. In contrast, the comparative examples 1-2 had poor shear hardening properties due to the absence of a solvent in the formulation for preparing the shear thickening gel, and the silicone rubber foam material obtained in comparative examples 1-2 was able to absorb as low as 70% of the impact force at 2500N, and therefore, the impact resistance of the silicone rubber foam material obtained in comparative examples 1-2 was poor.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (9)
1. The preparation method of the silicone rubber foaming material is characterized by comprising the following steps of:
preparing polydimethylsiloxane, boric acid and derivatives thereof and an organic solvent into a polydimethylsiloxane solution, performing polycondensation reaction, and then removing unreacted boric acid and derivatives thereof and the organic solvent to obtain a shear thickening gel;
mixing 1-10 parts by mass of the shear thickening gel with 100 parts by mass of vinyl-containing silicone rubber to obtain a silicone rubber base material;
mixing the silicone rubber base stock with 1 to 20 parts by mass of nanocellulose, 1 to 10 parts by mass of expanded microspheres and 0.01 to 0.5 part by mass of organic peroxide cross-linking agent to obtain silicone rubber compound; and
and (3) preforming and cross-linking foaming the silicone rubber compound to obtain a silicone rubber foaming material, wherein the cross-linking foaming temperature is 150-200 ℃.
2. The method for producing a silicone rubber foam according to claim 1, wherein the molar fraction of vinyl groups in the vinyl group-containing silicone rubber is 0.05% to 1%.
3. The method for producing a silicone rubber foam according to any one of claims 1 or 2, wherein the vinyl-containing silicone rubber is at least one selected from the group consisting of methyl vinyl hydroxyl silicone rubber, methyl vinyl phenyl silicone rubber, methyl vinyl silicone rubber, and methyl vinyl chloro silicone rubber.
4. The method for preparing a silicone rubber foam according to claim 1, wherein the mass fraction of the polydimethylsiloxane in the polydimethylsiloxane solution is 10% -15%, the mass fraction of the boric acid and derivatives thereof is 0.5% -2.5%, and the mass fraction of the organic solvent is 82.5% -89.5%.
5. The method of preparing a silicone rubber foam according to claim 1, wherein the polydimethylsiloxane is selected from hydroxyl-terminated polydimethylsiloxanes having a kinematic viscosity of 65cSt to 100 cSt.
6. The method for preparing the silicone rubber foaming material according to claim 1, wherein the nanocellulose is selected from silane coupling agent modified nanocellulose, and the nanocellulose has a cross-sectional diameter of 1nm-300nm and a length of 10 μm-4000 μm.
7. The method for producing a silicone rubber foam according to claim 1, wherein the organic peroxide crosslinking agent is at least one selected from the group consisting of dicumyl peroxide, bis (t-butylperoxyisopropyl) benzene, and t-butylcumyl peroxide.
8. The method for producing a silicone rubber foam according to claim 1, wherein the temperature of the polycondensation reaction is 100 ℃ to 140 ℃.
9. A silicone rubber foam obtained by the method for producing a silicone rubber foam according to any one of claims 1 to 8.
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