CN116218022B - Foaming silica gel material with asymmetric pore size structure and preparation method and application thereof - Google Patents

Foaming silica gel material with asymmetric pore size structure and preparation method and application thereof Download PDF

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CN116218022B
CN116218022B CN202310129606.4A CN202310129606A CN116218022B CN 116218022 B CN116218022 B CN 116218022B CN 202310129606 A CN202310129606 A CN 202310129606A CN 116218022 B CN116218022 B CN 116218022B
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silica gel
foaming
gel material
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CN116218022A (en
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陈涛
谷金翠
肖鹏
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Ningbo Institute of Material Technology and Engineering of CAS
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/32—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof from compositions containing microballoons, e.g. syntactic foams
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/36—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2205/00—Foams characterised by their properties
    • C08J2205/04—Foams characterised by their properties characterised by the foam pores
    • C08J2205/05—Open cells, i.e. more than 50% of the pores are open
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2205/00—Foams characterised by their properties
    • C08J2205/04—Foams characterised by their properties characterised by the foam pores
    • C08J2205/052—Closed cells, i.e. more than 50% of the pores are closed
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • 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
    • C08J2383/04—Polysiloxanes

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Porous Artificial Stone Or Porous Ceramic Products (AREA)
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Abstract

The invention discloses a foaming silica gel material with an asymmetric pore size structure, and a preparation method and application thereof, belonging to the technical field of foaming materials, wherein the preparation method comprises the following steps: (1) Placing the mixed solution of the raw material components including the prepolymerization solution, the curing agent and the foaming agent in a mould for hot press molding to obtain foaming silica gel; (2) And after the foaming silica gel is subjected to plasma treatment, transferring the mixed solution of the raw material components including the prepolymer solution, the curing agent and the foaming agent to the foaming silica gel subjected to plasma treatment, and further performing hot press molding to obtain the foaming silica gel material with the asymmetric pore diameter structure. The process is simple and efficient, the upper layer and the lower layer of the prepared foamed silica gel material are tightly combined, the upper layer is of a macroporous closed-pore structure, the lower layer is of a small-pore open-pore structure, the foamed silica gel material has good mechanical stretching and compression rebound resilience performance, and the problems that in the prior art, the pore size of the foamed silica gel of a homogeneous structure is too large, the mechanical property is insufficient, and the compression stress relaxation performance is poor due to too small pore size are solved.

Description

Foaming silica gel material with asymmetric pore size structure and preparation method and application thereof
Technical Field
The invention belongs to the technical field of foaming materials, and particularly relates to a foaming silica gel material with an asymmetric pore size structure, and a preparation method and application thereof.
Background
Silicone rubber is a linear organosiloxane polymer having alternate backbones of silicon-oxygen bonds (Si-O), and pendant groups of the polymer are formed from organic groups (e.g., methyl, ethyl, vinyl, phenyl, trifluoropropyl, etc.). Because of the special structure, the silicone rubber has various excellent performances such as excellent high temperature resistance and low temperature resistance, excellent oil resistance, solvent resistance, ultraviolet resistance and radiation resistance, good ageing resistance, excellent electrical insulation, chemical stability, physiological inertia and the like. The foaming silica gel is a porous polymer elastic material formed by the foaming process of the silicone rubber, is a multifunctional silica gel material, has the advantages of light weight, good damping effect and good heat insulation performance besides the excellent performance of the silicone rubber, also has the advantages of high and low temperature resistance, weather resistance, environmental protection and the like which are not available in other foam materials, and is mainly used for heat insulation foam pipes for vehicle-mounted air conditioners of automobiles, automobile shock absorption, foaming silica gel sealing gaskets for new energy automobile batteries and the like in the automobile field.
The cell structure has important influence on the mechanical properties and the like of the silica gel material, and in general, the mechanical strength of the open-cell material is lower, but the open-cell material has better compressive stress relaxation performance. The Chinese patent document with publication number of CN102093718A discloses a preparation method of a low-density high-aperture-ratio silicone rubber foam material, which is characterized in that two sections of chemical foaming is carried out on the silicone rubber material, the density of the prepared silicone rubber foam material is low, the aperture ratio is high, the application range of the silicone rubber foam material is enlarged, but the tensile strength of the silicone rubber foam material is not more than 0.41MPa. The mechanical strength of the closed-pore type material is better, but the compression stress relaxation performance is poorer. The chinese patent publication No. CN105331117a uses a mixed gas of air, oxygen and carbon dioxide as a foaming agent, but the prepared silicone rubber foam has poor resilience. The Chinese patent publication No. CN103289412A discloses a preparation method of a silicon rubber closed cell foam material, and the shrinkage stress of the obtained material is only 600-800Kpa. The properties of the hybrid cell structure material are intermediate. The Chinese patent publication No. CN104788967A discloses a preparation method of a silicon rubber microporous foam material with a mixed cell structure, which is characterized in that a silicon rubber base material, a reinforcing agent, a structure control agent, a pore-forming agent and a radiation sensitizer are mixed and molded, then are subjected to gamma-ray radiation to crosslink, and are subjected to sectional elution and drying to obtain the silicon rubber microporous foam material with excellent performance, but the tensile strength is not higher than 1.82Mpa, and the compression set is 2.70% -3.81% (50%, 23 ℃ and 22 h).
Therefore, how to obtain a silica gel material with excellent mechanical properties and compression retraction elastic properties is still a problem to be solved in the prior art, so as to meet the market demand of the automotive field for high-performance silica gel materials.
Disclosure of Invention
In order to solve the problems of insufficient mechanical properties and insufficient compression stress relaxation performance caused by too large pore diameter and too small pore diameter of the foamed silica gel with a homogeneous structure in the prior art, the invention provides a preparation method of the foamed silica gel material with an asymmetric pore diameter, which has simple and efficient process, wherein an upper layer and a lower layer of the prepared foamed silica gel material are tightly combined, the upper layer is of a macroporous closed pore structure, the lower layer is of a small pore open pore structure, and the foamed silica gel material has good mechanical stretching and compression retraction elastic properties.
The technical scheme adopted is as follows:
a preparation method of an asymmetric pore size structure foaming silica gel material comprises the following steps:
(1) Placing the mixed solution of the raw material components including the prepolymerization solution, the curing agent and the foaming agent in a mould for hot press molding to obtain foaming silica gel;
(2) And after the foaming silica gel is subjected to plasma treatment, transferring the mixed solution of the raw material components including the prepolymer solution, the curing agent and the foaming agent to the foaming silica gel subjected to plasma treatment, and further performing hot press molding to obtain the foaming silica gel material with the asymmetric pore diameter structure.
The foaming silica gel material with the asymmetric pore size structure is prepared by a step-by-step hot-pressing process and a plasma technology, and the surface chemical property of the foaming silica gel prepared in the step (1) can be changed by the plasma treatment, and silanol is generated on the surface of the foaming silica gel, so that interlayer binding force is improved, the prepared foaming silica gel material has a structure with an upper layer and a lower layer tightly combined, interlayer parts are internally penetrated, the pore diameter of the upper layer is larger, pores are not communicated with each other, the pore diameter of the lower layer is smaller, the pores are communicated with each other, and the foaming silica gel material has better mechanical stretching and compression retraction elastic energy.
In the mixed solution, the pre-polymerization solution is at least one of Polydimethylsiloxane (PDMS) or aliphatic aromatic random copolyester (Ecoflex), the curing agent is a platinum catalyst, the foaming agent is thermoplastic expandable hollow polymer microspheres with the diameter of 10-40 microns, and the components are at least one of polymalonic acid or polyacetoacetic acid. The thermoplastic expandable hollow polymer microsphere is heated to generate pressure to promote the outward expansion of the thermoplastic expandable hollow polymer microsphere to form a hollow closed foam, so that the performance of the silica gel is not influenced, and the mechanical strength performance of the silica gel is ensured.
In the mixed solution, the mass ratio of the prepolymerization solution to the curing agent to the foaming agent is 1:0.1:0.01-0.05.
In the step (1), the parameters of hot press molding are as follows: the temperature is 160-200 ℃, the pressure is 2-4 Mpa, and the time is 4-8 minutes. Excessive hot pressing temperature can lead to ageing and fragility of the silica gel, and the compression rebound resilience performance is reduced.
Preferably, in the step (2), oxygen or a mixed gas containing oxygen is used for the plasma treatment, the frequency is 100-500 Hz, and the time is 5-20 minutes. The plasma treatment can change the surface chemistry of the foamed silica gel prepared in step (1) and generate silanol on the surface thereof, which helps to improve interlayer bonding force. The too high frequency of plasma treatment can lead to too large acting force, too large density, enhanced mechanical property, smaller elongation at break and reduced compression capability of the interlayer structure of the large holes and the small holes.
In the step (2), the parameters of hot press molding are as follows: the temperature is 130-150 ℃, the pressure is 1-2 Mpa, and the time is 5-15 minutes. Excessive hot pressing temperature can lead to ageing and fragility of the silica gel, and the compression rebound resilience performance is reduced.
Preferably, in the mixed solution in the step (1), the diameter of the foaming agent is 10-20 micrometers, and the mass ratio of the prepolymer solution to the foaming agent is 1:0.02-0.05; in the mixed solution in the step (2), the diameter of the foaming agent is 20-40 micrometers, and the mass ratio of the prepolymerization solution to the foaming agent is 1:0.01-0.02.
The invention also provides the foaming silica gel material with the asymmetric pore size structure, which is prepared by the preparation method of the foaming silica gel material with the asymmetric pore size structure, and the density of the foaming silica gel material with the asymmetric pore size structure is 0.2-0.7 g/cm 3 The structure that two layers are tightly combined is provided, the inner part of the interlayer is penetrated, the pore diameter of the upper layer is larger, the pores are not communicated with each other, the pore diameter of the lower layer is smaller, the pores are communicated with each other, preferably, the pore diameter of the upper layer is 500-800 micrometers, and the pore diameter of the lower layer is 500-700 nanometers.
On the one hand, the mechanical strength of the small-pore open-pore structure is improved by the large-pore closed-pore structure, and on the other hand, the small-pore open-pore structure is beneficial to enhancing the compressive stress relaxation performance of the large-pore closed-pore structure. Most importantly, the transitional bonding area formed between the two materials improves the bonding capacity of the large pore closed structure and the small pore open structure, and improves the mechanical stretching and compression rebound resilience performance of the foaming silica gel material. Breaks through the limitation of the unbalanced relation between the mechanical property and the compression rebound resilience of the prior foaming silica gel material.
The invention also provides application of the foaming silica gel material with the asymmetric pore size structure in the fields of aerospace, automobiles or electronic appliances. In particular in the field of automobiles, the foaming silica gel material with the asymmetric pore diameter structure can be used as a heat insulation foam pipe for an automobile-mounted air conditioner, an automobile damping material, a foaming silica gel sealing gasket for a new energy automobile battery and the like.
Compared with the prior art, the invention has the beneficial effects that:
(1) The foamed silica gel material with the asymmetric pore size structure is divided into an upper layer and a lower layer, the inner part of the interlayer is penetrated, the pore diameter of the upper layer is larger, the pores are not communicated with each other, the pore diameter of the lower layer is smaller, the pores are communicated with each other, the porous structure is adopted, the binding force between the upper layer and the lower layer is strong, and compared with the conventional foamed silica gel material with a homogeneous structure, the mechanical property and compression retraction elastic property of the foamed silica gel material are greatly improved due to the ordered arrangement of the macroporous closed pore structure and the pore opening structure and the formation of the middle penetrated structure.
(2) The foaming silica gel material with the asymmetric pore size structure provided by the invention has excellent mechanical stretching and compression rebound resilience, the shrinkage stress is not lower than 1Mpa,75% of compression permanent deformation is not higher than 2%, the tensile strength is not lower than 5.0Mpa, the elongation at break is not lower than 250%, and the tearing strength is not lower than 25N/cm.
(3) The invention provides a preparation method of foaming silica gel with an asymmetric pore size structure, which is simple and controllable, and the obtained material has good application prospect in the fields of aerospace, rail transit, automobiles, electronic appliances and the like.
Drawings
Fig. 1 is a morphology diagram and a structure schematic diagram of the foamed silica gel material with an asymmetric pore size structure obtained in example 2, wherein a is a morphology diagram and B is a structure schematic diagram.
FIG. 2 is a morphology diagram of a silica gel material of a homogeneous mixed pore size structure in comparative example 3.
Detailed Description
The invention is further elucidated below in connection with the examples and the accompanying drawing. It is to be understood that these examples are for illustration of the invention only and are not intended to limit the scope of the invention.
In examples and comparative examples, the prepolymer solution and platinum catalyst used were purchased from Yitai, hangzhou, and the expandable hollow polymeric microspheres were purchased from Nanjiepu polymeric materials, inc.
Example 1
(1) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.2g of polymalonic acid expandable hollow microspheres (with the diameter of about 10 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to prepare a mixed solution A;
(2) Pouring the mixed solution A prepared in the step (1) into a silica gel mold with the size of 1cm 1.5cm, and performing hot press molding for 8 minutes at 160 ℃ and 4Mpa to obtain foamed silica gel;
(3) Taking the foamed silica gel prepared in the step (2) out of the die, and placing the foamed silica gel in plasma equipment for treatment, wherein the gas adopts oxygen, the frequency is 500Hz, and the time is 5 minutes, so that silanol is generated on the surface of the foamed silica gel;
(4) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.1g of polymalonic acid expandable hollow microspheres (with the diameter of about 20 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to obtain a mixed solution B;
(5) And (3) placing the foamed silica gel subjected to plasma treatment in the step (3) in a mould with the size of 1cm 2.5cm again, uniformly pouring the mixed solution B obtained in the step (4) above the mould, performing secondary hot press forming at the temperature of 130 ℃ and the pressure of 2Mpa for 15 minutes, taking out a sample after hot press forming, and cooling to obtain the foamed silica gel material with the asymmetric pore size structure.
The foaming silica gel material with the asymmetric pore size structure is subjected to the tests of morphology, mechanical property, compression property and the like. The results show that the foaming silica gel material with the asymmetric pore size structure prepared in the embodimentThe upper layer is a macroporous closed pore structure with the pore diameter of about 550 microns, the lower layer is a small pore open pore structure with the pore diameter of about 500 nanometers, and the density is 0.2g/cm 2 The shrinkage stress was 1.2MPa, the 75% compression set was 1.9%, the tensile strength was 5.3MPa, the elongation at break was 255%, and the tear strength was 25.3N/cm.
Example 2
(1) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.5g of polymalonic acid expandable hollow microspheres (with the diameter of about 10 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to prepare a mixed solution A;
(2) Pouring the mixed solution A prepared in the step (1) into a silica gel mold with the size of 1cm 1.5cm, and performing hot press molding for 8 minutes at 160 ℃ and 4Mpa to obtain foamed silica gel;
(3) Taking the foamed silica gel prepared in the step (2) out of the die, and placing the foamed silica gel in plasma equipment for treatment, wherein the gas adopts oxygen, the frequency is 500Hz, and the time is 5 minutes, so that silanol is generated on the surface of the foamed silica gel;
(4) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.2g of polymalonic acid expandable hollow microspheres (with the diameter of about 20 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to obtain a mixed solution B;
(5) And (3) placing the foamed silica gel subjected to plasma treatment in the step (3) in a mould with the size of 1cm 2.5cm again, uniformly pouring the mixed solution B obtained in the step (4) above the mould, performing secondary hot press forming at the temperature of 130 ℃ and the pressure of 2Mpa for 15 minutes, taking out a sample after hot press forming, and cooling to obtain the foamed silica gel material with the asymmetric pore size structure.
The foaming silica gel material with the asymmetric pore size structure is subjected to the tests of morphology, mechanical property, compression property and the like. The results show that the upper layer of the foamed silica gel material with the asymmetric pore diameter structure prepared in the embodiment is a macroporous closed pore structure with the pore diameter of about 580 microns, the lower layer is a small pore open pore structure with the pore diameter of about 600 nanometers (the morphology diagram is A in FIG. 1, the structure diagram is B in FIG. 1), and the density is 0.64g/cm 2 The shrinkage stress was 2.0MPa, the 75% compression set was 1.4%, the tensile strength was 5.7MPa, the elongation at break was 292%, and the tear strength was 28.6N/cm. Compared with the embodiment 1, the embodiment increases the relative dosage of the foaming agent, the pore diameter becomes more uniform and compact, and the mechanical property and the compression property are enhanced.
Example 3
(1) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.2g of polymalonic acid expandable hollow microspheres (with the diameter of about 20 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to prepare a mixed solution A;
(2) Pouring the mixed solution A prepared in the step (1) into a silica gel mold with the size of 1cm 1.5cm, and performing hot press molding for 8 minutes at 160 ℃ and 4Mpa to obtain foamed silica gel;
(3) Taking the foamed silica gel prepared in the step (2) out of the die, and placing the foamed silica gel in plasma equipment for treatment, wherein the gas adopts oxygen, the frequency is 500Hz, and the time is 5 minutes, so that silanol is generated on the surface of the foamed silica gel;
(4) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.1g of polymalonic acid expandable hollow microspheres (with the diameter of about 40 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to obtain a mixed solution B;
(5) And (3) placing the foamed silica gel subjected to plasma treatment in the step (3) in a mould with the size of 1cm 2.5cm again, uniformly pouring the mixed solution B obtained in the step (4) above the mould, performing secondary hot press forming at the temperature of 130 ℃ and the pressure of 2Mpa for 15 minutes, taking out a sample after hot press forming, and cooling to obtain the foamed silica gel material with the asymmetric pore size structure.
The foaming silica gel material with the asymmetric pore size structure is subjected to the tests of morphology, mechanical property, compression property and the like. The results show that the upper layer of the foaming silica gel material with the asymmetric pore size structure prepared in the embodiment is a macroporous closed pore structure with the pore size of about 780 microns, the lower layer of the foaming silica gel material is a small pore open pore structure with the pore size of about 690 nanometers, and the density of the foaming silica gel material is 0.3g/cm 2 A compression stress of 1.1MPa, a 75% compression set of 1.8% and a tensile strengthThe strength was 5.0MPa, elongation at break was 251%, and tear strength was 25.2N/cm. Compared with the embodiment 1, the embodiment improves the size of the foaming agent, enlarges the pore diameter and reduces the mechanical property.
Example 4
(1) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.5g of polymalonic acid expandable hollow microspheres (with the diameter of about 10 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to prepare a mixed solution A;
(2) Pouring the mixed solution A prepared in the step (1) into a silica gel mold with the size of 1cm 1.5cm, and performing hot press molding for 8 minutes at 160 ℃ and 4Mpa to obtain foamed silica gel;
(3) Taking the foamed silica gel prepared in the step (2) out of the die, and placing the foamed silica gel in plasma equipment for treatment, wherein the gas adopts oxygen, the frequency is 100Hz, and the time is 20 minutes, so that silanol is generated on the surface of the foamed silica gel;
(4) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.2g of polymalonic acid expandable hollow microspheres (with the diameter of about 20 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to obtain a mixed solution B;
(5) And (3) placing the foamed silica gel subjected to plasma treatment in the step (3) in a mould with the size of 1cm 2.5cm again, uniformly pouring the mixed solution B obtained in the step (4) above the mould, performing secondary hot press forming at the temperature of 130 ℃ and the pressure of 2Mpa for 15 minutes, taking out a sample after hot press forming, and cooling to obtain the foamed silica gel material with the asymmetric pore size structure.
The foaming silica gel material with the asymmetric pore size structure is subjected to the tests of morphology, mechanical property, compression property and the like. The results show that the upper layer of the foaming silica gel material with the asymmetric pore size structure prepared in the embodiment is a macroporous closed pore structure with the pore size of about 500 microns, the lower layer is a small pore open pore structure with the pore size of about 500 nanometers, and the density is 0.54g/cm 2 The shrinkage stress was 1.2MPa, the 75% compression set was 2.0%, the tensile strength was 5.1MPa, the elongation at break was 251%, and the tear strength was 25.4N/cm.
Example 5
(1) Sequentially adding 10g of Ecoflex, 1g of platinum catalyst and 0.5g of polymalonic acid expandable hollow microspheres (with the diameter of about 10 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to prepare a mixed solution A;
(2) Pouring the mixed solution A prepared in the step (1) into a silica gel mold with the size of 1cm 1.5cm, and performing hot press molding for 8 minutes at 160 ℃ and 4Mpa to obtain foamed silica gel;
(3) Taking the foamed silica gel prepared in the step (2) out of the die, and placing the foamed silica gel in plasma equipment for treatment, wherein the gas adopts oxygen, the frequency is 500Hz, and the time is 5 minutes, so that silanol is generated on the surface of the foamed silica gel;
(4) Sequentially adding 10g of Ecoflex, 1g of platinum catalyst and 0.2g of polymalonic acid expandable hollow microspheres (with the diameter of about 20 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to obtain a mixed solution B;
(5) And (3) placing the foamed silica gel subjected to plasma treatment in the step (3) in a mould with the size of 1cm 2.5cm again, uniformly pouring the mixed solution B obtained in the step (4) above the mould, performing secondary hot press forming at the temperature of 130 ℃ and the pressure of 2Mpa for 15 minutes, taking out a sample after hot press forming, and cooling to obtain the foamed silica gel material with the asymmetric pore size structure.
The foaming silica gel material with the asymmetric pore size structure is subjected to the tests of morphology, mechanical property, compression property and the like. The results show that the upper layer of the foaming silica gel material with the asymmetric pore size structure prepared in the embodiment is a macroporous closed pore structure with the pore size of about 580 microns, the lower layer is a small pore open pore structure with the pore size of about 620 nanometers, and the density is 0.65g/cm 2 The shrinkage stress was 1.8MPa, the 75% compression set was 1.2%, the tensile strength was 5.8MPa, the elongation at break was 287%, and the tear strength was 27.6N/cm.
Example 6
(1) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.5g of polymalonic acid expandable hollow microspheres (with the diameter of about 10 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to prepare a mixed solution A;
(2) Pouring the mixed solution A prepared in the step (1) into a silica gel mold with the size of 1cm 1.5cm, and performing hot press molding for 4 minutes at 200 ℃ and 2Mpa to obtain foamed silica gel;
(3) Taking the foamed silica gel prepared in the step (2) out of the die, and placing the foamed silica gel in plasma equipment for treatment, wherein the gas adopts oxygen, the frequency is 500Hz, and the time is 5 minutes, so that silanol is generated on the surface of the foamed silica gel;
(4) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.2g of polymalonic acid expandable hollow microspheres (with the diameter of about 20 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to obtain a mixed solution B;
(5) And (3) placing the foamed silica gel subjected to plasma treatment in the step (3) in a mould with the size of 1cm 2.5cm again, uniformly pouring the mixed solution B obtained in the step (4) above the mould, performing secondary hot press forming at the temperature of 150 ℃ and the pressure of 1Mpa for 5 minutes, taking out a sample after hot press forming, and cooling to obtain the foamed silica gel material with the asymmetric pore size structure.
The foaming silica gel material with the asymmetric pore size structure is subjected to the tests of morphology, mechanical property, compression property and the like. The results show that the upper layer of the foaming silica gel material with the asymmetric pore size structure prepared in the embodiment is a macroporous closed pore structure with the pore size of about 750 microns, the lower layer is a small pore open pore structure with the pore size of about 650 nanometers, and the density is 0.63g/cm 2 The shrinkage stress was 1.8MPa, the 75% compression set was 1.5%, the tensile strength was 5.8MPa, the elongation at break was 259% and the tear strength was 26.6N/cm.
Comparative example 1
(1) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.6g of polymalonic acid expandable hollow microspheres (with the diameter of about 10 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to prepare a mixed solution A;
(2) Pouring the mixed solution A prepared in the step (1) into a silica gel mold with the size of 1cm x 0.5cm, and performing hot press molding for 8 minutes at 160 ℃ and 4Mpa to obtain foamed silica gel;
(3) Taking the foamed silica gel prepared in the step (2) out of the die, and placing the foamed silica gel in plasma equipment for treatment, wherein the gas adopts oxygen, the frequency is 500Hz, and the time is 5 minutes, so that silanol is generated on the surface of the foamed silica gel;
(4) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.3g of polymalonic acid expandable hollow microspheres (with the diameter of about 20 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to obtain a mixed solution B;
(5) And (3) placing the foamed silica gel subjected to plasma treatment in the step (3) into a die with the size of 1cm & lt 1cm & gt and 3.0cm again, uniformly pouring the mixed solution B obtained in the step (4) above the die, performing secondary hot press forming at the temperature of 130 ℃ and the pressure of 2Mpa for 15 minutes, taking out a sample after hot press forming, and cooling to obtain the silica gel material.
The silica gel material is subjected to morphology, mechanical property, compression property and other tests. The results show that the upper layer of the silica gel material prepared in the comparative example has a macroporous structure with the pore diameter of about 900 microns, the lower layer has an open pore structure with the pore diameter of about 900 nanometers, and the density is 1.2g/cm 2 The shrinkage stress was 0.4MPa,75% compression set was 20.8%, the tensile strength was 1.2MPa, the elongation at break was 50%, and the tear strength was 8.2N/cm. The comparative example uses an excessive amount of foaming agent compared with example 1, resulting in too large a foaming pore size, hard and brittle silica gel materials, and reduced mechanical and compression properties.
Comparative example 2
(1) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.2g of polymalonic acid expandable hollow microspheres (with the diameter of about 30 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to prepare a mixed solution A;
(2) Pouring the mixed solution A prepared in the step (1) into a silica gel mold with the size of 1cm 1.5cm, and performing hot press molding for 8 minutes at 160 ℃ and 4Mpa to obtain foamed silica gel;
(3) Taking the foamed silica gel prepared in the step (2) out of the die, and placing the foamed silica gel in plasma equipment for treatment, wherein the gas adopts oxygen, the frequency is 500Hz, and the time is 5 minutes, so that silanol is generated on the surface of the foamed silica gel;
(4) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.1g of polymalonic acid expandable hollow microspheres (with the diameter of about 50 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to obtain a mixed solution B;
(5) And (3) placing the foamed silica gel subjected to plasma treatment in the step (3) in a mould with the size of 1cm 2.5cm again, uniformly pouring the mixed solution B obtained in the step (4) above the mould, performing secondary hot press forming at the temperature of 130 ℃ and the pressure of 2Mpa for 15 minutes, taking out a sample after hot press forming, and cooling to obtain the silica gel material.
The silica gel material prepared in the comparative example has a fragile structure, cannot be subjected to performance test, has an oversized foaming agent compared with the foaming agent in the example 1, has an unstable silica gel structure, is easy to crush, and has greatly reduced mechanical properties.
Comparative example 3
(1) Sequentially adding 10g of PDMS, 1g of platinum catalyst and 0.5g of polymalonic acid expandable hollow microspheres (with the diameter of about 10 microns) into a beaker, uniformly stirring for 30min at 500 rotation speed, and then placing the mixture into a vacuum drying oven to remove bubbles for 2h at 0.8MPa to prepare a mixed solution A;
(2) Pouring the mixed solution A prepared in the step (1) into a silica gel mold with the size of 1cm 1.5cm, and performing hot press molding for 8 minutes at 160 ℃ and 4Mpa to obtain foamed silica gel;
(3) And (3) taking the foaming silica gel prepared in the step (2) out of a mold, and cooling to obtain the silica gel material with the homogeneous phase mixed pore diameter structure.
The silica gel material with the homogeneous mixed pore diameter structure is subjected to the tests of morphology, mechanical property, compression property and the like. The result shows that the silica gel material with the homogeneous mixed pore diameter structure has uneven pore diameter (figure 2) and the density of 0.6g/cm 2 The shrinkage stress was 0.8MPa, the 75% compression set was 15.7%, the tensile strength was 1.5MPa, the elongation at break was 95%, and the tear strength was 8.9N/cm. Description of the inventionCompared with the foaming silica gel material with the asymmetric pore size structure prepared by the embodiment, the silica gel material with the homogeneous phase mixed pore size structure has the advantages that the mechanical property and the compression capability are reduced.
In summary, the invention provides the foamed silica gel material with the asymmetric pore size structure, which is prepared by a step-by-step hot-pressing process and a plasma technology, and the foamed silica gel material with the asymmetric pore size structure has better compression stress relaxation performance due to the macroporous closed pore structure, and has better mechanical strength due to the pore opening structure. The foaming silica gel material with the asymmetric pore size structure solves the problems that the prior foaming silica gel with the homogeneous structure has insufficient mechanical property due to too large pore size and has insufficient compression stress relaxation performance due to too small pore size. In addition, the preparation method is environment-friendly and simple in preparation process, and the prepared foaming silica gel material with the asymmetric pore size structure has good application prospects in the fields of aerospace, rail transit, automobiles, electronic appliances and the like.
While the foregoing embodiments have been described in detail in connection with the embodiments of the invention, it should be understood that the foregoing embodiments are merely illustrative of the invention and are not intended to limit the invention, and any modifications, additions, substitutions and the like made within the principles of the invention are intended to be included within the scope of the invention.

Claims (8)

1. The preparation method of the foaming silica gel material with the asymmetric pore size structure is characterized by comprising the following steps of:
(1) Placing the mixed solution of the raw material components including the prepolymerization solution, the curing agent and the foaming agent in a mould for hot press molding to obtain foaming silica gel;
(2) After the foaming silica gel is subjected to plasma treatment, transferring the mixed solution of the raw material components including the prepolymer solution, the curing agent and the foaming agent to the foaming silica gel subjected to plasma treatment, and further performing hot press molding to obtain the foaming silica gel material with the asymmetric pore diameter structure;
in the mixed solution, the pre-polymerized solution is at least one of polydimethylsiloxane or aliphatic aromatic random copolyester, and the foaming agent is thermoplastic expandable hollow polymer microspheres with the diameter of 10-40 micrometers;
in the mixed liquid in the step (1), the diameter of the foaming agent is 10-20 microns, and the mass ratio of the prepolymer liquid to the foaming agent is 1:0.02-0.05; in the mixed liquid in the step (2), the diameter of the foaming agent is 20-40 micrometers, and the mass ratio of the prepolymer liquid to the foaming agent is 1:0.01-0.02;
the foaming silica gel material with the asymmetric pore diameter structure has a structure that an upper layer and a lower layer are tightly combined, the pore diameter of a closed pore of the upper layer is 500-800 microns, and the pore diameter of an open pore of the lower layer is 500-700 nanometers.
2. The method for preparing the foamed silica gel material with the asymmetric pore size structure according to claim 1, wherein the curing agent is a platinum catalyst in the mixed solution.
3. The method for preparing the foamed silica gel material with the asymmetric pore size structure according to claim 1, wherein the mass ratio of the prepolymerization liquid to the curing agent in the mixed liquid is 1:0.1.
4. the method for preparing an asymmetric pore size structure foamed silica gel material according to claim 1, wherein in the step (1), parameters of hot press molding are as follows: the temperature is 160-200 ℃, the pressure is 2-4 Mpa, and the time is 4-8 minutes.
5. The method for preparing an asymmetric pore size structure foamed silica gel material according to claim 1, wherein in the step (2), oxygen or a mixed gas containing oxygen is adopted for plasma treatment, the frequency is 100-500 Hz, and the time is 5-20 minutes.
6. The method for preparing an asymmetric pore size structure foamed silica gel material according to claim 1, wherein in the step (2), parameters of hot press molding are as follows: the temperature is 130-150 ℃, the pressure is 1-2 Mpa, and the time is 5-15 minutes.
7. The foamed silica gel material of asymmetric pore size structure according to any one of claims 1 to 6.
8. The use of the foamed silica gel material with an asymmetric pore size structure according to claim 7 in the fields of aerospace, automobiles or electronic and electrical appliances.
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CN101703811A (en) * 2009-11-10 2010-05-12 成都迈狄美科技有限公司 Medical degradable polyester asymmetric membrane and preparation method thereof
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