CN114835941A - Porous polymer material and its preparation method and application - Google Patents

Abstract

The present invention provides a method for the preparation of a polymeric porous material, which is based on a reactive pre-crosslinked emulsion having both a ready-made polymer network, highly oriented and extended under the extrusion of ice crystals, and an unreacted portion for reaction fixation at low temperatures The characteristics of highly oriented and extended pore wall structure, combined with the advantages of ice template method, can obtain high porosity (up to 99.0%, density as low as 0.013 g/cm ³ ) polymeric porous materials. Due to the high porosity, the thermal conductivity is lower (minimum 18.7 mW/m·K) and the thermal insulation performance is better than the polymer porous material prepared by the traditional method, which can be used as a high-performance thermal insulation/sound insulation/shock absorption Material.

Description

Porous polymer material and its preparation method and application

technical field

The invention relates to the field of preparation of polymer porous materials, in particular to several preparation methods, products and applications of polymer porous materials.

Background technique

Porous polymer materials are an important class of polymer materials. Compared with non-porous polymer materials, porous polymer materials have many advantages, such as low density, good thermal insulation performance, high specific strength, and good sound insulation performance. It plays an important role in many fields such as water and land transportation, national defense and military, and civil engineering. According to the statistics of the "2021-2027 Foam Plastic Market Survey and Analysis and Investment Strategy Analysis and Forecast Report" released by China Gold Enterprise Credit International Consulting, my country's foam plastic products in 2019. The cumulative output has reached 2.5819 million tons, with a wide variety of products and a gradually increasing market share, playing a very important role in the national economy.

Nowadays, the methods of preparing porous polymer materials mainly include traditional foaming method, high internal emulsion method, salting-out method, 3D printing method and freezing casting method. Porous polymer materials are prepared through the process of gas dissolution, nucleation, growth and cell shaping. The preparation process is relatively simple, but the control methods for the pore structure are limited, and some foaming agents will remain; Salt particles of a certain size are mixed with resin powder, and the salt particles are washed away after melting and cooling. However, this method is limited by the degree of dispersion of the salt particles, and it is difficult to prepare porous materials with ultra-high porosity, and some salt particles will remain. In porous materials; the high internal emulsion method is to obtain polymer porous materials by polymerizing the continuous phase monomers in the emulsion and then drying them, but there will be emulsifier residues, and there is a lack of more abundant pore morphology control methods; 3D printing methods can be used in advance. The material structure is designed, but high-precision printing requires a very long printing time, which limits its large-scale application.

The ice template method is a typical method for preparing porous materials. In recent years, many different porous materials, especially aerogel materials with very high porosity, have been successfully prepared by freezing methods. The application of the ice template method is extremely dependent on the water solubility of the raw material or its dispersibility in water. For hydrophobic materials, especially hydrophobic polymers, the main possible route at present is to imitate the preparation process of porous ceramics, first prepare polymer emulsion, make pores through ice template, and then heat treatment to melt and connect the pore wall microspheres. The process of this route is cumbersome, and the post-treatment pore wall defects are large, and the self-supporting polymer porous material with high porosity cannot be obtained due to the collapse of the pore wall. Therefore, it is of great significance and value to find a method to obtain self-supporting polymeric porous materials with high porosity.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for preparing a high-porosity polymer porous material in view of the deficiencies of the prior art. Specifically, at least include:

(1) Freeze the active pre-crosslinked emulsion, and the emulsion particles in the emulsion further react with each other under freezing conditions; the ice crystals formed in the freezing stage extrude and fuse the polymer network in the active pre-crosslinked emulsion; The cross-linking degree of the reactive polymer emulsion is 10-90%;

And, (2) drying after freezing to obtain a polymer porous material.

On the one hand, the present invention overcomes the technical prejudice and applies the ice-template method to the hydrophobic polymer system; on the other hand, the present invention selects active pre-crosslinked emulsion, and combines the expansion extrusion of the ice-template method to produce extrusion up to hundreds of megapascals stress to obtain polymer porous materials with extremely high porosity. This further reactive reactive pre-crosslinked emulsion possesses both a ready-made polymer network to be highly oriented and extended under the extrusion of ice crystals, and an unreacted portion to react at low temperature to fix the highly oriented and extended pores wall structure. Specifically, in the freeze-casting process of the active pre-crosslinked emulsion, the ice crystals grown at low temperature will produce a violent extrusion fusion process on the pre-crosslinked emulsion particles, so that the polymer particles can be demulsified and fused into a uniform structure. Importantly, due to the huge extrusion stress induced a certain orientation of the polymer network, thinner, denser and more uniform pore walls were formed. Due to the reactive activity of the selected pre-crosslinked emulsion, after demulsification and fusion, further interchain reactions occur to form strong chemical bonds, which fix the orientation and pore wall structure, resulting in a thin and tough pore wall structure, which can be obtained during thawing and freezing. Self-supporting, elastic and polymeric porous materials with high porosity (up to 99.0% and densities as low as 0.013 g/cm ³ ) after drying.

Based on the present invention, the porosity of the product can be effectively controlled by adjusting the oil phase concentration of the pre-crosslinked emulsion, and the lower the concentration, the higher the porosity.

Preferably, the cross-linking degree of the pre-crosslinked emulsion is 10-90%, so as to ensure that the emulsion can be smoothly broken and fused, and at the same time, it has sufficient strength to support the pore wall without collapsing after drying;

The freezing described in the present invention is to allow the water in the emulsion to form ice crystals, which is generally achieved at a temperature lower than 0°C, and can also be higher than 0°C in some special environments.

The drying method of the present invention can be freeze drying or room temperature drying.

In certain embodiments, the porous material obtained after drying is further processed to enhance its properties or impart functional characteristics, including but not limited to heat treatment, chemical modification, and the like.

In some embodiments, the thermal conductivity is further reduced by means of multi-stage freezing. The multi-stage freezing method is: adding active polymer emulsion to the freeze-dried sample and freezing again.

The present invention also relates to the polymer porous material prepared by the above preparation method, the porosity is up to 99.0%, and the density is as low as 0.013 g/cm ³ .

Based on the high porosity of the above-mentioned polymer porous material, the present invention also relates to its application in thermal insulation materials, sound absorbing materials and shock absorbing materials.

Specifically, the above-mentioned pre-crosslinked emulsions include, but are not limited to, pre-crosslinked polysiloxane emulsions, pre-crosslinked polyepoxy resin emulsions, pre-crosslinked polyurethane emulsions, and pre-crosslinked polyacrylate emulsions.

The raw materials of the pre-crosslinked polysiloxane emulsion include siloxane monomer, emulsifier, crosslinking agent, catalyst and water; by controlling the ratio of each component and the reaction conditions, the crosslinking degree of the emulsion is 10-90% It is common knowledge in the field. The siloxane monomer can be octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, hexamethylcyclooctasiloxane, dodecamethylcyclopentasiloxane Cyclohexasiloxane, 2,4,6,8-tetramethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane or octaphenylcyclotetrasiloxane, methyltrimethoxy One of silane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, vinylmethyldiethoxysilane, vinyltriethoxysilane or Several; the emulsifier can be dimethyl dihexadecyl ammonium chloride, dimethyl dioctadecyl ammonium chloride, dodecylbenzenesulfonic acid, sodium dodecylbenzenesulfonate or One or more in sodium lauryl sulfate; Described crosslinking agent can be a kind of in ethyl orthosilicate, methyl hydrogen-containing silicone oil, dibenzoyl peroxide or dicumyl peroxide or several; the catalyst can be dodecylbenzenesulfonic acid, hydrochloric acid, sulfuric acid, sodium hydroxide, tetramethyl sodium hydroxide, ammonia water, dioctyltin dilaurate, dibutyltin dilaurate, polyalkoxy One or more of titanate or chloroplatinic acid or platinum-vinylsiloxane complex.

The raw materials of the pre-crosslinked polyepoxy resin emulsion include epoxy resin monomer, emulsifier, crosslinking agent, catalyst and water. It is common knowledge in the art to control the ratio of each component and reaction conditions to achieve a cross-linking degree of 10-90%. The epoxy resin monomer can be one or more of bisphenol A type epoxy resin monomers (E51, E54, E44, E29), bisphenol F type epoxy resin monomers, and epoxy-based silicone resins. The emulsifier can be dodecylbenzenesulfonic acid, Tween-80, sodium dodecylbenzenesulfonate, triton, sodium 3-allyloxy-2 hydroxy-1-propane sulfonate One or more of salt and ethoxylated alkyl ether ammonium sulfate; the crosslinking agent can be trifunctional epoxy resin triglycidyl m-aminophenol, 2,4,6-tris(dimethylamino) One or more of methyl) phenol, diisocyanate, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, diethylaminopropylamine, maleic anhydride, phthalic anhydride; The catalyst may be one or more of potassium persulfate, tertiary amine, imidazole, and boron trifluoride complex.

The raw materials of the pre-crosslinked polyurethane emulsion can be isocyanate monomers, oligomeric polyols or small molecular polyols, hydrophilic chain extenders, crosslinking agents, catalysts and water. It is common knowledge in the art to control the ratio of each component and reaction conditions to achieve a cross-linking degree of 10-90%. The isocyanate monomer can be toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, hexamethylene diisocyanate, methylcyclohexyl diisocyanate, isophorone diisocyanate, naphthalene-1,5 -One or more kinds of diisocyanates; oligomeric polyols and small molecular polyols can be polyethylene glycol, polypropylene glycol, polyester polyol, acrylic polyol, polycarbonate polyol, ethylene glycol, 1,4 One or more of -butanediol; the hydrophilic chain extender can be among N-methyldiethanolamine, bismethylolpropionic acid, bismethylolbutyric acid, sodium ethylenediamine ethanesulfonate one or more; the cross-linking agent can be ethylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, ethylenediamine, polyethylene One or more of polyamine, piperazine, trimethylol melamine, polyisocyanate crosslinking agent (Desmodur DA, Desmodur XP-7007, Desmodur XO-671, Desmodur XO-672, PBA 2236LX CR-60N) The catalyst can be one or more of 1,4-diazabicyclo[2,2,2]octane and dibutyltin dilaurate.

The raw materials of the pre-crosslinked polyacrylate emulsion include main monomer, functional crosslinking monomer, emulsifier, initiator and water. It is common knowledge in the art to control the ratio of each component and reaction conditions to achieve a cross-linking degree of 10-90%. The main monomer can be one or more of methyl acrylate, methyl methacrylate, butyl acrylate, and ethyl acrylate; the functional cross-linking monomer can be ethylene glycol dimethacrylate, One or more of hydroxyethyl methacrylate, diallyl phthalate, trimethylolpropane triacrylate, and acetoacetoxyethyl methacrylate; the emulsifier can be dodecane One or more of sodium alkyl sulfate, ER-10 emulsifier, disodium hydrogen phosphate dodecahydrate, OP-10 emulsifier; the initiator can be ammonium persulfate, potassium persulfate, azodiiso One or more of butyronitrile and N,N-dimethylaniline.

The beneficial effects of the present invention are as follows: the present invention overcomes the technical prejudice, applies the ice template method to the hydrophobic polymer system, selects active pre-crosslinked emulsion, and combines the expansion extrusion of the ice template method to generate an extrusion stress as high as several hundred megapascals , to obtain polymer porous materials with extremely high porosity. This reactive polymer emulsion possesses both a ready-made polymer network to be highly oriented and extended under the extrusion of ice crystals, and an unreacted portion to react at low temperature to fix the highly oriented and extended pore wall structure, bringing An unexpected technical effect is achieved: the high porosity of the porous material skeleton can reach up to 99.0%, and the density is as low as 0.013 g/cm ³ , which can achieve self-support and excellent elasticity.

Compared with the silicone rubber porous material prepared by the traditional method, the silicone rubber porous material obtained by the preparation method of the present invention has lower thermal conductivity (minimum 18.7 mW/m·K) and better thermal insulation performance due to the high porosity.

Compared with the traditional chemical foaming process, the preparation method of the present invention uses water or ice as the pore-forming agent, and is more environmentally friendly.

The preparation method of the present invention can prepare polymer porous materials with different pore sizes and different structures by adjusting the temperature field of freezing, and can be applied to other specific fields.

Description of drawings

Figure 1 is a picture of the extrusion fusion and extension orientation of the ice crystals to the emulsion particles during the preparation of the polymer emulsion ice template.

Figure 2 is a picture of the effect of ice crystals on particles during the preparation of the ice template of the monomer emulsion of the comparative example.

Figure 3 is a finished product of the silicone rubber porous material.

Figure 4 is a comparison chart of thermal stability of silicone rubber porous material and commercial polystyrene foam.

Figure 5 is a graph comparing the surface temperature of silicone rubber porous material and commercial polystyrene foam.

FIG. 6 is a SEM picture of the cross section of the silicone rubber porous material.

Detailed ways

Example 1: Preparation process of pre-crosslinked emulsion ice template method:

(1) Dissolve 1~2 g ER-10 emulsifier, 2~5 g sodium dodecyl sulfate and 0.4 g disodium hydrogen sulfate dodecyl hydrate in 180 ml deionized water.

(2) Mix 10 ml methyl methacrylate monomer, 10 ml butyl acrylate monomer and 1~5 ml functional cross-linking monomer trimethylolpropane triacrylate evenly, add the above solution, and ultrasonically disperse for 15 min An acrylic monomer pre-emulsion is obtained.

(3) Add 1 g of ammonium persulfate to the pre-emulsion to initiate the reaction, react at 85 °C for 1-4 h, and cool to room temperature. The degree of crosslinking was found to be 54%.

(4) Pour the diluted emulsion into the mold and freeze it in liquid nitrogen. After freezing, vacuum dry for 36 h.

(5) Calculate the density and porosity of the polyacrylate porous material, the density is 26.4-27.2 mg/cm ³ , and the emulsion is dried to obtain a transparent film, and the calculated film density (bulk density) is 1178 mg/cm ³ , and the porous material is obtained The porosity (1-porous material density/bulk density) is about 97.69-97.76%.

(6) Heat the dried porous material in a 90°C oven for 1-4 h.

(7) The thermal conductivity of the polyacrylate porous material was tested by the steady-state plate method, and the thermal conductivity at room temperature was 24.6-25.3 mW/(m*K).

Comparative Example 1: Different from Example 1, after the monomers methyl methacrylate, butyl acrylate and the crosslinking agent trimethylolpropane triacrylate were mixed uniformly, the initiator ammonium persulfate was added, and the After water emulsification of the same proportion of emulsifier, it was directly frozen in liquid nitrogen without pre-reaction. After freezing, it was placed in a -15 °C refrigerator for 24 h to carry out the reaction, and then the porous material was obtained by freeze-drying. Heating in an oven for 1-4 h to complete the reaction. At the same emulsion concentration of 2.86% (v/v%), the porous material obtained after monomer freezing could not support itself after freeze-drying and collapsed, and the final porosity was only 47.51%.

Figure 1 shows the assembly extrusion extension image of the pre-crosslinked emulsion ice template. Figure 2 shows the freezing process of the monomer emulsion ice template method. Comparing Figure 1 and Figure 2, it can be seen that for the ice template of the pre-crosslinked emulsion In terms of method, the emulsion particles undergo a process of demulsification and fusion and extrusion orientation under the extrusion of ice crystals, while the ice template freezing of the monomer emulsion only fixes the position and morphology of the emulsion, and there is no extrusion orientation process. , so the mechanical properties are poor and cannot support higher porosity.

In the widely used sol-gel method to prepare silicone rubber aerogel systems, cyclic monomers such as octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, Decamethylcyclopentasiloxane, hexadecamethylcyclooctasiloxane, dodecamethylcyclohexasiloxane, etc. cannot form a sol system due to their poor solubility in water, and it is difficult to undergo a hydrolysis ring-opening reaction. The use of traditional sol-gel methods to prepare high-porosity silicone rubber aerogels limits the application of this class of inexpensive and readily available materials, and also makes these materials more expensive. And through the present invention, the above-mentioned monomers with poor solubility in water that cannot form a sol system can be used to obtain high-porosity silicone rubber aerogels. The following is an example of octamethylcyclotetrasiloxane monomer to illustrate:

Example 2

(1) Mix 0.1~1 g of dodecylbenzenesulfonic acid, 0.1~1 g of octadecane and 10 g of octamethylcyclotetrasiloxane, heat to 60~90℃ and stir well.

(2) 90 ml of deionized water was added to it, mixed uniformly, and then dispersed by ultrasonic for 5 min to obtain a silicone monomer emulsion.

(3) The siloxane monomer emulsion was heated and stirred at 80 °C for 1-9 h to obtain a polysiloxane emulsion.

(4) Add 1~5 ml of ethyl orthosilicate to it, and continue to heat and stir at 80°C for 1~8 h. The degree of crosslinking was found to be 64%.

(5) Take 10 ml of the emulsion after step (4), add 90 ml of deionized water to dilute and stir well.

(6) Pour the diluted emulsion into the mold and place it in liquid nitrogen for freezing. The extrusion effect of ice crystal growth on the pre-crosslinked emulsion is shown in Figure 1. After freezing, vacuum dry for 36 h.

(7) Place the dried silicone rubber porous material in an oven at 80 °C and heat for 1 to 6 h to obtain the silicone rubber porous material, as shown in Figure 3.

(8) Calculate the density of the silicone rubber porous material, the density is 13.0~15.2 mg/cm ³ ; dry the emulsion to obtain a transparent film, calculate the film density (silicon rubber bulk density) to be 1221 mg/cm ³ , and obtain the silicone rubber porosity (1-porous material density/bulk density) is about 98.8~99.0%.

(9) The thermal conductivity of the silicone rubber porous material was tested by the steady-state plate method, and the thermal conductivity at room temperature was 26.6~28.2 mW/(m*K).

(10) Comparing the thermal insulation performance of the silicone rubber porous material with the traditional commercial PS foam, as shown in Figure 4, Figure 5 is the temperature change curve of each surface, the silicone rubber porous material shows better insulation than the traditional commercial PS foam. thermal performance.

(11) Using the standing wave tube method to test the sound absorption coefficient, the average sound absorption coefficient of the 15 mm thick silicone rubber porous material is 0.34~0.36.

(12) The damping and shock absorption performance at room temperature was measured by dynamic thermomechanical analyzer (DMA), and the measured damping factor was 0.32~0.35.

Example 3

(1) Mix 0.1~1 g of dodecylbenzenesulfonic acid, 0.1~1 g of octadecane and 10 g of octamethylcyclotetrasiloxane, and heat to 80°C and stir evenly.

(2) 90 ml of deionized water was added to it, mixed uniformly, and then dispersed by ultrasonic for 5 min to obtain a silicone monomer emulsion.

(3) The siloxane monomer emulsion was heated and stirred at 80 °C for 1-9 h to obtain a polysiloxane emulsion.

(4) Add 1~5 ml of ethyl orthosilicate to it, and continue to heat and stir at 80°C for 1~8 h. The degree of crosslinking was measured to be 10%.

(5) Take 10 ml of the emulsion after step (4), add 25 ml of deionized water, and stir well.

(6) Pour the diluted emulsion into the mold and place it in liquid nitrogen for freezing. After freezing, vacuum dry for 36 h.

(7) Place the dried silicone rubber porous material in an oven at 80 °C and heat for 1 to 6 h.

(8) Calculate the density and porosity of the silicone rubber porous material. The density is 45.3-47.2 mg/cm ³ and the porosity is about 96%.

(9) The thermal conductivity of the silicone rubber porous material was tested by the steady-state plate method, and the thermal conductivity at room temperature was 29.1~31.1 mW/(m*K).

(10) Scanning electron microscope (SEM) was used to observe the microstructure of the porous silicone rubber material. Figure 6 is the SEM image of the porous silicone rubber material.

(11) Using the standing wave tube method to test the sound absorption coefficient, the average sound absorption coefficient of the 15 mm thick silicone rubber porous material is 0.35~0.37.

(12) The damping and shock absorption performance at room temperature was measured by dynamic thermomechanical analyzer (DMA), and the measured damping factor was 0.29~0.31.

Example 4

(1) Mix 0.1~1 g of dodecylbenzenesulfonic acid, 0.1~1 g of octadecane and 10 g of tetramethyltetravinylcyclotetrasiloxane, and heat to 80°C and stir evenly.

(2) 90 ml of deionized water was added to it, and after uniform mixing, ultrasonic dispersion was performed for 5 min to obtain a silicone monomer emulsion.

(3) The siloxane monomer emulsion was heated and stirred at 80 °C for 1-9 h to obtain a polysiloxane emulsion.

(4) Add 1~5 ml of ethyl orthosilicate to it, and continue to heat and stir at 80°C for 1~6 h. The degree of crosslinking was measured to be 90%.

(5) Take 10 ml of the emulsion after step (4), add 25 ml of deionized water, and stir well.

(6) Pour the diluted emulsion into the mold and place it in liquid nitrogen for freezing. After freezing, vacuum dry for 36 h.

(7) Place the dried silicone rubber porous material in an oven at 80 °C and heat for 1 to 6 h.

(8) Calculate the density and porosity of the silicone rubber porous material. The density is 42.2-44.2 mg/cm ³ and the porosity is 97%.

(9) The thermal conductivity of the silicone rubber porous material was tested by the steady-state flat plate method, and the thermal conductivity at room temperature was 30.1~32.2 mW/(m*K).

(10) Using the standing wave tube method to test the sound absorption coefficient, the average sound absorption coefficient of the 15 mm thick silicone rubber porous material is 0.34~0.36.

(11) The damping and shock absorption performance at room temperature was measured by dynamic thermomechanical analyzer (DMA), and the measured damping factor was 0.33~0.35.

Example 5

(1) Mix 0.1-1 g sodium dodecylbenzenesulfonate, 0.1-1 g Tween-80 and 10 g bisphenol A epoxy resin (E51), and stir evenly.

(2) 90 ml of deionized water was added to it, uniformly mixed, and ultrasonically dispersed for 15 min to obtain an epoxy resin emulsion.

(3) Add a small amount of potassium persulfate initiator to the monomer emulsion and stir evenly.

(4) Add 0.5-5 ml of diethylenetriamine to it, and continue heating and stirring at 60°C for 10 min. The degree of crosslinking was found to be 34%.

(5) Take 10 ml of the emulsion after step (4), add 25 ml of deionized water, and stir well.

(6) Pour the diluted emulsion into the mold, and place it in liquid nitrogen for freezing. After freezing, vacuum dry for 36 h.

(7) Place the dried epoxy porous material in an oven at 60 °C and heat for 1 to 2 h.

(8) Calculate the density and porosity of the epoxy porous material, the density is ^29.6-31.4 mg/cm ³ , and the emulsion is dried to obtain a transparent film. Oxygen resin porosity (1-porous material density/bulk density) is about 98.25-98.35%.

(9) The thermal conductivity of the epoxy resin porous material was tested by the steady-state plate method, and the thermal conductivity at room temperature was 27.6-28.4 mW/(m*K).

(10) Using the standing wave tube method to test the sound absorption coefficient, the average sound absorption coefficient of the 15 mm thick epoxy resin porous material is 0.42~0.47.

Example 6

(1) Mix 0.1~1 g of dodecylbenzenesulfonic acid, 0.1~1 g of octadecane and 10 g of octamethylcyclotetrasiloxane, and heat to 80°C and stir evenly.

(2) 90 ml of deionized water was added to it, mixed uniformly, and then dispersed by ultrasonic for 5 min to obtain a silicone monomer emulsion.

(3) The siloxane monomer emulsion was heated and stirred at 80 °C for 1-9 h to obtain a polysiloxane emulsion.

(4) Add 1~5 ml of ethyl orthosilicate to it, and continue to heat and stir at 80°C for 1~8 h. The degree of crosslinking was found to be 62%.

(5) Take 10 ml of the emulsion after step (4), add 40 ml of deionized water, and stir well.

(6) Pour the diluted emulsion into the mold and place it in liquid nitrogen for freezing. After freezing, vacuum dry for 36 h.

(7) Calculate the density and porosity of the silicone rubber porous material, the density is 31.4-33.5 mg/cm3, and the porosity is about 97.4%.

(8) Take 10 ml of the emulsion of step (4), add 90 ml of deionized water, and stir well.

(9) Put the freeze-dried sample back into the mold, add the emulsion in step (8) to the mold, and place it in liquid nitrogen for freezing. After freezing, vacuum dry for 36 h.

(10) Place the dried silicone rubber porous material in an oven at 80 °C and heat for 1 to 6 h.

(11) Calculate the density and porosity of the silicone rubber porous material, the density is 68.5-73.3 mg/cm3, and the porosity is about 94.1%.

(12) The thermal conductivity of the silicone rubber porous material was tested by the steady-state flat plate method, and the thermal conductivity at room temperature was 18.7-20.6 mW/(m*K).

Example 7

(1) Add 10~20 g of dehydrated polypropylene glycol with molecular weight of 1000, 1~2 g of 1,4-butanediol and 1~2 g of hydrophilic chain extender dimethylol butyric acid into the flask, A small amount of dibutyltin dilaurate was added under nitrogen atmosphere.

(2) Add 15-30 g isophorone diisocyanate to the system at 80°C, and react at 80°C for 2-4 h.

(3) Take 5 ml of prepolymer, cool the prepolymer to 30°C after the reaction is completed, add a small amount of triethylamine to neutralize it, and add a certain amount of acetone to reduce the viscosity, add 45 ml of deionized water, and remove the acetone by distillation. After uniform mixing, ultrasonic dispersion was used for 15 min to obtain an aqueous polyurethane prepolymer emulsion.

(4) Add 1~5 g of triethylenediamine, a cross-linking agent, to it, and react at 80 °C for 1~2 h. The degree of crosslinking was measured to be 79%.

(5) Take 10 ml of the emulsion after step (4), add 25 ml of deionized water, and stir well.

(6) Pour the diluted emulsion into the mold, and place it in liquid nitrogen for freezing. After freezing, vacuum dry for 36 h.

( ⁷ ) Calculate the density and porosity ^of the polyurethane porous material. The porosity (1-porous material density/bulk density) is about 97.11-97.41%.

(8) The obtained porous material is placed in an oven at 80°C and heated for 1-4 h.

(9) The thermal conductivity of the epoxy resin porous material was tested by the steady-state plate method, and the thermal conductivity at room temperature was 16.7-18.3 mW/(m*K).

(10) Using the standing wave tube method to test the sound absorption coefficient, the average sound absorption coefficient of the 15 mm thick epoxy resin porous material is 0.37~0.39.

(11) The damping and shock absorption performance at room temperature was measured by dynamic thermomechanical analyzer (DMA), and the measured damping factor was 0.37~0.38.

Claims (12)

1. A method for preparing a polymeric porous material, characterized in that it comprises at least: freezing the active pre-crosslinked emulsion, and further reacting the emulsion particles in the emulsion with each other under the freezing condition; the ice crystals formed in the freezing stage extrude and fuse the polymer network in the active pre-crosslinked emulsion; the crosslinking degree of the active polymer emulsion is 10-90%;

and (2) freezing and then drying to obtain the polymer porous material.

2. The method of claim 1, wherein the pre-crosslinked emulsion is a pre-crosslinked polysiloxane emulsion, a pre-crosslinked polyepoxy resin emulsion, a pre-crosslinked polyurethane emulsion, or a pre-crosslinked polyacrylate emulsion.

3. The method of claim 2, wherein the pre-crosslinked polysiloxane emulsion is prepared from raw materials comprising siloxane monomers, emulsifiers, crosslinking agents, catalysts, and water; the siloxane monomer is selected from one or more of octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, hexadecylcyclooctasiloxane, dodecamethylcyclohexasiloxane, 2,4,6, 8-tetramethylcyclotetrasiloxane, tetramethyltetravinylcyclotetrasiloxane or octaphenylcyclotetrasiloxane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, vinylmethyldiethoxysilane and vinyltriethoxysilane; the emulsifier is selected from one or more of dimethyl dihexadecyl ammonium chloride, dimethyl dioctadecyl ammonium chloride, dodecyl benzene sulfonic acid, sodium dodecyl benzene sulfonate or sodium dodecyl sulfate; the cross-linking agent is selected from one or more of ethyl orthosilicate, methyl hydrogen-containing silicone oil, dibenzoyl peroxide or dicumyl peroxide; the catalyst is selected from one or more of dodecyl benzene sulfonic acid, hydrochloric acid, sulfuric acid, sodium hydroxide, tetramethyl sodium hydroxide, ammonia water, dioctyltin dilaurate, dibutyltin dilaurate, polyalkoxy titanate or chloroplatinic acid or platinum-vinyl siloxane complex.

4. The method according to claim 2, wherein the raw materials of the pre-crosslinked polyepoxy resin emulsion comprise an epoxy resin monomer, an emulsifier, a crosslinking agent, a catalyst and water; the epoxy resin monomer comprises one or more of bisphenol A epoxy resin monomer, bisphenol F epoxy resin monomer and epoxy organic silicon resin; the emulsifier comprises one or more of dodecylbenzene sulfonic acid, tween-80, sodium dodecylbenzene sulfonate, triton, 3-allyloxy-2 hydroxy-1-propane sulfonic acid sodium salt and ethoxylated alkyl ether ammonium sulfate; the cross-linking agent comprises one or more of trifunctional epoxy resin triglycidyl m-aminophenol, 2,4, 6-tris (dimethylaminomethyl) phenol, diisocyanate, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, diethylaminopropylamine, maleic anhydride and phthalic anhydride; the catalyst comprises one or more of potassium persulfate, tertiary amine, imidazole and boron trifluoride complex.

5. The method according to claim 2, wherein the raw materials of the pre-crosslinked polyurethane emulsion comprise isocyanate monomer, oligomeric polyol or small molecular polyol, hydrophilic chain extender, crosslinking agent, catalyst and water; the isocyanate monomer comprises one or more of toluene diisocyanate, diphenylmethane-4, 4' -diisocyanate, hexamethylene diisocyanate, methylcyclohexyl diisocyanate, isophorone diisocyanate and naphthalene-1, 5-diisocyanate; the oligomeric polyol and micromolecular polyol comprise one or more of polyethylene glycol, polypropylene glycol, polyester polyol, acrylic polyol, polycarbonate polyol, ethylene glycol and 1, 4-butanediol; the hydrophilic chain extender comprises one or more of N-methyldiethanolamine, bis-hydroxymethyl propionic acid, bis-hydroxymethyl butyric acid and ethylene diamine ethyl sodium sulfonate; the cross-linking agent comprises one or more of ethylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, ethylenediamine, polyethylene polyamine, piperazine, trimethylolmelamine, and polyisocyanate cross-linking agents (Desmodur DA, Desmodur XP-7007, Desmodur XO-671, Desmodur XO-672, PBA 2236LX CR-60N); the catalyst comprises one or more of 1, 4-diazabicyclo [2,2,2] octane and dibutyltin dilaurate.

6. The method according to claim 2, wherein the raw materials of the pre-crosslinked polyacrylate emulsion comprise a main monomer, a functional crosslinking monomer, an emulsifier, an initiator and water; the main monomer comprises one or more of methyl acrylate, methyl methacrylate, butyl acrylate and ethyl acrylate; the functional crosslinking monomer comprises one or more of ethylene glycol dimethacrylate, hydroxyethyl methacrylate, diallyl phthalate, trimethylolpropane triacrylate and acetoacetoxyethyl methacrylate; the emulsifier comprises one or more of sodium dodecyl sulfate, an ER-10 emulsifier, disodium hydrogen phosphate dodecahydrate and an OP-10 emulsifier; the initiator comprises one or more of ammonium persulfate, potassium persulfate, azobisisobutyronitrile and N, N-dimethylaniline.

7. The method for preparing a polymeric porous material according to any one of claims 1 to 6, wherein the low temperature field temperature is less than 0 ℃.

8. The method for preparing a polymeric porous material according to claim 1, wherein the drying in the step 2) is freeze-drying or room temperature drying.

9. The method for preparing a polymeric porous material according to any one of claims 1 to 8, further comprising: 3) further heat treating the porous material obtained in the step 2).

10. The method for preparing a polymeric porous material according to any one of claims 1 to 8, further comprising: 3) the living polymer emulsion was added to the freeze-dried sample and frozen again.

11. The polymer porous material prepared by the preparation method according to any one of claims 1 to 10.

12. Use of the polymeric porous material of claim 11 as thermal insulation, sound absorption or vibration damping material.

Images