Irradiation grafted polypropylene high-heat-insulation foaming material and preparation method thereof

Abstract

The invention provides an irradiation grafted polypropylene high-heat-insulation foaming material and a preparation method thereof, and belongs to the technical field of polypropylene foaming materials. The preparation method comprises the following steps: carrying out modification treatment on polypropylene by virtue of an irradiation grafting process, introducing an ester group on the polypropylene, and carrying out supercritical batch foaming by taking a nanoscale hollow molecular sieve as a nucleating agent, so as to obtain the high-porosity polypropylene foam material with the ester group and a micro-nano pore structure. Wherein the ester group has the effect of absorbing infrared radiation energy, the radiation absorption coefficient of the polypropylene foam material is greatly improved by introducing the ester group, and the solid volume ratio of the whole polypropylene foam material is far smaller than the air volume ratio by virtue of a micro-nano pore structure formed in the foaming process; and the micro-nano holes reduce the heat transfer efficiency of air heat convection by enhancing the Knudsen effect, so that the heat conduction coefficient of the foaming material is greatly reduced. The prepared foaming material has excellent heat insulation performance, and the problems that a traditional foaming material is poor in heat insulation performance and narrow in substrate selection are solved.

Description

Technical Field

[0001] The invention relates to the technical field of polypropylene foam materials, and in particular to a radiation grafted polypropylene high heat insulation foam material and a preparation method thereof. Background Art

[0002] Foam plastics are formed by a large number of gas micropores dispersed in solid plastics. They have the properties of light weight, heat insulation and shock absorption. They are widely used in many fields such as construction, furniture, automobiles, aerospace, etc. The market demand for polymer foam materials is growing at an annual rate of more than 10%. China's polymer foaming industry has also developed rapidly since the 1990s. It is mainly divided into three categories: polystyrene (PS), polyurethane (PU) and polyolefins (such as polyethylene PE, polypropylene PP, polyvinyl chloride PVC). However, polystyrene (PS) foam plastic products are difficult to degrade and recycle, causing "white pollution" to the environment. The United Nations Environmental Protection Organization decided to stop the production and use of foamed polystyrene worldwide in 2005. Polyurethane (PU) foam materials have residual isocyanates that are harmful to the human body during the foaming process and cannot be recycled. In recent years, with the enhancement of environmental awareness, people have been constantly exploring new environmentally friendly materials. It is a new challenge for us to continuously develop new environmentally friendly materials and optimize the production process of existing materials to improve the performance of foam plastics, reduce the impact on the environment, and promote the industry to green and sustainable development.

[0003] Polypropylene (PP) is a recyclable foam material. Compared with PU, PS and PE foam materials, it has outstanding advantages such as higher service temperature, high impact strength, environmental friendliness and low cost, and is favored by scholars at home and abroad. 2 ) As a non-toxic, pollution-free and environmentally friendly physical foaming agent, its application in the preparation of polymer foam materials has also attracted widespread attention from scientific researchers and the industrial community.

[0004] As an ideal environmentally friendly thermal insulation material, polypropylene foam, like polystyrene, has very poor absorption capacity for electromagnetic waves in the infrared radiation band, which leads to significant radiation heat transfer in polypropylene foam, thus seriously reducing the thermal insulation performance of polypropylene foam. 2 The foamed materials produced by foaming technology have problems such as uneven pore structure, large pore diameter, and low pore density, which will greatly limit the application of foamed materials as thermal insulation materials. Summary of the invention

[0005] In view of the technical problems existing in the background technology, the present application provides a radiation grafted polypropylene high thermal insulation foam material and a preparation method thereof, aiming to solve the problem of poor thermal insulation performance of existing polypropylene foam materials.

[0006] In a first aspect, the present application provides a method for preparing a radiation grafted polypropylene high thermal insulation foam material, comprising the following steps:

[0007] S1. dissolving polypropylene and methyl acrylate in a solvent, mixing them evenly to obtain a mixed solution; irradiating the mixed solution, washing, and drying the mixed solution to obtain a grafted polypropylene;

[0008] S2. The polypropylene, the grafted polypropylene, the antioxidant and the nano-scale hollow molecular sieve are uniformly mixed and granulated to obtain mixed plastic particles;

[0009] S3. The mixed plastic particles are hot pressed and cut to obtain a sample sheet;

[0010] S4. Place the sample sheet in a reactor and fill it with CO 2 To the set pressure, then heat the kettle to the foaming temperature, fully foam, and finally release CO 2 Gas, release pressure, and obtain high thermal insulation polypropylene foam material.

[0011] In the technical solution of the embodiment of the present application, polypropylene is modified by a radiation grafting process, an ester group is introduced into the polypropylene, and then supercritical intermittent foaming is performed using a nano-scale hollow molecular sieve as a nucleating agent to obtain a polypropylene foam material with a high porosity micro-nano pore structure having an ester group. Among them, the ester group has the function of absorbing infrared radiation energy, and the introduction of the ester group greatly improves the radiation absorption coefficient of the polypropylene foam material. The micro-nano pore structure formed during the foaming process makes the solid volume proportion of the entire polypropylene foam material much smaller than the air volume proportion, and the micro-nano pores reduce the heat transfer efficiency of air thermal convection by enhancing the Knudsen effect, thereby greatly reducing the thermal conductivity coefficient of the foam material.

[0012] In some embodiments, the amount of the nanoscale hollow molecular sieve added in step S2 is 1-2% of the total mass of the polypropylene and the grafted polypropylene.

[0013] In this embodiment, nano-scale hollow molecular sieves are added to the polypropylene foaming material, so that the modified polypropylene material forms a micro-nano pore structure during the foaming process.

[0014] In some embodiments, the mass of the methyl acrylate in step S1 accounts for 10-15% of the mass of the polypropylene, the solvent is anhydrous ethanol, the irradiation is electron beam irradiation, and the irradiation dose is 20-30 kGy.

[0015] In this embodiment, ester groups were introduced into polypropylene by grafting polypropylene and methyl acrylate under electron beam irradiation.

[0016] In some embodiments, the mass ratio of the polypropylene to the grafted polypropylene in step S2 is 8.5-9:1.5-1.

[0017] In some embodiments, the antioxidant is one or a combination of hindered phenol antioxidants, thiohindered phenol antioxidants, phosphite antioxidants, and amine antioxidants, and the amount of the antioxidant added is 1 to 2% of the total mass of the polypropylene and the grafted polypropylene.

[0018] In this embodiment, by adding an antioxidant into the polypropylene foam material, the aging of the polymer is prevented and its service life is extended.

[0019] In some embodiments, the temperature of the hot pressing in step S3 is 160-170°C.

[0020] In this embodiment, a sample sheet with a thickness of 2 mm and a diameter of 3 cm is obtained by hot pressing and cutting.

[0021] In some embodiments, the set pressure in step S4 is 20-25 MPa, the foaming temperature is 165-175° C., and the foaming time is 2-2.5 h.

[0022] In this embodiment, the polypropylene is fully foamed by controlling the foaming pressure, temperature, time and other conditions, and the microporous structure formed by the foaming is stabilized.

[0023] In the second aspect, an embodiment of the present application provides a radiation grafted polypropylene high thermal insulation foam material, which is prepared by the above-mentioned preparation method of the radiation grafted polypropylene high thermal insulation foam material, and has a high porosity micro-nanoporous structure with an ester group. The thermal conductivity of the radiation grafted polypropylene high thermal insulation foam material is 29.3mW / m·k.

[0024] In the technical solution of the embodiment of the present application, the obtained radiation grafted polypropylene high thermal insulation foam material has ultra-low thermal conductivity, so that the radiation grafted polypropylene high thermal insulation foam material has excellent thermal insulation performance.

[0025] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 This is a flow chart for preparing the radiation grafted polypropylene high thermal insulation foam material according to the embodiment of the present application;

[0028] Figure 2 This is a diagram of the thermal insulation mechanism of the micro-nano pore structure in the radiation grafted polypropylene high thermal insulation foam material of the present application embodiment;

[0029] Figure 3 The infrared images of the grafted polypropylene powder prepared in Example 1 of the present application and the conventional ungrafted polypropylene powder;

[0030] Figure 4 The SEM images of the grafted polypropylene powder prepared in Example 1 of the present application and the conventional ungrafted polypropylene powder;

[0031] Figure 5 This is a comparison chart of thermal conductivity of the foamed materials prepared in Example 1 of the present application and Comparative Example 1;

[0032] Figure 6 This is a temperature state comparison chart of the foaming materials prepared in Example 1 of the present application and Comparative Example 1. DETAILED DESCRIPTION

[0033] The following embodiments of the technical solution of the present application will be described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0035] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0036] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0037] In order to solve the problem of poor thermal insulation performance of existing polypropylene foam materials, the present application provides a radiation grafted polypropylene high thermal insulation foam material and a preparation method thereof. Among them, the present application found that the ester group has the function of absorbing infrared radiation energy, and the introduction of the ester group in the foam material can reduce the thermal conductivity by reducing the radiation heat conduction efficiency of the material. Therefore, the present application introduces ester groups into polypropylene through radiation grafting technology. In addition, the present application also adds nano-scale hollow molecular sieves as nucleating agents during the supercritical intermittent foaming process, so that the modified polypropylene material simultaneously forms a micro-nano pore structure during the foaming process, thereby obtaining a polypropylene foam material with a high porosity micro-nano pore structure of ester groups. This method greatly reduces the thermal conductivity coefficient of conventional polypropylene foam materials and greatly improves thermal insulation performance.

[0038] On the one hand, the present application embodiment provides a method for preparing a radiation grafted polypropylene high thermal insulation foam material, the flow diagram of which is as follows Figure 1 As shown, the following steps are included:

[0039] S1. dissolving polypropylene and methyl acrylate in a solvent, mixing them evenly to obtain a mixed solution; irradiating the mixed solution, washing, and drying the mixed solution to obtain a grafted polypropylene;

[0040] S2. The polypropylene, the grafted polypropylene, the antioxidant and the nano-scale hollow molecular sieve are uniformly mixed and granulated to obtain mixed plastic particles;

[0041] S3. The mixed plastic particles are hot pressed and cut to obtain a sample sheet;

[0042] S4. Place the sample sheet in a reactor and fill it with CO 2 To the set pressure, then heat the kettle to the foaming temperature, fully foam, and finally release CO 2 Gas, release pressure, and obtain high thermal insulation polypropylene foam material.

[0043] In the technical solution of the embodiment of the present application, polypropylene is modified by the radiation grafting process, ester groups are introduced into the polypropylene, and then supercritical intermittent foaming is performed using nano-scale hollow molecular sieves as nucleating agents to obtain a polypropylene foam material with a high porosity micro-nano pore structure having an ester group. Among them, the ester group has the function of absorbing infrared radiation energy. The introduction of the ester group greatly improves the radiation absorption coefficient of the polypropylene foam material. The micro-nano pore structure formed during the foaming process makes the solid volume proportion of the entire polypropylene foam material much smaller than the air volume proportion, and the micro-nano pores reduce the heat transfer efficiency of air thermal convection by enhancing the Knudsen effect. The heat insulation principle of the micro-nano pore structure is as follows: Figure 2 As shown, the thermal conductivity of the foamed material is greatly reduced, thereby improving the thermal insulation performance of the material.

[0044] Further, in some embodiments, in step S1, the mass of methyl acrylate accounts for 10-15% of the mass of the polypropylene, the solvent is anhydrous ethanol, the irradiation is electron beam irradiation, and the irradiation dose is 20-30 kGy.

[0045] In the technical solution of the embodiment of the present application, ester groups are introduced into polypropylene by electron beam irradiation grafting modification of polypropylene and methyl acrylate.

[0046] Furthermore, in some embodiments, in step S2, the mass ratio of polypropylene to the grafted polypropylene is 8.5-9:1.5-1, and the added amount of the nano-scale hollow molecular sieve and the antioxidant is 1-2% of the total mass of the polypropylene and the grafted polypropylene, wherein the antioxidant is one or a combination of hindered phenol antioxidants, thiohindered phenol antioxidants, phosphite antioxidants, and amine antioxidants.

[0047] In the technical solution of the embodiment of the present application, nanoscale hollow molecular sieves are used as nucleating agents to enable the foaming material to form a high-porosity micro-nanoporous structure; adding antioxidants to the polypropylene foaming material can prevent the aging of the foaming material and extend its service life.

[0048] Furthermore, in some embodiments, the temperature of the hot pressing in step S3 is 160-170°C.

[0049] In the technical solution of the embodiment of the present application, a sample sheet with a thickness of 2 mm and a diameter of 3 cm can be obtained by hot pressing and cutting.

[0050] Furthermore, in some embodiments, the set pressure in step S4 is 20-25 MPa, the foaming temperature is 165-175° C., and the foaming time is 2-2.5 h.

[0051] In the technical solution of the embodiment of the present application, by controlling the pressure, temperature, time, pressure release rate and other conditions of supercritical intermittent foaming, the polypropylene is fully foamed and the microporous structure formed by foaming is stabilized.

[0052] In the second aspect, an embodiment of the present application provides a radiation grafted polypropylene high thermal insulation foam material, which is prepared by the above-mentioned preparation method of the radiation grafted polypropylene high thermal insulation foam material, and has a high porosity micro-nanoporous structure with an ester group. The thermal conductivity of the radiation grafted polypropylene high thermal insulation foam material is 29.3mW / m·k.

[0053] In the technical solution of the embodiment of the present application, the obtained radiation grafted polypropylene high thermal insulation foam material has ultra-low thermal conductivity, so that the radiation grafted polypropylene high thermal insulation foam material has excellent thermal insulation performance.

[0054] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0055] Example 1

[0056] This embodiment provides a method for preparing a radiation grafted polypropylene high thermal insulation foam material, and its preparation flow chart is as follows: Figure 1 As shown, the specific steps include:

[0057] 50g of polypropylene powder and 5g of methyl acrylate were weighed, dissolved in a beaker filled with anhydrous ethanol, stirred evenly with a high-speed stirrer, poured into a radiation tube, evacuated, irradiated with an electron beam, absorbed 20kGy, washed 5 times with anhydrous ethanol, and dried to obtain grafted polypropylene powder; then, polypropylene powder and grafted polypropylene powder were weighed in a mass ratio of 9:1, wherein the polypropylene powder was conventional ungrafted polypropylene powder; at the same time, 2,6-di-tert-butyl-p-cresol and nano-scale hollow molecular sieve (particle size of 50nm, hollow pore size of 15nm) were added, and the addition amount of both was 1% of the total mass of the polypropylene powder and the grafted polypropylene powder, mixed, extruded and granulated by a twin-screw extruder, and mixed plastic particles were obtained; then, the mixed plastic particles were hot pressed into 2mm sheets at 165℃ on a flat vulcanizing molding machine, and the sheets were cut into 3cm diameter sample sheets by a laser cutting machine; the sample sheets were placed in a high-pressure reactor and heated with CO 2 The gas repeatedly cleans the reactor to exhaust the air in the reactor, and CO is charged into the reactor through a plunger metering pump. 2 When the pressure reaches 25 MPa, the kettle temperature is then heated to 170°C, and this temperature and pressure are maintained for 2 hours, and finally the pressure is released to release CO.2 The gas is released and foamed to obtain a polypropylene foam material with a high porosity and micro-nano pore structure having an ester group.

[0058] The infrared images and SEM images of the grafted polypropylene powder and the ungrafted conventional polypropylene powder prepared in this example are shown in FIG. Figure 3 , Figure 4 As shown. Figure 3 It can be seen that ester groups were successfully introduced into polypropylene according to the method provided in this embodiment.

[0059] Comparative Example 1

[0060] This comparative example provides a method for preparing a radiation grafted polypropylene high thermal insulation foam material. Compared with Example 1, the difference is that the polypropylene is not grafted, but conventional polypropylene powder is directly used to replace the grafted polypropylene powder in Example 1 in an equal amount. The other steps are roughly the same as Example 1 and will not be repeated here.

[0061] In order to compare the thermal insulation performance of the foamed materials prepared in Example 1 and Comparative Example 1, the thermal conductivity of the foamed materials prepared in Example 1 and Comparative Example 1 was tested respectively. The results are as follows: Figure 5 As shown. Among them, the thermal conductivity of the foamed material prepared in Example 1 is 29.3mW / m·k, which is significantly lower than that of the foamed material in Comparative Example 1. In addition, the sum of the thermal conductivity contributions of solid and radiation in Example 1 is about 3.0mW / m·k, accounting for only 10% of the total thermal conductivity, which significantly reduces the thermal conductivity of solid and radiation compared with Comparative Example 1, proving that the ester group introduced after grafting has the function of absorbing infrared radiation energy. The introduction of the ester group can greatly increase the radiation absorption coefficient of the polypropylene foamed material, thereby greatly reducing the solid and radiation thermal conductivities.

[0062] The foaming materials prepared in Example 1 and Comparative Example 1 were placed in the same temperature environment and the temperatures of the two were tested. The results are as follows: Figure 6 As shown. Figure 6 It can be seen that the foamed material prepared in Example 1 has better thermal insulation performance.

[0063] Comparative Example 2

[0064] This comparative example provides a method for preparing a radiation grafted polypropylene high thermal insulation foam material. Compared with Example 1, the difference is that the nucleating agent is replaced by a conventional zeolite molecular sieve without a hollow structure (particle size is 30nm), and the other steps are roughly the same as Example 1 and will not be repeated here.

[0065] The thermal conductivity of the foamed material prepared in this comparative example was tested and compared with the thermal conductivity of the foamed material prepared in Example 1. The results are shown in Table 1.

[0066] Table 1 Nucleating agent types and product properties in Example 1 and Comparative Example 2

[0067]

[0068] It can be seen from Table 1 that after the nucleating agent is replaced with a normal molecular sieve without a hollow structure, the thermal conductivity of the foamed material obtained is significantly higher than the thermal conductivity of the foamed material obtained by using a hollow molecular sieve as the nucleating agent in Example 1, that is, the thermal insulation effect is significantly reduced.

[0069] Example 2 and Comparative Example 3

[0070] Example 2 and Comparative Example 3 respectively provide a method for preparing a radiation grafted polypropylene high thermal insulation foam material. Compared with Example 1, the difference is that the mass ratio of polypropylene powder and grafted polypropylene powder is changed, and the other steps are substantially the same as Example 1, which will not be repeated here. The mass ratio of polypropylene powder and grafted polypropylene powder in Example 2 and Comparative Example 3 and the thermal conductivity test results of the foam materials prepared therefrom are shown in Table 2.

[0071] Table 2 Process parameters and product performance in Example 2 and Comparative Example 3

[0072]

[0073] It can be seen from Table 2 that with the increase of the content of grafted polypropylene powder, the thermal conductivity of the obtained foamed material gradually increases, that is, the thermal insulation effect gradually decreases.

[0074] Examples 3-4 and Comparative Example 4

[0075] Examples 3 to 4 and Comparative Example 4 respectively provide a method for preparing a radiation grafted polypropylene high thermal insulation foam material. Compared with Example 1, the difference is that the pressure and temperature during supercritical carbon dioxide foaming are changed. The other steps are roughly the same as Example 1 and will not be repeated here.

[0076] The foaming conditions in Examples 3 to 4 and Comparative Example 4 and the thermal conductivity test results of the foamed materials prepared therefrom are shown in Table 3.

[0077] Table 3 Process parameters and product performance in Examples 3 to 4 and Comparative Example 4

[0078]

[0079] It can be seen from Table 3 that the thermal conductivity of the foamed material obtained when the foaming pressure is 25 MPa and the foaming temperature is 175°C is the lowest, that is, the thermal insulation performance is the best.

[0080] In summary, the present application provides a radiation grafted polypropylene high thermal insulation foam material and a preparation method thereof, which belongs to the technical field of polypropylene foam materials. Polypropylene is modified by a radiation grafting process, an ester group is introduced into the polypropylene, and then supercritical intermittent foaming is performed using a nanoscale hollow molecular sieve as a nucleating agent to obtain a polypropylene foam material with a high porosity micro-nano pore structure having an ester group. Among them, the ester group has the function of absorbing infrared radiation energy. The introduction of the ester group greatly improves the radiation absorption coefficient of the polypropylene foam material. The micro-nano pore structure formed during the foaming process makes the solid volume proportion of the entire polypropylene foam material much smaller than the air volume proportion, and the micro-nano pores reduce the heat transfer efficiency of air thermal convection by enhancing the Knudsen effect, thereby greatly reducing the thermal conductivity coefficient of the foam material. The foam material prepared by the present application has excellent thermal insulation performance, which solves the problems of poor thermal insulation performance of traditional foam materials and narrow substrate selection.

[0081] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a radiation grafted polypropylene high thermal insulation foam material, characterized in that: The steps include: S1. dissolving polypropylene and methyl acrylate in a solvent, mixing them evenly to obtain a mixed solution; irradiating the mixed solution, washing, and drying the mixed solution to obtain a grafted polypropylene; S2. The polypropylene, the grafted polypropylene, the antioxidant and the nano-scale hollow molecular sieve are uniformly mixed and granulated to obtain mixed plastic particles; S3. The mixed plastic particles are hot pressed and cut to obtain a sample sheet; S4. Place the sample sheet in a reactor, fill it with CO2 to a set pressure, heat the reactor to the foaming temperature, foam it fully, and finally release the CO2 gas and release the pressure to obtain a high thermal insulation polypropylene foam material.

2. The method for preparing the radiation grafted polypropylene high thermal insulation foam material according to claim 1, characterized in that: The amount of the nanoscale hollow molecular sieve added in step S2 is 1-2% of the total mass of the polypropylene and the grafted polypropylene.

3. The method for preparing the radiation grafted polypropylene high thermal insulation foam material according to claim 1, characterized in that: In step S1, the mass of the methyl acrylate accounts for 10-15% of the mass of the polypropylene, and the solvent is anhydrous ethanol.

4. The method for preparing the radiation grafted polypropylene high thermal insulation foam material according to claim 1, characterized in that: The irradiation in step S1 is electron beam irradiation, and the irradiation dose is 20 to 30 kGy.

5. The method for preparing the radiation grafted polypropylene high thermal insulation foam material according to claim 1, characterized in that: The mass ratio of the polypropylene to the grafted polypropylene in step S2 is 8.5-9:1.5-1.

6. The method for preparing the radiation grafted polypropylene high thermal insulation foam material according to claim 1, characterized in that: The antioxidant in step S2 is one or a combination of hindered phenol antioxidants, thiohindered phenol antioxidants, phosphite antioxidants, and amine antioxidants, and the amount of the antioxidant added is 1-2% of the total mass of the polypropylene and the grafted polypropylene.

7. The method for preparing the radiation grafted polypropylene high thermal insulation foam material according to claim 1, characterized in that: The temperature of the hot pressing in step S3 is 160-170°C.

8. The method for preparing the radiation grafted polypropylene high thermal insulation foam material according to claim 1, characterized in that: In step S4, the set pressure is 20-25 MPa, the foaming temperature is 165-175° C., and the foaming time is 2-2.5 h.

9. A radiation grafted polypropylene high thermal insulation foam material, characterized in that: The high thermal insulation foam material is prepared by the method for preparing the radiation grafted polypropylene according to any one of claims 1 to 8.

10. The radiation grafted polypropylene high thermal insulation foam material according to claim 9, characterized in that: The radiation grafted polypropylene high thermal insulation foam material is a micro-nano pore structure with high porosity and ester groups, and the thermal conductivity of the radiation grafted polypropylene high thermal insulation foam material is 29.3 mW / m·k.

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