Preparation method of light ablative thermal protection internal insulation layer material

Abstract

The invention discloses a preparation method of a light ablative thermal protection internal insulation layer material. The material is prepared from the following raw materials: 100 parts of a non-polar polyolefin elastomer or a polyolefin elastomer containing an epoxy group, 0.01 to 5 parts of an initiator, 0.1 to 10 parts of glycidyl methacrylate, 0.05 to 0.2 part of an antioxidant, 0 to 50 parts of aminophenylboronic acid, 0 to 50 parts of fumed silica, 0 to 30 parts of chopped aramid fibers, 0 to 10 parts of aramid nanofibers and 0 to 10 parts of a chemical foaming agent. The preparation method comprises the following steps: preparing an epoxy modified polyolefin elastomer A by utilizing reactive mixing; secondly, preparing a polyolefin elastomer composite material B by utilizing reactive mixing; and finally performing secondary processing and forming. The invention develops a method which is simple to operate and can be used for preparing the internal thermal insulation layer composite material in batches, and the obtained elastomer composite material has thermoplastic repeated processing capacity and foamable capacity, and has controllable interface bonding capacity and excellent ablation-resistant thermal protection performance.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and specifically relates to a method for preparing a lightweight ablative thermal protection inner insulation layer material Background Art

[0002] The inner insulation layer is an important component of the thermal protection of solid rocket engines. It is exposed to high temperature and high-speed particle flow for a long time in the working state. It usually absorbs a large amount of heat through its own physical and chemical reactions such as melting, sublimation, and degradation, thereby maintaining the safety of the shell composite material. Among them, representative flexible matrices of the inner insulation layer include nitrile rubber, EPDM rubber, silicone rubber, polyphosphazene elastomer, etc. At the same time, fillers such as silica, aramid, and flame retardants are usually configured in the flexible rubber matrix to promote consolidation into carbon at high temperature, thereby improving the mechanical and erosion resistance of the insulation layer. However, the existing inner insulation layer still faces several problems. First, the vulcanization process based on traditional rubber obtains thermosetting rubber, and its molding process needs to consider the compatibility and co-curing applicability with the fiber winding shell molding process; second, with the development of new propellants, particle erosion has intensified, and the traditional physical filling type inner insulation layer has poor interface or interface debonding between fibers, fillers and rubber matrix, which leads to the limitation of erosion resistance. In response to the above problems, we use reaction processing technology to introduce a dynamic covalent cross-linking network into polyolefin elastomers to improve heat resistance and take into account thermal reprocessing capabilities; at the same time, based on the special surface treatment of fillers and fibers, dynamic covalent cross-linking of the elastomer matrix and fillers is simultaneously achieved to promote the stability of the carbonized structure at high temperatures. Therefore, the present invention has developed a method for simple operation and batch preparation of internal insulation layer composite materials. The resulting elastomer composite material has thermoplastic reprocessing capabilities and foaming capabilities, controllable interface bonding capabilities and excellent ablation-resistant thermal protection performance. Summary of the invention

[0003] In order to avoid the shortcomings of the prior art, the present invention develops a method for preparing a lightweight ablative thermal protection inner insulation layer material, which solves the technical dependence of co-curing molding of the traditional rubber-based inner insulation layer and the shell, improves the problem of poor organic-inorganic interface interaction in the elastomer composite material, and enhances the anti-erosion thermal protection capability of the inner insulation layer.

[0004] In order to achieve the above purpose, the technical solution is as follows:

[0005] Step 1: weigh 100 parts of non-polar polyolefin elastomer, 0.01-5 parts of initiator, 0.1-10 parts of glycidyl methacrylate, and 0.05-0.2 parts of antioxidant, use a Haake internal mixer or a twin-screw extruder, set the heating temperature to 160-200° C., and reactively mix for 5-30 minutes to obtain epoxy-modified polyolefin elastomer A;

[0006] Step 2: Weigh 100 parts of a polyolefin elastomer containing epoxy groups, weigh 0 to 50 parts of aminophenylboric acid, weigh 0 to 50 parts of fumed silica, weigh 0 to 30 parts of chopped aramid fibers, weigh 0 to 5 parts of aramid nanofibers, weigh 0 to 10 parts of a chemical foaming agent, and use a twin-roll mill, a Hake internal mixer or a twin-screw extruder to reactively mix for 10 to 60 minutes to obtain a polyolefin elastomer composite material B;

[0007] Step 3: Take an appropriate amount of polyolefin elastomer composite material B, adopt conventional polymer processing methods, and use a melt temperature of 130-250° C. to obtain an inner insulation layer material of a specific thickness, and cut it into specimens for testing.

[0008] The non-polar polyolefin elastomer described in step 1 is any one or a combination of ethylene-octene block copolymer (OBC), ethylene-octene random copolymer (POE), and ethylene-propylene diene monomer elastomer (EPDM).

[0009] The epoxy group-containing polyolefin elastomer in step 2 is any one or a combination of epoxy-modified polyolefin elastomer A or ethylene-methyl acrylate-glycidyl methacrylate random terpolymer (EGMA).

[0010] The initiator described in step 1 is any one of diisopropylbenzene peroxide or 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane.

[0011] The aminophenylboronic acid in step 2 is any one of 3-aminophenylboronic acid and 4-aminophenylboronic acid.

[0012] The chemical foaming agent in step 2 is any one of 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH) and azodicarbonamide (AC).

[0013] The conventional polymer processing method described in step 3 includes any one of extrusion calender, compression molding, and injection molding.

[0014] The invention aims at the problems of limitation of curing process of traditional inner heat insulation layer and poor interface bonding between filler and substrate, and introduces boron-containing dynamic covalent bonds to realize dynamic covalent crosslinking of elastomer and composite material thereof.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The present invention retains the thermoplastic reprocessing capability of the elastomer composite material, and the obtained elastomer can be further lightweighted by foaming.

[0017] 2. The present invention constructs dynamic covalent crosslinking between inorganic fillers and fibers and the elastomer matrix, thereby improving its basic mechanical properties and anti-erosion thermal protection capabilities.

[0018] 3. The present invention uses conventional equipment for polymer processing, has a simple operation process, low production cost, is expected to be produced continuously, and is suitable for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 . Room temperature tensile properties of different samples

[0020] Figure 2 . Machining torque diagram of typical embodiment samples

[0021] Figure 3 . Photograph of the ablation appearance of a typical embodiment sample

[0022] Figure 4 Typical Example Samples in the Chopping-Hot Pressing Process of Thermoplastic Repeated Processing Photo DETAILED DESCRIPTION

[0023] In order to further explain the technical solution of the present invention, the following is a specific description in conjunction with the embodiments, but the protection scope of the present invention is not limited to these embodiments, and non-essential improvements and adjustments made to the present invention by those skilled in the art all fall within the protection scope of the present invention.

[0024] Example 1

[0025] Take 100 parts of polyolefin elastomer EGMA containing epoxy groups and 10 parts of 3-aminophenylboric acid, mix them in an internal mixer at a high temperature of 240°C for 50 minutes to obtain boron-modified EGMA elastomer 1, and use compression molding or microinjection molding for secondary processing. The temperature is set to 190°C, the fixed pressure during molding is 10MPa, and hot pressing is performed for 10 minutes. Dumbbell-shaped specimens are cut with a cutting knife, and dumbbell-shaped specimens are directly prepared by microinjection molding for testing.

[0026] Example 2

[0027] Take 100 parts of polyolefin elastomer EGMA containing epoxy groups and 20 parts of 3-aminophenylboric acid, mix them in an internal mixer at a high temperature of 240°C for 50 minutes to obtain boron-modified EGMA elastomer 2, and use compression molding or microinjection molding for secondary processing. The temperature is set to 190°C, the fixed pressure during molding is 10MPa, and hot pressing is performed for 10 minutes. Dumbbell-shaped specimens are cut with a cutting knife, and dumbbell-shaped specimens are directly prepared by microinjection molding for testing.

[0028] Example 3

[0029] Take 100 parts of polyolefin elastomer EGMA containing epoxy groups and 10 parts of 3-aminophenylboric acid, mix them at high temperature of 240°C in an internal mixer for 50 minutes, then add 20 parts of silica white carbon black, and continue to mix at high temperature for 15 minutes to obtain silica-filled EGMA boron-containing cross-linked elastomer 3, and use compression molding or microinjection molding for secondary processing, set the temperature to 190°C, the fixed pressure during molding is 10MPa, hot press for 10 minutes, use a cutting knife to cut to obtain dumbbell-shaped specimens, and microinjection molding to directly prepare dumbbell-shaped specimens for testing.

[0030] Example 4

[0031] Take 100 parts of polyolefin elastomer EGMA containing epoxy groups and 20 parts of 3-aminophenylboric acid, mix them at high temperature of 240°C in an internal mixer for 50 minutes, then add 40 parts of silica white carbon black, and continue to mix at high temperature for 15 minutes to obtain silica-filled EGMA boron-containing cross-linked elastomer 4, and use compression molding or microinjection molding for secondary processing, set the temperature to 190°C, the fixed pressure during molding is 10MPa, hot press for 10 minutes, use a cutting knife to cut to obtain dumbbell-shaped specimens, and microinjection molding directly prepares dumbbell-shaped specimens for testing.

[0032] Example 5

[0033] Take 100 parts of non-polar elastomer OBC, 0.1 parts of antioxidant 1010, 5 parts of glycidyl methacrylate, and 0.5 parts of diisopropylbenzene peroxide, and mix them in an internal mixer at a high temperature of 170°C for 30 minutes to obtain epoxy-modified polyolefin elastomer A; weigh 100 parts of epoxy-modified polyolefin elastomer A, 10 parts of 3-aminophenylboric acid, 10 parts of chopped aramid fibers, and 20 parts of silica white carbon black, and mix them in an internal mixer at a high temperature of 170°C for 15 minutes to obtain aramid / silica-filled boron-containing cross-linked elastomer 5, and use compression molding or microinjection molding for secondary processing, set the temperature to 190°C, the fixed pressure during molding is 10 MPa, hot press for 10 minutes, use a cutting knife to cut to obtain dumbbell-shaped specimens, and microinjection molding to directly prepare dumbbell-shaped specimens for testing.

[0034] Comparative Example 1

[0035] Take 100 parts of polyolefin elastomer EGMA containing epoxy groups and 20 parts of silica white carbon black, mix them in an internal mixer at a high temperature of 170°C for 15 minutes to obtain silica physically filled EGMA elastomer 1, and use compression molding or microinjection molding for secondary processing. The temperature is set to 190°C, the fixed pressure during molding is 10MPa, and hot pressing is performed for 10 minutes. Dumbbell-shaped specimens are cut with a cutting knife, and dumbbell-shaped specimens are directly prepared by microinjection molding for testing.

[0036] Comparative Example 2

[0037] Take 100 parts of polyolefin elastomer EGMA containing epoxy groups and 40 parts of silica white carbon black, mix them in an internal mixer at a high temperature of 170°C for 15 minutes to obtain silica physically filled EGMA elastomer 2, and use compression molding or microinjection molding for secondary processing. The temperature is set to 190°C, the fixed pressure during molding is 10MPa, and hot pressing is performed for 10 minutes. Dumbbell-shaped specimens are cut with a cutting knife, and dumbbell-shaped specimens are directly prepared by microinjection molding for testing.

[0038] Comparative Example 3

[0039] Take 100 parts of non-polar elastomer OBC, 10 parts of short-cut aramid fiber, 0.1 parts of antioxidant 1010, and 20 parts of silica white carbon black, mix them in an internal mixer at a high temperature of 170°C for 15 minutes to obtain aramid / silica co-filled OBC elastomer 3, and use compression molding or microinjection molding for secondary processing. The temperature is set to 190°C, the fixed pressure during molding is 10MPa, and hot pressing is performed for 10 minutes. Dumbbell-shaped specimens are cut with a cutting knife, and dumbbell-shaped specimens are directly prepared by microinjection molding for testing.

[0040] In order to examine the thermal reprocessability of the products obtained in the examples, the appearance of the samples before and after hot pressing was compared, and the tensile properties and ablation resistance of the prepared samples were further examined. The experimental results show that the boron-modified polyolefin elastomer composite material of the present invention has a wide operating temperature, excellent basic mechanical properties, thermal reprocessability and foaming ability, and has the advantages of excellent ablation resistance and chemical stability.

Claims

1. A method for preparing a lightweight ablative thermal protection inner insulation layer material, characterized in that The steps include: Step 1: weigh 100 parts of non-polar polyolefin elastomer, 0.01-5 parts of initiator, 0.1-10 parts of glycidyl methacrylate, and 0.05-0.2 parts of antioxidant, use a Haake internal mixer or a twin-screw extruder, set the heating temperature to 160-200° C., and reactively mix for 5-30 minutes to obtain epoxy-modified polyolefin elastomer A; Step 2: Weigh 100 parts of a polyolefin elastomer containing epoxy groups, weigh 0 to 50 parts of aminophenylboric acid, weigh 0 to 50 parts of fumed silica, weigh 0 to 30 parts of chopped aramid fibers, weigh 0 to 5 parts of aramid nanofibers, weigh 0 to 10 parts of a chemical foaming agent, and use a twin-roll mill, a Hake internal mixer or a twin-screw extruder to reactively mix for 10 to 60 minutes to obtain a polyolefin elastomer composite material B; Step 3: Take an appropriate amount of polyolefin elastomer composite material B, adopt conventional polymer processing methods, and use a melt temperature of 130-250° C. to obtain an inner insulation layer material of a specific thickness, and cut it into specimens for testing.

2. The method for preparing the lightweight ablative thermal protection inner insulation layer material according to claim 1, characterized in that The non-polar polyolefin elastomer is any one or a combination of ethylene-octene block copolymer (OBC), ethylene-octene random copolymer (POE), and ethylene-propylene diene monomer elastomer (EPDM).

3. The method for preparing the lightweight ablative thermal protection inner insulation layer material according to claim 1, characterized in that The epoxy group-containing polyolefin elastomer is any one or a combination of epoxy-modified polyolefin elastomer A or ethylene-methyl acrylate-glycidyl methacrylate random terpolymer (EGMA).

4. The method for preparing the lightweight ablative thermal protection inner insulation layer material according to claim 1, characterized in that The initiator is any one of diisopropylbenzene peroxide or 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane.

5. The method for preparing the lightweight ablative thermal protection inner insulation layer material according to claim 1, characterized in that The aminophenylboronic acid is any one of 3-aminophenylboronic acid and 4-aminophenylboronic acid.

6. The method for preparing the lightweight ablative thermal protection inner insulation layer material according to claim 1, characterized in that The chemical foaming agent is any one of 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH) and azodicarbonamide (AC).

7. The method for preparing the lightweight ablative thermal protection inner insulation layer material according to claim 1, characterized in that The conventional polymer processing method includes any one of extrusion calender, compression molding, and injection molding.

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