Polyolefin composite material, method for producing the same, and use thereof

Abstract

The application discloses a kind of polyolefin wave-absorbing material and its preparation method and application, belong to polymer composite field;A kind of polyolefin wave-absorbing composite material includes the following mass fraction of raw materials: copolymerized polypropylene 32-66 parts, talcum powder 10-20 parts, toughening agent 10-14 parts, wave-absorbing master batch 5-15 parts, inorganic wave-absorbing filler 5-10 parts compatible agent 3-5 parts, antioxidant 0.4-0.6 parts, lubricant 0.1-0.2 parts and light stabilizer 0.3-0.5 parts;Using hollow polyaniline microspheres with high specific surface area as conductive filler, combined with chopped carbon fiber as reinforcing phase, the synergistic effect of multi-scale filler in polypropylene matrix is utilized, the pain points of large amount of traditional conductive filler and performance decline are solved, and finally through melt blending and extrusion molding process, a plate with excellent performance is prepared.Based on the above composite system, extrusion-calendering-suction molding continuous molding technology is developed.The process can not only ensure that the orientation structure of carbon fiber is not damaged during extrusion, but also can give the plate a very high shape freedom through subsequent suction molding.This makes the multifunctional plate can cover the surface of most special-shaped components, has good processability and large-scale application potential, truly realizes the engineering integration of wave-absorbing function and structural support.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, specifically relating to a microwave absorbing polyolefin composite material, its preparation method, and its application. Background Technology

[0002] Electrification, intelligentization, connectivity, and sharing (the "new four modernizations") have become the strategic direction of the global automotive industry. Intelligent connected vehicles, as a product of cross-industry integration, are becoming a core engine for industrial upgrading. With the upgrading of ADAS levels and the large-scale deployment of millimeter-wave radar (24 / 77GHz), lidar, and V2X antennas, the complexity of the automotive electromagnetic environment has increased dramatically, mainly bringing two major problems: first, the risk of electromagnetic interference between in-vehicle electronic devices, threatening driving safety; second, the chaotic reflected waves generated by the metal structural components behind the radar dome area, interfering with the radar's accurate identification of obstacles. Traditional metal shielding components are heavy, costly, and have low design freedom. Developing a lightweight, easily moldable polypropylene (PP) material with wave-absorbing properties to solve electromagnetic pollution at its source is key to achieving a deep integration of automotive "lightweighting" and "intelligentization."

[0003] Currently, traditional microwave absorbing materials have high density but unsatisfactory absorption effects, necessitating optimization of their absorption performance. 1. Introducing high-specific-surface-area polyaniline microspheres, synergistically sizing carbon fibers, requires precise control of the polyaniline microsphere to carbon fiber ratio to achieve optimal dielectric properties and thus improve absorption performance. 2. Maintaining anisotropy during the molding process. Studies have shown that the microwave absorption performance of carbon fiber composites exhibits a significant direction dependence—the relative position of the fiber to the direction of the electromagnetic wave electric field determines the material's response characteristics. Numerous studies have shown that, under specific conditions, absorption capacity in the perpendicular direction is superior to that in the parallel direction. Employing extrusion-pressing-vacuum forming can significantly ensure that the incident direction of the electromagnetic wave is perpendicular to the surface. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a polyolefin microwave absorbing composite material, its preparation method, and its application, thereby solving the problems in the prior art.

[0005] The objective of this invention can be achieved through the following technical solutions: A polyolefin microwave absorbing composite material, comprising the following raw materials in parts by weight: The composition includes 32-66 parts copolymer polypropylene, 10-20 parts talc, 10-14 parts toughening agent, 5-15 parts microwave absorbing masterbatch, 5-10 parts inorganic microwave absorbing filler, 3-5 parts compatibilizer, 0.4-0.6 parts antioxidant, 0.1-0.2 parts lubricant, and 0.3-0.5 parts light stabilizer.

[0006] Furthermore, the preparation process of the microwave absorbing masterbatch includes: To prevent the hollow microspheres from breaking or dispersing unevenly during direct blending, the prepared hollow polyaniline microspheres, compatibilizer, polypropylene and related additives are pre-blended, extruded and granulated in a twin-screw extruder at a barrel temperature of 150-180℃. Further, the preparation process of the polyaniline microspheres is as follows (taking the preparation of 100 g as an example): 223 g of dopant (p-toluenesulfonic acid TSA, with a TSA:aniline molar ratio of 1:0.8) is dissolved in 5 L of deionized water and stirred until completely dissolved. Then, 136 g of aniline monomer is added, and stirring is continued to obtain a milky white or slightly yellow mixture. This mixture is pre-cooled to 0-5℃ in an ice-water bath. 267 g of ammonium persulfate (APS, with An:APS = 1:0.5-1:1) is dissolved in 3 L of pre-cooled deionized water and slowly added dropwise to the above mixture, maintaining an ice bath and slow stirring during the addition. After the addition is complete, the solution color gradually changes from colorless to dark green. The mixture is allowed to stand at 0-5℃ for 12-24 hours. After the reaction is complete, the mixture is centrifuged (8000-10000 rpm, 10-15 minutes) and washed 2-3 times each with deionized water and anhydrous ethanol. Finally, the mixture was vacuum dried at 60-80℃ for 12-24 hours to obtain dark green polyaniline microsphere powder.

[0007] Further, the antioxidant is any one or more of the following: pentaerythritol diisodecyl diphosphite, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,4-bis((dodecylthio)methyl)-6-methylphenol, octadecyl-3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionate, tris(2,4-di-tert-butylphenyl) phosphite, and N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine.

[0008] Furthermore, the lubricant is any one of stearic acid, oleic acid, lauryl acid, tetradecanoic acid, polyethylene wax, and polypropylene wax; The light stabilizer is any one of 5-chlorobenzotriazole, methyl 3-[3-(benzotriazole-2-yl)-5-tert-butyl-4-hydroxyphenyl]propionate, and bis(2,2,6,6-tetramethylpiperidinol ester].

[0009] Further, the compatibilizer is MAH-g-PP; the toughening agent is any one of ethylene-octene copolymer, styrene-ethylene-butadiene-styrene copolymer, styrene-butadiene block copolymer, and polyethylene.

[0010] Furthermore, in the microwave absorbing masterbatch, the ratio of polyaniline hollow microspheres, copolymer polypropylene, and compatibilizer is 13:6:1; the inorganic microwave absorbing filler is sized short-cut carbon fiber. The above-mentioned method for preparing a polyolefin microwave absorbing composite material includes the following steps: pre-blending copolymer polypropylene, microwave absorbing masterbatch, inorganic microwave absorbing filler, toughening agent, compatibilizer, antioxidant, lubricant and light stabilizer, and then using a twin-screw extruder for blending and granulation.

[0011] The above-mentioned polyolefin microwave absorbing composite material is used in the preparation of automotive interior parts.

[0012] The beneficial effects of this invention are: 1. This invention proposes a preparation scheme for a multifunctional composite material based on the synergistic reinforcement of polyaniline microspheres and carbon fibers, introducing polyaniline microspheres with intrinsically rough surfaces. Compared with traditional smooth fillers, this rough structure not only increases the bonding interface with the matrix, but more importantly, it constructs abundant heterogeneous interfaces within the composite material. This structure can effectively induce multiple reflections, scattering, and interfacial polarization relaxation of electromagnetic waves, significantly enhancing the ability to dissipate electromagnetic energy. Through the design of the material's microstructure and the control of the molding process, a balance between excellent wave absorption performance and structural load-bearing capacity is achieved.

[0013] 2. This invention fully utilizes the high specific strength and high modulus characteristics of carbon fiber. Through precise control of the extrusion-pressing process, carbon fibers are induced to be highly oriented along the melt flow direction, forming a directional reinforcement structure. This not only endows the sheet with excellent anisotropic mechanical properties, enabling it to have structural load-bearing capacity in a specific direction, but also achieves anisotropic control of wave absorption performance to meet the electromagnetic wave protection requirements of different polarization directions.

[0014] 3. Based on the aforementioned composite material system, this invention develops a continuous extrusion-calendering-vacuum forming technology. This process ensures that the orientation structure of the carbon fibers is not damaged during extrusion, while the subsequent vacuum forming process grants the sheet material a high degree of shape freedom. This allows the multifunctional sheet material to cover the surface of most irregularly shaped components, possessing excellent processability and large-scale application potential, truly achieving the engineering integration of wave absorption function and structural support. Attached Figure Description

[0015] Figure 1 The image shows the device casing according to an embodiment of this application. Detailed Implementation

[0016] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] A polyolefin composite material comprising the following parts by weight of raw materials: The composition includes 32-66 parts copolymer polypropylene, 10-20 parts talc, 10-14 parts toughening agent, 5-15 parts microwave absorbing masterbatch, 5-10 parts inorganic microwave absorbing filler, 3-5 parts compatibilizer, 0.4-0.6 parts antioxidant, 0.1-0.2 parts lubricant, and 0.3-0.5 parts light stabilizer.

[0018] The manufacturer's grade of the copolymer polypropylene is any one or more of the following: Dushanzi T4401, Guangzhou Petrochemical 4220, Yanshan Petrochemical 4220, and Yanshan B8101.

[0019] In some embodiments, to avoid the agglomeration of polyaniline and the amount of microwave absorbing masterbatch added, the ratio of polyaniline hollow microspheres, copolymer polypropylene, and compatibilizer is 13:6:1. The technical solution of the present invention will be described in detail below through the following embodiments; Examples 1-4: Exploring the performance of inorganic absorbing materials and absorbing masterbatches by adjusting their proportions. Example 1 was prepared as follows: Step 1: Polyaniline hollow microspheres, copolymer polypropylene and maleic anhydride grafted compatibilizer (PP-g-MAH) in a ratio of 13:6:1 are pre-blended, extruded and granulated to obtain microwave absorbing masterbatch; Step 2: Pre-blend 5 parts of the above-mentioned microwave absorbing masterbatch, 37 parts of copolymer polypropylene T4401, 10 parts of copolymer polypropylene B8101, 13 parts of POE 8842, 20 parts of talc, 10 parts of Baoding Jingnan sheet-like short-cut carbon fiber (T400), 5 parts of compatibilizer, 0.4 parts of antioxidant, 0.1 parts of lubricant, and 0.3 parts of light stabilizer; then granulate the blended mixture using a micro twin-screw extruder. The micro twin-screw extruder feed speed was 25 rpm, the main extruder speed was 400 rpm, and the temperature control for zones 1-10 was set to 160, 170, 170, 180, 170, 170, 170, 160, 160, 160℃. After drying, the granules were used to prepare tensile and impact bending test strips using an injection molding machine. Then, it is extruded and calendered into 100 mm × 100 mm × 2.5 mm square plates for microwave absorption performance testing. The extrusion temperature is 180℃ and the die temperature is 50℃.

[0020] Examples 2 and 3 differ from Example 1 in that they increase the proportion of absorbing masterbatch and adjust the absorbing performance. In Example 2, the proportion of absorbing masterbatch is increased to 10 parts; in Example 3, the proportion of absorbing masterbatch is increased to 15 parts.

[0021] Example 4 differs from Example 3 in that it reduces the proportion of inorganic microwave absorbing filler to find the optimal performance / cost balance. In Example 4, the proportion of inorganic microwave absorbing filler is reduced to 5 parts.

[0022] Comparative Example 1: Comparative Example 1 is a blank control sample, without any microwave absorbing filler added; the specific implementation steps are as follows: 57 parts of copolymer polypropylene T4401, 10 parts of copolymer polypropylene B8101, 13 parts of POE 8842, 20 parts of talc, 5 parts of compatibilizer, 0.4 parts of antioxidant, 0.1 parts of lubricant, and 0.3 parts of light stabilizer were pre-blended; then, the blends were granulated using a micro twin-screw extruder. The micro twin-screw extruder had a feed speed of 25 rpm, a main extruder speed of 400 rpm, and temperature controls for zones 1-10 set to 160, 170, 170, 180, 170, 170, 170, 160, 160, and 160℃, respectively. After drying, the granules were used to prepare tensile and impact bending test strips using an injection molding machine. These strips were then extruded and calendered into 100 mm × 100 mm × 2.5 mm square plates for microwave absorption performance testing. The extrusion temperature was 180℃, and the die temperature was 50℃.

[0023] Comparative Examples 2-4 and 2-3 verify the effect of carbon fiber content on the properties of the composite material; The specific preparation steps for Comparative Example 2 are as follows: 47 parts of copolymer polypropylene T4401, 10 parts of copolymer polypropylene B8101, 13 parts of POE 8842, 5 parts of inorganic microwave absorbing filler, 20 parts of talc, 5 parts of compatibilizer, 0.4 parts of antioxidant, 0.1 parts of lubricant, and 0.3 parts of light stabilizer were pre-blended; then, the blends were granulated using a micro twin-screw extruder. The micro twin-screw extruder had a feed speed of 25 rpm, a main extruder speed of 400 rpm, and temperature controls for zones 1-10 set to 160, 170, 170, 180, 170, 170, 170, 160, 160, and 160℃, respectively. After drying, the granules were used to prepare tensile and impact bending test strips using an injection molding machine. These strips were then extruded and calendered into 100 mm × 100 mm × 2.5 mm square plates for microwave absorption performance testing. The extrusion temperature was 180℃, and the die temperature was 50℃.

[0024] The difference between Comparative Example 3 and Comparative Example 2 is that the proportion of inorganic microwave absorbing filler - carbon fiber is increased in Comparative Example 3; the proportion of inorganic microwave absorbing filler in Comparative Example 3 is increased to 10 parts. The difference between Comparative Example 4 and Comparative Example 2 is that the proportion of inorganic microwave absorbing filler - carbon fiber is increased; the proportion of inorganic microwave absorbing filler in Comparative Example 3 is increased to 15 parts. Comparative Example 5 aims to investigate single-component polyaniline microspheres; the specific preparation is as follows: Step 1: Polyaniline hollow microspheres, copolymer polypropylene and compatibilizer in a ratio of 13:6:1 are pre-blended, extruded and granulated to obtain microwave absorbing masterbatch; Step 2: 5 parts of the above-mentioned microwave absorbing masterbatch were pre-blended with 47 parts of copolymer polypropylene T4401, 10 parts of copolymer polypropylene B8101, 13 parts of POE 8842, 20 parts of talc, 5 parts of compatibilizer, 0.4 parts of antioxidant, 0.1 parts of lubricant, and 0.3 parts of light stabilizer. Then, the blending was granulated using a micro twin-screw extruder. The micro twin-screw extruder had a feed speed of 25 rpm, a main extruder speed of 400 rpm, and temperature controls for zones 1-10 set to 160, 170, 170, 180, 170, 170, 170, 160, 160, and 160℃ respectively. After drying, the granules were used to prepare tensile and impact bending test strips using an injection molding machine. These strips were then extruded and calendered into 100 mm × 100 mm × 2.5 mm square plates for microwave absorption performance testing. The extrusion temperature was 180℃, and the die temperature was 50℃.

[0025] The difference between Comparative Example 6 and Comparative Example 5 lies in the morphology of the polyaniline used to prepare the microwave absorbing masterbatch. Comparative Example 5 uses polyaniline microspheres (0.1-5 µm hollow microspheres with abundant specific surface area) to prepare the microwave absorbing masterbatch, while Comparative Example 6 uses irregular granular polyaniline (without a specific design structure). The difference between Comparative Example 7 and Example 4 is that the absorbing masterbatch is different; Comparative Example 7 uses a conventional polyaniline absorbing masterbatch; Example 4 uses a polyaniline microsphere absorbing masterbatch. Example 5: The extruded and calendered sheet from Example 3 was used to prepare a concave-shaped equipment shell in a semi-automatic / dedicated thick plate vacuum forming machine at 160-175℃ and 0.4-0.7 MPa.

[0026] The properties of the polyolefin composite materials prepared in the examples and comparative examples are tested and analyzed below; 1) Basic performance testing; the testing standards for each item are as follows: 1.1) Density: The test standard is GB / T1033.1, and the test condition is 23℃.

[0027] 1.2) Ash content: The test standard is GB / T9345.1, and the test conditions are 600±25℃.

[0028] 1.3) Melt flow rate: The test standard is GB / T3682, and the test conditions are 230℃ / ±2.16kg.

[0029] 1.4) Tensile strength: The test standard is GB / T1040.2, and the test condition is 50 mm / min.

[0030] 1.5) Bending strength and bending modulus: The test standard is GB / T9341, and the test condition is 2 mm / min.

[0031] 1.6) Cantilever beam notched impact strength: The test standard is GB / T1843, and the test conditions are 4mm and 23℃.

[0032] 1.7) Reflection loss: Refer to GJB 2038A-2011 standard to test its reflection loss in the 75-110GHz frequency band.

[0033] The test results are shown in Table 1: Table 1. Basic properties of polyolefin microwave absorbing composite materials Table 2. Microwave absorption performance of different molding methods Table 3 Wave Absorption Performance of Equipment Housing As can be seen from Table 1: Comparative examples 1-4 show that there is an optimal content window for carbon fiber (approximately 7-8 parts). Beyond this content, surface impedance mismatch occurs, and RL (reflectance ratio) deteriorates. At 15 parts carbon fiber, the material becomes a reflector (RL = -4.5 dB) and lacks practical wave absorption capability.

[0034] Comparative Examples 5 and 6 show that the wave-absorbing advantage of the microspheres can only be manifested in the presence of the three-dimensional carbon fiber network, rather than the effect of the microspheres alone.

[0035] Examples 1-4 demonstrate that spherical polyaniline microspheres (1-2 μm) are key to solving the impedance mismatch in high carbon fiber content. The microspheres uniformly fill the gaps in the carbon fiber network, optimizing surface impedance matching and significantly reducing electromagnetic wave reflectivity while contributing additional dielectric loss. The "network-sphere" synergistic structure achieves a significant improvement in microwave absorption performance. The optimal formulation (Example 3: 10 parts carbon fiber + 15 parts polyaniline microsphere masterbatch) achieves RL_min = -32.0 dB, while maintaining a tensile strength of 36 MPa and a notched impact toughness of 16.0 kJ / m², demonstrating significantly better overall performance than ordinary polyaniline systems with the same content.

[0036] Comparative Example 7 and Example 4 show that hollow polyaniline microspheres have a large specific surface area, which can provide better surface impedance matching and dielectric loss.

[0037] The mechanical advantages of spherical PANI microspheres are consistently demonstrated. Whether used alone or in combination with carbon fiber, the tensile strength and impact toughness of the microsphere system are superior to those of ordinary PANI systems (mechanical properties improved by 14-32%), reflecting the unique advantage of "low stress concentration" of spherical particles.

[0038] The data in Table 2 show that the extrusion-calendering molding method can greatly preserve the orientation structure of the microwave-absorbing inorganic filler carbon fiber, thus significantly improving its microwave absorption performance in a single direction.

[0039] This invention successfully prepared a device housing product with good wave absorption performance.

[0040] This invention successfully resolves the contradiction between "high absorption and excellent mechanical properties" in the field of microwave absorbing materials, providing a practical material solution for engineering applications.

[0041] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0042] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. An electromagnetic wave absorbing composite material, characterized in that, include: Polyolefin matrix; Conductive fibers dispersed in the polyolefin matrix and forming a three-dimensional conductive network; as well as Hollow conductive polymer microspheres dispersed in the gaps of the three-dimensional conductive network; The conductive fibers and the hollow conductive polymer microspheres exist separately in the polyolefin matrix.

2. The electromagnetic wave absorbing composite material according to claim 1, characterized in that, The polyolefin matrix is ​​copolymer polypropylene; the conductive fiber is chopped carbon fiber, and the content of chopped carbon fiber is 5-10 parts per 100 parts by weight; the hollow conductive polymer microspheres are hollow doped polyaniline microspheres with a particle size of 0.1-5 μm.

3. The electromagnetic wave absorbing composite material according to claim 2, characterized in that, The hollow doped polyaniline microspheres exist in the form of microwave absorbing masterbatch, which comprises hollow doped polyaniline microspheres, copolymer polypropylene and compatibilizer, with a weight ratio of 13:6:

1.

4. The electromagnetic wave absorbing composite material according to claim 2, characterized in that, The chopped carbon fibers are oriented along the melt flow direction in the polyolefin matrix.

5. The electromagnetic wave absorbing composite material according to claim 2, characterized in that, Based on 100 parts by weight, it also includes 10-20 parts of talc, 10-14 parts of ethylene-octene copolymer, and 1-3 parts of maleic anhydride-grafted polypropylene.

6. The electromagnetic wave absorbing composite material according to claim 2, characterized in that, The hollow doped polyaniline microspheres are prepared by a template-free method, with salicylic acid or p-toluenesulfonic acid as the dopant and ammonium persulfate as the oxidant.

7. A method for preparing an electromagnetic wave absorbing composite material, characterized in that, Includes the following steps: Hollow conductive polymer microspheres were blended with polyolefin resin and compatibilizer and granulated to obtain masterbatch; The masterbatch is blended and granulated with conductive fibers and polyolefin resin to obtain a blended material; and The blended material is extruded and calendered to obtain a sheet material.

8. The preparation method according to claim 7, characterized in that, The hollow conductive polymer microspheres are hollow doped polyaniline microspheres, the polyolefin resin is copolymer polypropylene, and the conductive fibers are chopped carbon fibers.

9. The preparation method according to claim 8, characterized in that, During the extrusion process, the chopped carbon fibers are oriented along the melt flow direction, and the method further includes the step of vacuum forming the sheet.

10. An electromagnetic wave absorbing component, characterized in that, Including the electromagnetic wave absorbing composite material as described in claim 1.

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