Polypropylene composite material with high-selectivity infrared transmission and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a polypropylene composite material with high-selectivity infrared transmission and a preparation method thereof.The preparation method comprises the following steps that S1, a polypropylene matrix, a fluorine-containing acrylate monomer, an epoxy-group-containing acrylate monomer, an initiator and an antioxidant are subjected to premixing and dipping treatment, and a premix is obtained; and S2, putting the premix into a double-screw extruder, extruding, cooling and pelletizing to obtain the composite material. According to the technical scheme provided by the invention, the polypropylene composite material with high infrared transmittance, high visible light shielding rate, high selectivity coefficient and good mechanical property and processability is prepared through collaborative design of the fluorine-containing acrylate monomer and the epoxy group-containing acrylate monomer and a reactive extrusion process.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a polypropylene composite material with high selective infrared transmittance and its preparation method. Background Technology

[0002] Highly selective infrared-transmitting materials are a class of polymeric materials that achieve specific thermal management functions by intelligently filtering incident light radiation. Their core lies in the ability to precisely control the material's response to different wavelengths of infrared light: for example, efficiently transmitting infrared bands beneficial to specific applications (such as near-infrared light in the solar spectrum or mid-to-far-infrared bands corresponding to the thermal radiation of objects at room temperature), while effectively blocking or reflecting other irrelevant or harmful infrared radiation. This characteristic makes them show significant application potential in fields such as energy-saving windows in smart buildings, spectrally selective covering films in agriculture, industrial thermal process control, and infrared stealth.

[0003] Polypropylene is a highly crystalline thermoplastic resin with outstanding advantages such as light weight, chemical resistance, easy processing and molding, and low cost, and is widely used in packaging, automobiles, and daily necessities. However, unmodified pure polypropylene itself does not possess infrared spectral selectivity, and it exhibits broad-spectrum, passive transmission or absorption behavior for different wavelengths of infrared light.

[0004] Patent publication number CN110240750A discloses a high-gloss polypropylene material with near-infrared transmittance and its preparation method. The material comprises the following components by weight: 100 parts polypropylene, 0.5-2 parts infrared transmittance enhancer, 0.3-2 parts nucleating agent, 0.2-0.5 parts crystallization inhibitor, and 0.3-2 parts dispersant. This material has an infrared transmittance of over 90% and a gloss level of over 85, and can be used in smart home enclosures, remote control enclosures, infrared sensor enclosures, etc.

[0005] In existing technologies, many methods for achieving spectral selectivity by adding functional nanofillers often significantly sacrifice the transparency of the material in the visible light region or cause severe haze while improving transmittance or blocking rate in specific wavelength bands, greatly limiting their application in fields requiring high visual clarity. Simultaneously, the introduction of large amounts of inorganic fillers usually impairs the inherent flexibility and impact resistance of the polypropylene matrix, leading to brittle composites and decreased mechanical properties. Furthermore, under complex photothermal and humid environments (such as prolonged outdoor exposure to sunlight and rain), the organic-inorganic interface in the composite material may deteriorate due to a mismatch in thermal expansion coefficients, resulting in performance degradation. Some functional nanoparticles (especially metal particles) may exhibit photocatalytic or oxidation problems, affecting the long-term optical stability of the material. Summary of the Invention

[0006] To address the problems mentioned in the background section, this invention provides a polypropylene composite material with high selective infrared transmission and a method for preparing the same.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing a polypropylene composite material with high selective infrared transmittance, characterized by comprising the following steps: S1. Premix and impregnate polypropylene matrix, fluorinated acrylate monomer, epoxy acrylate monomer, initiator and antioxidant to obtain premix; S2. The premixed material is placed in a twin-screw extruder, melt-extruded, cooled, and pelletized to obtain a polypropylene composite material with high selective infrared transmittance. The fluorinated acrylate monomers are selected from trifluoroethyl methacrylate or hexafluorobutyl methacrylate, and the epoxy-containing acrylate monomers are selected from glycidyl methacrylate or glycidyl acrylate. The polypropylene matrix is ​​homopolymer polypropylene or copolymer polypropylene, and its melt flow rate (230℃ / 2.16kg) is preferably 2-50g / 10min.

[0008] Specifically, in step S1, based on 100 parts by weight of the polypropylene matrix, the amount of fluorinated acrylate monomer is 8-18 parts by weight, and the amount of epoxy acrylate monomer is 3-8 parts by weight. The amount of initiator is 0.3-0.8 wt% of the polypropylene matrix, and the total amount of antioxidant is 0.1-0.5 wt% of the polypropylene matrix. The initiator is preferably dicumyl peroxide or benzoyl peroxide, and the antioxidant is preferably at least one of antioxidant 1010, antioxidant 1076, antioxidant 168, and antioxidant DSTP.

[0009] In step S1, the premixing and impregnation conditions are as follows: under a closed or inert gas protection environment, mixing and impregnation are carried out at 40-50°C with a stirring speed of 200-400 rpm for 30-120 min. Preferably, when the treatment temperature is 40-45°C, the impregnation time is set to 60-120 min; when the treatment temperature is 45-50°C, the impregnation time is set to 30-60 min.

[0010] In step S2, the length-to-diameter ratio (L / D) of the twin-screw extruder is preferably 36-44, and the temperature of each section from the feed port to the die head is set within the range of 160-190℃. More specifically, the temperature distribution can be: Zone 1 (feeding section) 160-170℃, Zone 2 (melting section) 170-180℃, Zone 3 (reaction section) 175-185℃, Zone 4 (homogenization section) and die head 180-190℃; the screw speed is set to 200-400 rpm, and the feeding rate is coordinated with the screw speed to control the average residence time of the material in the extruder to be 1.5-3.0 min.

[0011] Furthermore, the twin-screw extruder is equipped with a vacuum exhaust port at the rear of the reaction section. During the extrusion process, a vacuum of (-0.06) to (-0.10) MPa is maintained at the vacuum exhaust port to remove unreacted monomers and small molecule volatiles. The vacuum exhaust port is connected to a vacuum pump through a pipeline. Preferably, the pumping speed of the vacuum pump is not less than 20 m³ / h to ensure effective devolatilization.

[0012] In step S2, the molten strip extruded by the twin-screw extruder is cooled and solidified in a cooling water tank. The water temperature of the cooling water tank is controlled at 10-25℃, and the length of the cooling water tank is preferably 2-4 meters to ensure sufficient cooling. The traction speed of the strip before entering the cooling water tank is preferably 5-15 m / min. After cooling and solidification, the strip is cut into regular particles with a length of 2-5 mm by a pelletizer.

[0013] Secondly, the present invention provides a polypropylene composite material with high selective infrared transmittance prepared by the above preparation method. The composite material has an average infrared transmittance of not less than 70% in the 8-14μm band, an average visible light transmittance of not more than 20% in the 0.4-0.76μm band, and a haze greater than 90%.

[0014] Thirdly, the present invention also provides a selective infrared transmission device, characterized in that it comprises a polypropylene composite material with high selective infrared transmission as described above, and the device may be an infrared filter, an infrared sensor window, an agricultural greenhouse film, or an energy-saving building window film, etc.

[0015] The beneficial effects of this invention are: 1. In the technical solution of this invention, during the premixing and impregnation stage, fluorinated acrylate monomers and epoxy-containing acrylate monomers initially penetrate and adsorb onto the polypropylene matrix under the action of an initiator. Subsequently, in the high-temperature, high-shear field of a twin-screw extruder, the initiator decomposes to generate free radicals, which first induce active sites in the polypropylene molecular chains, and then induce graft copolymerization of the two functional monomers. Specifically, the fluorinated acrylate monomer is polymerized and grafted onto the polypropylene chain, introducing CF chemical bonds with specific infrared vibrational characteristics; the epoxy-containing acrylate monomer participates in grafting through its epoxy groups and may form a moderate cross-linked network. The entire process ultimately forms a multi-scale composite structure with polypropylene as the continuous phase, on which fluorinated branches are chemically bonded and stabilized by cross-linking points. Since functionalization modification mainly occurs at the polymer molecular structure level, it is more beneficial to maintain the original optical homogeneity of the matrix compared to physical blending of inorganic fillers. The chemically grafted fluorinated segments, through the specific infrared vibrational characteristics of their CF bonds, can effectively regulate the infrared absorption spectrum of the material, thereby forming a relatively high transmission window in a specific infrared band, which helps to impart spectral selectivity to the material.

[0016] 2. In the technical solution of the present invention, the moderate cross-linking structure introduced by the epoxy monomer can enhance the interaction between molecular chains, produce a certain enhancement effect on the mechanical properties of the material, improve the compatibility between functional components and matrix, and enable the material to maintain good melt flow and molding stability during processing, avoiding the problem of decreased processability that may be caused by adding a large amount of inorganic filler.

[0017] 3. In the technical solution of the present invention, the composite method mainly based on chemical bonding enhances the internal uniformity of the material, reduces the potential stress caused by the mismatch of the thermal expansion coefficients of the multiphase interface, and helps to improve the dimensional stability and performance retention of the material under temperature change environment. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the present invention; Figure 2 A schematic diagram illustrating the structure and working principle of the selective infrared transmission device provided by the present invention. Detailed Implementation

[0019] 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.

[0020] like Figure 1-2As shown, in each embodiment, after premixing and impregnation, the raw materials are melted, reacted, and homogenized using a twin-screw extruder. Combined with vacuum devolatilization, cooling, and pelletizing processes, the composite material is obtained. This composite material can ultimately be processed into… Figure 2 The core functional layer of the selective infrared transmitting device shown achieves the application effect of high selective infrared transmission.

[0021] In the following preparation examples and embodiments, homopolymer polypropylene (melt flow rate MFR of 10 g / 10 min, test conditions 230℃ / 2.16 kg) was purchased from Tianjin Jiujiu Rubber & Plastics Technology Co., Ltd.; trifluoroethyl methacrylate (CAS No.: 352-87-4) and hexafluorobutyl methacrylate (CAS No.: 36405-47-7) were purchased from Dialor International Trading (Shanghai) Co., Ltd.; glycidyl methacrylate (purity ≥97%) was purchased from Qingdao Zhishi Trading Co., Ltd.; benzoyl peroxide (CAS No.: 94-36-0) was purchased from Tianjin Jiujiu Rubber & Plastics Technology Co., Ltd.; and antioxidants were purchased from Hanxian (Tianjin) Trading Co., Ltd. Example 1

[0022] A method for preparing a polypropylene composite material with high selective infrared transmission includes the following steps: S1. Add 100 parts by weight of homopolymer polypropylene, 12 parts by weight of trifluoroethyl methacrylate, 5 parts by weight of glycidyl methacrylate, 0.5 parts by weight of benzoyl peroxide, 0.15 parts by weight of antioxidant 1010 and 0.15 parts by weight of antioxidant 168 to a high-speed mixer, mix and impregnate at 300 rpm for 60 minutes under nitrogen protection at 45°C to obtain a premix. S2. Add the above premixed material to a twin-screw extruder (screw length-to-diameter ratio L / D is 40). Set the temperature of each section of the extruder from the feed port to the die head as follows: Zone 1 165℃, Zone 2 175℃, Zone 3 180℃, Zone 4 185℃, and die head 185℃. Set the screw speed to 300 rpm. Match the feed rate with the screw speed so that the average residence time of the material in the barrel is about 2.2 min. Set a vacuum exhaust port at the rear of the reaction section of the extruder and connect it to a vacuum pump with a pumping speed of 30 m³ / h to maintain a vacuum of -0.08 MPa to remove unreacted monomers and volatiles. The extruded molten strip is pulled through a 3 m long cooling water tank (water temperature controlled at 15℃) at a speed of 10 m / min for cooling and solidification. The cooled and solidified strip is fed into a pelletizer and cut into uniform particles with a length of 3 mm to obtain a polypropylene composite material with high selective infrared transmission. Example 2

[0023] A method for preparing a polypropylene composite material with high selective infrared transmission includes the following steps: S1. Add 100 parts by weight of homopolymer polypropylene, 8 parts by weight of hexafluorobutyl methacrylate, 3 parts by weight of glycidyl methacrylate, 0.3 parts by weight of benzoyl peroxide, and 0.1 parts by weight of antioxidant 1076 to a high-speed mixer. Mix and impregnate at 200 rpm for 120 min under nitrogen protection at 40°C to obtain a premix. S2. Add the above premixed material to a twin-screw extruder (screw length-to-diameter ratio L / D is 36). Set the temperature of each section of the extruder from the feed port to the die head as follows: Zone 1 160℃, Zone 2 170℃, Zone 3 175℃, Zone 4 180℃, and the die head 180℃. Set the screw speed to 200 rpm. Match the feed rate with the screw speed so that the average residence time of the material in the barrel is about 2.8 min. Set a vacuum exhaust port at the rear of the reaction section of the extruder and connect it to a vacuum pump to maintain a vacuum of -0.06 MPa. The extruded molten strip is pulled at a speed of 10 m / min through a 3 m long cooling water tank (water temperature controlled at 15℃) for cooling and solidification. The cooled and solidified strip is fed into a pelletizer and cut into uniform particles with a length of 2 mm to obtain polypropylene composite material. Example 3

[0024] A method for preparing a polypropylene composite material with high selective infrared transmission includes the following steps: S1. Add 100 parts by weight of homopolymer polypropylene, 18 parts by weight of trifluoroethyl methacrylate, 8 parts by weight of glycidyl methacrylate, 0.8 parts by weight of benzoyl peroxide, 0.2 parts by weight of antioxidant 1010 and 0.3 parts by weight of antioxidant DSTP to a high-speed mixer, mix and impregnate at 400 rpm for 30 minutes under nitrogen protection at 50°C to obtain a premix.

[0025] S2. Add the above premixed material to a twin-screw extruder (screw length-to-diameter ratio L / D is 44). Set the temperature of each section of the extruder from the feed port to the die head as follows: Zone 1 170℃, Zone 2 180℃, Zone 3 185℃, Zone 4 190℃, and die head 190℃. Set the screw speed to 400 rpm. Match the feed rate with the screw speed so that the average residence time of the material in the barrel is about 1.8 min. Set a vacuum exhaust port at the rear of the reaction section of the extruder and connect it to a vacuum pump with a pumping speed of 50 m³ / h to maintain a vacuum of -0.10 MPa to remove unreacted monomers and volatiles. The extruded molten strip is pulled through a 3 m long cooling water tank (water temperature controlled at 15℃) at a speed of 10 m / min for cooling and solidification. The cooled and solidified strip is fed into a pelletizer and cut into uniform particles with a length of 5 mm to obtain polypropylene composite material. Example 4

[0026] The main difference between this embodiment and Embodiment 1 is that: In S1, 100 parts by weight of homopolymer polypropylene, 8 parts by weight of trifluoroethyl methacrylate, 8 parts by weight of glycidyl methacrylate, 0.3 parts by weight of benzoyl peroxide, 0.2 parts by weight of antioxidant 1010 and 0.1 parts by weight of antioxidant 168 are added to a high-speed mixer and mixed and impregnated at 250 rpm for 90 min under nitrogen protection at 42°C; the remaining steps are the same as in Example 1. Example 5

[0027] The main difference between this embodiment and Embodiment 2 is that: In S1, 100 parts by weight of homopolymer polypropylene, 15 parts by weight of hexafluorobutyl methacrylate, 6 parts by weight of glycidyl methacrylate, 0.7 parts by weight of benzoyl peroxide, 0.25 parts by weight of antioxidant 1076 and 0.1 parts by weight of antioxidant 168 are added to a high-speed mixer and mixed and impregnated at 350 rpm for 40 min under nitrogen protection at 48°C. In S2, the temperatures of each section of the extruder from the feed port to the die head are set as follows: Zone 1 168℃, Zone 2 178℃, Zone 3 183℃, Zone 4 188℃, and the die head 188℃. The screw speed is set to 350 rpm, and the vacuum exhaust port maintains a vacuum of -0.09 MPa. The extruded molten strip is pulled through a cooling water tank (water temperature controlled at 20℃) at a rate of 12 m / min to cool and solidify. The remaining steps are the same as in Example 2. Example 6

[0028] The main difference between this embodiment and Embodiment 3 is that: In S1, 100 parts by weight of homopolymer polypropylene, 10 parts by weight of hexafluorobutyl methacrylate, 4 parts by weight of glycidyl methacrylate, 0.4 parts by weight of benzoyl peroxide, 0.1 parts by weight of antioxidant 1010, 0.1 parts by weight of antioxidant 168 and 0.1 parts by weight of antioxidant DSTP are added to a high-speed mixer and mixed and impregnated at 380 rpm for 50 min under nitrogen protection at 47°C. In S2, the temperatures of each section of the extruder from the feed port to the die head are set as follows: Zone 1 162℃, Zone 2 172℃, Zone 3 177℃, Zone 4 182℃, and the die head 182℃. The screw speed is set to 250 rpm. The extruded molten strip is pulled through a 3.5m long cooling water tank (water temperature controlled at 12℃) at a speed of 8 m / min for cooling and solidification. The remaining steps are the same as in Example 3. Example 7

[0029] The main difference between this embodiment and Embodiment 1 is that: In S1, 100 parts by weight of homopolymer polypropylene, 9 parts by weight of trifluoroethyl methacrylate, 3.5 parts by weight of glycidyl methacrylate, 0.35 parts by weight of benzoyl peroxide, 0.08 parts by weight of antioxidant 1010 and 0.12 parts by weight of antioxidant 168 are added to a high-speed mixer and mixed and impregnated at 280 rpm for 100 min under nitrogen protection at 43°C. In S2, the temperatures of each section of the extruder from the feed port to the die head are set as follows: Zone 1 163℃, Zone 2 173℃, Zone 3 178℃, Zone 4 183℃, and the die head 183℃. The screw speed is set to 280 rpm, and the vacuum exhaust port maintains a vacuum of -0.07 MPa. The extruded molten strip is pulled through a cooling water tank (water temperature controlled at 18℃) at a rate of 9 m / min to cool and solidify. The remaining steps are the same as in Example 1.

[0030] Comparative Example 1 The main difference between this comparative example and Example 1 is that no epoxy-containing acrylate monomer is added: In S1, 100 parts by weight of homopolymer polypropylene, 12 parts by weight of trifluoroethyl methacrylate, 0.5 parts by weight of benzoyl peroxide, 0.15 parts by weight of antioxidant 1010 and 0.15 parts by weight of antioxidant 168 are mixed and impregnated at 45°C and 300 rpm for 60 min; the remaining steps are the same as in Example 1.

[0031] Comparative Example 2 The main difference between this comparative example and Example 1 is that a fluorine-free acrylate monomer is used instead of a fluorine-containing acrylate monomer: In S1, 100 parts by weight of homopolymer polypropylene, 12 parts by weight of methyl methacrylate, 5 parts by weight of glycidyl methacrylate, 0.5 parts by weight of benzoyl peroxide, 0.15 parts by weight of antioxidant 1010 and 0.15 parts by weight of antioxidant 168 are mixed and impregnated at 45°C and 300 rpm for 60 min; the remaining steps are the same as in Example 1.

[0032] The composite material particles prepared in each embodiment and comparative example were placed in a vacuum drying oven and dried at 80°C and -0.1MPa for 4 hours. The dried particles were placed in a mold and preheated at 190°C for 5 minutes (without pressure). Then, they were hot-pressed at 10MPa for 5 minutes. After that, they were quickly transferred to another cold press (water temperature 25°C) and cooled to room temperature at 10MPa (about 10 minutes). The particles were then demolded and removed to obtain an optical test piece.

[0033] Referring to GB / T 2410-2008 "Determination of transmittance and haze of transparent plastics" and GB / T 6040-2019 "General Rules for Infrared Spectroscopic Analysis Methods", an optical test piece with a thickness of 1.0±0.05 mm, prepared by the above steps, was tested at 1250 cm⁻¹. -1 Up to 714cm -1 (Corresponding to the 8-14 μm wavelength range) Calculate the average height value under the transmittance curve within this band. This value is the infrared average transmittance (T) of the sample. IR For each set of examples and comparative samples, at least three parallel samples were tested, and the average value was taken as the final result. The haze value (H) of each sample was measured using a haze meter. The visible light transmittance (T) of the same circular sample was then measured at a spectral range of 300-800 nm, a data interval of 1 nm, and a scanning speed of 266 nm / min. Vis Each sample was tested three times, and the average value was taken. The selective infrared transmittance coefficient (α) was calculated, α = T IR / T Vis The results are shown in Table 1: Table 1. Optical property test results of the composite materials in the examples and comparative examples

[0034] Referring to GB / T 1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics", tensile specimens (GB / T 1040.2-2022, Type 1A) and flexural specimens (GB / T9341-2008, 80mm x 10mm x 4mm) conforming to the standard were prepared using an injection molding machine. The injection molding process parameters were as follows: barrel temperature (from feed port to nozzle) set to 180℃, 185℃, 190℃, and 195℃; mold temperature set to 40℃; injection pressure to 60MPa; holding pressure to 40MPa; holding time to 10s; and cooling time to 20s.

[0035] Take the standard 1A type tensile specimens prepared above (4 mm thick, approximately 10 mm wide, gauge length 50 mm). Accurately measure the thickness and width of each specimen's gauge length segment at the middle and both ends using vernier calipers, and record the minimum value for stress calculation. Set the beam movement speed (i.e., test speed) to 50 mm / min. Calculate the tensile strength (MPa) and elongation at break (%). The tensile strength is the maximum load divided by the original minimum cross-sectional area of ​​the specimen, and the elongation at break is the elongation of the gauge length at break divided by the original gauge length (50 mm), then multiplied by 100%. Test each sample three times and take the average value.

[0036] Take the standard bending specimen prepared above (dimensions: 80mm x 10mm x 4mm), install a three-point bending fixture on a universal testing machine, and set the span L of the lower support (two supports) to 64mm (L is 16 times the specimen thickness, i.e., 64mm). Confirm that the upper indenter radius R1 is 5mm and the lower support radius R2 is 2mm. Place the specimen smoothly and centrally on the center of the lower support, ensuring that the length direction of the specimen is perpendicular to the support. Input the width (b) and thickness (h) of the specimen, as well as the span (L=64mm). Set the test control mode to displacement control, and set the indenter descent speed (i.e., test speed) to 2mm / min. The upper indenter will move downward at a constant speed of 2 mm / min, applying a bending load to the specimen, and record the load-deflection curve. The test continues until the specimen breaks. Calculate the bending modulus (E). f ), E f =(L³×m) / (4×b×h³). Where L is the span (m), b is the specimen width (m), h is the specimen thickness (m), and m is the slope of the initial straight segment of the load-deflection curve (N / m). The results are shown in Table 2. Table 2. Mechanical property test results of the composite materials in the examples and comparative examples

[0037] Table 1 shows that the average infrared transmittance of Examples 1-7 ranges from 73.2% to 80.1%, the visible light transmittance from 12.8% to 21.5%, the selective infrared transmittance from 3.40 to 6.26, and the haze value from 88.8% to 94.3%. This indicates that by adjusting the type and amount of each raw material, as well as the mixing and extrusion process parameters, the prepared polypropylene composite material has high average infrared transmittance and selective infrared transmittance, and also a high haze value, suggesting that the material has good transmittance in the infrared band and a certain degree of blocking effect on visible light.

[0038] Comparative Example 1 did not add epoxy-containing acrylate monomers, and its T IR The percentage (62.4%) was significantly lower than in the example, and α (1.75) was also greatly reduced. This indicates that epoxy-containing acrylate monomers play an important role in improving the infrared transmittance of materials. The epoxy groups may participate in the reaction to form specific chemical structures, which are beneficial to the transmission of infrared light, while inhibiting the transmission of visible light to a certain extent, thereby improving the selective infrared transmittance coefficient. Comparative Example 2 used fluorine-free acrylate monomers instead of fluorinated acrylate monomers, T IR (45.8%) further decreased, and α (0.67) was even lower. Fluorine-containing groups have unique electronic and steric effects, which can change the electronic structure and intermolecular forces of materials, and have a special influence on the absorption and scattering of infrared light, thereby improving the transmittance of materials in the infrared band. Fluorine-free monomers cannot achieve this effect.

[0039] As shown in Table 2, the tensile strength of Examples 1-7 ranges from 28.8 to 35.2 MPa, the elongation at break ranges from 38% to 58%, and the flexural modulus ranges from 1680 to 1950 MPa. This indicates that the prepared polypropylene composite materials possess certain mechanical strength and toughness, and can meet certain application requirements.

[0040] Comparative Example 1 exhibited the highest elongation at break (120%), but its tensile strength (25.5 MPa) and flexural modulus (1350 MPa) were significantly lower than those of the Example. The absence of epoxy-containing acrylate monomers may reduce the degree of internal cross-linking in the material, making the molecular chains more prone to sliding, thus resulting in a higher elongation at break, but also leading to a decrease in the material's strength and stiffness. Comparative Example 2 showed lower tensile strength (28.0 MPa), elongation at break (85%), and flexural modulus (1550 MPa) compared to the Example. The use of fluorine-free acrylate monomers may affect the internal molecular structure and interactions of the material, resulting in mechanical properties inferior to those of the Example using fluorine-containing monomers.

[0041] In summary, the technical solution provided by this invention, through the synergistic design and reactive extrusion process of fluorinated acrylate monomers and epoxy acrylate monomers, prepares a polypropylene composite material with high infrared transmittance, high visible light shielding (high haze), high selectivity coefficient, and good mechanical properties and processability.

[0042] In the description of this specification, the reference to terms such as "embodiment," "various embodiments," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or preparation example is included in at least one embodiment of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a polypropylene composite material with high selective infrared transmittance, characterized in that, Includes the following steps: S1. Premix and impregnate polypropylene matrix, fluorinated acrylate monomer, epoxy acrylate monomer, initiator and antioxidant to obtain premix; S2. The premixed material is placed in a twin-screw extruder, and after extrusion, cooling, and pelletizing, a polypropylene composite material with high selective infrared transmittance is obtained. The fluorinated acrylate monomers are selected from trifluoroethyl methacrylate or hexafluorobutyl methacrylate, and the epoxy-containing acrylate monomers are selected from glycidyl methacrylate or glycidyl acrylate.

2. The method for preparing a polypropylene composite material with high selective infrared transmission according to claim 1, characterized in that, In step S1, based on 100 parts by weight of polypropylene matrix, the amount of fluorinated acrylate monomer is 8-18 parts by weight, and the amount of epoxy acrylate monomer is 3-8 parts by weight.

3. The method for preparing a polypropylene composite material with high selective infrared transmission according to claim 1, characterized in that, In step S1, the amount of initiator is 0.3-0.8 wt% of the polypropylene matrix, and the total amount of antioxidant is 0.1-0.5 wt% of the polypropylene matrix.

4. A method for preparing a polypropylene composite material with high selective infrared transmission according to claim 1 or 3, characterized in that, In step S1, the initiator is selected from benzoyl peroxide, and the antioxidant is selected from at least one of antioxidant 1010, antioxidant 1076, antioxidant 168, and antioxidant DSTP.

5. The method for preparing a polypropylene composite material with high selective infrared transmission according to claim 1, characterized in that, The conditions for premixing and impregnation in step S1 are: temperature of 40-50℃, stirring speed of 200-400rpm, and impregnation time of 30-120min.

6. The method for preparing a polypropylene composite material with high selective infrared transmission according to claim 1, characterized in that, In step S2, the length-to-diameter ratio (L / D) of the twin-screw extruder is 36-44; the temperature of each section from the feed port to the die head is set to 160-190℃, and the screw speed is 200-400rpm.

7. The method for preparing a polypropylene composite material with high selective infrared transmission according to claim 1, characterized in that, In step S2, the twin-screw extruder is also equipped with a vacuum exhaust port at the rear of the reaction section. During the extrusion process, a vacuum of (-0.06) - (-0.10) MPa is maintained at the vacuum exhaust port.

8. The method for preparing a polypropylene composite material with high selective infrared transmission according to claim 1, characterized in that, In step S2, the melt extruded by the twin-screw extruder is cooled and solidified in a cooling water tank, where the water temperature is controlled at 10-25℃. The cooled and solidified strip is then cut into pellets with a length of 2-5mm by a pelletizer.

9. A polypropylene composite material with high selective infrared transmittance prepared by the preparation method according to any one of claims 1-8.

10. A selective infrared transmitting device, characterized in that, It comprises a polypropylene composite material with high selective infrared transmission as described in claim 9.

Images