A PP thin plate and its preparation method

Abstract

The present invention belongs to the technical field of polypropylene materials, and particularly relates to a PP thin plate and a preparation method thereof. A PP thin plate, by weight components, comprises 85-90 parts of polypropylene particles and also 10-15 parts of an additive; the additive uses SiO2@ZIF-67 as a precursor, and through etching with iron nitrate, a hollow polyhedral shell-core type SiO2@FeCo-LDH is obtained, and then SiO2@FeCo-LDH@PA-PEI is obtained through coating with PA-PEI. This additive has an organic PA-PEI and an inorganic double shell of FeCo-LDH, and nano-silica is dispersed in the core. Through the synergistic effect of nitrogen, phosphorus, and iron-cobalt metal elements, it plays a flame retardant and smoke suppression effect. When used for the preparation of a PP thin plate, it not only has significant flame retardant and smoke suppression performance, but also has good mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of polypropylene materials, and particularly relates to a PP thin plate and a preparation method thereof. Background Art

[0002] Polypropylene (PP) is polymerized from propylene, a petroleum cracking product. It is a non-toxic, odorless, tasteless, semi-transparent milky white, highly crystalline non-polar polymer. PP has a wide range of market applications in clothing, blankets and other textiles, medical equipment, automobiles, bicycles, parts, transportation pipelines and chemical containers, pharmaceutical and food packaging, etc. However, PP is a highly flammable polymer material. When exposed to an open flame or heated and burned, it will decompose to produce a large amount of macromolecular hydrocarbon products, release a large amount of thick smoke and toxic gases, and has a relatively large smoke density, which poses a serious threat to people's lives, health and property, thus restricting its application in life and production.

[0003] Traditional halogen flame retardants have been widely used due to their advantages such as high efficiency and low price. However, they will decompose to produce a large amount of toxic gases containing halogen elements during the combustion process, deviating from the concept of environmental friendliness and the needs of people's health. Therefore, it is very important to develop new, environmentally friendly and highly efficient flame retardants to improve the flame retardancy and smoke suppression performance of PP. Summary of the Invention

[0004] In view of the above problems, the present invention provides a PP thin plate and a preparation method thereof, which well solve the problem of poor flame retardancy and smoke suppression performance of PP.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: A PP thin plate, by weight components, comprises 85 - 90 parts of polypropylene particles and further comprises 10 - 15 parts of an additive; the additive is prepared by the following method: S1, prepare SiO2@ZIF-67; S2, prepare SiO2@FeCo-LDH; S3, prepare SiO2@FeCo-LDH@PA-PEI.

[0006] Further, the specific steps of S1 are as follows: S1.1, disperse nano-silica and polyethylene glycol in deionized water, stir at room temperature for 24 h, wash and dry to obtain modified SiO2; S1.2, disperse the modified SiO2 in methanol, then add a methanol solution of cobalt nitrate, ultrasonically disperse evenly, quickly add a methanol solution of 2-methylimidazole, stand for aging for 20 - 24 h, cool to room temperature, centrifuge, wash, dry and grind to obtain SiO2@ZIF-67.

[0007] Further, the dosage ratio of nano-silica, polyethylene glycol and deionized water in S1.1 is (0.5 - 0.8) g : (2 - 3) g : (100 - 120) mL.

[0008] Further, in S1.2, the dosage ratio of the modified SiO2, methanol, the methanol solution of cobalt nitrate, and the methanol solution of 2-methylimidazole is (30 - 50) mg:(40 - 60) mL:(25 - 30) m L :(20 - 25) mL; the concentration of the methanol solution of cobalt nitrate is 0.04 - 0.05 mol / L; the concentration of the methanol solution of 2-methylimidazole is 0.21 - 0.25 mol / L.

[0009] Further, the S2 specifically includes: dispersing SiO2@ZIF-67 into ethanol, ultrasonically dispersing it evenly, then adding the ethanol solution of iron nitrate, mixing evenly, reacting at 90 - 95 °C for 2 - 3 h, cooling to room temperature, centrifuging, washing, drying, and grinding to obtain SiO2@FeCo-LDH.

[0010] Further, in S2, the dosage ratio of SiO2@ZIF-67, ethanol, and the ethanol solution of iron nitrate is (32 - 38) mg:(60 - 70) mL:(30 - 35) mL; the concentration of iron nitrate in the ethanol solution of iron nitrate is 0.06 - 0.09 mol / L.

[0011] Through the above technical solution, a hollow polyhedral FeCo-LDH is prepared using the metal-organic framework material ZIF-67 as a precursor, and it acts as a nanocapsule to help the confined monodispersion of SiO2 nanoparticles, realizing a core-shell nanostructure, and greatly improving the flame retardancy and smoke suppression performance of the PP thin plate.

[0012] Further, in S3.1, add triethylamine to the ethanol solution of polyethyleneimine, under stirring conditions, slowly add phosphate ester, react at 50 - 70 °C for 7 - 9 h, cool to room temperature, add a precipitating agent, precipitate, filter, wash, and dry to obtain PA-PEI; in S3.2, ultrasonically disperse PA-PEI in N,N-dimethylformamide, then add SiO2@FeCo-LDH, ultrasonically disperse for 0.5 - 1 h, then vigorously stir magnetically for 20 - 24 h, and finally centrifuge, wash, and dry to obtain SiO2@FeCo-LDH@PA-PEI, that is, the additive.

[0013] Further, in S3.1, the dosage ratio of triethylamine, the ethanol solution of polyethyleneimine, and phosphate ester is (0.01 - 0.03) g:(10 - 15) mL:(2.2 - 2.5) g; the concentration of polyethyleneimine in the ethanol solution of polyethyleneimine is 0.1 - 0.2 g / mL; the phosphate ester is trimethyl phosphate or triethyl phosphate.

[0014] Further, in S3.2, the dosage ratio of PA-PEI, N,N-dimethylformamide, and SiO2@FeCo-LDH is (0.2-0.4) g:(50-80) mL:(0.3-0.6) g.

[0015] Through the above technical solution, a phosphorus-doped polyethyleneimine is synthesized using phosphate as the phosphorus source, and it is coated on the surface of SiO2@FeCo-LDH by the adsorption method. Further, an organically coated hybrid double-shell additive is obtained, achieving the synergistic flame retardancy of nitrogen, phosphorus, and iron-cobalt metal elements, fully exerting the catalytic carbonization effect of the flame retardant, and improving the flame retardant effect. At the same time, the modification with the organic material PA-PEI improves the compatibility and interfacial adhesion between SiO2@FeCo-LDH and the PP matrix, and improves its mechanical properties.

[0016] Further, a preparation method of a PP thin plate includes the following steps: mixing the additive and polypropylene particles in proportion, placing them in a high-speed mixer, stirring at a speed of 250-300 rpm at 160-180 °C for 15-20 min, then extruding and granulating through a twin-screw extruder, and then heating to 220-240 °C through a micro-injection molding machine, performing hot pressing under a constant pressure for 30-50 s, and cooling to obtain the PP thin plate.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention uses SiO2@ZIF-67 as a precursor, obtains a hollow polygonal core-shell type SiO2@FeCo-LDH through etching with iron nitrate, and then obtains SiO2@FeCo-LDH@PA-PEI through coating with PA-PEI, which is used for the preparation of PP thin plates, and can effectively improve the flame retardant performance and smoke suppression performance of PP thin plates, and at the same time its mechanical properties are also improved.

[0019] Through the synergistic effect of the iron-cobalt hydrotalcite shell layer and SiO2 nanoparticles, in the condensed phase, the SiO2 nanoparticles and the iron-cobalt hydrotalcite shell layer can respectively form refractory metal oxides on the surface of the PP matrix, thereby isolating heat and oxygen, blocking the overflow of combustible gases, and protecting the lower-layer PP matrix from being damaged by the flame; through coating with PA-PEI, an organic-inorganic hybrid double-shell hydrotalcite-based additive containing nitrogen, phosphorus, and iron-cobalt transition metal elements is obtained, achieving the synergistic flame retardancy of nitrogen, phosphorus, and iron-cobalt metal elements, fully exerting the catalytic carbonization effect of the additive, jointly acting on the flame retardancy of the gas phase and the condensed phase, and at the same time using organic material modification to improve the compatibility and interfacial adhesion between SiO2@FeCo-LDH and the PP matrix, thereby improving its mechanical properties. Description of the Drawings

[0020] Figure 1SEM and TEM images of SiO2@FeCo-LDH and SiO2@FeCo-LDH@PA-PEI prepared in Example 1. Among them, A is the SEM of SiO2@FeCo-LDH, B is the TEM of SiO2@FeCo-LDH, C is the SEM of SiO2@FeCo-LDH@PA-PEI, and D is the TEM of SiO2@FeCo-LDH@PA-PEI;

[0021] Figure 2 XRD pattern of SiO2@FeCo-LDH@PA-PEI prepared in Example 1;

[0022] Figure 3 EDS pattern of SiO2@FeCo-LDH@PA-PEI prepared in Example 1;

[0023] Figure 4 Cross-sectional SEM images of PP thin plates. Among them, the left figure is a pure PP thin plate, the middle figure is the PP thin plate of Comparative Example 2, and the right figure is the PP thin plate of Example 1. Detailed implementation manners

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] Example 1

[0026] A PP thin plate, characterized in that it comprises 85 parts by weight of polypropylene particles and 10 parts of additives;

[0027] The additive is prepared by the following method:

[0028] S1, prepare SiO2@ZIF-67:

[0029] S1.1, disperse 0.5 g of nano-silica and 2 g of polyethylene glycol in 100 mL of deionized water, stir at room temperature for 24 h, wash alternately with deionized water and ethanol 3 times, and dry at 80 °C for 12 h to obtain modified SiO2;

[0030] S1.2. Disperse 30 mg of modified SiO2 in 40 mL of methanol, then add 25 mL of a methanol solution of cobalt nitrate with a concentration of 0.04 mol / L, ultrasonically disperse it evenly, quickly add 20 mL of a methanol solution of 2-methylimidazole with a concentration of 0.21 mol / L, let it stand and age for 20 h, cool to room temperature, centrifuge, wash, dry, and grind to obtain SiO2@ZIF-67;

[0031] S2. Prepare SiO2@FeCo-LDH: Disperse 32 mg of SiO2@ZIF-67 in 60 mL of ethanol, ultrasonically disperse it evenly, then add 30 mL of an ethanol solution of iron nitrate with a concentration of 0.06 mol / L, mix evenly, react at 90 °C for 2 h, cool to room temperature, centrifuge, wash with deionized water, dry at 95 °C for 8 h, and grind to obtain SiO2@FeCo-LDH;

[0032] S3. Prepare SiO2@FeCo-LDH@PA-PEI:

[0033] S3.1. Add 0.01 g of triethylamine to 10 mL of an ethanol solution of polyethyleneimine with a concentration of 0.1 g / mL. Under stirring conditions, slowly add 2.2 g of trimethyl phosphate, react at 50 °C for 7 h, cool to room temperature, add the precipitant acetone, precipitate, filter, wash with ethanol, and dry at 60 °C for 12 h to obtain PA-PEI;

[0034] S3.2. Ultrasonically disperse 0.2 g of PA-PEI in 50 mL of N,N-dimethylformamide, then add 0.3 g of SiO2@FeCo-LDH, ultrasonically disperse for 0.5 h, then stir vigorously with a magnetic stirrer for 20 h, finally centrifuge, wash alternately with deionized water and ethanol 3 times, and dry overnight at 60 °C to obtain SiO2@FeCo-LDH@PA-PEI, which is the additive.

[0035] Perform scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations on the SiO2@FeCo-LDH and SiO2@FeCo-LDH@PA-PEI prepared in Example 1. The results are as Figure 1 shown. From Figure 1It can be seen that SEM shows that the surface of SiO2@FeCo-LDH is composed of many nanosheets with regular geometric shapes. The surface of SiO2@FeCo-LDH@PA-PEI is covered by substances with irregular shapes, and the nanosheet structure can be faintly observed at the edges. TEM shows that SiO2@FeCo-LDH has a clear hollow cage-like structure with clear edges, presenting a regular dodecahedron structure, and granular substances are distributed inside, indicating the successful synthesis of SiO2@FeCo-LDH. SiO2@FeCo-LDH@PA-PEI also has a hollow cage-like structure, and other substances are distributed inside the cage-like structure. However, the edges of SiO2@FeCo-LDH@PA-PEI are blurred, with flocculent substances distributed, and the substances distributed inside its cavity also change from clear granular to a mass of shadows, indicating that other substances covering the surface of SiO2@FeCo-LDH@PA-PEI affect its visibility.

[0036] X-ray diffraction analysis (XRD) was performed on the SiO2@FeCo-LDH@PA-PEI prepared in Example 1, and the results are as Figure 2 shown. It can be seen from Figure 2 that a broad peak characteristic of amorphous silica appears at about 2θ = 24°, and characteristic peaks appear at 11.4°, 23.3°, 33.9°, 35.5°, 38.4°, 44.2°, 47.1°, 59.4° and 60.4°. These characteristic peaks correspond to the diffraction of different crystal planes of FeCo-LDH, namely (003), (006), (012), (009), (015), (107), (019), (110), (113). In addition, no other diffraction peaks were observed, probably because PA-PEI is an organic substance with inconspicuous diffraction peaks in XRD and a small adsorbed amount. At the same time, it also shows that the structure of FeCo-LDH was not damaged during the chemical adsorption process.

[0037] Energy spectrum analysis (EDS) was performed on the SiO2@FeCo-LDH@PA-PEI prepared in Example 1, and the results are as Figure 3 shown. It can be seen from Figure 3 that elements such as P, N, Co, Fe and Si exist in SiO2@FeCo-LDH@PA-PEI. Among them, elements such as P, N, Co and Fe are distributed on its surface, with more distributed at the edges and less in the middle, confirming its cage-like structure, while the Si element is only distributed inside its cavity, indicating that silica is restricted to be distributed inside its cavity.

[0038] Example 2

[0039] A PP thin plate, characterized in that it comprises 88 parts by weight of polypropylene particles and 12 parts by weight of additives;

[0040] The additive is prepared by the following method:

[0041] S1. Prepare SiO2@ZIF-67:

[0042] S1.1. Disperse 0.65 g of nano-silica and 2.5 g of polyethylene glycol in 110 mL of deionized water, stir at room temperature for 24 h, wash alternately with deionized water and ethanol three times, and dry at 80 °C for 12 h to obtain modified SiO2;

[0043] S1.2. Disperse 40 mg of modified SiO2 in 50 mL of methanol, then add 28 mL of a methanol solution of cobalt nitrate with a concentration of 5 mol / L, disperse evenly by ultrasonic treatment, quickly add 22 mL of a methanol solution of 2-methylimidazole with a concentration of 0.23 mol / L, stand for aging for 22 h, cool to room temperature, centrifuge, wash, dry, and grind to obtain SiO2@ZIF-67;

[0044] S2. Prepare SiO2@FeCo-LDH: Disperse 35 mg of SiO2@ZIF-67 in 65 mL of ethanol, disperse evenly by ultrasonic treatment, then add 33 mL of an ethanol solution of iron nitrate with a concentration of 0.07 mol / L, mix evenly, react at 92 °C for 2.5 h, cool to room temperature, centrifuge, wash with deionized water, dry at 95 °C for 8 h, and grind to obtain SiO2@FeCo-LDH;

[0045] S3. Prepare SiO2@FeCo-LDH@PA-PEI:

[0046] S3.1. Add 0.02 g of triethylamine to 12 mL of an ethanol solution of polyethyleneimine with a concentration of 0.15 g / mL. Under stirring conditions, slowly add 2.3 g of triethyl phosphate, react at 60 °C for 8 h, cool to room temperature, add the precipitant acetone, precipitate, filter, wash with ethanol, and dry at 60 °C for 12 h to obtain PA-PEI;

[0047] S3.2. Ultrasonically disperse 0.3 g of PA-PEI in 65 mL of N,N-dimethylformamide, then add 0.5 g of SiO2@FeCo-LDH, ultrasonically disperse for 40 min, then stir vigorously with a magnetic stirrer for 22 h, finally centrifuge, wash alternately with deionized water and ethanol three times, and dry at 60 °C overnight to obtain SiO2@FeCo-LDH@PA-PEI, which is the additive.

[0048] Example 3

[0049] A PP thin plate, characterized in that it comprises 90 parts of polypropylene particles and 15 parts of an additive by weight components;

[0050] The additive is prepared by the following method:

[0051] S1. Prepare SiO2@ZIF-67:

[0052] S1.1. Disperse 0.8 g of nano-silica and 3 g of polyethylene glycol in 120 mL of deionized water, stir at room temperature for 24 h, wash alternately with deionized water and ethanol three times, and dry at 80 °C for 12 h to obtain modified SiO2;

[0053] S1.2. Disperse 50 mg of modified SiO2 in 60 mL of methanol, then add 30 mL of a methanol solution of cobalt nitrate with a concentration of 0.05 mol / L, ultrasonically disperse evenly, quickly add 25 mL of a methanol solution of 2-methylimidazole with a concentration of 0.25 mol / L, let stand and age for 24 h, cool to room temperature, centrifuge, wash, dry, and grind to obtain SiO2@ZIF-67;

[0054] S2. Prepare SiO2@FeCo-LDH: Disperse 38 mg of SiO2@ZIF-67 in 70 mL of ethanol, ultrasonically disperse evenly, then add 35 mL of an ethanol solution of iron nitrate with a concentration of 0.09 mol / L, mix evenly and react at 95 °C for 3 h, cool to room temperature, centrifuge, wash with deionized water, dry at 95 °C for 8 h, and grind to obtain SiO2@FeCo-LDH;

[0055] S3. Prepare SiO2@FeCo-LDH@PA-PEI:

[0056] S3.1. Add 0.03 g of triethylamine to 15 mL of an ethanol solution of polyethyleneimine with a concentration of 0.2 g / mL. Under stirring conditions, slowly add 2.5 g of triethyl phosphate, react at 70 °C for 9 h, cool to room temperature, add the precipitant acetone, precipitate, filter, wash with ethanol, and dry at 60 °C for 12 h to obtain PA-PEI;

[0057] S3.2. Ultrasonically disperse 0.4 g of PA-PEI in 80 mL of N,N-dimethylformamide, then add 0.6 g of SiO2@FeCo-LDH, ultrasonically disperse for 1 h, then stir vigorously with a magnetic stirrer for 24 h, finally centrifuge, wash alternately with deionized water and ethanol three times, and dry at 60 °C overnight to obtain SiO2@FeCo-LDH@PA-PEI, which is the additive.

[0058] The preparation method of the PP thin plate includes the following steps: Mix additives and polypropylene particles in proportion, place them in a high-speed mixer, stir at 180 °C and a speed of 300 rpm for 20 min, then extrude and pelletize through a twin-screw extruder, and then heat to 230 °C through a micro-injection molding machine, and perform hot pressing at a constant pressure of 80 MPa for 30 s, and then cool to obtain a PP thin plate with a thickness of about 3 mm.

[0059] Comparative Example 1

[0060] Same as Example 1, the difference is: S1.2, Mix 25 mL of an aqueous solution of cobalt nitrate with a concentration of 0.04 mol / L and 30 mL of an aqueous solution of iron nitrate with a concentration of 0.06 mol / L evenly, then under stirring, at 40 °C, slowly add a NaOH solution with a concentration of 1 mol / L to adjust the pH to 10, and then let the reaction solution stand and age at room temperature for 18 h, and then centrifuge, wash with deionized water, dry at 95 °C for 8 h, and grind to obtain FeCo-LDH;

[0061] Mix FeCo-LDH and modified SiO2 in a ratio of 4:1, instead of SiO2@FeCo-LDH@PA-PEI, to participate in the preparation of the PP thin plate, and the total amount used is the same as that of SiO2@FeCo-LDH@PA-PEI.

[0062] Comparative Example 2

[0063] Same as Example 1, the difference is that directly use the SiO2@FeCo-LDH obtained in step S2 instead of SiO2@FeCo-LDH@PA-PEI to participate in the preparation of the PP thin plate, and the amount used is the same as that of SiO2@FeCo-LDH@PA-PEI.

[0064] Comparative Example 3

[0065] Same as Example 1, the difference is that without going through step S3.1, in S3.2, Ultrasonically disperse 0.2 g of polyethyleneimine in 50 mL of N,N-dimethylformamide, then add 0.3 g of SiO2@FeCo-LDH, ultrasonically disperse for 0.5 h, then vigorously stir magnetically for 20 h, finally centrifuge, wash alternately with deionized water and ethanol 3 times, and dry overnight at 60 °C to obtain SiO2@FeCo-LDH@PEI, that is, the additive. Use the obtained SiO2@FeCo-LDH@PEI instead of SiO2@FeCo-LDH@PA-PEI to participate in the preparation of the PP thin plate, and the amount used is the same as that of SiO2@FeCo-LDH@PA-PEI.

[0066] Performance detection:

[0067] Prepare a pure PP thin plate (that is, without adding any additives) according to the above method.

[0068] The cross-sections of the pure PP thin sheet, the PP thin sheet prepared in Comparative Example 2, and the PP thin sheet prepared in Example 1 after being brittlely fractured with liquid nitrogen were observed by scanning electron microscopy, and the results are as Figure 4 shown. As can be seen from Figure 4 , the cross-section of the pure PP thin sheet is relatively flat and smooth, with a few cracks, which are caused by the stress during brittle fracture. For the PP thin sheet in Comparative Example 2, single hydrotalcite can be observed to be distributed in the PP matrix with good dispersibility, but the interface between it and the PP matrix is relatively obvious, and the SiO2@FeCo-LDH particles are not embedded in the PP matrix at all. This may be due to the poor compatibility and interfacial adhesion between the inherent inorganic properties of SiO2@FeCo-LDH and the organic PP matrix, resulting in an "undercooked" phenomenon and damaging the mechanical properties of the PP thin sheet. However, there are many protrusions in the PP thin sheet of Example 1, but the flatness of the cross-section is greatly improved compared with that of Comparative Example 2. At the same time, the interface between SiO2@FeCo-LDH@PA-PEI and the PP matrix is blurred, and some SiO2@FeCo-LDH@PA-PEI particles have been embedded in the PP matrix. This may be because the coating of PA-PEI changes the surface properties of SiO2@FeCo-LDH. As an organic macromolecule, PA-PEI improves its compatibility and interfacial adhesion with the PP matrix, making it difficult for SiO2@FeCo-LDH@PA-PEI to migrate to the surface of the PP matrix, and thus the PP thin sheet of Example 1 has excellent flame retardant effect and relatively excellent mechanical properties.

[0069] Mechanical property test:

[0070] a. The tensile strength and elongation at break of the PP thin sheets obtained in Examples 1-3 and Comparative Examples 1-3 were tested according to the standard of GB / T1040.1-2018.

[0071] Flame retardant and smoke suppression performance test:

[0072] b. The oxygen index of the PP thin sheets of Examples 1-3 and Comparative Examples 1-3 was measured using an oxygen index meter according to GB / T2406.2-2009;

[0073] c. The vertical burning grade (UL-94) of the PP thin sheets of Examples 1-3 and Comparative Examples 1-3 was measured using a vertical burning tester according to GB / T2408-2021.

[0074] d. The cone calorimeter test was carried out on the PP thin sheets prepared in Examples 1-3 and Comparative Examples 1-3 according to the standard of ISO5660 using a cone calorimeter tester.

[0075] The test results are shown in Table 1:

[0076]

[0077] As can be seen from Table 1, the PP thin plates prepared in Examples 1-3 of this application have excellent mechanical properties compared with pure PP thin plates, with improved tensile strength and elongation at break, strong flame retardancy and smoke suppression performance, an oxygen index reaching 30%, passing the UL-94 test at the V-0 level, and pSPR and TSP being as low as 0.030 m 2 / s and 4.61 m 2 , and the generation amounts of CO and CO2 are reduced to 2.4×10 -3 g / s and 0.18 g / s respectively. Combining the tests of pure PP and Comparative Example 1, it can be seen that directly adding FeCo-LDH and modified SiO 2， has a greater negative impact on its mechanical properties. Combining Comparative Example 1 and Comparative Example 2, it can be seen that SiO2@FeCo-LDH is still not conducive to its compatibility with PP materials. Combining Comparative Example 3, it can be seen that SiO2@FeCo-LDH@PEI has good compatibility with PP materials and helps to improve its mechanical properties; combining Comparative Example 3 and Example 1, it can be seen that SiO2@FeCo-LDH@PA-PEI has the most excellent flame retardancy and smoke suppression performance.

[0078] Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A PP thin plate, characterized in that, By weight components, it includes 85 - 90 parts of polypropylene particles and also includes 10 - 15 parts of additives; the additives are prepared by the following method: S1, prepare SiO2@ZIF-67; S2, prepare SiO2@FeCo-LDH; S3, prepare SiO2@FeCo-LDH@PA-PEI; The specific steps of S1 include: S1.1, disperse nano-silica and polyethylene glycol in deionized water, stir at room temperature for 24 h, wash, and dry to obtain modified SiO2; S1.2, disperse the modified SiO2 in methanol, then add a methanol solution of cobalt nitrate, ultrasonically disperse evenly, quickly add a methanol solution of 2-methylimidazole, stand for aging for 20 - 24 h, cool to room temperature, centrifuge, wash, dry, and grind to obtain SiO2@ZIF-67; The specific steps of S2 include: Disperse SiO2@ZIF-67 in ethanol, ultrasonically disperse evenly, then add an ethanol solution of iron nitrate, mix evenly, react at 90 - 95 °C for 2 - 3 h, cool to room temperature, centrifuge, wash, dry, and grind to obtain SiO2@FeCo-LDH; The specific steps of S3 include: S3.1, add triethylamine to an ethanol solution of polyethyleneimine, under stirring conditions, slowly add phosphate ester, react at 50 - 70 °C for 7 - 9 h, cool to room temperature, add a precipitant, precipitate, filter, wash, and dry to obtain PA-PEI; S3.2, ultrasonically disperse PA-PEI in N,N-dimethylformamide, then add SiO2@FeCo-LDH, ultrasonically disperse for 0.5 - 1 h, then stir vigorously with magnetic stirring for 20 - 24 h, finally centrifuge, wash, and dry to obtain SiO2@FeCo-LDH@PA-PEI, that is, the additive.

2. A PP thin plate according to claim 1, characterized in that, In S1.1, the dosage ratio of nano-silica, polyethylene glycol, and deionized water is (0.5 - 0.8) g : (2 - 3) g : (100 - 120) mL.

3. A PP thin plate according to claim 1, characterized in that, In S1.2, the dosage ratio of modified SiO2, methanol, the methanol solution of cobalt nitrate, and the methanol solution of 2-methylimidazole is (30 - 50) mg : (40 - 60) mL : (25 - 30) mL : (20 - 25) mL; the concentration of the methanol solution of cobalt nitrate is 0.04 - 0.05 mol / L; the concentration of the methanol solution of 2-methylimidazole is 0.21 - 0.25 mol / L.

4. A PP thin plate according to claim 1, characterized in that, In S2, the dosage ratio of SiO2@ZIF-67, ethanol, and the ethanol solution of iron nitrate is (32 - 38) mg : (60 - 70) mL : (30 - 35) mL; the concentration of iron nitrate in the ethanol solution of iron nitrate is 0.06 - 0.09 mol / L.

5. A PP thin plate according to claim 1, characterized in that, In S3.1, the dosage ratio of triethylamine, the ethanol solution of polyethyleneimine, and phosphate ester is (0.01 - 0.03) g : (10 - 15) mL : (2.2 - 2.5) g; the concentration of polyethyleneimine in the ethanol solution of polyethyleneimine is 0.1 - 0.2 g / mL; the phosphate ester is trimethyl phosphate or triethyl phosphate.

6. A PP thin plate according to claim 1, characterized in that, In S3.2, the dosage ratio of PA-PEI, N,N-dimethylformamide, and SiO2@FeCo-LDH is (0.2-0.4) g : (50-80) mL : (0.3-0.6) g.

7. A method for preparing a PP thin plate according to any one of claims 1-6, characterized in that, It includes the following steps: Mix the additive and polypropylene particles in proportion, place them in a high-speed mixer, stir at a speed of 250-300 rpm at 160-180 °C for 15-20 min, then extrude and pelletize through a twin-screw extruder, and then heat to 220-240 °C through a micro-injection molding machine, perform hot pressing at a constant pressure for 30-50 s, and cool to obtain a PP thin plate.

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