A graphene-modified polypropylene composite material and a preparation method thereof

Abstract

This invention discloses a graphene-modified polypropylene composite material and its preparation method. By weight, it comprises the following raw materials: 90-100 parts polypropylene, 3-5 parts maleic anhydride-grafted polypropylene, 1.5-2.5 parts modified graphene, 0.2-0.3 parts composite nucleating agent, 0.3-0.6 parts antioxidant, and 0.3-0.5 parts lubricant. This graphene-modified polypropylene composite material utilizes a specific method to prepare surface-functionalized graphene, which is then synergistically combined with a highly efficient composite nucleating agent. A two-step melt blending process using masterbatch is employed, leveraging the heterogeneous nucleation effect of modified graphene on polypropylene to significantly improve the material's crystallinity. The resulting polypropylene composite material exhibits a fine and uniform α-crystalline microstructure, thereby achieving comprehensive improvements in mechanical properties, thermal properties, and dimensional stability.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a graphene-modified polypropylene composite material and its preparation method. Background Technology

[0002] Polypropylene, as an important general-purpose thermoplastic resin, is widely used in various fields such as automobiles, home appliances, packaging, building materials, and medical devices due to its advantages such as low cost, low density, ease of processing and molding, excellent chemical corrosion resistance, and recyclability. However, conventional polypropylene materials also have some inherent performance defects, such as low mechanical properties such as flexural modulus and tensile strength, low heat distortion temperature, and large molding shrinkage. These shortcomings largely limit its application in the field of high-performance engineering plastics.

[0003] To improve the overall performance of polypropylene and meet higher application requirements, modification is a major technological development direction in the industry. Currently, adding inorganic fillers (such as talc, calcium carbonate, and glass fiber) to the polypropylene matrix is ​​a common method for strengthening and increasing rigidity. However, the addition amount of these traditional inorganic fillers is usually high (above 10% wt.), which leads to a significant increase in the density of the composite material, a decrease in the surface gloss of the product, and, at high filler levels, a weak interfacial bond between the filler and the polymer matrix, which easily becomes a stress concentration point and may actually degrade the impact toughness of the material.

[0004] In recent years, graphene, as a two-dimensional nanomaterial, has been considered a highly promising nano-reinforcing filler for polypropylene due to its excellent mechanical properties, ultra-high specific surface area, and superior thermal conductivity. Theoretically, only extremely low addition amounts of graphene can significantly improve the mechanical and thermal properties of polymers. However, in practical applications, the preparation of graphene-reinforced polypropylene composites faces severe technical challenges. On the one hand, the extremely large specific surface area and strong π-π packing of graphene sheets make them prone to irreversible aggregation in non-polar polypropylene matrices, making it difficult to achieve uniform dispersion at the nanoscale, and thus its excellent properties cannot be effectively transferred to the polymer matrix. On the other hand, the chemically inert surface of graphene lacks effective interfacial interactions with saturated polypropylene molecular chains, resulting in poor interfacial bonding. Under external forces, interfacial debonding easily occurs, significantly reducing the reinforcing effect.

[0005] Furthermore, as a semi-crystalline polymer, polypropylene's mechanical properties and dimensional stability are closely related to its crystal morphology (such as crystal form, crystallinity, and spherulite size). In existing technologies, introducing nanofillers such as graphene into polypropylene may affect its crystallization process to some extent, but there is often a lack of proactive, precise, and efficient means to control this process. How to combine the nano-reinforcing effect of graphene with its potential as a heterogeneous nucleating agent to systematically optimize the microcrystalline structure of composite materials—for example, inducing the formation of a superior α-crystal form and achieving grain refinement—to achieve a comprehensive improvement in overall performance on a macroscopic scale, remains a technical direction that requires further exploration.

[0006] Therefore, how to effectively solve the problems of graphene dispersion and interfacial compatibility in polypropylene matrix, and synergistically regulate the crystallization behavior of composite materials to give full play to the nano-reinforcing effect of graphene, so as to prepare high-performance polypropylene composite materials at low cost and high efficiency, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a graphene-modified polypropylene composite material and its preparation method.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A graphene-modified polypropylene composite material, comprising the following raw materials in parts by weight: 90-100 parts polypropylene, 3-5 parts maleic anhydride-grafted polypropylene, 1.5-2.5 parts modified graphene, 0.2-0.3 parts composite nucleating agent, 0.3-0.6 parts antioxidant, and 0.3-0.5 parts lubricant.

[0009] Preferably, a graphene-modified polypropylene composite material comprises, by weight, the following raw materials: 95-100 parts polypropylene, 3-4 parts maleic anhydride-grafted polypropylene, 1.5-2 parts modified graphene, 0.25-0.3 parts composite nucleating agent, 0.4-0.6 parts antioxidant, and 0.3-0.4 parts lubricant.

[0010] Preferably, the method for preparing the modified graphene includes the following steps: S1. Add graphene oxide to an aqueous ethanol solution, then add γ-glycidyl etheroxypropyltrimethoxysilane, stir and react. After the reaction is complete, filter, wash and dry to obtain organic graphene oxide. S2. Add the organic graphene oxide from step S1 to DMF, then add 2-amino-4-methylbenzothiazole and boron trifluoride ether, and heat the reaction. After the set time is reached, add octadecylamine and continue the reaction for 1-2 hours. After the reaction is completed, filter, wash and dry to obtain modified graphene.

[0011] Preferably, in step S1, the volume ratio of ethanol to water in the aqueous ethanol solution is 4-5:1, the mass ratio of graphene oxide to γ-glycidyl etheroxypropyltrimethoxysilane is 100:4.5-7, the temperature of the stirring reaction is 65-75℃, and the time is 3-5h.

[0012] In this invention, the modified graphene uses graphene oxide as raw material. Compared with the original graphene, the surface of graphene oxide is rich in oxygen-containing functional groups, which gives it good water dispersibility and chemical reactivity, which is beneficial to subsequent chemical reactions. The highly active reactive group, epoxy group, is introduced by reacting γ-glycidoxypropyltrimethoxysilane with graphene oxide.

[0013] Preferably, the mass ratio of the organic graphene oxide, 2-amino-4-methylbenzothiazole, octadecylamine, and boron trifluoride ether in step S2 is 100:2.4-3.3:2.7-4:0.05-0.1.

[0014] In this invention, boron trifluoride diethyl ether is used as a ring-opening catalyst. 2-Amino-4-methylbenzothiazole is added first, followed by octadecylamine. Through the ring-opening reaction of the epoxy groups, two key functional molecules—2-amino-4-methylbenzothiazole and octadecylamine—are introduced onto graphene oxide. The sulfur and nitrogen heteroatoms on the thiazole ring of 2-amino-4-methylbenzothiazole provide additional polar sites at the interface, enabling stronger polar interactions with maleic anhydride-grafted polypropylene in the system, thus forming a stable interfacial layer and ensuring efficient stress transfer. Octadecylamine has a flexible alkyl chain of up to 18 carbon atoms. The chemical structure of this long chain is very similar to that of polypropylene. It can physically interpenetrate and entangle into the polypropylene molecular chain, generating strong van der Waals forces. This greatly improves the interfacial compatibility between graphene and the non-polar PP matrix, effectively preventing graphene aggregation and ensuring effective stress transfer at the interface under external forces.

[0015] 2-Amino-4-methylbenzothiazole is used for nucleation regulation to solve the crystallization problem of PP; octadecylamine improves interfacial compatibility and solves the dispersion problem of graphene. Both optimize the microstructure of the composite material from two dimensions. At the same time, the flexible long chain of octadecylamine can also play a steric hindrance role between graphene layers, physically preventing the re-stacking of the sheets, and providing a more sufficient exposed surface for the rigid benzothiazole nucleating agent, so that it can more effectively contact the PP melt and play its role in inducing crystallization.

[0016] Preferably, the heating reaction is carried out at a temperature of 90-100°C for 3-4 hours.

[0017] Preferably, the composite nucleating agent is composed of sodium 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate, bis(3,4-dimethylbenzyl) sorbitol and melamine cyanurate in a mass ratio of 4-6:2-3:1-2.

[0018] In this invention, the composite nucleating agent is a ternary composite system consisting of phosphates, sorbitols, and melamine cyanurate. Sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate is a highly efficient α-crystalline nucleating agent with extremely high nucleation efficiency. It can significantly increase the crystallization temperature of PP, shorten the molding cycle, and greatly improve the rigidity of the material at very low addition levels. Di(3,4-dimethylphenylmethylene)sorbitol is also a highly efficient α-nucleating agent, which can further refine the grains and improve the transparency and gloss of the product. The lamellar structure of melamine cyanurate gives it a certain heterogeneous nucleation ability, which can further refine the grains. More importantly, its interfacial bonding with the polymer matrix is ​​relatively weak. When the material is impacted, it can absorb and dissipate impact energy, thereby compensating for the impact toughness lost due to the high crystallinity and high rigidity of the system and playing a regulating role in the balance of rigidity and toughness.

[0019] Preferably, the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1-3; the lubricant is one or more of polyethylene wax, calcium stearate or ethylene bis-stearamide.

[0020] This invention also protects a method for preparing a graphene-modified polypropylene composite material as described above, comprising the following steps: (1) Weigh the raw materials according to the formula, mix the modified graphene with 30% of the total amount of polypropylene and 50% of the total amount of lubricant in a high-speed mixer, melt extrude and granulate through a twin-screw extruder to obtain modified graphene masterbatch. (2) The modified graphene masterbatch, the remaining polypropylene, maleic anhydride grafted polypropylene, composite nucleating agent, antioxidant and the remaining lubricant are mixed evenly in a high-speed mixer, and then melt-blended, extruded, cooled, pelletized and dried by a twin-screw extruder to obtain the final product.

[0021] Preferably, in step (1), the extrusion temperature of the twin-screw extruder is 160-210℃ and the screw speed is 150-200r / min; in step (2), the extrusion temperature of the twin-screw extruder is 170-220℃ and the screw speed is 200-300r / min.

[0022] In this invention, a two-step process of first preparing masterbatch and then diluting and blending is adopted. First, surface-functionalized modified graphene is mixed with a portion of polypropylene and a lubricant under high shear conditions to prepare graphene masterbatch. The concentrated mechanical and thermal energy in this process is sufficient to overcome the van der Waals forces between graphene sheets, achieving preliminary exfoliation and pre-dispersion. Then, this masterbatch is diluted and blended with other components, and the viscous shearing action of the matrix melt is used to achieve the final uniform distribution of graphene. This process avoids the problem of difficulty in uniform mixing when adding trace amounts of powdered graphene directly to the total amount of material, significantly improving the stability and repeatability of the dispersion effect, and meeting the requirements of industrial production.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The graphene-modified polypropylene composite material provided by the present invention uses a specific method to prepare surface-functionalized graphene, and combines it with a high-efficiency composite nucleating agent, and then combines it with a two-step melt blending process of masterbatch method. This not only solves the problem of graphene dispersion and interfacial compatibility in non-polar matrix, but more importantly, it utilizes the heterogeneous nucleation effect of modified graphene on polypropylene to significantly improve the crystallization performance of the material. The final polypropylene composite material forms a fine and uniform α-crystalline microstructure, thereby achieving a comprehensive improvement in mechanical properties, thermal properties and dimensional stability.

[0024] (2) The graphene-modified polypropylene composite material provided by the present invention introduces two molecules with different but complementary functions on the graphene surface through a specific method, thereby achieving the synergistic effect of interfacial compatibility and heterogeneous nucleation. First, the flexible octadecylamine long chain serves as a compatibility anchor, and its long alkyl chain can effectively penetrate into the polypropylene molecular chain. Through physical entanglement and van der Waals forces, the interfacial bonding between graphene and the nonpolar matrix is ​​greatly enhanced, fundamentally solving the problem of graphene dispersion and constructing steric hindrance to prevent it from agglomerating again in the melt. On this basis, the rigid 2-amino-4-methylbenzothiazole group serves as a nucleation template. Its unique heterocyclic aromatic structure can serve as an efficient heterogeneous nucleation site, inducing the polypropylene molecular chain to arrange in an orderly manner on its surface. The synergistic effect of these two functional groups preferentially forms a thermodynamically stable α-crystal form, ensuring that the modified graphene can be evenly dispersed and play a role in the matrix, thus laying a solid foundation for subsequent crystallization behavior.

[0025] (3) The graphene-modified polypropylene composite material provided by the present invention synergistically combines modified graphene with a composite nucleating agent to construct a composite crystallization control system. A large number of uniformly dispersed modified graphene sheets first divide the polypropylene matrix into countless tiny regions and provide preliminary α-nucleation induction. Subsequently, the highly efficient phosphate / sorbitol composite nucleating agent further provides a large number of nucleation centers in these micro-regions, resulting in a significant increase in crystal nucleus density compared to a single nucleation system. Through synergistic action, the two substances can effectively inhibit the growth of spherulites and form a highly uniform and dense microcrystalline / nanocrystalline structure, giving the polypropylene composite material excellent comprehensive performance. On the one hand, the fine grains and dispersed graphene work together to effectively deflect and pin cracks, significantly improving puncture strength. On the other hand, the rapid, homogeneous and perfect crystallization process greatly reduces the molding shrinkage rate of the material and provides excellent dimensional stability. Attached Figure Description

[0026] Figure 1 The image shows the XRD diffraction pattern of the polypropylene composite material prepared in Example 1 of this invention. Detailed Implementation

[0027] 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0029] The polypropylene is grade T03, and the graphene oxide has a sheet diameter of 5-10 μm.

[0030] Example 1 A graphene-modified polypropylene composite material, comprising the following raw materials in parts by weight: 95 parts polypropylene, 4 parts maleic anhydride-grafted polypropylene, 2 parts modified graphene, 0.25 parts composite nucleating agent, 0.5 parts antioxidant, and 0.4 parts lubricant.

[0031] The method for preparing the modified graphene includes the following steps: S1. Add 50g of graphene oxide to 1L of ethanol aqueous solution (ethanol to water volume ratio of 5:1), then add 3g of γ-glycidyl etheroxypropyltrimethoxysilane, stir at 70℃ for 4h, filter, wash and dry after the reaction is completed to obtain organic graphene oxide. S2. Add 50g of organic graphene oxide from step S1 to 1L of DMF, then add 1.4g of 2-amino-4-methylbenzothiazole and 0.04g of boron trifluoride ether. After reacting at 95°C under a nitrogen atmosphere for 3.5h, add 1.6g of octadecylamine and continue the reaction for 1.5h. After the reaction is complete, filter, wash three times with anhydrous ethanol, then wash three times with deionized water, and dry to obtain modified graphene.

[0032] The composite nucleating agent is composed of sodium 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate, bis(3,4-dimethylbenzyl) sorbitol, and melamine cyanurate in a mass ratio of 5:2.5:1.5; the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2; and the lubricant is calcium stearate.

[0033] A method for preparing a graphene-modified polypropylene composite material includes the following steps: (1) Weigh the raw materials according to the formula, mix the modified graphene with 30% of the total amount of polypropylene and 50% of the total amount of lubricant in a high-speed mixer, melt extrude and granulate through a twin-screw extruder, and set the screw temperature and speed conditions of the extruder as follows: 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 200℃, and the screw speed is 180r / min to obtain modified graphene masterbatch; (2) The modified graphene masterbatch, the remaining polypropylene, maleic anhydride grafted polypropylene, composite nucleating agent, antioxidant and the remaining lubricant are mixed evenly in a high-speed mixer, and then melt-blended, extruded, cooled, pelletized and dried in a twin-screw extruder. The screw temperature and speed conditions of the extruder are set as follows: 170℃, 190℃, 200℃, 210℃, 220℃, 210℃, 210℃, and the screw speed is 250r / min.

[0034] like Figure 1 As shown, the red line represents the original test data, and the blue line (-BackSub) represents the data after background subtraction processing. The XRD pattern of this polypropylene composite material shows sharp and strong characteristic diffraction peaks near 2θ of 14.1°, 16.9°, 18.5°, and 21.8°, corresponding to the (110), (040), (130), and (111) crystal planes of the polypropylene α-crystal form, respectively. No β-crystal characteristic peak was observed at 2θ=16.1° in the pattern. These diffraction pattern characteristics clearly confirm that the composite system of this invention successfully induced the polypropylene matrix to form a highly regular and single α-crystal structure.

[0035] Example 2 A graphene-modified polypropylene composite material, comprising the following raw materials in parts by weight: 90 parts polypropylene, 3 parts maleic anhydride-grafted polypropylene, 1.5 parts modified graphene, 0.2 parts composite nucleating agent, 0.3 parts antioxidant, and 0.3 parts lubricant.

[0036] The method for preparing the modified graphene includes the following steps: S1. Add 50g of graphene oxide to 1L of ethanol aqueous solution (ethanol to water volume ratio of 4:1), then add 2.25g of γ-glycidyl etheroxypropyltrimethoxysilane, stir and react at 65℃ for 5h, filter, wash and dry after the reaction is completed to obtain organic graphene oxide. S2. Add 50g of organic graphene oxide from step S1 to 1L of DMF, then add 1.2g of 2-amino-4-methylbenzothiazole and 0.025g of boron trifluoride ether. After reacting for 4h under a nitrogen atmosphere at 90℃, add 1.35g of octadecylamine and continue reacting for 2h. After the reaction is complete, filter, wash 3 times with anhydrous ethanol, then wash 3 times with deionized water, and dry to obtain modified graphene.

[0037] The composite nucleating agent is composed of sodium 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate, bis(3,4-dimethylbenzyl) sorbitol, and melamine cyanurate in a mass ratio of 4:2:1; the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1; and the lubricant is calcium stearate.

[0038] A method for preparing a graphene-modified polypropylene composite material includes the following steps: (1) Weigh the raw materials according to the formula, mix the modified graphene with 30% of the total amount of polypropylene and 50% of the total amount of lubricant in a high-speed mixer, melt extrude and granulate through a twin-screw extruder, and set the screw temperature and speed conditions of the extruder as follows: 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 200℃, and the screw speed is 180r / min to obtain modified graphene masterbatch; (2) The modified graphene masterbatch, the remaining polypropylene, maleic anhydride grafted polypropylene, composite nucleating agent, antioxidant and the remaining lubricant are mixed evenly in a high-speed mixer, and then melt-blended, extruded, cooled, pelletized and dried in a twin-screw extruder. The screw temperature and speed conditions of the extruder are set as follows: 170℃, 190℃, 200℃, 210℃, 220℃, 210℃, 210℃, and the screw speed is 250r / min.

[0039] Example 3 A graphene-modified polypropylene composite material, comprising the following raw materials in parts by weight: 100 parts polypropylene, 5 parts maleic anhydride-grafted polypropylene, 2.5 parts modified graphene, 0.3 parts composite nucleating agent, 0.6 parts antioxidant, and 0.5 parts lubricant.

[0040] The method for preparing the modified graphene includes the following steps: S1. Add 50g of graphene oxide to 1L of ethanol aqueous solution (ethanol to water volume ratio of 5:1), then add 3.5g of γ-glycidyl etheroxypropyltrimethoxysilane, stir and react at 75℃ for 3h, filter, wash and dry after the reaction is completed to obtain organic graphene oxide. S2. Add 50g of organic graphene oxide from step S1 to 1L of DMF, then add 1.65g of 2-amino-4-methylbenzothiazole and 0.05g of boron trifluoride ether. After reacting for 3 hours under a nitrogen atmosphere at 100°C, add 2g of octadecylamine and continue reacting for 1 hour. After the reaction is complete, filter, wash 3 times with anhydrous ethanol, then wash 3 times with deionized water, and dry to obtain modified graphene.

[0041] The composite nucleating agent is composed of sodium 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate, bis(3,4-dimethylbenzyl) sorbitol, and melamine cyanurate in a mass ratio of 6:3:2; the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:3; and the lubricant is calcium stearate.

[0042] A method for preparing a graphene-modified polypropylene composite material includes the following steps: (1) Weigh the raw materials according to the formula, mix the modified graphene with 30% of the total amount of polypropylene and 50% of the total amount of lubricant in a high-speed mixer, melt extrude and granulate through a twin-screw extruder, and set the screw temperature and speed conditions of the extruder as follows: 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 200℃, and the screw speed is 180r / min to obtain modified graphene masterbatch; (2) The modified graphene masterbatch, the remaining polypropylene, maleic anhydride grafted polypropylene, composite nucleating agent, antioxidant and the remaining lubricant are mixed evenly in a high-speed mixer, and then melt-blended, extruded, cooled, pelletized and dried in a twin-screw extruder. The screw temperature and speed conditions of the extruder are set as follows: 170℃, 190℃, 200℃, 210℃, 220℃, 210℃, 210℃, and the screw speed is 250r / min.

[0043] Comparative Example 1 A graphene-modified polypropylene composite material, comprising the following raw materials in parts by weight: 95 parts polypropylene, 4 parts maleic anhydride-grafted polypropylene, 2 parts modified graphene, 0.25 parts composite nucleating agent, 0.5 parts antioxidant, and 0.4 parts lubricant.

[0044] The method for preparing the modified graphene includes the following steps: S1. Add 50g of graphene oxide to 1L of ethanol aqueous solution (ethanol to water volume ratio of 5:1), then add 3g of γ-glycidyl etheroxypropyltrimethoxysilane, stir at 70℃ for 4h, filter, wash and dry after the reaction is completed to obtain organic graphene oxide. S2. Add 50g of organic graphene oxide from step S1 to 1L of DMF, then add 1.4g of 2-amino-4-methylbenzothiazole and 0.04g of boron trifluoride ether. React at 95°C for 5 hours under a nitrogen atmosphere. After the reaction is complete, filter, wash three times with anhydrous ethanol, then wash three times with deionized water, and dry to obtain modified graphene.

[0045] The composite nucleating agent is composed of sodium 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate, bis(3,4-dimethylbenzyl) sorbitol, and melamine cyanurate in a mass ratio of 5:2.5:1.5; the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2; and the lubricant is calcium stearate.

[0046] A method for preparing a graphene-modified polypropylene composite material includes the following steps: (1) Weigh the raw materials according to the formula, mix the modified graphene with 30% of the total amount of polypropylene and 50% of the total amount of lubricant in a high-speed mixer, melt extrude and granulate through a twin-screw extruder, and set the screw temperature and speed conditions of the extruder as follows: 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 200℃, and the screw speed is 180r / min to obtain modified graphene masterbatch; (2) The modified graphene masterbatch, the remaining polypropylene, maleic anhydride grafted polypropylene, composite nucleating agent, antioxidant and the remaining lubricant are mixed evenly in a high-speed mixer, and then melt-blended, extruded, cooled, pelletized and dried in a twin-screw extruder. The screw temperature and speed conditions of the extruder are set as follows: 170℃, 190℃, 200℃, 210℃, 220℃, 210℃, 210℃, and the screw speed is 250r / min.

[0047] Compared to Example 1, this comparative example did not introduce 1.6g of octadecylamine onto the modified graphene.

[0048] Comparative Example 2 A graphene-modified polypropylene composite material, comprising the following raw materials in parts by weight: 95 parts polypropylene, 4 parts maleic anhydride-grafted polypropylene, 2 parts modified graphene, 0.25 parts composite nucleating agent, 0.5 parts antioxidant, and 0.4 parts lubricant.

[0049] The method for preparing the modified graphene includes the following steps: S1. Add 50g of graphene oxide to 1L of ethanol aqueous solution (ethanol to water volume ratio of 5:1), then add 3g of γ-glycidyl etheroxypropyltrimethoxysilane, stir at 70℃ for 4h, filter, wash and dry after the reaction is completed to obtain organic graphene oxide. S2. Add 50g of organic graphene oxide from step S1 to 1L of DMF, then add 1.6g of octadecylamine and 0.04g of boron trifluoride ether. React at 95°C for 5 hours under a nitrogen atmosphere. After the reaction is complete, filter, wash three times with anhydrous ethanol, then wash three times with deionized water, and dry to obtain modified graphene.

[0050] The composite nucleating agent is composed of sodium 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate, bis(3,4-dimethylbenzyl) sorbitol, and melamine cyanurate in a mass ratio of 5:2.5:1.5; the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2; and the lubricant is calcium stearate.

[0051] A method for preparing a graphene-modified polypropylene composite material includes the following steps: (1) Weigh the raw materials according to the formula, mix the modified graphene with 30% of the total amount of polypropylene and 50% of the total amount of lubricant in a high-speed mixer, melt extrude and granulate through a twin-screw extruder, and set the screw temperature and speed conditions of the extruder as follows: 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 200℃, and the screw speed is 180r / min to obtain modified graphene masterbatch; (2) The modified graphene masterbatch, the remaining polypropylene, maleic anhydride grafted polypropylene, composite nucleating agent, antioxidant and the remaining lubricant are mixed evenly in a high-speed mixer, and then melt-blended, extruded, cooled, pelletized and dried in a twin-screw extruder. The screw temperature and speed conditions of the extruder are set as follows: 170℃, 190℃, 200℃, 210℃, 220℃, 210℃, 210℃, and the screw speed is 250r / min.

[0052] Compared to Example 1, this comparative example did not introduce 2-amino-4-methylbenzothiazole onto the modified graphene.

[0053] Comparative Example 3 A graphene-modified polypropylene composite material, comprising the following raw materials in parts by weight: 95 parts polypropylene, 4 parts maleic anhydride-grafted polypropylene, 2 parts modified graphene, 0.25 parts composite nucleating agent, 0.5 parts antioxidant, and 0.4 parts lubricant.

[0054] The preparation method of the composite graphene includes the following steps: 50g of graphene oxide was mixed with 1.4g of 2-amino-4-methylbenzothiazole and 1.6g of octadecylamine to obtain composite graphene.

[0055] The composite nucleating agent is composed of sodium 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate, bis(3,4-dimethylbenzyl) sorbitol, and melamine cyanurate in a mass ratio of 5:2.5:1.5; the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2; and the lubricant is calcium stearate.

[0056] A method for preparing a graphene-modified polypropylene composite material includes the following steps: (1) Weigh the raw materials according to the formula, mix the modified graphene with 30% of the total amount of polypropylene and 50% of the total amount of lubricant in a high-speed mixer, melt extrude and granulate through a twin-screw extruder, and set the screw temperature and speed conditions of the extruder as follows: 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 200℃, and the screw speed is 180r / min to obtain modified graphene masterbatch; (2) The modified graphene masterbatch, the remaining polypropylene, maleic anhydride grafted polypropylene, composite nucleating agent, antioxidant and the remaining lubricant are mixed evenly in a high-speed mixer, and then melt-blended, extruded, cooled, pelletized and dried in a twin-screw extruder. The screw temperature and speed conditions of the extruder are set as follows: 170℃, 190℃, 200℃, 210℃, 220℃, 210℃, 210℃, and the screw speed is 250r / min.

[0057] Compared with Example 1, the composite graphene in this comparative example was prepared by physically mixing graphene oxide with 2-amino-4-methylbenzothiazole and octadecylamine.

[0058] Comparative Example 4 A graphene-modified polypropylene composite material, comprising the following raw materials in parts by weight: 95 parts polypropylene, 4 parts maleic anhydride-grafted polypropylene, 2 parts modified graphene, 0.25 parts nucleating agent, 0.5 parts antioxidant, and 0.4 parts lubricant.

[0059] The method for preparing the modified graphene includes the following steps: S1. Add 50g of graphene oxide to 1L of ethanol aqueous solution (ethanol to water volume ratio of 5:1), then add 3g of γ-glycidyl etheroxypropyltrimethoxysilane, stir at 70℃ for 4h, filter, wash and dry after the reaction is completed to obtain organic graphene oxide. S2. Add 50g of organic graphene oxide from step S1 to 1L of DMF, then add 1.4g of 2-amino-4-methylbenzothiazole and 0.04g of boron trifluoride ether. After reacting at 95°C under a nitrogen atmosphere for 3.5h, add 1.6g of octadecylamine and continue the reaction for 1.5h. After the reaction is complete, filter, wash three times with anhydrous ethanol, then wash three times with deionized water, and dry to obtain modified graphene.

[0060] The nucleating agent is sodium 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate; the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2; and the lubricant is calcium stearate.

[0061] A method for preparing a graphene-modified polypropylene composite material includes the following steps: (1) Weigh the raw materials according to the formula, mix the modified graphene with 30% of the total amount of polypropylene and 50% of the total amount of lubricant in a high-speed mixer, melt extrude and granulate through a twin-screw extruder, and set the screw temperature and speed conditions of the extruder as follows: 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 200℃, and the screw speed is 180r / min to obtain modified graphene masterbatch; (2) The modified graphene masterbatch, the remaining polypropylene, maleic anhydride grafted polypropylene, nucleating agent, antioxidant and the remaining lubricant are mixed evenly in a high-speed mixer, and then melt-blended, extruded, cooled, pelletized and dried in a twin-screw extruder. The screw temperature and speed conditions of the extruder are set as follows: 170℃, 190℃, 200℃, 210℃, 220℃, 210℃, 210℃, and the screw speed is 250r / min.

[0062] Compared with Example 1, the nucleating agent in this comparative example is sodium 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate.

[0063] The polypropylene composites prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests. Tensile strength and elongation at break were tested according to GB / T 1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molding and extruding plastics" using a 180mm × 10mm × 4mm specimen and a tensile speed of 10mm / min. Flexural strength was tested according to GB / T 9341-2008 "Determination of flexural properties of plastics" using an 80mm × 10mm × 4mm specimen. Notched impact strength was tested according to GB / T 1843-2008 "Determination of impact strength of cantilever beam plastics" using an 80mm × 10mm × 4mm specimen with a remaining notch thickness of 2mm. The test results are shown in Table 1 below.

[0064] Table 1. Performance test results of polypropylene composite materials in each embodiment and comparative example. As can be seen from Table 1 above, the polypropylene composite material prepared by this invention has good mechanical properties, as well as high crystallinity and α-crystal content, exhibiting excellent comprehensive performance. However, in Comparative Examples 1 and 2, the lack of corresponding functional small molecules leads to a significant decrease in certain properties of the polypropylene composite material. In Comparative Example 3, graphene and functional small molecules are physically blended, and the graphene and polypropylene matrix are only bonded by weak van der Waals forces or the limited effect of compatibilizers, resulting in weak interfacial bonding. This makes it prone to interfacial slippage and secondary agglomeration during processing shearing or when the material is under stress, leading to a decrease in the performance of the polypropylene composite material. Comparative Example 4, due to the use of a single nucleating agent, although exhibiting good rigidity, suffers from a significant loss of material toughness, resulting in an imbalance in mechanical properties.

[0065] The above description is a further detailed explanation of the present invention in conjunction with specific implementation examples. It should not be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the protection scope of the present invention.

[0066] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A graphene-modified polypropylene composite material, characterized in that, By weight, it includes the following ingredients: 90-100 parts polypropylene, 3-5 parts maleic anhydride-grafted polypropylene, 1.5-2.5 parts modified graphene, 0.2-0.3 parts composite nucleating agent, 0.3-0.6 parts antioxidant, and 0.3-0.5 parts lubricant; The method for preparing the modified graphene includes the following steps: S1. Add graphene oxide to an aqueous ethanol solution, then add γ-glycidyl etheroxypropyltrimethoxysilane, stir and react. After the reaction is complete, filter, wash and dry to obtain organic graphene oxide. S2. Add the organic graphene oxide from step S1 to DMF, then add 2-amino-4-methylbenzothiazole and boron trifluoride diethyl ether, and heat the reaction. After the reaction reaches the set time, add octadecylamine and continue the reaction for 1-2 hours. After the reaction is completed, filter, wash and dry to obtain modified graphene. The composite nucleating agent is composed of sodium 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate, bis(3,4-dimethylbenzyl) sorbitol, and melamine cyanurate in a mass ratio of 4-6:2-3:1-2.

2. The graphene-modified polypropylene composite material according to claim 1, characterized in that, By weight, it includes the following raw materials: 95-100 parts polypropylene, 3-4 parts maleic anhydride-grafted polypropylene, 1.5-2 parts modified graphene, 0.25-0.3 parts composite nucleating agent, 0.4-0.6 parts antioxidant, and 0.3-0.4 parts lubricant.

3. The graphene-modified polypropylene composite material according to claim 1, characterized in that, In step S1, the volume ratio of ethanol to water in the aqueous ethanol solution is 4-5:1, the mass ratio of graphene oxide to γ-glycidyl etheroxypropyltrimethoxysilane is 100:4.5-7, the stirring reaction temperature is 65-75℃, and the time is 3-5h.

4. The graphene-modified polypropylene composite material according to claim 1, characterized in that, The mass ratio of the organic graphene oxide, 2-amino-4-methylbenzothiazole, octadecylamine, and boron trifluoride ether in step S2 is 100:2.4-3.3:2.7-4:0.05-0.

1.

5. The graphene-modified polypropylene composite material according to claim 1, characterized in that, The heating reaction is carried out at a temperature of 90-100℃ for 3-4 hours.

6. The graphene-modified polypropylene composite material according to claim 1, characterized in that, The antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1-3; the lubricant is one or more of polyethylene wax, calcium stearate or ethylene bis-stearamide.

7. A method for preparing a graphene-modified polypropylene composite material as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Weigh the raw materials according to the formula, mix the modified graphene with 30% of the total amount of polypropylene and 50% of the total amount of lubricant in a high-speed mixer, melt extrude and granulate through a twin-screw extruder to obtain modified graphene masterbatch. (2) The modified graphene masterbatch, the remaining polypropylene, maleic anhydride grafted polypropylene, composite nucleating agent, antioxidant and the remaining lubricant are mixed evenly in a high-speed mixer, and then melt-blended, extruded, cooled, pelletized and dried by a twin-screw extruder to obtain the final product.

8. The preparation method according to claim 7, characterized in that, In step (1), the extrusion temperature of the twin-screw extruder is 160-210℃ and the screw speed is 150-200r / min; in step (2), the extrusion temperature of the twin-screw extruder is 170-220℃ and the screw speed is 200-300r / min.

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