High-performance polypropylene composite material and preparation method thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a high-performance polypropylene composite material and a preparation method thereof. The high-performance polypropylene composite material comprises the following raw materials in parts by weight: 100 parts of polypropylene, 10-30 parts of modified cellulose nanocrystals, 1-5 parts of maleic anhydride grafted polypropylene, 0.1-0.5 part of an antioxidant and 0.1-0.5 part of a lubricant. Cellulose nanocrystals (CNC) are subjected to accurate molecular design modification, an intermediate with a P-N-Si flame-retardant structure is grafted to a CNC skeleton through chemical bonds, and the modified cellulose nanocrystals can fully play a flame-retardant role in a polypropylene matrix and have good compatibility with the polypropylene matrix; and the material can be used as a nano-reinforced filler to synchronously improve the mechanical properties of the composite material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer materials, and particularly relates to a high-performance polypropylene composite material and a preparation method thereof. BACKGROUND

[0002] Polypropylene (PP) has an important position in the fields of communication, power, automobile, etc. due to its excellent electrical insulation, chemical corrosion resistance, low density and good processing performance. However, PP itself is a flammable material, and its limiting oxygen index (LOI) is only about 17%-18%, which is easy to burn and produce melt drops under the action of fire, and there is a serious safety hazard, which is difficult to meet the requirements of UL-94 V-0 level or IEC 60332 flame retardant standard.

[0003] At present, the industry generally uses the way of adding flame retardants to improve the flame retardant performance of PP. Traditional halogen-based flame retardants (such as brominated cycloalkanes, chlorinated paraffin, etc.) have good flame retardant efficiency, but they will release a large amount of toxic and corrosive gases (such as hydrogen halide acid, dioxin, etc.) in the combustion process, which will cause great harm to the environment and human health, and has been gradually restricted or eliminated. Although halogen-free flame retardant systems (such as phosphorus-based, nitrogen-based, inorganic hydroxides, etc.) are environmentally friendly, they usually need a high addition amount to achieve ideal flame retardant effect, which will significantly affect the mechanical properties and processing performance of the material. For example, when the addition amount of inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide exceeds 40 wt%, although the LOI value can be improved, the brittleness of the material increases, the tensile strength decreases, and the processing flowability becomes poor.

[0004] In addition, in order to improve the mechanical properties of PP, glass fibers, talc, calcium carbonate and other reinforcing fillers are often added. These inorganic reinforcing materials can improve the rigidity and dimensional stability, but have poor interfacial compatibility with the PP matrix, which can easily cause interfacial debonding, stress concentration and other problems, resulting in the decrease of the impact toughness of the composite material. At the same time, the addition of reinforcing fillers can also affect the distribution and synergistic effect of the flame retardant, and reduce the overall flame retardant efficiency. Therefore, how to achieve efficient flame retardation without sacrificing the mechanical properties has become a technical bottleneck in the design of current PP composites.

[0005] In recent years, cellulose nanocrystals (CNC) as a kind of green and renewable nanomaterial, have attracted extensive attention due to its high specific surface area, good mechanical properties and surface modifiability. CNC not only can be used as reinforcing fillers to improve the strength and toughness of polymers, but also provides an ideal platform for functionalization modification due to its surface hydroxyl structure. By grafting phosphorus-nitrogen flame retardant monomers on the surface of CNC, not only the flame retardant function can be endowed, but also the interfacial compatibility between CNC and PP matrix can be improved, realizing the synergistic effect of reinforcement and flame retardance. However, there is still a lack of a composite system which can combine the mechanical enhancement characteristics of CNC with high efficient flame retardant performance, and realize stable dispersion and processing in polypropylene matrix. Therefore, it has important engineering application value and practical significance to develop a high performance polypropylene composite material based on grafted CNC. SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the primary purpose of the present application is to provide a high performance polypropylene composite material.

[0007] Another purpose of the present application is to provide a preparation method of the high performance polypropylene composite material.

[0008] The purpose of the present application is realized by the following technical solutions: A high performance polypropylene composite material, comprising the following raw materials in parts by weight: polypropylene 100 parts, modified cellulose nanocrystals 10-30 parts, maleic anhydride grafted polypropylene 1-5 parts, antioxidant 0.1-0.5 parts, lubricant 0.1-0.5 parts; The modified cellulose nanocrystals are prepared by the following preparation process: (1) arginine and phosphorous acid are added to water and stirred, then formaldehyde solution is added, and the reaction is carried out under heating condition; after the reaction is completed, the reaction liquid is purified to obtain intermediate 1; the structural formula of the intermediate 1 is as follows: (2) cyanuric chloride is added to 1,4-dioxane, and a 1,4-dioxane solution of γ-aminopropyl triethoxysilane and triethylamine is added at-5-5℃, and stirring is continued for 2.5-3h, then the reaction liquid is heated to 50-55℃, and a 1,4-dioxane solution of intermediate 1 and triethylamine is added, and stirring is continued until the temperature rises to 100-105℃; after the reaction is completed, the reaction liquid is purified to obtain intermediate 2; the structural formula of the intermediate 2 is as follows: (3) cellulose nanocrystals are dispersed in water, and after ultrasonic treatment, a cellulose nanocrystal dispersion liquid is obtained; under the atmosphere of inert gas, an ethanol solution of intermediate 2 is added to the cellulose nanocrystal dispersion liquid, and the reaction is carried out under heating condition; after the reaction is completed, the reaction liquid is purified to obtain the modified cellulose nanocrystals.

[0009] The reaction principle for synthesizing the modified cellulose nanocrystal is as follows: first, the amino group of arginine, formaldehyde and the active hydrogen of phosphorous acid in step (1) undergo Mannich reaction to prepare intermediate 1 with high-density P-N flame-retardant structure; then, in step (2), one chlorine atom of cyanuric chloride and the amino group of γ-aminopropyl triethoxysilane undergo nucleophilic substitution at a low temperature stage (-5-5 ℃) to connect the silane molecule to the triazine ring, and the remaining two chlorine atoms of cyanuric chloride and the amino group of intermediate 1 undergo nucleophilic substitution at 50-55 ℃ to prepare intermediate 2 with P-N-Si flame-retardant structure; finally, in step (3), the siloxane group at the end of intermediate 2 is hydrolyzed to generate a silanol group, and the generated silanol group and the hydroxyl group on the surface of the cellulose nanocrystal undergo dehydration condensation reaction to form a stable Si-O-C covalent bond, so that intermediate 2 is firmly anchored on the surface of the cellulose nanocrystal, avoiding migration and interface problems.

[0010] Further, in step (1), the molar ratio of arginine to phosphorous acid is 1: (4-5), and the molar ratio of arginine to formaldehyde in the formaldehyde solution is 1: (4-5).

[0011] Further, in step (1), the heating temperature is 110-130 ℃, and the reaction time is 4-8 h.

[0012] Further, in step (2), the molar ratio of cyanuric chloride, γ-aminopropyl triethoxysilane and intermediate 1 is 1: (1-1.1): (2-2.4).

[0013] Further, in step (2), the molar ratio of γ-aminopropyl triethoxysilane to triethylamine in the 1,4-dioxane solution of γ-aminopropyl triethoxysilane and triethylamine is 1: (1-1.2), and the molar ratio of triethylamine to intermediate 1 in the 1,4-dioxane solution of triethylamine and intermediate 1 is (1.2-1.4): 1.

[0014] Further, in step (3), the mass ratio of cellulose nanocrystal to intermediate 2 is 1: (2-2.5).

[0015] Further, in step (3), the ultrasonic treatment time is 20-30 min, the heating temperature is 80-90 ℃, and the reaction time is 12-14 h.

[0016] Further, the antioxidant is antioxidant 1010 or antioxidant 1098, and the lubricant is magnesium stearate or zinc stearate.

[0017] A preparation method of the high-performance polypropylene composite material is provided, which comprises the following steps: (a) Premixing polypropylene, modified cellulose nanocrystal, maleic anhydride grafted polypropylene, antioxidant and lubricant according to the weight fraction to obtain a mixture; (b) Adding the mixture into a twin-screw extruder to melt extrude and granulate to obtain the high-performance polypropylene composite material.

[0018] Further, the premixing time in step (a) is 3-5 min; the temperature range of each region of the twin-screw extruder in step (b) is 180-210℃, and the screw rotation speed is 50-80 rpm.

[0019] The present application has the following effects relative to the prior art: 1. The present application modifies cellulose nanocrystal (CNC) through precise molecular design, grafts the intermediate 2 with P-N-Si flame-retardant structure onto the CNC skeleton through chemical bonds, and the modified cellulose nanocrystal can fully play a flame-retardant role in the polypropylene matrix, promotes the formation of a dense and stable expanded carbon layer during combustion of the composite material, effectively insulates heat and oxygen, and terminates the combustion reaction. Experimental results show that the limiting oxygen index of the composite material can reach 32.6%, and it passes the UL-94 V-0 level without melting and dripping, and has excellent flame-retardant performance.

[0020] 2. The modified cellulose nanocrystal in the present application not only acts as a flame retardant, but also acts as a nano-enhanced filler to simultaneously improve the mechanical properties of the composite material. The introduction of a large structure on the surface of the modified cellulose nanocrystal produces a steric hindrance effect, which can prevent the agglomeration of cellulose nanocrystal, make it uniformly dispersed in the polypropylene matrix, ensure effective stress transmission, and enhance the mechanical properties of the composite material, while overcoming the technical difficulty of deterioration of the mechanical properties of the material caused by traditional additive flame retardants.

[0021] 3. The modified cellulose nanocrystal in the present application has good compatibility with the polypropylene matrix, and the present application also uses maleic anhydride grafted polypropylene as a compatibilizer to further promote the dispersion of the modified cellulose nanocrystal in the matrix, and has good processing characteristics. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The FT-IR graph of the cellulose nanocrystal and the modified cellulose nanocrystal in Example 1 of the present application. DETAILED DESCRIPTION

[0023] The technical solutions of the present application are further described below in conjunction with the specific embodiments. However, those skilled in the art should understand that the following examples are only used to illustrate the present application and should not be regarded as limiting the present application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturers. The reagents or instruments used are conventional products obtained through commercial channels, unless otherwise specified.

[0024] Example 1 Example 1 provides a high-performance polypropylene composite material, which comprises the following raw materials in parts by weight: polypropylene 100 parts, modified cellulose nanocrystals 20 parts, maleic anhydride grafted polypropylene 3 parts, antioxidant 1010 0.2 parts, magnesium stearate 0.3 parts; The modified cellulose nanocrystals are prepared by the following preparation process: (1) arginine (0.1 mol) and phosphorous acid (0.45 mol) are added to deionized water (40 mL) and stirred to dissolve, heated to 50°C and slowly added with formaldehyde solution (37wt%, 0.45 mol), reacted at 120°C for 6 h; after the reaction is completed, the reaction liquid is distilled under reduced pressure to remove the solvent, then the crude product is dissolved in hot water and hot solution is slowly added with acetone until turbidity appears, then cooled to room temperature to precipitate the product, the product is collected by filtration, washed with cold acetone, dried to obtain intermediate 1; 1 HNMR(C 10 H 26 N4O 14 P4, 400 MHz, d6-DMSO) δ 12.39(s, 1H, OH), 7.84(s, 1H, N H =C), 5.90(s, 1H, CH2N H ), 5.10(s, 8H, OH), 3.74(s, 4H, CH2), 3.40-3.34 (m, 3H, CH2, CH),2.74 (s, 4H, CH2), 1.60-1.50(m, 4H, CH2) ; HRMS (ESI + ): [M+H] + calculated 551.04, found 551.05.

[0025] The reaction process is as follows: (2) cyanuric chloride (0.05 mol) was added into 1,4-dioxane (70 mL) and stirred, a solution of γ-aminopropyltriethoxysilane (0.055 mol) and triethylamine (0.055 mol) in 1,4-dioxane (70 mL) was added into the cyanuric chloride solution at 0 °C, and the stirring was continued for 3 h; when the reaction solution was warmed to 55 °C, a solution of intermediate 1 (0.11 mol) and triethylamine (0.14 mol) in 1,4-dioxane (70 mL) was added dropwise into the reaction solution, and the stirring was continued for 3 h until the reaction temperature was increased to 100 °C; then the reaction solution was cooled to room temperature, poured into dichloromethane (300 mL), filtered, and the collected solid was washed with dichloromethane for three times to obtain a crude product; the crude product was dissolved in hot DMF and slowly added into dichloromethane into the hot solution until turbidity appeared, then cooled to room temperature to precipitate the product, which was collected by filtration and washed with dichloromethane, and dried to obtain intermediate 2; 1 H NMR (CDCI3, 400 MHz) δ 7.82 (s, 2H, N 32 H 72 N 12 O 31 P8Si, 400MHz, d6-DMSO) δ 12.39(s, 2H, OH), 7.84(s, 2H, N H =C), 7.01(s, 1H, N H CH2), 5.10(s, 16H, OH), 3.83-3.80(m, 6H, CH2), 3.74(s, 8H, CH2), 3.40-3.34 (m, 8H, CH2,CH), 2.74 (s, 8H, CH2), 1.60-1.48(m, 10H, CH2), 1.21(t, 9H, CH3), 0.56(t, 2H,CH2) ;HRMS (ESI + ): [M+H] + Calcd 1397.21, found 1397.21.

[0026] The reaction process was as follows: (3) cellulose nanocrystals (CNCs, 10 g) were dispersed into deionized water (55 mL) and ultrasonically treated for 25 min to obtain a cellulose nanocrystal dispersion; under N2 atmosphere and at 85 °C, a solution of intermediate 2 in ethanol (22 g, 100 mL) was added into the cellulose nanocrystal dispersion, and the reaction was carried out for 13 h; after the reaction was completed, centrifugation was performed, the collected precipitate was washed with deionized water for three times, and dried to obtain modified cellulose nanocrystals; The cellulose nanocrystals and the modified cellulose nanocrystals were characterized by FT-IR, and the results were as follows:Figure 1 As shown in the figure, curves a and b correspond to cellulose nanocrystals and modified cellulose nanocrystals, respectively. Compared with curve a, in curve b, a characteristic tooth-shaped peak of Si-O-C appears at 1000-1100 cm -1 The characteristic peak of C-H bond at 2940 cm -1 is significantly enhanced, and the peak intensity at 1550-1650 cm -1 is larger, which is derived from the C=N stretching vibration of the triazine ring of intermediate 2. The above results show that intermediate 2 is successfully grafted onto the surface of cellulose nanocrystals.

[0027] Example 1 also provides a preparation method of the above high-performance polypropylene composite material, and the specific steps are as follows: (a) The raw materials are weighed according to the above weight fractions, and pre-mixed in a mixer for 4 min to obtain a mixture; (b) The mixture is added to a twin-screw extruder, and melt-extruded and granulated to obtain the high-performance polypropylene composite material; wherein the processing temperature of each zone of the twin-screw extruder is: Zone 1 180°C, Zone 2 195°C, Zone 3 210°C, Zone 4 205°C, and the screw rotation speed is 70 rpm.

[0028] Example 2 Example 2 provides a high-performance polypropylene composite material, which comprises the following raw materials by weight fraction: polypropylene 100 parts, modified cellulose nanocrystals 10 parts, maleic anhydride grafted polypropylene 1 part, antioxidant 1098 0.1 part, and zinc stearate 0.1 part. The modified cellulose nanocrystals are prepared by the following preparation process: (1) Arginine (0.1 mol) and phosphorous acid (0.4 mol) are added to deionized water (30 mL) and stirred to dissolve, heated to 40-60°C and slowly added with formaldehyde solution (37wt%, 0.4 mol), and reacted at 110°C for 8 h; after the reaction is completed, the reaction liquid is distilled under reduced pressure to remove the solvent, and then the crude product is dissolved in hot water and slowly added with acetone to the hot solution until turbidity appears, and then cooled to room temperature to precipitate the product, which is collected by filtration, washed with cold acetone, and dried to obtain intermediate 1; the 1 H NMR and HRMS results are consistent with those of Example 1.

[0029] (2) cyanuric chloride (0.05 mol) was stirred in 1,4-dioxane (60 mL), and a solution of γ-aminopropyltriethoxysilane (0.05 mol) and triethylamine (0.06 mol) in 1,4-dioxane (60 mL) was added to the cyanuric chloride solution at -5 °C, and the stirring was continued for 2.5 h; when the reaction solution was warmed to 50 °C, a solution of intermediate 1 (0.1 mol) and triethylamine (0.12 mol) in 1,4-dioxane (60 mL) was added dropwise, and the stirring was continued for 2.5 h until the reaction temperature was raised to 100 °C; then the reaction solution was cooled to room temperature, poured into dichloromethane (300 mL), filtered, and the collected solid was washed with dichloromethane three times to obtain a crude product; the crude product was dissolved in hot DMF and dichloromethane was slowly added to the hot solution until turbidity appeared, and then the solution was cooled to room temperature to precipitate the product, which was collected by filtration and washed with dichloromethane, and dried to obtain intermediate 2; the intermediate 2 was characterized by H NMR and HRMS, and the results were consistent with those of Example 1. 1 H NMR and HRMS results were consistent with those of Example 1.

[0030] (3) cellulose nanocrystals (10 g) were dispersed in deionized water (50 mL) and ultrasonically treated for 20 min to obtain a cellulose nanocrystal dispersion; under a N2 atmosphere at 80 °C, a solution of intermediate 2 in ethanol (20 g, 100 mL) was added to the cellulose nanocrystal dispersion, and the reaction was carried out for 12 h; after the reaction was completed, centrifugation was performed, the collected precipitate was washed with deionized water three times, and dried to obtain modified cellulose nanocrystals; the FT-IR results of the modified cellulose nanocrystals were consistent with those of Example 1.

[0031] Example 2 also provides a preparation method of the high-performance polypropylene composite material described above, and the specific steps are as follows: (a) the raw materials were weighed according to the above weight proportions, and pre-mixed in a mixer for 3 min to obtain a mixture; (b) the mixture was added to a twin-screw extruder, and melt-extruded and pelletized to obtain the high-performance polypropylene composite material; the processing temperatures of the zones of the twin-screw extruder were as follows: 180 °C for zone 1, 195 °C for zone 2, 210 °C for zone 3, 205 °C for zone 4, and the screw rotation speed was 50 rpm.

[0032] Example 3 Example 3 provides a high-performance polypropylene composite material, which comprises the following raw materials in weight proportions: polypropylene 100 parts, modified cellulose nanocrystals 30 parts, maleic anhydride grafted polypropylene 5 parts, antioxidant 1010 0.5 parts, and zinc stearate 0.5 parts. The modified cellulose nanocrystals are prepared by the following preparation process: (1) arginine (0.1 mol) and phosphorous acid (0.5 mol) were added into deionized water (50 mL) and stirred to dissolve, heated to 40-60 °C and slowly added formaldehyde solution (37 wt%, 0.5 mol), reacted at 130 °C for 4 h; after the reaction was completed, the reaction liquid was distilled under reduced pressure to remove the solvent, then the crude product was dissolved in hot water and slowly added acetone into the hot solution until turbidity appeared, then cooled to room temperature to precipitate the product, the product was collected by filtration and washed with cold acetone, dried to obtain intermediate 1; the H NMR and HRMS results of intermediate 1 were consistent with those of example 1. 1 The H NMR and HRMS results were consistent with those of example 1.

[0033] (2) cyanuric chloride (0.05 mol) was added into 1,4-dioxane (80 mL) and stirred, at 5 °C, a solution of γ-aminopropyltriethoxysilane (0.055 mol) and triethylamine (0.055 mol) in 1,4-dioxane (80 mL) was added into the stirred solution, continued to stir for 3 h; when the reaction liquid was heated to 50 °C, a solution of intermediate 1 (0.12 mol) and triethylamine (0.16 mol) in 1,4-dioxane (80 mL) was added into the stirred solution, continued to stir for 3 h until the reaction temperature was increased to 105 °C; then the reaction liquid was cooled to room temperature, poured into dichloromethane (300 mL), filtered, the collected solid was washed with dichloromethane three times to obtain the crude product; the crude product was dissolved in hot DMF and slowly added dichloromethane into the hot solution until turbidity appeared, then cooled to room temperature to precipitate the product, the product was collected by filtration and washed with dichloromethane, dried to obtain intermediate 2; the H NMR and HRMS results of intermediate 2 were consistent with those of example 1. 1 The H NMR and HRMS results were consistent with those of example 1.

[0034] (3) cellulose nanocrystals (10 g) were dispersed into deionized water (60 mL) and ultrasonically treated for 30 min to obtain a cellulose nanocrystal dispersion; under N2 atmosphere and at 90 °C, a solution of intermediate 2 in ethanol (25 g, 100 mL) was added into the cellulose nanocrystal dispersion and reacted for 14 h; after the reaction was completed, centrifuged, the collected precipitate was washed with deionized water three times, dried to obtain modified cellulose nanocrystals; the FT-IR results of the modified cellulose nanocrystals were consistent with those of example 1.

[0035] Example 3 also provides a preparation method of the above high-performance polypropylene composite material, and the specific steps are as follows: (a) the raw materials were weighed according to the above weight parts, pre-mixed in a mixer for 5 min to obtain a mixture; (b) adding the mixture into a twin-screw extruder, melt-extruding and granulating to obtain the high-performance polypropylene composite material; wherein the processing temperature of each zone of the twin-screw extruder is: 180℃ for the first zone, 195℃ for the second zone, 210℃ for the third zone, and 205℃ for the fourth zone, and the screw rotation speed is 80 rpm.

[0036] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that the modified cellulose nanocrystals in Example 1 are replaced by cellulose nanocrystals.

[0037] Test Example The products prepared in Examples 1-3 and Comparative Example 1 were tested for flame retardant performance and mechanical properties, and the testing methods were as follows: ① Flame retardant performance: UL-94 vertical burning test was performed according to GB / T 2408-2021 “Determination of the Burning Behavior of Plastics Horizontal and Vertical Methods”, and limiting oxygen index test was performed according to GB / T 2406.2-2009 “Determination of the Burning Behavior of Plastics Part 2: Room Temperature Test by the Oxygen Index Method”, 5 times of testing were performed for each group of samples to take the average value, and the results are shown in Table 1.

[0038] ② Mechanical properties: tensile strength test was performed on the samples according to GB / T 1040.1-2018 “Determination of the Tensile Properties of Plastics Part 1: General Principles”, flexural strength test was performed on the samples according to GB / T 9341-2008 “Determination of the Flexural Properties of Plastics”, and impact strength test was performed on the samples according to GB / T 1843-2008 “Determination of the Izod Impact Strength of Plastics”, 5 times of testing were performed for each group of samples to take the average value, and the results are shown in Table 1.

[0039] Table 1 As can be seen from Table 1, the polypropylene composite material prepared in Examples 1-3 has excellent flame retardant performance and mechanical properties.

[0040] In Comparative Example 1, the modified cellulose nanocrystals in Example 1 are replaced by cellulose nanocrystals, and the flame retardant efficiency of the material is much lower than that of Example 1 due to the absence of grafted flame retardant groups, the limiting oxygen index is only slightly higher than that of pure polypropylene, and there are melt drops during the burning process; moreover, the aggregation of cellulose nanocrystals leads to a significant decrease in tensile and flexural strength. The above results show that, by precisely modifying the cellulose nanocrystals (CNC) through molecular design, the intermediate 2 with P-N-Si flame retardant structure is grafted onto the CNC skeleton through chemical bonds, and the modified cellulose nanocrystals not only fully play a flame-retardant role in the polypropylene matrix, but also have good compatibility with the polypropylene matrix, and can simultaneously improve the mechanical properties of the composite material as a nano-enhancing filler.

[0041] Application Example The composite materials prepared in Examples 1-3 and Comparative Example 1 were made into films by using a casting method, wound up, slitted to make polypropylene films, and the following performance tests were conducted.

[0042] ①Tensile strength: The tensile strength was determined according to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: test conditions for films and sheets", and the results are shown in Table 2.

[0043] ②Water vapor transmission: The water vapor transmission was determined according to GB / T 1037-2021 "Determination of water vapor transmission properties of plastics films and sheets - Cup method for gain and loss in weight", and the results are shown in Table 2.

[0044] Table 2 As can be seen from Table 2, the tensile strength of the casting film made of the composite material described in Examples 1-3 is significantly higher than that of Comparative Example 1 in both the transverse and longitudinal directions. This indicates that the modified cellulose nanocrystals in the present application achieve good dispersion and interfacial bonding in the polypropylene matrix, giving the film excellent mechanical strength, making it more durable during subsequent processing and use. In addition, the barrier properties of the composite material film of the present application are also improved compared to Comparative Example 1, which is due to the interfacial compatibility of the modified cellulose nanocrystals with the matrix, reducing the interfacial defects, forming a more dense and complete film microstructure, thereby effectively blocking the penetration path of water vapor molecules.

[0045] In summary, the present application provides a high-performance polypropylene composite material, which can be used to prepare packaging films with high strength and high barrier properties, showing broad application prospects.

[0046] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and not to limit it. The basic principles and main features of the present application have been described above with specific embodiments, and some modifications or substitutions can be made on the basis of the present application, but these modifications or substitutions do not make the corresponding technical solutions deviate from the scope of the present application.

Claims

1. A high performance polypropylene composite material, characterized in that, The raw materials include the following components in parts by weight: polypropylene 100 parts, modified cellulose nanocrystal 10-30 parts, maleic anhydride grafted polypropylene 1-5 parts, antioxidant 0.1-0.5 parts, lubricant 0.1-0.5 parts; The modified cellulose nanocrystal is prepared by the following process: (1) arginine and phosphorous acid are added into water and stirred, then formaldehyde solution is added, and the reaction is carried out under heating; after the reaction is completed, the reaction solution is purified to obtain intermediate 1; the structural formula of the intermediate 1 is: (2) cyanuric chloride is added into 1,4-dioxane, and a 1,4-dioxane solution of γ-aminopropyl triethoxysilane and triethylamine is added at -5-5 ℃, and stirring is continued for 2.5-3 h; then the reaction solution is warmed to 50-55 ℃, and a 1,4-dioxane solution of intermediate 1 and triethylamine is added, and stirring is continued until the temperature rises to 100-105 ℃; after the reaction is completed, the reaction solution is purified to obtain intermediate 2; the structural formula of the intermediate 2 is: (3) cellulose nanocrystal is dispersed into water, and a cellulose nanocrystal dispersion is obtained after ultrasonic treatment; under an inert gas atmosphere, an ethanol solution of intermediate 2 is added into the cellulose nanocrystal dispersion, and the reaction is carried out under heating; after the reaction is completed, the reaction solution is purified to obtain the modified cellulose nanocrystal.

2. The high performance polypropylene composite according to claim 1, characterized in that, In step (1), the molar ratio of arginine to phosphorous acid is 1:(4-5), and the molar ratio of arginine to formaldehyde in the formaldehyde solution is 1:(4-5).

3. The high performance polypropylene composite of claim 1, wherein, In step (1), the temperature of heating is 110-130 ℃, and the reaction time is 4-8 h.

4. The high performance polypropylene composite of claim 1, wherein, In step (2), the molar ratio of cyanuric chloride, γ-aminopropyl triethoxysilane, and intermediate 1 is 1:(1-1.1):(2-2.4).

5. The high performance polypropylene composite of claim 1, wherein, In step (2), the molar ratio of γ-aminopropyl triethoxysilane to triethylamine in the 1,4-dioxane solution of γ-aminopropyl triethoxysilane and triethylamine is 1:(1-1.2); and the molar ratio of triethylamine to intermediate 1 in the 1,4-dioxane solution of intermediate 1 and triethylamine is (1.2-1.4):

1.

6. The high performance polypropylene composite of claim 1, wherein, In step (3), the mass ratio of cellulose nanocrystal to intermediate 2 is 1:(2-2.5).

7. The high performance polypropylene composite of claim 1, wherein, In step (3), the ultrasonic treatment time is 20-30 min; the heating temperature is 80-90 ℃, and the reaction time is 12-14 h.

8. The high performance polypropylene composite of claim 1, wherein, The antioxidant is antioxidant 1010 or antioxidant 1098; and the lubricant is magnesium stearate or zinc stearate.

9. A process for the preparation of a high performance polypropylene composite according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: (a) polypropylene, modified cellulose nanocrystal, maleic anhydride grafted polypropylene, antioxidant, and lubricant are premixed according to the weight parts to obtain a mixture; (b) the mixture is added into a twin-screw extruder, and melt extrusion and granulation are carried out to obtain the high-performance polypropylene composite material.

10. The method of producing a high performance polypropylene composite according to claim 9, characterized in that, In step (a), the premixing time is 3-5 min; and in step (b), the temperature range of each region of the twin-screw extruder is 180-210 ℃, and the screw rotation speed is 50-80 rpm.

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