Super-hydrophobic polypropylene plastic composite material and preparation method thereof

Abstract

The application discloses a super-hydrophobic polypropylene plastic composite material and a preparation method thereof, and relates to the technical field of high-performance polypropylene. The method comprises the following steps: dispersing and embedding hydrophobic modified nano silicon dioxide in a low-molecular-weight polymer wax matrix to prepare composite microspheres; grafting polydimethylsiloxane to polypropylene molecular chains to prepare polydimethylsiloxane grafted modified low-surface-energy master batches; performing surface hydrophobic modification treatment on natural tubular silicate minerals to prepare hydrophobic modified nanotubes; and melt blending polypropylene matrix resin, the composite microspheres, the low-surface-energy master batches, the hydrophobic modified nanotubes and processing aids, and then performing cooling solidification and molding to obtain the super-hydrophobic polypropylene composite material. The polypropylene plastic composite material prepared by the application has excellent super-hydrophobic performance.

Description

Technical Field

[0001] This invention relates to the field of high-performance polypropylene technology, specifically to a superhydrophobic polypropylene plastic composite material and its preparation method. Background Technology

[0002] Polypropylene (PP), one of the five major general-purpose plastics, is widely used in daily necessities, appliance housings, automotive parts, and building decoration materials due to its low density, excellent mechanical properties, good chemical corrosion resistance, and ease of processing and molding. However, the surface water contact angle of polypropylene materials is typically only 100°–105°, falling into the category of weak hydrophobicity. Under conditions such as outdoor use, kitchen and bathroom environments, and humid industrial settings, moisture easily adheres to and spreads on the surface of polypropylene products, leading to a series of problems such as dirt deposition, microbial growth, and accelerated surface aging, severely restricting the further promotion of polypropylene materials in high-end applications. Researchers both domestically and internationally have conducted extensive explorations into the hydrophobic modification of polypropylene materials. One approach is to reduce the surface energy of the material by physically blending hydrophobic fillers or hydrophobic agents into the polypropylene matrix. This method is simple, but the hydrophobic effect is limited and still falls far short of superhydrophobic standards. Another approach is to perform post-processing on the surface of polypropylene products, such as plasma etching, femtosecond laser processing, and chemical vapor deposition, to construct micro-nano rough structures on the surface. Although this can obtain superhydrophobic surfaces, the process is complex, the equipment investment is high, it is not suitable for continuous large-scale production, and the durability of the surface structure is often not ideal. Summary of the Invention

[0003] The purpose of this invention is to provide a superhydrophobic polypropylene plastic composite material and its preparation method, so as to solve the technical problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a superhydrophobic polypropylene plastic composite material includes the following steps: (1) Hydrophobically modified nano-silica is dispersed and embedded in a low molecular weight polymer wax matrix to prepare composite microspheres; (2) Polydimethylsiloxane was grafted onto the polypropylene molecular chain to obtain polydimethylsiloxane graft-modified low surface energy masterbatch. (3) Hydrophobic modification of natural tubular silicate minerals was performed to obtain hydrophobic modified nanotubes; (4) The polypropylene matrix resin, the composite microspheres, the low surface energy masterbatch, the hydrophobic modified nanotubes and processing aids are melt-blended, and then cooled, cured and shaped to obtain a superhydrophobic polypropylene composite material.

[0005] In the technical solution of this invention, the hydrophobic properties of polypropylene plastic composite materials are improved synergistically from the following aspects: (1) Constructing a multi-level micro-nano rough structure: First, the nano-silica is hydrophobically modified by a long-chain alkylsilane coupling agent, so that its surface changes from hydrophilic to hydrophobic; then, the hydrophobically modified nano-silica is uniformly dispersed and embedded in a molten low molecular weight polymer wax matrix, and multi-level composite microspheres are prepared by quenching, solidification and mechanical crushing. The composite microsphere itself is a multi-level structure in which nano-level hydrophobic particles are uniformly embedded in a micron-level wax carrier. In the subsequent melt blending and cooling solidification process, the polypropylene matrix crystallizes first due to its high crystallization temperature, and the low molecular weight polymer wax is repelled to the crystal boundary and material surface area due to its limited compatibility with the polypropylene crystal region, and crystallizes and solidifies at a lower temperature to form micron-level protrusions and island-like distribution; the hydrophobically modified nano-silica is embedded and anchored on the surface of these micron-level protrusions and the exposed surface of the polypropylene matrix, and self-assembles to construct a multi-level rough morphology of micron-level protrusions superimposed with nanoparticles. When a water droplet comes into contact with this multi-level rough surface, a large amount of air trapped in the pits and pores forms a stable air cushion layer, which greatly reduces the actual solid-liquid contact area and significantly increases the apparent water contact angle.

[0006] (2) Persistent reduction of surface free energy at the material bulk level: First, hydroxyl-terminated polydimethylsiloxane and amino-containing alkoxysilane undergo a dealcoholization condensation reaction under the action of a catalyst, introducing active amino functional groups at the end of the polydimethylsiloxane molecular chain to obtain an amino-terminated polydimethylsiloxane prepolymer; then, the prepolymer is uniformly coated on the surface of maleic anhydride-grafted polypropylene granules, and the primary amino groups at the end of the prepolymer undergo a ring-opening amidation reaction with the maleic anhydride groups on the polypropylene main chain through reactive extrusion, permanently grafting the polydimethylsiloxane segments onto the polypropylene molecular chain in a covalent manner to obtain a low surface energy masterbatch. Polydimethylsiloxane is one of the polymer materials with the lowest known surface energy. Its flexible silicon-oxygen main chain endows the molecular chain with extremely high segment mobility, and the regularly arranged methyl side groups form a dense low-energy surface shielding layer. During melt processing and cooling solidification, the grafted polydimethylsiloxane segments spontaneously migrate to the polymer-air interface under thermodynamic drive and preferentially accumulate, forming a continuous molecular-level low surface energy silicone thin layer on the outermost layer of the composite material. Unlike the traditional approach of physically adding silicone oil or small molecule hydrophobic agents, the chemically bonded polydimethylsiloxane segments will not be detached or lost due to water erosion, friction, or long-term use, fundamentally ensuring the long-term effectiveness and durability of the low surface energy modification effect. When this low surface energy layer is superimposed on the multi-level micro-nano rough structure constructed in the first aspect, the rough structure amplifies the solid-liquid interface effect, multiplying the advantages of low surface energy in the contact angle. The low surface energy layer, on the other hand, maintains the thermodynamic stability of the air cushion layer by reducing adhesion work. The synergistic effect of the two can significantly improve the water contact angle to a superhydrophobic level.

[0007] As a preferred step, the specific preparation process in step (1) includes: Nano-silica was dispersed in an alcohol solvent containing a small amount of deionized water, a long-chain alkylsilane coupling agent was added, and the mixture was refluxed under acidic conditions to undergo a condensation reaction. After separation, purification, drying and grinding, the hydrophobic modified nano-silica was obtained. The low molecular weight polymer wax is heated and melted, and then the hydrophobic modified nano-silica is added for high-speed shear dispersion. After being fully dispersed, it is rapidly quenched and solidified, and then mechanically crushed and sieved to obtain the composite microspheres.

[0008] Preferably, the nano-silica is fumed nano-silica with a particle size of 15-20 nm; the long-chain alkylsilane coupling agent is hexadecyltrimethoxysilane. The low molecular weight polymer wax is polyethylene wax with a number average molecular weight of 2000-4000.

[0009] Preferably, the mass ratio of the nano-silica to the long-chain alkylsilane coupling agent is 1:(0.2-0.4). The mass ratio of the polymer wax to the hydrophobically modified nano-silica is 100:(15-25).

[0010] As a priority, step (2) specifically includes the following preparation process: Hydroxyl-terminated polydimethylsiloxane and aminoalkylalkoxysilane undergo a de-alcoholization condensation reaction under the action of a catalyst, and after purification by vacuum distillation, an amino-terminated polydimethylsiloxane prepolymer is obtained. The amino-terminated polydimethylsiloxane prepolymer is uniformly coated onto the surface of maleic anhydride-grafted polypropylene granules, which are then fed into a twin-screw extruder for reactive extrusion. Chemical bonding is achieved through the ring-opening amidation reaction of the amino groups and maleic anhydride. After pelleting and drying, the low surface energy masterbatch is obtained.

[0011] As a preferred embodiment, the mass ratio of the terminal hydroxyl polydimethylsiloxane to the aminoalkylalkoxysilane is 100:(8-15); The mass ratio of amino-terminated polydimethylsiloxane prepolymer to maleic anhydride-grafted polypropylene is (10-20):100.

[0012] As a preferred step, the specific preparation process in step (3) includes: The natural tubular silicate mineral is subjected to high-temperature drying pretreatment to fully remove surface adsorbed water; the natural tubular silicate mineral is preferably halloysite nanotubes, whose characteristic tube length is distributed in the range of 0.5 to 2 μm; The dried halloysite nanotubes were ultrasonically dispersed in an alcohol-water mixed solvent, and a dodecyl silane coupling agent was added. Under acidic conditions, hydrolysis and dehydration condensation reactions were carried out, which anchored the dodecyl groups to the defects and edges of the halloysite outer tube wall. After washing and drying, the hydrophobic modified nanotubes were obtained.

[0013] This invention discovered in experiments that when nano-silica is released into the high-temperature melt after the polymer wax carrier melts, even after hydrophobic modification, it is still difficult to completely avoid collisional aggregation driven by residual surface energy, gradually forming large-sized aggregates. On the one hand, this severely weakens the fine and rough nanoscale structure; on the other hand, these isolated and closed aggregates form high specific surface area traps inside the material, physically trapping polydimethylsiloxane segments and hindering their migration and enrichment to the outermost surface of the material. This leads to the disruption of the continuity and integrity of the low surface energy thin layer, thereby limiting further improvement of the hydrophobic properties of polypropylene materials. To solve this technical problem, this invention selects natural tubular silicate minerals and uses a silane coupling agent containing dodecyl groups to perform surface hydrophobic modification treatment on the outer tube wall. After hydrolysis, the methoxy group of the dodecylsilane coupling agent undergoes a dehydration condensation reaction with the silanol groups at the defects and edges of the tube wall, anchoring the dodecyl group to the tube wall surface via covalent bonds. This transforms the outer surface of the natural tubular mineral from hydrophilic to hydrophobic, significantly improving its interfacial compatibility with the nonpolar polypropylene matrix. This ensures that the hydrophobically modified nanotubes can be uniformly dispersed in the polypropylene matrix during melt blending without self-aggregation. Halloysite nanotubes (M-HNTs) are a natural tubular silicate mineral with a characteristic tube length of 0.5–2 μm, falling precisely in the submicron to micron mesoscopic range between nano-silica (15–20 nm) and polyethylene wax microspheres (tens to hundreds of micrometers). M-HNTs form a three-dimensional interconnected tubular fiber network framework in the polypropylene melt. Through steric hindrance, SiO2 nanoparticles are confined within the interwoven fiber microcells, effectively blocking collision and aggregation paths between nanoparticles, fundamentally inhibiting secondary aggregation, and allowing the nanoscale fine-rough structure to be fully preserved. Furthermore, M-HNTs, with their tube length of 0.5–2 μm, compensate for the roughness difference between nano-SiO2 and PE wax microspheres, upgrading the multi-level roughness structure from a nano-micron secondary system to a nano-submicron-micron tertiary system. Simultaneously, because M-HNTs eliminate the aggregate traps that trap polydimethylsiloxane segments, these segments can resume their normal migration and enrichment behavior at the polymer-air interface, forming a more continuous and uniform low surface energy coating layer. These effects further improve the hydrophobic properties of polypropylene materials.

[0014] Preferably, the mass ratio of the dried halloysite nanotubes to the dodecyl silane coupling agent is (4-6):1.

[0015] As a preference, in step (4), based on 100 parts by weight of polypropylene matrix resin, the amounts of the remaining components are 5 to 15 parts of composite microspheres, 8 to 20 parts of low surface energy masterbatch, and 2 to 8 parts of hydrophobic modified nanotubes.

[0016] A superhydrophobic polypropylene plastic composite material is prepared by the method described above.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. By embedding hydrophobically modified nano-silica into polymer wax microspheres, a composite morphology of micron-sized protrusions superimposed on nanoparticles is formed on the material surface through self-assembly. This effectively traps air, significantly reduces the solid-liquid contact area, and thus significantly increases the water contact angle.

[0018] 2. Low surface energy polydimethylsiloxane is permanently grafted onto the polypropylene backbone via reactive extrusion, forming a molecular-level organosilicon thin layer on the material surface. This solves the problem of easy loss of hydrophobic effect caused by physical addition, fundamentally ensuring the long-term durability of hydrophobic modification effect, and synergistically enhancing the effect with the rough structure to achieve superhydrophobicity.

[0019] 3. By using hydrophobically modified halloysite nanotubes of specific sizes, a three-dimensional network framework is constructed in the matrix. The secondary aggregation of nano-silica is effectively blocked by steric hindrance. At the same time, its mesoscopic size makes up for the roughness difference in the original structure, making the multi-level rough structure more perfect and ensuring that low surface energy materials can migrate and accumulate smoothly to form a more continuous and uniform hydrophobic layer. Attached Figure Description

[0020] Figure 1 This is a low-magnification SEM image of the surface of the superhydrophobic polypropylene plastic composite material prepared in Example 1 of the present invention.

[0021] Figure 2 This is a high-magnification SEM image of the surface of the superhydrophobic polypropylene plastic composite material prepared in Example 1 of the present invention. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0023] Example 1 A method for preparing a superhydrophobic polypropylene plastic composite material includes the following steps: Step (1): 20g of fumed silica nanoparticles (particle size 15-20nm) were ultrasonically dispersed in 400mL of anhydrous ethanol containing 5mL of deionized water. Then, 7g of hexadecyltrimethoxysilane was added, and glacial acetic acid was added dropwise to adjust the pH of the system to 4.5. The system was refluxed and condensed at 70℃ for 4h. After centrifugation, washing, vacuum drying at 80℃, and grinding, hydrophobic modified silica nanoparticles were obtained. 100g of polyethylene wax (number average molecular weight 3000) was heated to 130℃ to melt it completely. Then, 23g of the above hydrophobic modified silica nanoparticles were added in batches and dispersed at a high speed of 2500r / min for 15min. After full dispersion, the mixture was quickly poured into ice water at 5℃ for quenching and solidification. The mixture was then mechanically crushed and passed through an 80-mesh sieve to obtain composite microspheres.

[0024] Step (2): 100g of hydroxyl-terminated polydimethylsiloxane and 13g of aminopropylmethyldiethoxysilane were subjected to a de-alcoholization condensation reaction at 80°C under nitrogen protection for 6h in the presence of 0.1g dibutyltin dilaurate catalyst. Then, the mixture was purified by vacuum distillation at 100°C and 0.01MPa for 2h to obtain an amino-terminated polydimethylsiloxane prepolymer. 18g of the amino-terminated polydimethylsiloxane prepolymer was uniformly sprayed onto the surface of 100g of maleic anhydride-grafted polypropylene granules and quantitatively fed into a twin-screw extruder for blending and melt extrusion. The temperatures of each zone of the screw were set sequentially from the feed port to the die head as follows: Zone 1 175°C, Zone 2 185°C, Zone 3 190°C, Zone 4 195°C, Zone 5 190°C, and Die head 185°C. Chemical bonding was achieved through the ring-opening amidation reaction of the amino groups and maleic anhydride. After cooling, pelletizing, and drying at 80°C for 4h, low surface energy masterbatch was obtained.

[0025] Step (3): 30g halloysite nanotubes (characteristic tube length 0.5-2μm) were spread flat in a porcelain dish and pretreated at 105℃ for 12h to fully remove surface adsorbed water; 22g of dried halloysite nanotubes were ultrasonically dispersed in 300mL of anhydrous ethanol, 4g of dodecyltrimethoxysilane and 2mL of deionized water were added, and glacial acetic acid was added dropwise to adjust the pH value to 4.0. The mixture was refluxed and stirred at 70℃ for 6h to carry out hydrolysis and dehydration condensation reaction, so that the dodecyl group was anchored to the defects and edges of the halloysite outer tube wall. After centrifugation and washing, the reaction solution was vacuum dried at 80℃ for 10h to obtain hydrophobically modified nanotubes.

[0026] Step (4): Weigh 100 parts of isotactic polypropylene matrix resin, 13 parts of the above composite microspheres, 18 parts of the above low surface energy masterbatch, 6 parts of the above hydrophobic modified nanotubes, 0.15 parts of antioxidant 1010, 0.15 parts of antioxidant 168 and 0.3 parts of calcium stearate, and put all the above components into a high-speed mixer and mix them evenly; then feed the material into a twin-screw extruder for co-melt extrusion. The temperature of each zone of the screw from the feed port to the die head is set as follows: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 210℃, Zone 5 205℃, and the die head 200℃. Cool and pelletize and dry; finally, place the obtained pellets in a flat vulcanizing machine and perform hot pressing molding at 210℃ and 12MPa pressure for 5 minutes, and cool and solidify to 40℃ under pressure to demold, thus obtaining the superhydrophobic polypropylene composite material.

[0027] Example 2 A method for preparing a superhydrophobic polypropylene plastic composite material includes the following steps: Step (1): 20g of fumed silica nanoparticles (particle size 15-20nm) were ultrasonically dispersed in 400mL of anhydrous ethanol containing 5mL of deionized water. Then, 5g of hexadecyltrimethoxysilane was added, and glacial acetic acid was added dropwise to adjust the pH of the system to 4.5. The system was refluxed and condensed at 70℃ for 4h. After centrifugation, washing, vacuum drying at 80℃, and grinding, hydrophobic modified silica nanoparticles were obtained. 100g of polyethylene wax (number average molecular weight 3000) was heated to 130℃ to melt it completely. Then, 18g of the above hydrophobic modified silica nanoparticles were added in batches and dispersed at a high speed of 2500r / min for 15min. After full dispersion, the mixture was quickly poured into ice water at 5℃ for quenching and solidification. The mixture was then mechanically crushed and passed through an 80-mesh sieve to obtain composite microspheres.

[0028] Step (2): 100g of hydroxyl-terminated polydimethylsiloxane and 9g of aminopropylmethyldiethoxysilane were subjected to a de-alcoholization condensation reaction at 80°C under nitrogen protection for 6h in the presence of 0.1g dibutyltin dilaurate catalyst. Then, the mixture was purified by vacuum distillation at 100°C and 0.01MPa for 2h to obtain an amino-terminated polydimethylsiloxane prepolymer. 12g of the amino-terminated polydimethylsiloxane prepolymer was uniformly sprayed onto the surface of 100g of maleic anhydride-grafted polypropylene granules and quantitatively fed into a twin-screw extruder for blending and melt extrusion. The temperatures of each zone of the screw were set sequentially from the feed port to the die head as follows: Zone 1 175°C, Zone 2 185°C, Zone 3 190°C, Zone 4 195°C, Zone 5 190°C, and Die head 185°C. Chemical bonding was achieved through the ring-opening amidation reaction of the amino groups and maleic anhydride. After cooling, pelletizing, and drying at 80°C for 4h, low surface energy masterbatch was obtained.

[0029] Step (3): 30g halloysite nanotubes (characteristic tube length 0.5-2μm) were spread flat in a porcelain dish and pretreated at 105℃ for 12h to fully remove surface adsorbed water; 18g of dried halloysite nanotubes were ultrasonically dispersed in 300mL of anhydrous ethanol, 4g of dodecyltrimethoxysilane and 2mL of deionized water were added, and glacial acetic acid was added dropwise to adjust the pH value to 4.0. The mixture was refluxed and stirred at 70℃ for 6h to carry out hydrolysis and dehydration condensation reaction, so that the dodecyl group was anchored to the defects and edges of the halloysite outer tube wall. After centrifugation and washing, the reaction solution was vacuum dried at 80℃ for 10h to obtain hydrophobically modified nanotubes.

[0030] Step (4): Weigh 100 parts of isotactic polypropylene matrix resin, 7 parts of the above composite microspheres, 10 parts of the above low surface energy masterbatch, 4 parts of the above hydrophobic modified nanotubes, 0.15 parts of antioxidant 1010, 0.15 parts of antioxidant 168 and 0.3 parts of calcium stearate, and put all the above components into a high-speed mixer and mix them evenly; then feed the material into a twin-screw extruder for co-melt extrusion. The temperature of each zone of the screw from the feed port to the die head is set as follows: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 210℃, Zone 5 205℃, and the die head 200℃. Cool and granulate and dry; finally, place the obtained granules in a flat vulcanizing machine and perform hot pressing molding at 210℃ and 12MPa pressure for 5 minutes, and cool and solidify to 40℃ under pressure to demold, thus obtaining the superhydrophobic polypropylene composite material.

[0031] Example 3 A method for preparing a superhydrophobic polypropylene plastic composite material includes the following steps: Step (1): 20g of fumed silica nanoparticles (particle size 15-20nm) were ultrasonically dispersed in 400mL of anhydrous ethanol containing 5mL of deionized water. Then, 6g of hexadecyltrimethoxysilane was added, and glacial acetic acid was added dropwise to adjust the pH of the system to 4.5. The system was refluxed and condensed at 70℃ for 4h. After centrifugation, washing, vacuum drying at 80℃, and grinding, hydrophobic modified silica nanoparticles were obtained. 100g of polyethylene wax (number average molecular weight 3000) was heated to 130℃ to melt it completely. Then, the above 20g of hydrophobic modified silica nanoparticles were added in batches and dispersed at a high speed of 2500r / min for 15min. After full dispersion, the mixture was quickly poured into ice water at 5℃ for quenching and solidification. The mixture was then mechanically crushed and passed through an 80-mesh sieve to obtain composite microspheres.

[0032] Step (2): 100g of hydroxyl-terminated polydimethylsiloxane and 10g of aminopropylmethyldiethoxysilane were subjected to a de-alcoholization condensation reaction at 80°C under nitrogen protection for 6h in the presence of 0.1g dibutyltin dilaurate catalyst. Then, the mixture was purified by vacuum distillation at 100°C and 0.01MPa for 2h to obtain an amino-terminated polydimethylsiloxane prepolymer. 15g of the amino-terminated polydimethylsiloxane prepolymer was uniformly sprayed onto the surface of 100g of maleic anhydride-grafted polypropylene granules and quantitatively fed into a twin-screw extruder for blending and melt extrusion. The temperatures of each zone of the screw were set sequentially from the feed port to the die head as follows: Zone 1 175°C, Zone 2 185°C, Zone 3 190°C, Zone 4 195°C, Zone 5 190°C, and Die head 185°C. Chemical bonding was achieved through the ring-opening amidation reaction of the amino groups and maleic anhydride. After cooling, pelletizing, and drying at 80°C for 4h, low surface energy masterbatch was obtained.

[0033] Step (3): 30g halloysite nanotubes (characteristic tube length 0.5-2μm) were spread flat in a porcelain dish and pretreated at 105℃ for 12h to fully remove surface adsorbed water; 20g of dried halloysite nanotubes were ultrasonically dispersed in 300mL of anhydrous ethanol, 4g of dodecyltrimethoxysilane and 2mL of deionized water were added, and glacial acetic acid was added dropwise to adjust the pH value to 4.0. The mixture was refluxed and stirred at 70℃ for 6h to carry out hydrolysis and dehydration condensation reaction, so that the dodecyl group was anchored to the defects and edges of the halloysite outer tube wall. After centrifugation and washing, the reaction solution was vacuum dried at 80℃ for 10h to obtain hydrophobically modified nanotubes.

[0034] Step (4): Weigh 100 parts of isotactic polypropylene matrix resin, 10 parts of the above composite microspheres, 12 parts of the above low surface energy masterbatch, 5 parts of the above hydrophobic modified nanotubes, 0.15 parts of antioxidant 1010, 0.15 parts of antioxidant 168 and 0.3 parts of calcium stearate, and put all the above components into a high-speed mixer and mix them evenly; then feed the material into a twin-screw extruder for co-melt extrusion. The temperature of each zone of the screw from the feed port to the die head is set as follows: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 210℃, Zone 5 205℃, and the die head 200℃. Cool and pelletize and dry; finally, place the obtained pellets in a flat vulcanizing machine and perform hot pressing molding at 210℃ and 12MPa pressure for 5 minutes, and cool and solidify at 40℃ while maintaining pressure to demold, thus obtaining the superhydrophobic polypropylene composite material.

[0035] Example 4 A method for preparing a superhydrophobic polypropylene plastic composite material includes the following steps: Step (1): 20g of fumed silica nanoparticles (particle size 15-20nm) were ultrasonically dispersed in 400mL of anhydrous ethanol containing 5mL of deionized water. Then, 8g of hexadecyltrimethoxysilane was added, and glacial acetic acid was added dropwise to adjust the pH of the system to 4.5. The system was refluxed and condensed at 70℃ for 4h. After centrifugation, washing, vacuum drying at 80℃, and grinding, hydrophobic modified silica nanoparticles were obtained. 100g of polyethylene wax (number average molecular weight 4000) was heated to 130℃ to melt it completely. Then, 25g of the above hydrophobic modified silica nanoparticles were added in batches and dispersed at a high speed of 2500r / min for 15min. After full dispersion, the silica nanoparticles were quickly poured into ice water at 5℃ for quenching and solidification. After mechanical crushing and passing through an 80-mesh sieve, composite microspheres were obtained.

[0036] Step (2): 100g of hydroxyl-terminated polydimethylsiloxane and 15g of aminopropylmethyldiethoxysilane were subjected to a de-alcoholization condensation reaction at 80℃ under nitrogen protection for 6h in the presence of 0.1g dibutyltin dilaurate catalyst. Then, the mixture was purified by vacuum distillation at 100℃ and 0.01MPa for 2h to obtain an amino-terminated polydimethylsiloxane prepolymer. 20g of the amino-terminated polydimethylsiloxane prepolymer was uniformly sprayed onto the surface of 100g of maleic anhydride-grafted polypropylene granules and quantitatively fed into a twin-screw extruder for blending and melt extrusion. The temperatures of each zone of the screw were set sequentially from the feed port to the die head as follows: Zone 1 175℃, Zone 2 185℃, Zone 3 190℃, Zone 4 195℃, Zone 5 190℃, and Die head 185℃. Chemical bonding was achieved through the ring-opening amidation reaction of amino groups and maleic anhydride. After cooling, pelletizing, and drying at 80℃ for 4h, low surface energy masterbatch was obtained.

[0037] Step (3): 30g halloysite nanotubes (characteristic tube length 0.5-2μm) were spread flat in a porcelain dish and pretreated at 105℃ for 12h to fully remove surface adsorbed water; 24g of dried halloysite nanotubes were ultrasonically dispersed in 300mL of anhydrous ethanol, 4g of dodecyltrimethoxysilane and 2mL of deionized water were added, and glacial acetic acid was added dropwise to adjust the pH value to 4.0. The mixture was refluxed and stirred at 70℃ for 6h to carry out hydrolysis and dehydration condensation reaction, so that the dodecyl group was anchored to the defects and edges of the halloysite outer tube wall. After centrifugation and washing, the reaction solution was vacuum dried at 80℃ for 10h to obtain hydrophobically modified nanotubes.

[0038] Step (4): Weigh 100 parts of isotactic polypropylene matrix resin, 15 parts of the above composite microspheres, 20 parts of the above low surface energy masterbatch, 8 parts of the above hydrophobic modified nanotubes, 0.15 parts of antioxidant 1010, 0.15 parts of antioxidant 168 and 0.3 parts of calcium stearate, and put all the above components into a high-speed mixer and mix them evenly; then feed the material into a twin-screw extruder for co-melt extrusion. The temperature of each zone of the screw from the feed port to the die head is set as follows: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 210℃, Zone 5 205℃, and the die head 200℃. Cool and granulate and dry; finally, place the obtained granules in a flat vulcanizing machine and perform hot pressing molding at 210℃ and 12MPa pressure for 5 minutes, and cool and solidify to 40℃ under pressure to demold, thus obtaining the superhydrophobic polypropylene composite material.

[0039] Example 5 A method for preparing a superhydrophobic polypropylene plastic composite material includes the following steps: Step (1): 20g of fumed silica nanoparticles (particle size 15-20nm) were ultrasonically dispersed in 400mL of anhydrous ethanol containing 5mL of deionized water. Then, 4g of hexadecyltrimethoxysilane was added, and glacial acetic acid was added dropwise to adjust the pH of the system to 4.5. The system was refluxed and condensed at 70℃ for 4h. After centrifugation, washing, vacuum drying at 80℃, and grinding, hydrophobic modified silica nanoparticles were obtained. 100g of polyethylene wax (number average molecular weight 2000) was heated to 130℃ to melt it completely. Then, 15g of the above hydrophobic modified silica nanoparticles were added in batches and dispersed at a high speed of 2500r / min for 15min. After full dispersion, the mixture was quickly poured into ice water at 5℃ for quenching and solidification. The mixture was then mechanically crushed and passed through an 80-mesh sieve to obtain composite microspheres.

[0040] Step (2): 100g of hydroxyl-terminated polydimethylsiloxane and 8g of aminopropylmethyldiethoxysilane were subjected to a de-alcoholization condensation reaction at 80°C under nitrogen protection for 6h in the presence of 0.1g dibutyltin dilaurate catalyst. Then, the mixture was purified by vacuum distillation at 100°C and 0.01MPa for 2h to obtain an amino-terminated polydimethylsiloxane prepolymer. 10g of the amino-terminated polydimethylsiloxane prepolymer was uniformly sprayed onto the surface of 100g of maleic anhydride-grafted polypropylene granules and quantitatively fed into a twin-screw extruder for blending and melt extrusion. The temperatures of each zone of the screw were set sequentially from the feed port to the die head as follows: Zone 1 175°C, Zone 2 185°C, Zone 3 190°C, Zone 4 195°C, Zone 5 190°C, and Die head 185°C. Chemical bonding was achieved through the ring-opening amidation reaction of the amino groups and maleic anhydride. After cooling, pelletizing, and drying at 80°C for 4h, a low surface energy masterbatch was obtained.

[0041] Step (3): 30g halloysite nanotubes (characteristic tube length 0.5-2μm) were spread flat in a porcelain dish and pretreated at 105℃ for 12h to fully remove surface adsorbed water; 16g of dried halloysite nanotubes were ultrasonically dispersed in 300mL of anhydrous ethanol, 4g of dodecyltrimethoxysilane and 2mL of deionized water were added, and glacial acetic acid was added dropwise to adjust the pH value to 4.0. The mixture was refluxed and stirred at 70℃ for 6h to carry out hydrolysis and dehydration condensation reaction, so that the dodecyl group was anchored to the defects and edges of the halloysite outer tube wall. After centrifugation and washing, the reaction solution was vacuum dried at 80℃ for 10h to obtain hydrophobically modified nanotubes.

[0042] Step (4): Weigh 100 parts of isotactic polypropylene matrix resin, 5 parts of the above composite microspheres, 8 parts of the above low surface energy masterbatch, 2 parts of the above hydrophobic modified nanotubes, 0.15 parts of antioxidant 1010, 0.15 parts of antioxidant 168 and 0.3 parts of calcium stearate, and put all the above components into a high-speed mixer and mix them evenly; then feed the material into a twin-screw extruder for co-melt extrusion. The temperature of each zone of the screw from the feed port to the die head is set as follows: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 210℃, Zone 5 205℃, and the die head 200℃. Cool and granulate and dry; finally, place the obtained granules in a flat vulcanizing machine and perform hot pressing molding at 210℃ and 12MPa pressure for 5 minutes, and cool and solidify to 40℃ under pressure to demold, thus obtaining the superhydrophobic polypropylene composite material.

[0043] Comparative Example 1: Compared with Example 4, no composite microspheres were added (the composite microspheres were removed in step four, and the remaining components and process conditions were exactly the same), which was used to verify the contribution of the multi-level micro-nano rough structure to the superhydrophobic performance.

[0044] Comparative Example 2: Compared with Example 4, no low surface energy masterbatch was added (the low surface energy masterbatch was removed in step four, and the remaining components and process conditions were exactly the same), which was used to verify the contribution of the low surface energy layer provided by polydimethylsiloxane graft modification to the superhydrophobic properties.

[0045] Comparative Example 3: Compared with Example 4, no hydrophobically modified nanotubes M-HNTs were added (the hydrophobically modified nanotubes were removed in step four, and the remaining components and process conditions were exactly the same), which was used to verify the synergistic effect of the three-dimensional fiber network framework of M-HNTs on inhibiting nanoparticle aggregation and promoting PDMS segment migration and enrichment.

[0046] Comparative Example 4: Compared with Example 4, in step one, the nano-silica was not subjected to hexadecyltrimethoxysilane hydrophobic modification treatment. Instead, the unmodified nano-silica was directly dispersed and embedded in polyethylene wax to prepare composite microspheres (the other components and process conditions were exactly the same). This was used to verify the effect of surface hydrophobic modification of nano-silica on the construction effect of rough structure.

[0047] Comparative Example 5: Compared with Example 4, the polyethylene wax embedding method was not used in step one. Instead, hydrophobic modified nano-silica was directly added to the polypropylene matrix in powder form in step 4 for melt blending (the polyethylene wax component in the composite microspheres was removed, and the remaining components and process conditions were exactly the same) to verify the necessity of the crystallization repulsion mechanism of the polyethylene wax carrier for the formation of the surface micron-level rough structure.

[0048] Comparative Example 6: Compared with Example 4, in step two, a chemically grafted low surface energy masterbatch was not prepared. Instead, in the melt blending of step four, an equal amount of polydimethylsiloxane silicone oil was directly physically blended (the remaining components and process conditions were exactly the same) to verify the superiority of the chemical bonding grafting method over the physical blending method in terms of the durability of low surface energy modification.

[0049] Comparative Example 7: Compared with Example 4, in step three, halloysite nanotubes were not subjected to dodecyltrimethoxysilane hydrophobic modification. Unmodified halloysite nanotubes were directly added to the melt blending system in step four (the remaining components and process conditions were exactly the same) to verify the effect of hydrophobic modification of the halloysite nanotube surface on its uniform dispersion in the polypropylene matrix and its effective construction of a three-dimensional network framework. Performance testing: (1) Water contact angle test: The static water contact angle of each sample was determined using an optical contact angle meter (droplet method). A 5 μL deionized water droplet was used as the probe droplet and gently placed on the sample surface using a microsyringe. The droplet was collected after stabilizing for 3 seconds in a constant temperature and humidity environment of 25 ± 1 °C and 50 ± 5% relative humidity. The instrument software automatically fitted the droplet profile and calculated the contact angle. Five different locations were randomly selected on the surface of each sample for measurement, and the arithmetic mean of the five measurements was taken as the water contact angle test result for that sample.

[0050] (2) Roll-off angle test: Performed on the tiltable sample stage of the contact angle measuring instrument. Fix the sample horizontally on the tilting stage, and gently place a 10 μL drop of deionized water on the sample surface using a microsyringe. Tilt the sample stage slowly at a rate of 0.5° / s, and record the angle between the sample stage and the horizontal plane when the water droplet begins to roll. This is the roll-off angle. Measure each sample 5 times and take the average value. If the water droplet does not roll when tilted to 35°, it is recorded as ">35°".

[0051] (3) Abrasion resistance test: Place the sample face down on the surface of 800-grit wet sandpaper, apply a uniform normal pressure of 5 kPa above the sample (achieved by placing a weight of appropriate mass), and push the sample 10 cm at a uniform speed in the same direction as one abrasion cycle. After completing one cycle, rotate the sample 90° in place, and then push it 10 cm in the new direction to complete the second cycle. Repeat this process until a total of 100 abrasion cycles are completed. Remove the sample and retest its water contact angle according to the above method (1).

[0052] (4) UV aging resistance test: The sample was placed in a UV accelerated aging test chamber with a UV lamp wavelength of 340nm and an irradiation intensity of 0.77W / (m²). 2 ·nm), blackboard temperature 60±3℃, after continuous irradiation for 200h, take out the sample, gently wipe the surface with a lint-free cloth, and then retest its water contact angle according to the above method (1).

[0053] (5) Tensile strength test: The composite material granules prepared in each embodiment and comparative example (obtained by extrusion cutting in step 4) were injection molded into 1A dumbbell-shaped standard tensile specimens on an injection molding machine (Note: the superhydrophobic performance test specimens were hot-pressed to retain the surface functional structure, while the mechanical property test specimens were injection molded to meet the geometric requirements of the standard specimens). Tensile tests were performed on a universal testing machine at a tensile rate of 50 mm / min, and the maximum tensile strength at the time of specimen fracture was recorded. The average value of 5 specimens in each group of tests was taken.

[0054] (6) Notched impact strength test of simply supported beam: The composite material granules prepared in each embodiment and comparative example were injection molded into standard impact specimens of 80mm×10mm×4mm. A V-shaped notch was machined in the middle of the specimen (notch depth 2mm, notch bottom curvature radius 0.25mm). Impact test was performed on a simply supported beam pendulum impact testing machine, and the notched impact strength of the specimens was recorded. The average value of 5 specimens in each group was taken.

[0055] Table 1: Test Results of Examples and Comparative Samples As shown in the table above, Examples 1-5 all achieved superhydrophobic effects with a water contact angle >150° and a roll-off angle <10°. Furthermore, after 100 cycles of sandpaper abrasion and 200 hours of UV aging, the water contact angle remained above 147°, demonstrating excellent durability. Comparative Example 1 (without composite microspheres) had a water contact angle of only 122.3°, indicating that without a multi-level micro / nano rough structure, a low surface energy layer alone cannot achieve superhydrophobicity. Comparative Example 2 (without low surface energy masterbatch) had a water contact angle of only 127.4°, indicating that without a low surface energy coating layer, a rough structure alone cannot achieve superhydrophobicity. Both examples demonstrate the necessity of structure-energy synergy. Comparative Example 3 (without M-HNTs) had a water contact angle of 137.2°, a difference of 20.1° from Example 4's 157.3°, confirming the crucial role of M-HNTs as a synergistic component in inhibiting nanoparticle aggregation and promoting PDMS migration and enrichment. The water contact angles of Comparative Example 4 (unmodified SiO2) and Comparative Example 5 (without PE wax encapsulation) were 130.8° and 133.5°, respectively, indicating that hydrophobic modification of nano-silica and the carrier encapsulation strategy of polyethylene wax are both indispensable for constructing an effective multi-level rough structure. Comparative Example 6 (physically blended silicone oil replacing chemically grafted PDMS) had an initial water contact angle of 151.6°, close to that of Example 4, but after 100 wear cycles, the water contact angle plummeted to 117.3° (Example 4 only decreased from 157.3° to 153.8°), fully demonstrating that the chemically bonded grafting method is significantly superior to the physical blending method in terms of hydrophobic durability. The water contact angle of Comparative Example 7 (unmodified HNTs) was 140.3°, lower than the 157.3° of Example 4, indicating that hydrophobic modification of HNTs is a prerequisite for their uniform dispersion in the polypropylene matrix and the effective construction of a three-dimensional network framework.

[0056] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the essence and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a superhydrophobic polypropylene plastic composite material, characterized in that, Includes the following steps: (1) Hydrophobically modified nano-silica is dispersed and embedded in a low molecular weight polymer wax matrix to prepare composite microspheres; (2) Polydimethylsiloxane was grafted onto the polypropylene molecular chain to obtain polydimethylsiloxane graft-modified low surface energy masterbatch. (3) Hydrophobic modification of natural tubular silicate minerals was performed to obtain hydrophobic modified nanotubes; (4) The polypropylene matrix resin, the composite microspheres, the low surface energy masterbatch, the hydrophobic modified nanotubes and processing aids are melt-blended, and then cooled, cured and shaped to obtain a superhydrophobic polypropylene composite material.

2. The method for preparing a superhydrophobic polypropylene plastic composite material according to claim 1, characterized in that, In step (1), the specific preparation process includes: Nano-silica was dispersed in an alcohol solvent containing a small amount of deionized water, a long-chain alkylsilane coupling agent was added, and the mixture was refluxed under acidic conditions to undergo a condensation reaction. After separation, purification, drying and grinding, the hydrophobic modified nano-silica was obtained. The low molecular weight polymer wax is heated and melted, and then the hydrophobic modified nano-silica is added for high-speed shear dispersion. After being fully dispersed, it is rapidly quenched and solidified, and then mechanically crushed and sieved to obtain the composite microspheres.

3. The method for preparing a superhydrophobic polypropylene plastic composite material according to claim 2, characterized in that, The nano-silica is fumed nano-silica with a particle size of 15-20 nm; the long-chain alkylsilane coupling agent is hexadecyltrimethoxysilane. The low molecular weight polymer wax is polyethylene wax with a number average molecular weight of 2000-4000.

4. The method for preparing a superhydrophobic polypropylene plastic composite material according to claim 2, characterized in that, The mass ratio of the nano-silica to the long-chain alkylsilane coupling agent is 1:(0.2-0.4). The mass ratio of the polymer wax to the hydrophobically modified nano-silica is 100:(15-25).

5. The method for preparing a superhydrophobic polypropylene plastic composite material according to claim 1, characterized in that, In step (2), the specific preparation process includes: Hydroxyl-terminated polydimethylsiloxane and aminoalkylalkoxysilane undergo a de-alcoholization condensation reaction under the action of a catalyst, and after purification by vacuum distillation, an amino-terminated polydimethylsiloxane prepolymer is obtained. The amino-terminated polydimethylsiloxane prepolymer is uniformly coated onto the surface of maleic anhydride-grafted polypropylene granules, which are then fed into a twin-screw extruder for reactive extrusion. Chemical bonding is achieved through the ring-opening amidation reaction of the amino groups and maleic anhydride. After pelleting and drying, the low surface energy masterbatch is obtained.

6. The method for preparing a superhydrophobic polypropylene plastic composite material according to claim 5, characterized in that, The mass ratio of the terminal hydroxyl polydimethylsiloxane to the aminoalkylalkoxysilane is 100:(8-15); The mass ratio of amino-terminated polydimethylsiloxane prepolymer to maleic anhydride-grafted polypropylene is (10-20):

100.

7. The method for preparing a superhydrophobic polypropylene plastic composite material according to claim 1, characterized in that, In step (3), the specific preparation process includes: The natural tubular silicate mineral is subjected to high-temperature drying pretreatment to fully remove surface adsorbed water; the natural tubular silicate mineral is preferably halloysite nanotubes, whose characteristic tube length is distributed in the range of 0.5 to 2 μm; The dried halloysite nanotubes were ultrasonically dispersed in an alcohol-water mixed solvent, and a dodecyl silane coupling agent was added. Under acidic conditions, hydrolysis and dehydration condensation reactions were carried out, which anchored the dodecyl groups to the defects and edges of the halloysite outer tube wall. After washing and drying, the hydrophobic modified nanotubes were obtained.

8. The method for preparing a superhydrophobic polypropylene plastic composite material according to claim 7, characterized in that, The mass ratio of the dried halloysite nanotubes to the dodecyl silane coupling agent is (4-6):

1.

9. The method for preparing a superhydrophobic polypropylene plastic composite material according to claim 1, characterized in that, In step (4), based on 100 parts by weight of polypropylene matrix resin, the amounts of the remaining components are 5 to 15 parts of composite microspheres, 8 to 20 parts of low surface energy masterbatch, and 2 to 8 parts of hydrophobic modified nanotubes.

10. A superhydrophobic polypropylene plastic composite material, characterized in that, It is prepared by the method described in any one of claims 1 to 9 above.

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