Graphene-silicone core-shell defoamer and preparation method thereof

Abstract

The application discloses a kind of graphene-silicone core-shell defoaming agent and preparation method thereof, defoaming agent has the core-shell structure with graphene as core, silicone as shell, both synergies, so that defoaming agent monodispersity is good and can stably play defoaming function at high temperature, preparation method first natural flake graphite oxidation peeling, to prepare graphene oxide dispersion liquid;While preparing PDMS prepolymer, graphene oxide dispersion liquid is added dropwise into PDMS prepolymer system, so that silicone monomer occurs graft polymerization reaction on the surface of graphene oxide.Subsequently, the reaction product is reduced and treated, so that graphene oxide is converted into reduced graphene oxide, and a core-shell structure is formed.After centrifugal separation, washing and vacuum drying, a graphene-silicone core-shell defoaming agent is obtained.The application solves the problems of poor dispersibility, weak interfacial adhesion and insufficient high temperature resistance of existing defoaming agents during the molding process of polymer materials, and improves the defoaming efficiency and product quality.

Description

Technical Field

[0001] This invention relates to the field of polymer material additives preparation technology, and in particular to a graphene-organosilicon core-shell defoamer and its preparation method. Background Technology

[0002] In the field of polymer molding, such as the production of rotationally molded nylon products, air bubbles have always been a key factor affecting product quality. The presence of air bubbles not only reduces the appearance quality of the product but also leads to a decrease in its mechanical properties, such as strength and toughness. Therefore, the application of defoamers is crucial to solving this problem.

[0003] Traditional silicone defoamers, while possessing excellent defoaming effects, suffer from poor dispersibility, easy migration, and insufficient high-temperature resistance in polymer systems, making them unsuitable for high-temperature molding processes such as rotational molding. Graphene, as a novel nanomaterial, exhibits superior mechanical properties, thermal conductivity, and a large specific surface area. Combining it with silicone holds promise for developing defoamers with even better performance.

[0004] Currently, the method of preparing defoamers by combining graphene and organosilicon has the following shortcomings: First, graphene is prone to agglomeration and is difficult to disperse uniformly in organosilicon; second, the interfacial bonding between the two is weak, resulting in unstable performance of the composite defoamer. Summary of the Invention

[0005] To address the aforementioned shortcomings, this invention proposes a graphene-organosilicon core-shell defoamer and its preparation method, thereby solving the problems of poor dispersibility, weak interfacial bonding, and insufficient high-temperature resistance of existing defoamers in the molding process of polymer materials, and improving defoaming efficiency and product quality.

[0006] The present invention provides the following technical solution: a graphene-organosilicon core-shell defoamer, wherein the defoamer has a core-shell structure with a particle size of 50-100nm. The core-shell structure uses graphene as the core to puncture bubbles and organosilicon as the shell to reduce surface tension. The two work synergistically to make the defoamer have good monodispersity and can stably exert its defoaming effect at a rotational molding temperature of 240-260℃.

[0007] As an improvement, the amount of defoamer added during the molding process of polymer materials to eliminate bubbles is 0.1-0.5% of the mass of the polymer material. This allows the defoamer to eliminate bubbles, ensuring that the bubble rate in the polymer material is no more than 3.8%, while also increasing the tensile strength of the polymer material by 20%-30% and the impact strength by 15%-25% compared to the system without defoamer.

[0008] As an improvement, the polymer material is nylon, and the molding process is rotational molding.

[0009] As an improvement, the preparation method of any of the graphene-organosilicon core-shell defoamers described above includes the following steps: S1: Prepare graphene oxide dispersion. Graphene oxide is prepared by the modified Hummers method and dispersed in deionized water. The graphene oxide dispersion with a concentration of 1-2 mg / mL is obtained by ultrasonic dispersion. S2: Prepare polydimethylsiloxane prepolymer. Select polydimethylsiloxane prepolymer with a viscosity of 500-1500 mPa·s and perform degassing pretreatment before use to prevent air bubbles from being mixed into the prepolymer during preparation or storage, which could affect the performance and quality of the product. S3: In a reaction vessel equipped with a reflux condenser and a mechanical stirrer, the pretreated polydimethylsiloxane prepolymer is slowly added to the graphene oxide dispersion to promote the graft polymerization reaction of organosilicon monomers on the surface of graphene oxide, so that a strong interfacial bonding force is formed between the two and the graphene is uniformly dispersed in the organosilicon. The mass ratio of polydimethylsiloxane prepolymer to graphene oxide is controlled at 10:1-20:1, and the reaction is stirred for 2-4 hours at 60-80℃ under inert gas protection. S4: Add a reducing agent to the reaction system and stir to reduce it. The mass ratio of the reducing agent to graphene oxide is 1:1-2:1. The reduced product is centrifuged, washed and dried to obtain graphene-organosilicon core-shell composite particles.

[0010] As an improvement, the reaction temperature in step S3 is 70-80℃.

[0011] As an improvement, the reducing agent in step S4 is one of hydrazine hydrate, ascorbic acid, or sodium borohydride.

[0012] As an improvement, the reduction reaction in step S4 lasts for 22-26 hours.

[0013] As an improvement, step S4 involves washing with ethanol 3-5 times and vacuum drying for 12-24 hours.

[0014] Compared with the prior art, the advantages of the present invention are as follows: Through a unique core-shell structure design, using graphene as the core and organosilicon as the shell, this structure combines the high surface activity of graphene and the low surface tension of organosilicon to achieve excellent defoaming effect. The graphene core can quickly puncture bubbles, while the organosilicon shell can effectively reduce the surface tension of the liquid and prevent bubbles from reforming. The synergistic effect of the two significantly improves the defoaming efficiency. Furthermore, due to the good high-temperature resistance of the organosilicon shell, the defoamer can stably exert its defoaming effect at rotational molding temperatures of 240-260℃. This makes the defoamer particularly suitable for high-temperature processing, such as rotational molding, ensuring the durability and stability of the defoaming effect under high-temperature environments. At the same time, the defoamer has a core-shell structure with a particle size of 50-100nm and good monodispersity, which means that the defoamer particles can be evenly distributed in the liquid and are not prone to agglomeration, thereby improving the utilization rate and defoaming effect of the defoamer.

[0015] The addition of defoamer to polymer materials (such as nylon) at only 0.1-0.5% of the material mass can achieve a significant bubble elimination effect. This not only reduces production costs but also avoids the potential performance degradation caused by excessive defoamer addition. Furthermore, after adding this defoamer, the bubble rate in the molding process of polymer materials, particularly nylon, can be reduced to below 3.8%, while tensile strength increases by 20%-30% and impact strength increases by 15%-25%. This means that the defoamer, while eliminating bubbles, can also be optimized for the characteristics of nylon materials, achieving a better bubble elimination effect, significantly improving the mechanical properties of the material, and broadening its application areas. This is further enhanced because the polarity of nylon (polyamide) and the high-temperature characteristics of the rotational molding process are highly compatible with the structure of the defoamer. The molecular chain contains amide bonds (-CONH-), which are polar. This polarity matches the small amount of oxygen-containing functional groups remaining on the surface of graphene oxide (enhancing polarity) and the moderate compatibility of the silicone shell (weak interaction between the siloxane chain and nylon), ensuring uniform dispersion of the defoamer. Simultaneously, the rotational molding temperature (240-260℃) aligns with the high-temperature resistance of the silicone shell (for stable operation), while traditional silicone defoamers are prone to volatilization and failure at this temperature. The graphene core, however, exhibits enhanced stability due to its high-temperature resistance (>300℃). Furthermore, for non-polar polymers (such as polyethylene), excessive compatibility with the silicone shell may lead to defoamer aggregation. For low-temperature molding processes (such as injection molding below 200℃), such high high-temperature resistance is unnecessary, and traditional defoamers are sufficient. Therefore, this defoamer is specifically optimized for nylon rotational molding, demonstrating its focused application.

[0016] The preparation method employs conventional chemical synthesis steps, requiring no complex equipment or conditions, making it easy to achieve industrial-scale production. Furthermore, raw materials such as graphene oxide and polydimethylsiloxane (PDMS) prepolymer are readily available and have low costs, resulting in good economic benefits. Pretreatment steps (such as vacuum drying) ensure the initial stability of the raw materials, improving the controllability of the preparation process and the purity of the product. By precisely controlling conditions such as reaction temperature, stirring speed, and the type and amount of reducing agent, sufficient reaction and uniform dispersion between graphene oxide and PDMS prepolymer can be ensured, forming a stable core-shell structure. Post-processing steps such as centrifugation, washing, and drying thoroughly remove unreacted reducing agents and impurities, yielding high-purity graphene-organosilicon core-shell composite particles. These particles exhibit excellent defoaming, dispersibility, and high-temperature resistance. The reducing agent used in the preparation process (such as ascorbic acid) is a green reducing agent, suitable for preparation scenarios with high safety requirements. Moreover, the entire preparation process is carried out in a fume hood, avoiding the risk of harmful gas volatilization and personnel exposure. Attached Figure Description

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Figure 1 A schematic diagram of the graphene-organosilicon core-shell structure of the defoamer; Figure 2 The graphene-organosilicon core-shell structure of the defoamer is shown in SEM images, where (a) is the SEM image of the graphene-organosilicon core-shell structure before it is broken, and (b) is the SEM image of the graphene-organosilicon core-shell structure after it is broken. Detailed Implementation

[0018] Example 1 S1: Preparation of graphene oxide dispersion. Graphene oxide was prepared by the modified Hummers method. 1g of graphene oxide powder was added to 1000mL of deionized water and ultrasonically dispersed for 2 hours to obtain a graphene oxide dispersion with a concentration of 1mg / mL. S2: Prepare polydimethylsiloxane prepolymer. Select 10g of polydimethylsiloxane prepolymer with a viscosity of 500mPa·s and perform degassing pretreatment before use to prevent air bubbles from being mixed into the prepolymer during preparation or storage, which could affect the performance and quality of the product. S3: In a reaction vessel equipped with a reflux condenser and a mechanical stirrer, the pretreated polydimethylsiloxane prepolymer is slowly added to the graphene oxide dispersion to promote the graft polymerization reaction of organosilicon monomers on the surface of graphene oxide, so that a strong interfacial bonding force is formed between the two and the graphene is uniformly dispersed in the organosilicon. The mass ratio of polydimethylsiloxane prepolymer to graphene oxide is controlled at 10:1, and the reaction is stirred for 2 hours at 70°C under the protection of an inert gas atmosphere, i.e. nitrogen. S4: Add 1g of hydrazine hydrate to the reaction system and stir and reduce at room temperature for 24 hours. The mass ratio of reducing agent to graphene oxide is 1:1. The reduced product is centrifuged, washed three times with ethanol, and vacuum dried for 12 hours to obtain graphene-organosilicon core-shell composite particles with a particle size of 50-80nm.

[0019] The defoamer was added to nylon 6 raw material at a dosage of 0.3%, mixed evenly, and then subjected to rotational molding. The product had a bubble rate of 3.8%, a tensile strength of 85 MPa, and an impact strength of 55 kJ / m².

[0020] Example 2 S1: Preparation of graphene oxide dispersion. Graphene oxide was prepared by the modified Hummers method. 2g of graphene oxide powder was added to 1000mL of deionized water and ultrasonically dispersed for 3 hours to obtain a graphene oxide dispersion with a concentration of 2mg / mL. S2: Prepare polydimethylsiloxane prepolymer. Select 20g of polydimethylsiloxane prepolymer with a viscosity of 1000mPa·s and perform degassing pretreatment before use to prevent air bubbles from being mixed into the prepolymer during preparation or storage, which could affect the performance and quality of the product. S3: In a reaction vessel equipped with a reflux condenser and a mechanical stirrer, the pretreated polydimethylsiloxane prepolymer is slowly added to the graphene oxide dispersion to promote the graft polymerization reaction of organosilicon monomers on the surface of graphene oxide, so that a strong interfacial bonding force is formed between the two and the graphene is uniformly dispersed in the organosilicon. The mass ratio of polydimethylsiloxane prepolymer to graphene oxide is controlled at 10:1, and the reaction is stirred for 3 hours at 80°C under the protection of an inert gas atmosphere, i.e., nitrogen. S4: Add 2g of ascorbic acid to the reaction system and stir for 24 hours at room temperature to reduce the product. The mass ratio of reducing agent to graphene oxide is 1:1. The reduced product is centrifuged, washed with ethanol 5 times, and vacuum dried for 24 hours to obtain graphene-organosilicon core-shell composite particles with a particle size of 80-100nm.

[0021] The defoamer was added to nylon 66 raw material at a dosage of 0.5%, mixed evenly, and then subjected to rotational molding. The product had a bubble rate of 3.2%, a tensile strength of 90 MPa, and an impact strength of 60 kJ / m².

[0022] Example 3 S1: Preparation of graphene oxide dispersion. Graphene oxide was prepared using the modified Hummers method. 1.5g of graphene oxide powder was added to 1000mL of deionized water and ultrasonically dispersed for 2.5 hours to obtain a graphene oxide dispersion with a concentration of 1.5mg / mL. S2: Prepare polydimethylsiloxane prepolymer. Select 15g of polydimethylsiloxane prepolymer with a viscosity of 800mPa·s and perform degassing pretreatment before use to prevent air bubbles from being mixed into the prepolymer during preparation or storage, which could affect the performance and quality of the product. S3: In a reaction vessel equipped with a reflux condenser and a mechanical stirrer, the pretreated polydimethylsiloxane prepolymer is slowly added to the graphene oxide dispersion to promote the graft polymerization reaction of organosilicon monomers on the surface of graphene oxide, so that a strong interfacial bonding force is formed between the two and the graphene is uniformly dispersed in the organosilicon. The mass ratio of polydimethylsiloxane prepolymer to graphene oxide is controlled at 10:1, and the reaction is stirred for 2.5 hours at 75°C under the protection of an inert gas atmosphere, i.e. nitrogen. S4: Add 3g of sodium borohydride to the reaction system and stir and reduce at room temperature for 24 hours. The mass ratio of reducing agent to graphene oxide is 2:1. The reduced product is centrifuged, washed with ethanol 4 times, and vacuum dried for 18 hours to obtain graphene-organosilicon core-shell composite particles with a particle size of 60-90nm.

[0023] The defoamer was added to nylon 1010 raw material at a dosage of 0.1%, mixed evenly, and then subjected to rotational molding. The product had a bubble rate of 3.5%, a tensile strength of 88 MPa, and an impact strength of 58 kJ / m².

[0024] Comparative Example 1 Traditional silicone defoamer (polydimethylsiloxane) was added to nylon 6 raw material at a dosage of 0.3% and then subjected to rotational molding. The resulting product had a bubble rate of 10%, a tensile strength of 65 MPa, and an impact strength of 40 kJ / m².

[0025] Comparative Example 2 Graphene oxide was directly mixed with PDMS prepolymer without reaction or reduction treatment, and then added to nylon 6 raw material at an addition rate of 0.3% for rotational molding. The resulting product had a bubble rate of 8%, a tensile strength of 70 MPa, and an impact strength of 45 kJ / m².

[0026] The comparison between the examples and comparative examples shows that the graphene-organosilicon core-shell defoamer prepared by the present invention has excellent defoaming performance and product performance improvement effect, which is significantly better than traditional organosilicon defoamers and untreated graphene oxide and polydimethylsiloxane mixtures, fully demonstrating the innovation and practicality of the present invention.

[0027] The above description only illustrates the preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All modifications made within the scope of the independent claims of this invention are also within the scope of protection of this invention.

Claims

1. A graphene-organosilicon core-shell defoamer, characterized in that: The defoamer has a core-shell structure with a particle size of 50-100nm. The core-shell structure uses graphene as the core to puncture bubbles and organosilicon as the shell to reduce surface tension. The two work synergistically to make the defoamer have good monodispersity and can stably exert its defoaming effect at a rotational molding temperature of 240-260℃.

2. The graphene-organosilicon core-shell defoamer according to claim 1, characterized in that: The amount of defoamer added during the molding process of polymer materials to eliminate bubbles is 0.1-0.5% of the mass of the polymer material. This defoamer eliminates bubbles, ensuring that the bubble rate in the polymer material is no more than 3.8%, while also increasing the tensile strength of the polymer material by 20%-30% and the impact strength by 15%-25% compared to the system without defoamer.

3. The graphene-organosilicon core-shell defoamer according to claim 2, characterized in that: The polymer material is nylon, and the molding process is rotational molding.

4. A method for preparing a graphene-organosilicon core-shell defoamer according to any one of claims 1-3, characterized in that, The method for preparing the defoamer includes the following steps: S1: Prepare graphene oxide dispersion. Graphene oxide is prepared by the modified Hummers method and dispersed in deionized water. The graphene oxide dispersion with a concentration of 1-2 mg / mL is obtained by ultrasonic dispersion. S2: Prepare polydimethylsiloxane prepolymer. Select polydimethylsiloxane prepolymer with a viscosity of 500-1500 mPa·s and perform degassing pretreatment before use to prevent air bubbles from being mixed into the prepolymer during preparation or storage, which could affect the performance and quality of the product. S3: In a reaction vessel equipped with a reflux condenser and a mechanical stirrer, the pretreated polydimethylsiloxane prepolymer is slowly added to the graphene oxide dispersion to promote the graft polymerization reaction of organosilicon monomers on the surface of graphene oxide, so that a strong interfacial bonding force is formed between the two and the graphene is uniformly dispersed in the organosilicon. The mass ratio of polydimethylsiloxane prepolymer to graphene oxide is controlled at 10:1-20:1, and the reaction is stirred for 2-4 hours at 60-80℃ under inert gas protection. S4: Add a reducing agent to the reaction system and stir to reduce it. The mass ratio of the reducing agent to graphene oxide is 1:1-2:

1. The reduced product is centrifuged, washed and dried to obtain graphene-organosilicon core-shell composite particles.

5. The preparation method of a graphene-organosilicon core-shell defoamer according to claim 4, characterized in that: The reaction temperature in step S3 is 70-80℃.

6. The preparation method of a graphene-organosilicon core-shell defoamer according to claim 4, characterized in that: The reducing agent in step S4 is one of hydrazine hydrate, ascorbic acid, or sodium borohydride.

7. The preparation method of a graphene-organosilicon core-shell defoamer according to claim 4, characterized in that: The reduction reaction in step S4 lasts for 22-26 hours.

8. The preparation method of a graphene-organosilicon core-shell defoamer according to claim 4, characterized in that: In step S4, the product is washed with ethanol 3-5 times and then vacuum dried for 12-24 hours.

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