A polystyrene porous foam and a method for preparing the same

Abstract

This invention provides a porous polystyrene foam material and its preparation method, belonging to the field of polymer porous materials technology. It addresses the problem that the limited stability of a single emulsion system in a high internal phase emulsion system leads to insufficient uniformity of the pore structure and limited improvement in the compressive strength of the prepared foam material. The preparation method includes: mixing and emulsifying bio-based nanoparticles, a choline-based ionic liquid, a continuous phase, and an internal phase to obtain a high internal phase emulsion; the continuous phase includes styrene monomer, a crosslinking agent, and an initiator; the amount of bio-based nanoparticles is 0.1–10 wt% of the total mass of the continuous phase, and the amount of the choline-based ionic liquid is 0.05–5 wt% of the total mass of the continuous phase; the high internal phase emulsion is polymerized and cured, and dried to obtain the porous polystyrene foam material. The porous polystyrene foam material prepared by this method has a relatively uniform pore structure and high compressive strength.

Description

Technical Field

[0001] This invention belongs to the field of polymer porous materials technology, specifically relating to a polystyrene porous foam material and its preparation method. Background Technology

[0002] Polystyrene porous foam materials prepared by high internal phase emulsion polymerization have advantages such as high porosity, tunable structure, and light weight, making them highly valuable for applications in adsorption separation, thermal insulation, buffering, and structural support. Traditional polystyrene high internal phase emulsion systems typically rely on synthetic surfactants such as Span and Tween for emulsion stabilization. However, these surfactants suffer from problems such as insufficiently eco-friendly sources, difficulty in removing interfacial residues, and complex impacts on the final material properties.

[0003] In recent years, Pickering emulsions have attracted attention due to the use of solid particles instead of traditional surfactants. Bio-based nanoparticles have advantages such as wide availability, biodegradability, and good biocompatibility, and are expected to serve as green and stable components for high internal phase emulsions. However, when relying solely on bio-based nanoparticles, the adsorption stability of the particles at the oil-water interface, the density of the interfacial layer, and the long-term stability of the emulsion are still insufficient. This leads to problems such as inhomogeneous pore structure, insufficient pore wall integrity, and limited compressive strength of the resulting porous foam materials. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a porous polystyrene foam material and its preparation method, which can use the combined effect of bio-based nanoparticles and trace synergistic components to replace traditional surfactants, improve the stability of high internal phase emulsions, and improve the pore structure and mechanical properties of the polymerized foam material.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: On one hand, the present invention provides a method for preparing a porous polystyrene foam material, comprising: Bio-based nanoparticles, choline-based ionic liquids, a continuous phase, and an internal phase are mixed and emulsified to obtain a high internal phase emulsion. The continuous phase includes styrene monomers, a crosslinking agent, and an initiator. The amount of bio-based nanoparticles is 0.1–10 wt% of the total mass of the continuous phase, and the amount of choline-based ionic liquid is 0.05–5 wt% of the total mass of the continuous phase. The high internal phase emulsion was polymerized, cured, and dried to obtain a porous polystyrene foam material.

[0006] Optionally, the process of mixing and emulsifying bio-based nanoparticles, choline-based ionic liquids, a continuous phase, and an internal phase to obtain a high internal phase emulsion includes: Bio-based nanoparticles, choline-based ionic liquids, styrene monomers, crosslinking agents, and initiators are mixed, and then the resulting mixed continuous phase is emulsified with the internal phase; or, Bio-based nanoparticles, choline-based ionic liquids, and an internal phase are mixed, and then the resulting mixed internal phase is emulsified with a continuous phase containing styrene monomers, crosslinking agents, initiators, and emulsifiers.

[0007] Optionally, the bio-based nanoparticles are at least one of modified starch nanoparticles, cellulose nanocrystals, and cellulose nanofibers.

[0008] Optionally, the choline-based ionic liquid is a polymerizable ionic liquid.

[0009] Optionally, the choline-based ionic liquid is at least one of choline acrylate, choline methacrylate, and glycine choline.

[0010] Optionally, in the high internal phase emulsion, the volume fraction of the internal phase is 60% to 98%.

[0011] Optionally, the internal phase is an aqueous phase.

[0012] Optionally, the continuous phase may also include an emulsifier.

[0013] Optionally, the polymerization curing temperature is 40–90°C and the time is 4–24 hours.

[0014] Secondly, the present invention also provides a polystyrene porous foam material, which is prepared by the above-mentioned method for preparing polystyrene porous foam material.

[0015] The above-described solution of the present invention has at least the following beneficial effects: The above-described scheme of this invention employs bio-based nanoparticles and choline-based ionic liquids as synergistic stabilizing components in an emulsion system. The bio-based nanoparticles, acting as the main Pickering emulsion stabilizers, are adsorbed at the oil-water interface. The choline-based ionic liquid, due to its hydrogen bonding, tunable surface activity, and reactivity, can act as a trace synergistic component to regulate the surface wettability of the bio-based nanoparticles, the density of the interfacial layer, and the continuous phase polymerization behavior, thereby improving the stability of the high internal phase emulsion and enhancing the pore structure and compressive strength of the resulting foam material. However, excessive addition of choline-based ionic liquid may excessively alter the interfacial tension and the microenvironment of continuous phase polymerization, weakening the dominant role of the particle-stabilized interface and thus hindering emulsion stability and uniform pore structure construction. The synergistic stabilizing system of bio-based nanoparticles and choline-based ionic liquids proposed in this invention solves the problems of limited stabilization capacity of a single emulsion system in high internal phase emulsion systems, insufficient pore structure uniformity of the prepared foam material, and limited improvement in the compressive strength of the product. Attached Figure Description

[0016] Figure 1 This is a microscopic morphology diagram of the pore size of the polystyrene-based foam material prepared in Example 1 of the present invention; Figure 2 This is a microscopic morphology diagram of the pore size of the polystyrene-based foam material prepared in Comparative Example 1 of this invention; Figure 3 This is a microscopic morphology diagram of the pore size of the polystyrene-based foam material prepared in Comparative Example 3 of this invention; Figure 4 These are the stress-strain curves of polystyrene-based foam materials prepared in Examples 1-5, Comparative Example 1, and Comparative Example 3 of the present invention. Detailed Implementation

[0017] On one hand, this invention proposes a method for preparing a porous polystyrene foam material, comprising: Bio-based nanoparticles, choline-based ionic liquids, a continuous phase, and an internal phase are mixed and emulsified to obtain a high internal phase emulsion. The continuous phase comprises styrene monomer, a crosslinking agent, and an initiator. The amount of styrene monomer is preferably 60–98 wt% of the total mass of the continuous phase, more preferably 65–90 wt%. The amount of crosslinking agent is preferably 1–40 wt% of the mass of the styrene monomer, more preferably 5–25 wt%. The amount of initiator is preferably 0.1–10 wt% of the total mass of the styrene monomer and crosslinking agent, more preferably 0.5–5 wt%. The continuous phase may further include an emulsifier, the amount of which is preferably 0-10 wt% of the total mass of the continuous phase, more preferably 0-3 wt%; the amount of the bio-based nanoparticles is 0.1-10 wt% of the total mass of the continuous phase, preferably 0.5-5 wt%; the amount of the choline-based ionic liquid is 0.05-5 wt% of the total mass of the continuous phase, preferably 0.1-2 wt%; preferably, the amount of the choline-based ionic liquid added is 5-50 wt% of the mass of the bio-based nanoparticles, more preferably 10-30 wt%. Within this range, the choline-based ionic liquid can effectively exert a synergistic regulatory effect on the surface wettability and interfacial layer compactness of the bio-based nanoparticles; when its addition amount is too low, the synergistic regulatory effect is not obvious; when its addition amount is too high, it may excessively alter the interfacial environment and the polymerization behavior of the continuous phase.

[0018] The high internal phase emulsion was polymerized, cured, and dried to obtain a polystyrene porous foam material with a relatively uniform pore structure and high compressive strength.

[0019] The preparation method of the present invention can be carried out without the use of conventional synthetic surfactants, or with the amount of conventional synthetic surfactants (e.g., Span, Tween) being less than 1 wt% of the total mass of the continuous phase.

[0020] The bio-based nanoparticles and choline-based ionic liquids of the present invention can be added to a continuous phase or an internal phase. Exemplarily, the step of mixing and emulsifying the bio-based nanoparticles, choline-based ionic liquid, continuous phase, and internal phase to obtain a high internal phase emulsion includes: Bio-based nanoparticles, choline-based ionic liquids, styrene monomers, crosslinking agents, initiators, and emulsifiers are mixed, and then the resulting mixed continuous phase is emulsified with the internal phase; or, Bio-based nanoparticles, choline-based ionic liquids, and an internal phase are mixed, and then the resulting mixed internal phase is emulsified with a continuous phase containing styrene monomers, crosslinking agents, initiators, and emulsifiers.

[0021] This invention disperses bio-based nanoparticles in an internal or continuous phase system and adds choline-based ionic liquid as a synergistic stabilizing component. The continuous phase containing styrene monomer, crosslinking agent and other components is mixed and emulsified with the internal phase to form a high internal phase emulsion. Under the condition of not using traditional synthetic surfactants or reducing their usage, the bio-based nanoparticles and choline-based ionic liquid synergistically stabilize the emulsion interface, and then initiate continuous phase polymerization to obtain polystyrene porous foam material.

[0022] For example, the bio-based nanoparticles are at least one of modified starch nanoparticles, cellulose nanocrystals, and cellulose nanofibers.

[0023] For example, the choline-based ionic liquid is a polymerizable ionic liquid. Polymerizable ionic liquids are beneficial for enhancing the bonding between the interfacial layer and the polystyrene skeleton during polymerization, thereby improving the continuity of the foam material skeleton and its compressive strength.

[0024] For example, the choline-based ionic liquid is at least one of choline acrylate, choline methacrylate, and glycine choline.

[0025] In this invention, the bio-based nanoparticles can be prepared using conventional methods in the art or obtained commercially. Preferably, the bio-based nanoparticles have amphiphilic surface features suitable for stabilizing oil-water interfaces.

[0026] In this invention, the choline-based ionic liquid is added to the system in trace amounts. Its main function is not to replace the bio-based nanoparticles as the main stabilizer, but to act as a synergistic component to regulate the adsorption behavior of the particle interface and the binding state of the skeleton after polymerization. Furthermore, the choline-based ionic liquid can partially participate in the continuous phase polymerization, thereby enhancing the bonding between the interface layer and the polystyrene skeleton and improving the load-bearing capacity of the foam skeleton.

[0027] For example, in the high internal phase emulsion, the volume fraction of the internal phase is 60-98%, preferably 65-75%.

[0028] For example, the internal phase is an aqueous phase.

[0029] For example, the polymerization curing temperature is 40-90°C, preferably 50-75°C; the polymerization curing time is 4-24 hours, preferably 8-16 hours.

[0030] In this invention, bio-based nanoparticles are adsorbed at the oil-water interface as the main Pickering stabilizers, and choline-based ionic liquids are used as trace synergistic components to regulate the wettability of the particle surface, the density of the interface layer, and the continuous phase polymerization behavior, thereby improving the stability of the high internal phase emulsion and improving the pore structure and compressive strength of the resulting foam material.

[0031] The method for preparing polystyrene porous foam material based on the synergistic stabilization of bio-based nanoparticles and choline-based ionic liquids of the present invention has the following advantages: (1) The present invention uses bio-based nanoparticles to replace traditional synthetic surfactants or significantly reduce their usage, which is beneficial to improving the bio-based characteristics and green properties of the system; (2) By synergistically stabilizing the emulsion interface with trace amounts of choline-based ionic liquid and bio-based nanoparticles, the stability of high internal phase emulsions can be improved, and the tendency of droplet coalescence and emulsion stratification can be reduced. (3) Choline-based ionic liquids are polymerizable ionic liquids, which are beneficial to enhance the bonding between the interface layer and the polystyrene skeleton during the polymerization process, thereby improving the continuity and compressive strength of the foam skeleton. (4) The polystyrene porous foam material prepared by this method has a more uniform pore size distribution, a more complete pore wall structure and higher compressive strength.

[0032] Secondly, the present invention also provides a porous polystyrene foam material, prepared by the above-described method for preparing porous polystyrene foam. This porous polystyrene foam material has a more uniform pore size distribution, a more complete pore wall structure, and higher compressive strength.

[0033] This invention relates to a polystyrene porous foam material and its preparation method based on the synergistic stabilization of bio-based nanoparticles and choline-based ionic liquids. The process flow is well-defined and suitable for scale-up implementation. By introducing bio-based nanoparticles and trace amounts of choline-based ionic liquids into a high internal phase emulsion system, a stable emulsion can be obtained with reduced or no use of traditional synthetic surfactants. This allows for the preparation of polystyrene porous foam materials with a relatively uniform pore structure and high compressive strength, demonstrating promising prospects for industrial applications.

[0034] This invention achieves the green preparation of porous polystyrene foam materials by constructing a highly stable internal phase emulsion system synergistically composed of bio-based nanoparticles and choline-based ionic liquids. This synergistic system improves emulsion stability, enhances pore structure uniformity and pore wall integrity, and strengthens the compressive strength of the material, thereby obtaining a high-performance porous polystyrene foam material.

[0035] The following specific embodiments further illustrate the polystyrene porous foam material and its preparation method of the present invention.

[0036] Example 1 This embodiment provides a method for preparing a porous polystyrene foam material.

[0037] Cellulose nanocrystals, choline acrylate, styrene monomer, crosslinking agent divinylbenzene, initiator azobisisobutyronitrile, and emulsifier Span80 were mixed to obtain a mixed continuous phase. The inner phase was added dropwise to the mixed continuous phase and stirred, and emulsified at room temperature to obtain a high inner phase emulsion. The high inner phase emulsion was polymerized and cured at a temperature of 60°C for 12 hours to obtain a polystyrene porous foam material.

[0038] The amount of bio-based nanoparticles is 3 wt% of the total mass of the continuous phase; the amount of choline-based ionic liquid is 0.6 wt% of the total mass of the continuous phase; the amount of styrene monomer is 14 g, the amount of crosslinking agent is 6 g, the amount of initiator is 0.2 g, and the amount of emulsifier is 0.1 g; in the high internal phase emulsion, the volume fraction of the internal phase is 68%.

[0039] Example 2 This embodiment provides a method for preparing a polystyrene porous foam material similar to that in Embodiment 1, except that the amount of choline-based ionic liquid used is 2 wt% of the total mass of the continuous phase.

[0040] Example 3 This embodiment provides a method for preparing a porous polystyrene foam material similar to that in Embodiment 1, except that the amount of bio-based nanoparticles used is 5 wt% of the total mass of the continuous phase.

[0041] Example 4 Cellulose nanofibers and choline methacrylate were added to the inner phase to prepare a mixed aqueous phase containing the components. Styrene monomer, crosslinking agent divinylbenzene, initiator azobisisobutyronitrile, and emulsifier Span80 were mixed to obtain a continuous phase. The mixed inner phase was then added dropwise to the continuous phase and stirred to emulsify at room temperature to obtain a high-internal-phase emulsion. The high-internal-phase emulsion was polymerized and cured at 60°C for 12 hours to obtain a polystyrene porous foam material.

[0042] The internal phase is an aqueous phase containing cellulose nanofibers and choline methacrylate; the amount of bio-based nanoparticles is 4 wt% of the total mass of the continuous phase; the amount of choline-based ionic liquid is 0.8 wt% of the total mass of the continuous phase; the amount of styrene monomer is 15 g, the amount of crosslinking agent is 3 g, the amount of initiator is 0.4 g, and the amount of emulsifier is 0.2 g; in the high internal phase emulsion, the volume fraction of the internal phase is 68%.

[0043] Example 5 Cellulose nanofibers, choline methacrylate, styrene monomer, crosslinking agent divinylbenzene, and initiator azobisisobutyronitrile were mixed to obtain a mixed continuous phase without the addition of traditional synthetic emulsifiers. The inner phase was added dropwise to the mixed continuous phase and stirred to emulsify at room temperature to obtain a high inner phase emulsion. The high inner phase emulsion was then polymerized and cured at a temperature of 60°C for 12 hours to obtain a polystyrene porous foam material.

[0044] The amount of bio-based nanoparticles is 3 wt% of the total mass of the continuous phase; the amount of choline-based ionic liquid is 0.6 wt% of the total mass of the continuous phase; the amount of styrene monomer is 16 g, the amount of crosslinking agent is 4 g, and the amount of initiator is 0.6 g; in the high internal phase emulsion, the volume fraction of the internal phase is 68%.

[0045] Comparative Example 1 This comparative example provides a method for preparing a polystyrene porous foam material similar to that in Example 1. The difference is that the same weight of bio-based nanoparticles is used instead of choline-based ionic liquid. That is, no choline-based ionic liquid is added, and the bio-based nanoparticles are used to stabilize the high internal phase emulsion.

[0046] Comparative Example 2 This comparative example provides a method for preparing a polystyrene porous foam material similar to that in Example 1. The difference is that the same weight of choline-based ionic liquid is used instead of bio-based nanoparticles. That is, no bio-based nanoparticles are added, and the high internal phase emulsion is stabilized solely by choline-based ionic liquid.

[0047] Comparative Example 3 This comparative example provides a method for preparing polystyrene porous foam material similar to that in Example 1. The difference is that the same weight of the conventional surfactant Span80 is used instead of the choline-based ionic liquid and the bio-based nanoparticles. That is, the conventional surfactant is used instead of the bio-based nanoparticle / choline-based ionic liquid synergistic system.

[0048] The results of observing the static stability of the high internal phase emulsion, testing the compression performance of the foam materials after polymerization, and characterizing the pore structure of the polystyrene porous foam materials prepared in the examples and comparative examples are shown in Table 1. Figures 1 to 4 .

[0049] Table 1

[0050] As shown in Table 1, the static stability of the high internal phase emulsions in Examples 1-3 is better than that in Comparative Examples 1-3, indicating that the synergistic system of bio-based nanoparticles and choline-based ionic liquids can effectively improve the interfacial stability of the emulsion. Furthermore, the polystyrene porous foam materials prepared in Examples 1-3 have a more uniform pore size distribution, more intact pore walls, and higher compressive strength than those in Comparative Examples 1-3, indicating that the synergistic system of bio-based nanoparticles and choline-based ionic liquids not only improves emulsion stability but also promotes the post-polymerization framework structure and mechanical properties. Example 4 further demonstrates that adding bio-based nanoparticles and choline-based ionic liquids to the internal phase can still form a stable emulsion and obtain porous foam materials. Example 5 further demonstrates that, without using traditional synthetic emulsifiers, the synergistic system of the present invention can still stabilize high internal phase emulsions and prepare polystyrene porous foam materials. A comparison of the results of Comparative Examples 1, 2, and Example 1 shows that using bio-based nanoparticles alone or choline-based ionic liquids alone is insufficient to achieve the comprehensive effect of the present invention, indicating a significant synergistic stabilizing and enhancing effect between bio-based nanoparticles and choline-based ionic liquids. A comparison of the results of Comparative Example 3 and Example 1 shows that although traditional surfactants can form emulsions, they are still inferior to the bio-based nanoparticle and choline-based ionic liquid synergistic system of the present invention in terms of pore structure uniformity and overall performance.

[0051] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a porous polystyrene foam material, characterized in that, include: Bio-based nanoparticles, choline-based ionic liquids, a continuous phase, and an internal phase are mixed and emulsified to obtain a high internal phase emulsion. The continuous phase includes styrene monomers, a crosslinking agent, and an initiator. The amount of bio-based nanoparticles is 0.1–10 wt% of the total mass of the continuous phase, and the amount of choline-based ionic liquid is 0.05–5 wt% of the total mass of the continuous phase. The high internal phase emulsion was polymerized, cured, and dried to obtain a porous polystyrene foam material.

2. The method for preparing polystyrene porous foam material according to claim 1, characterized in that, The process of mixing and emulsifying bio-based nanoparticles, choline-based ionic liquids, a continuous phase, and an internal phase to obtain a high internal phase emulsion includes: Bio-based nanoparticles, choline-based ionic liquids, styrene monomers, crosslinking agents, initiators, and emulsifiers are mixed, and then the resulting mixed continuous phase is emulsified with the internal phase; or, Bio-based nanoparticles, choline-based ionic liquids, and an internal phase are mixed, and then the resulting mixed internal phase is emulsified with a continuous phase containing styrene monomers, crosslinking agents, initiators, and emulsifiers.

3. The method for preparing polystyrene porous foam material according to claim 1, characterized in that, The bio-based nanoparticles are at least one of modified starch nanoparticles, cellulose nanocrystals, and cellulose nanofibers.

4. The method for preparing polystyrene porous foam material according to claim 1, characterized in that, The choline-based ionic liquid is a polymerizable ionic liquid.

5. The method for preparing polystyrene porous foam material according to claim 4, characterized in that, The choline-based ionic liquid is at least one of choline acrylate, choline methacrylate, and glycine choline.

6. The method for preparing polystyrene porous foam material according to claim 1, characterized in that, In the high internal phase emulsion, the volume fraction of the internal phase is 60% to 98%.

7. The method for preparing polystyrene porous foam material according to claim 1, characterized in that, The internal phase is an aqueous phase.

8. The method for preparing polystyrene porous foam material according to claim 1, characterized in that, The continuous phase also includes an emulsifier.

9. The method for preparing polystyrene porous foam material according to claim 1, characterized in that, The polymerization and curing temperature is 40–90°C, and the time is 4–24 hours.

10. A porous polystyrene foam material, characterized in that, It is prepared by the method for preparing polystyrene porous foam material according to any one of claims 1 to 9.

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