A method for preparing a bio-based high-toughness vitrimer crosslinked network

Abstract

The application provides a preparation method of a bio-based high-toughness Vitrimer crosslinking network, and belongs to the field of polymer preparation. The Vitrimer is prepared by using vanillin and aminomethylpropanediol as raw materials, and performing an epoxidation reaction on a hydroxyl Schiff base by using epichlorohydrin under the action of a phase transfer catalyst. The prepared epoxy resin is mixed with commercially available glycerol triglycidyl ether and graphene oxide to form a mixed system, and then is cured and crosslinked by using a curing agent. The Vitrimer prepared by the application has high toughness and mechanical strength. In addition, the raw materials selected by the application are green and non-toxic, the cost is low, the synthesis steps are simple, the operation is convenient, and the application has high practicability.

Description

Technical Field

[0001] This invention belongs to the field of polymer preparation, and specifically relates to a method for preparing a bio-based high-toughness Vitrimer crosslinked network. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Vitrimer is a polymer containing a dynamically cross-linked network. Under high-temperature conditions, rapid dynamic exchange reactions alter and rearrange the network's topology, giving the material viscoelasticity and fluidity. It also exhibits plasticity and reprocessing properties while maintaining the integrity of the material's chemical structure and properties. As a novel material, Vitrimer not only solves the problem of the difficulty in reshaping and reprocessing thermosetting plastics but also compensates for the shortcomings of thermoplastics in terms of mechanical properties and thermal stability. This makes Vitrimer a promising candidate for applications in the construction industry, transportation packaging, optics, aerospace, and other fields.

[0004] A conjugated system is a system capable of forming conjugated π bonds, resulting in a special interaction between atoms within the system. This produces an effect that makes conjugated systems more stable, with lower internal energy and more evenly distributed bond lengths compared to non-conjugated systems. Crosslinking density, also known as the degree of crosslinking, refers to the number of crosslinks in a crosslinked polymer, typically expressed as the molecular weight of the network chain. A higher crosslinking density means more crosslinks per unit volume, indicating a greater degree of crosslinking. For crosslinked polymers used in plastics, such as epoxy resins, a higher crosslinking density results in better heat resistance and increased tensile strength; however, excessively high crosslinking degrees can lead to a decrease in impact strength.

[0005] Fillers are powder materials whose main raw materials are inorganic or non-metallic minerals, which, after processing, possess specific chemical compositions, geometric shapes, and surface properties. In polymer chemistry, fillers (extenders) are the most widely used additives; almost all plastics (including thermoplastics and thermosetting plastics), natural rubber, and coatings use large quantities of fillers. Fillers not only reduce the cost of plastic raw materials but also allow for the modification of certain properties of plastics or the attribution of new functions by utilizing the unique physical, chemical, and geometric properties of different types of fillers.

[0006] However, Vitrimer in the general sense only has excellent mechanical strength, while the toughness of the material itself is greatly reduced. As research has deepened, some high-toughness Vitrimers have been developed. These materials often have good toughness but no significant mechanical strength. In this case, the defect of Vitrimer's strength and toughness being coordinated and unified has gradually become apparent, which has further limited the application fields of Vitrimer. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects in existing materials and to provide a method for preparing a bio-based high-toughness Vitrimer crosslinked network.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A first aspect of the present invention provides a method for preparing a bio-based, high-toughness Vitrimer crosslinked network, comprising:

[0010] Vanillin was dissolved in an aqueous ethanol solution, and then aminomethylpropanediol was added to react and a hydroxySchiff base was obtained.

[0011] The hydroxy Schiff base was subjected to an epoxidation reaction in the presence of epichlorohydrin, NaOH and phase transfer catalysis at 80-100°C to obtain an epoxide product.

[0012] The epoxy product is compounded with glycerol triglycidyl ether to form an epoxy resin system;

[0013] The epoxy resin system is mixed with graphene oxide to form an epoxy resin composite system;

[0014] The epoxy resin system and curing agent are cured at 120-160℃ for 4-12 hours to obtain the final product.

[0015] Vanillin is an organic compound extracted from vanilla beans, a plant in the Rutaceae family. As a common bio-based raw material, it has wide applications in the chemical, biological, pharmaceutical, and food fields. Vanillin molecules can provide hydroxyl and aldehyde groups, making it an ideal precursor for epoxy functionalization and Schiff base synthesis products. Graphene oxide, as a filler rich in functional groups, has abundant internal functional groups that can interact with the structure in the polymer network, thereby endowing or improving certain properties of the material. Therefore, graphene oxide is an ideal filler for polymer networks. Based on this, this invention designs a conjugated complementary structure of benzene rings and imine bonds, causing a shift in the electron cloud distribution within the structure, which significantly improves the toughness of the material under external force. In this case, to avoid the loss of mechanical strength due to the increase in toughness, polyepoxy groups are set on the basis of the conjugated design to increase the crosslinking density of the three-dimensional structure. Under the dual synergy of crosslinking density and conjugated structure, the relationship between the mechanical strength and toughness of the material is regulated. On this basis, by introducing graphene oxide filler into the polymer system, the coordination and unity between the polymer's mechanical strength and toughness are enhanced, and a bio-based high-toughness Vitrimer is prepared.

[0016] In a second aspect, the present invention provides a bio-based high-toughness Vitrimer crosslinked network prepared by the above-described method.

[0017] A third aspect of the present invention provides applications of the aforementioned Vitrimer crosslinking network in the fields of construction, transport packaging, optics, and aerospace.

[0018] Beneficial effects of the present invention

[0019] (1) Before preparation, this invention proposes a method to solve the problem of low toughness of cross-linked structure by designing the conjugated structure of Schiff base monomer. The prepared Vitrimer has good toughness.

[0020] (2) This invention introduces multifunctional groups, and improves the crosslinking density of the three-dimensional crosslinking network through epoxy curing. Graphene oxide filler is added to adjust the proportion of hydrogen bonds inside the network, so as to improve toughness while avoiding loss of mechanical strength. The prepared Vitrimer can maintain mechanical strength comparable to traditional epoxy resin with high toughness.

[0021] (3) The preparation method of this invention is simple, inexpensive, and practical. It uses bio-based materials, which is in line with the country's green development and is easy to promote. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 The image shows the 1H NMR spectrum of the hydroxySchiff base monomer prepared in Example 1 of this invention.

[0024] Figure 2 The mechanical properties of the high-toughness Vitrimer prepared in Example 1 of this invention are compared with those of Comparative Examples 1 and 2.

[0025] Figure 3 The loss tangent of the high-toughness Vitrimer prepared in Example 1 of the present invention is compared with that of Comparative Examples 1 and 2. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] A method for preparing a bio-based, high-toughness Vitrimer crosslinked network includes:

[0028] Vanillin was dissolved in an aqueous ethanol solution, and then aminomethylpropanediol was added to react and a hydroxySchiff base was obtained.

[0029] The hydroxy Schiff base was subjected to an epoxidation reaction in the presence of epichlorohydrin, NaOH and phase transfer catalysis at 80-100°C to obtain an epoxide product.

[0030] The epoxy product is compounded with glycerol triglycidyl ether to form an epoxy resin system;

[0031] The epoxy resin system is mixed with graphene oxide to form an epoxy resin composite system;

[0032] The epoxy resin system and curing agent are cured at 120-160℃ for 4-12 hours to obtain the final product.

[0033] This invention uses vanillin and aminomethyl propylene glycol as raw materials, and epichlorohydrin epoxidizes hydroxy Schiff base monomers under the action of a phase transfer catalyst. An epoxy resin system is formed by mixing a certain proportion of glycerol triglycidyl ether, and graphene oxide filler is fully mixed. Polyetheramine D400 is used as a curing agent to cure and crosslink, thus preparing a bio-based high-toughness Vitr imer crosslinked network.

[0034] In some embodiments, the molar ratio of vanillin to aminomethylpropanediol is 1:1 to 1.2. The synthesized hydroxySchiff base monomer has a conjugated shift, resulting in an uneven electron cloud distribution, which in turn provides the material with excellent flexibility.

[0035] Specifically, vanillin is dissolved in an aqueous ethanol solution under heating and stirring. Then, aminomethyl propylene glycol is added to the above solution. The product is then subjected to an epoxidation reaction with epichlorohydrin, NaOH, and a phase transfer catalyst in an oil bath at 80-100°C. The synthesized product is compounded with glycerol triglycidyl ether at a mass ratio of 1:1 to form an epoxy resin system. 0.5% of graphene oxide is added to the system and thoroughly mixed. The mixture is then cured with polyetheramine D400 at 120-160°C for 4-12 hours to obtain bio-based high-toughness Vitrimer.

[0036] The introduction of polyepoxy groups and graphene oxide increases the crosslinking density of the system, thereby avoiding the loss of mechanical strength.

[0037] In some embodiments, the phase transfer catalyst is one of benzyltriethylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium chloride.

[0038] In some embodiments, the amount of phase transfer catalyst added is 0.5% to 0.9% based on the total mass of the epoxidation reaction system.

[0039] In some embodiments, the amount of graphene oxide added is 0.5% based on the total mass of the epoxy resin system.

[0040] In some embodiments, the mass concentration of NaOH in the reaction system is 10-40%.

[0041] In some embodiments, the ratio of the hydroxySchiff base monomer to epichlorohydrin is 1:6 to 10.

[0042] In some embodiments, the mass ratio of the epoxy product to glycerol triglycidyl ether is 1–9:1–9.

[0043] In some embodiments, the curing agent is one of polyetheramine D400, 4,4'-diaminodicyclohexylmethane, and 4,4'-diaminodiphenyl disulfide.

[0044] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0045] In the following examples, all raw materials are commercially available products, among which glycerol triglycidyl ether was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0046] Example 1:

[0047] 0.1 mol vanillin and 0.1 mol aminomethyl propylene glycol were dissolved in 250 ml of 70% ethanol aqueous solution and reacted. 0.1 mol hydroxySchiff base monomer, 0.6 mol epichlorohydrin, and 0.5% tetrabutylammonium chloride (total mass of the system) were mixed and reacted for 3 hours. Then, 120 g of 40% NaOH was added and the reaction was continued to obtain the synthesized product. The synthesized product was compounded with glycerol triglycidyl ether at a mass ratio of 1:9 to form an epoxy resin system, and 0.5% graphene oxide filler (total mass of the system) was mixed in. The mixture was heated to a fluid state, and polyetheramine D400 with an equimolar ratio of epoxy groups to active hydrogen was added for curing. Curing was carried out at 120 °C for 12 hours to obtain Vitrimer.

[0048] Example 2:

[0049] 0.1 mol vanillin and 0.1 mol aminomethyl propylene glycol were dissolved in 250 ml of 70% ethanol aqueous solution and reacted. 0.1 mol hydroxy Schiff base, 0.8 mol epichlorohydrin, and 0.7% tetrabutylammonium bromide (total mass of the system) were mixed and reacted for 3 hours. Then, 120 g of 35% NaOH was added and the reaction proceeded further to obtain the synthesized product. The synthesized product was compounded with glycerol triglycidyl ether at a mass ratio of 7:3 to form an epoxy resin system, and 0.5% graphene oxide filler (total mass of the system) was mixed in. The mixture was heated to a fluid state, and 4,4'-diaminodiphenyl disulfide (equal molar ratio of epoxy groups to active hydrogen) was added for curing. Curing was carried out at 130 °C for 10 hours to obtain Vitrimer.

[0050] Example 3:

[0051] 0.1 mol vanillin and 0.1 mol aminomethyl propylene glycol were dissolved in 250 ml of 70% ethanol aqueous solution and reacted. 0.1 mol hydroxy Schiff base, 0.7 mol epichlorohydrin, and 0.9% benzyltriethylammonium chloride (total mass of the system) were mixed and reacted for 3 hours. Then, 120 g of 30% NaOH was added and the reaction proceeded further to obtain the synthesized product. The synthesized product was compounded with glycerol triglycidyl ether at a mass ratio of 5:5 to form an epoxy resin system, and 0.5% graphene oxide filler (total mass of the system) was mixed in. The mixture was heated to a fluid state, and polyetheramine D400 with an equimolar ratio of epoxy groups to active hydrogen was added for curing. Curing was carried out at 140 °C for 8 hours to obtain Vitrimer.

[0052] Example 4:

[0053] 0.1 mol vanillin and 0.1 mol aminomethyl propylene glycol were dissolved in 250 ml of 70% ethanol aqueous solution and reacted. 0.1 mol hydroxy Schiff base, 0.6 mol epichlorohydrin, and 0.7% tetrabutylammonium chloride (total mass of the system) were mixed and reacted for 3 hours. Then, 120 g of 25% NaOH was added and the reaction proceeded further to obtain the synthesized product. The synthesized product was compounded with glycerol triglycidyl ether at a mass ratio of 4:6 to form an epoxy resin system, and 0.5% graphene oxide filler (total mass of the system) was mixed in. The mixture was heated to a fluid state, and 4,4'-diaminodicyclohexylmethane with an equimolar ratio of epoxy groups to active hydrogen was added for curing. Curing was carried out at 150 °C for 6 hours to obtain Vitrimer.

[0054] Example 5:

[0055] 0.1 mol vanillin and 0.1 mol aminomethyl propylene glycol were dissolved in 250 ml of 70% ethanol aqueous solution and reacted. 0.1 mol hydroxy Schiff base, 1 mol epichlorohydrin, and 0.8% tetrabutylammonium bromide (total mass) were mixed and reacted for 3 hours. Then, 120 g of 20% NaOH was added and the reaction proceeded further to obtain the synthesized product. The synthesized product was compounded with glycerol triglycidyl ether at a mass ratio of 6:4 to form an epoxy resin system, and 0.5% graphene oxide filler (total mass) of the system was mixed in. The mixture was heated to a fluid state, and 4,4'-diaminodicyclohexylmethane (equal molar ratio of epoxy groups to active hydrogen) was added for curing. Curing was carried out at 160 °C for 4 hours to obtain Vitrimer.

[0056] Example 6:

[0057] 0.1 mol vanillin and 0.1 mol aminomethyl propylene glycol were dissolved in 250 ml of 70% ethanol aqueous solution and reacted. 0.1 mol hydroxy Schiff base, 0.9 mol epichlorohydrin, and 0.8% tetrabutylammonium chloride (total mass of the system) were mixed and reacted for 3 hours. Then, 120 g of 15% NaOH was added and the reaction was continued to obtain the synthesized product. The synthesized product was compounded with glycerol triglycidyl ether at a mass ratio of 1:9 to form an epoxy resin system, and 0.5% graphene oxide filler (total mass of the system) was mixed in. The mixture was heated to a fluid state, and 4,4'-diaminodiphenyl disulfide (equal molar ratio of epoxy groups to active hydrogen) was added for curing. Curing was carried out at 135 °C for 9 hours to obtain Vitrimer.

[0058] Example 7:

[0059] 0.1 mol vanillin and 0.1 mol aminomethyl propylene glycol were dissolved in 250 ml of 70% ethanol aqueous solution and reacted. 0.1 mol hydroxy Schiff base, 0.6 mol epichlorohydrin, and 0.6% benzyltriethylammonium chloride (total mass of the system) were mixed and reacted for 3 hours. Then, 120 g of 10% NaOH was added and the reaction was continued to obtain the synthesized product. The synthesized product was compounded with glycerol triglycidyl ether at a mass ratio of 9:1 to form an epoxy resin system, and 0.5% graphene oxide filler (total mass of the system) was mixed in. The mixture was heated to a fluid state, and polyetheramine D400 with an equimolar ratio of epoxy groups to active hydrogen was added for curing. Curing was carried out at 145 °C for 7 hours to obtain Vitrimer.

[0060] Comparative Example 1:

[0061] 0.1 mol vanillin and 0.1 mol p-aminophenol were dissolved in 250 ml of 70% ethanol aqueous solution and reacted. 0.1 mol hydroxy Schiff base, 0.6 mol epichlorohydrin, and 0.5% benzyltriethylammonium chloride (total mass of the system) were mixed and reacted for 3 hours. Then, 120 g of 40% NaOH was added and the reaction proceeded further to obtain the synthesized product. The synthesized product was compounded with glycerol triglycidyl ether at a mass ratio of 1:9 to form an epoxy resin system, and 0.5% graphene oxide filler (total mass of the system) was mixed in. The mixture was heated to a fluid state, and polyetheramine D400 with an equimolar ratio of epoxy groups to active hydrogen was added for curing. Curing was carried out at 120 °C for 12 hours to obtain Vitrimer.

[0062] Comparative Example 2:

[0063] 0.1 mol of protocatechuic aldehyde and 0.1 mol of p-aminophenol were dissolved in 250 ml of 70% ethanol aqueous solution and reacted. 0.1 mol of hydroxy Schiff base was mixed with 0.6 mol of epichlorohydrin and 0.5% benzyltriethylammonium chloride (total mass of the system) and reacted for 3 hours. Then, 120 g of 40% NaOH was added and the reaction proceeded further to obtain the synthesized product. The synthesized product was compounded with glycerol triglycidyl ether at a mass ratio of 1:9 to form an epoxy resin system, and 0.5% graphene oxide filler (total mass of the system) was mixed in. The mixture was heated to a fluid state, and polyetheramine D400 with an equimolar ratio of epoxy groups to active hydrogen was added for curing. Curing was carried out at 120℃ for 12 hours to obtain Vitrimer.

[0064] Experimental Example

[0065] The performance of Examples 1-7 and the comparative examples was tested.

[0066] Table 1 shows a comparison of the mechanical properties of different embodiments and comparative examples. The test methods are described in GB / T1040.1-2006. The different embodiments and comparative examples all used three sets of repeated experiments, which proved that the high-toughness Vitrimer synthesized in this invention has excellent tensile strength and outstanding elongation at break.

[0067] Table 1

[0068]

[0069] like Figure 1 The image shown is the 1H NMR spectrum of the Schiff base monomer obtained in Example 1. The Schiff base monomer was dissolved in deuterated DMSO and the spectrum was recorded on an NMR spectrometer, proving the successful preparation of the Schiff base monomer.

[0070] like Figure 2 The figure shows the mechanical properties of the high-toughness Vitrimer of Example 1 and Comparative Examples 1 and 2. The test methods are as described in GB / T 1040.1-2006. The mechanical strength shows a trend of first increasing and then decreasing, and the stress of the high-toughness Vitrimer synthesized in this invention shows a trend of first increasing and then decreasing. It can also be seen that, compared with Comparative Example 1 (vanillin and aminomethyl propylene glycol) and Comparative Example 2 (protocatechuic aldehyde and p-aminophenol), the conjugated structure of the Schiff base monomer formed by vanillin and aminomethyl propylene glycol in Example 1 effectively solves the problem of low toughness in the cross-linked structure. The prepared Vitrimer has good toughness. The Vitrimer prepared in this invention can significantly enhance toughness while maintaining the mechanical strength of traditional epoxy resins, and still maintains good toughness even when the tensile strain reaches 240%.

[0071] like Figure 3 As shown, the Vitrimer prepared in Example 1 has a higher tanδ value and excellent toughness compared to Comparative Examples 1 and 2. Tests were recorded on a dynamic thermomechanical analyzer using a rectangular specimen with a length of 15 mm, a thickness of 1 mm, and a width of 4.0 mm. DMA tests were conducted at a frequency of 1 Hz and a clamping distance of 10 mm. The tests were performed within a temperature range of 0–150 °C at 3 °C / min. -1 The loss factor of the material was monitored at the heating rate.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a bio-based high-toughness Vitrimer crosslinked network, characterized in that, include: Vanillin was dissolved in an aqueous ethanol solution, and then aminomethylpropanediol was added to react and a hydroxySchiff base was obtained. The hydroxy Schiff base was subjected to an epoxidation reaction in the presence of epichlorohydrin, NaOH and a phase transfer catalyst at 80-100°C to obtain an epoxy product. The epoxy product is compounded with glycerol triglycidyl ether to form an epoxy resin system; The epoxy resin system is mixed with graphene oxide to form an epoxy resin composite system; The epoxy resin system and curing agent are cured at 120-160℃ for 4-12 hours to obtain the product. The mass ratio of the epoxy product to glycerol triglycidyl ether is 1~9:1~9; The amount of graphene oxide added is 0.5% to 0.8% based on the total mass of the epoxy resin system.

2. The method for preparing the bio-based high-toughness Vitrimer crosslinked network as described in claim 1, characterized in that, The molar ratio of vanillin to aminomethylpropanediol is 1:1 to 1.

2.

3. The method for preparing the bio-based high-toughness Vitrimer crosslinked network as described in claim 1, characterized in that, The phase transfer catalyst is one of benzyltriethylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium chloride; The amount of phase transfer catalyst added is 0.5%~0.9%, based on the total mass of the epoxidation reaction system.

4. The method for preparing the bio-based high-toughness Vitrimer crosslinked network as described in claim 1, characterized in that, The mass concentration of NaOH in the reaction system is 10-40%.

5. The method for preparing the bio-based high-toughness Vitrimer crosslinked network as described in claim 1, characterized in that, The ratio of Schiff base, epichlorohydrin, and phase transfer catalyst is 1:6~10.

6. The method for preparing the bio-based high-toughness Vitrimer crosslinked network as described in claim 1, characterized in that, The curing agent is one of polyetheramine D400, 4,4'-diaminodicyclohexylmethane, and 4,4'-diaminodiphenyl disulfide.

7. The bio-based high-toughness Vitrimer crosslinked network prepared by the method according to any one of claims 1-6.

8. The application of the Vitrimer crosslinking network of claim 7 in the fields of construction, transport packaging, optics, and aerospace.

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