Conductive hydrogel composite foam material and preparation method thereof

Abstract

The application provides a conductive hydrogel composite foamed material and a preparation method thereof, and belongs to the technical field of polymer foaming. The strong acidity of phytic acid is used to ionize a large amount of hydrogen ions in the hydrogel to form a proton conductive channel; a large amount of hydroxyl groups on a polyvinyl alcohol chain form hydrogen bonds with phosphorus of the phytic acid, and meanwhile, the hydroxyl groups contained in the phytic acid also form a large amount of hydrogen bonds with the polyvinyl alcohol, so that the crystallinity of the polyvinyl alcohol is reduced, a hydrogen bond network is formed, the mechanical properties of the hydrogel are improved, the hydrogen ions can also migrate on the hydrogen bond network, and the conductive properties of the hydrogel are improved; the pores of the foamed material are filled with a conductive hydrogel precursor, the conductive hydrogel is formed in the pores of the foamed material, the in-situ generated conductive hydrogel can be closely combined with the foamed material, and the stability of the material is improved; the good toughness and conductivity of the conductive hydrogel are used to improve the mechanical properties and conductive properties of the composite material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer foaming, and particularly relates to a conductive hydrogel composite foaming material and a preparation method thereof. BACKGROUND

[0002] Foaming materials are widely used in the fields of aerospace, automobile industry, medical devices and electronic products due to their light weight, good cushioning property and porous structure. However, traditional foaming materials such as polyurethane (PU), polystyrene (PS) and polyethylene (PE) are usually insulators and have low strength (tensile strength of 30-100 kPa), which limits their application in conductive or structure-function integrated scenarios, especially in application scenarios with high toughness and conductivity requirements. Conventional foaming materials often cannot meet the dual requirements of high strength and conductivity.

[0003] Existing preparation methods of conductive foaming materials are mostly to composite and foam conductive fillers (such as carbon nanotubes and graphene) with matrix materials. Although the conductive fillers can improve the conductivity of the materials, they have no effect on improving the mechanical properties of the materials, and it is difficult to meet the high toughness requirement. SUMMARY

[0004] The application aims to provide a conductive hydrogel composite foaming material and a preparation method thereof. The preparation method provided by the application can make the conductive hydrogel composite foaming material have good conductivity and high mechanical properties at the same time.

[0005] In order to achieve the above application purposes, the application provides the following technical solutions:

[0006] The application provides a preparation method of a conductive hydrogel composite foaming material, which comprises: mixing polyvinyl alcohol and phytic acid in water to perform a pre-crosslinking reaction to obtain a conductive hydrogel precursor; and filling the conductive hydrogel precursor into the pores of an open-cell foaming material, and then performing a cyclic freezing and thawing to obtain the conductive hydrogel composite foaming material.

[0007] The mass ratio of the polyvinyl alcohol to the phytic acid is (0.2-1):1.

[0008] The temperature of the pre-crosslinking reaction is 50-150 DEG C, and the time of the pre-crosslinking reaction is 0.5-5 h.

[0009] The freezing temperature of the cyclic freezing and thawing is -40 to -5 DEG C, and the thawing temperature is 5-40 DEG C; the number of cycles of the cyclic freezing and thawing is 2-10, and the time of each freezing and thawing is 5-10 h.

[0010] Preferably, the open-cell foaming material comprises one or more of open-cell polyurethane foaming material, open-cell polyester elastomer foaming material and nylon elastomer open-cell foaming material.

[0011] Preferably, the mass ratio of the polyvinyl alcohol to the phytic acid is (0.2-0.75):1.

[0012] Preferably, the temperature of the pre-crosslinking reaction is 80-120℃.

[0013] Preferably, the time of the pre-crosslinking reaction is 1-3h.

[0014] Preferably, the freezing temperature of the cyclic freezing and thawing is -30--15℃.

[0015] Preferably, the thawing temperature of the cyclic freezing and thawing is 15-30℃.

[0016] Preferably, the time ratio of freezing to thawing in each cycle is 2:(1-2).

[0017] Preferably, the cycle number of the cyclic freezing and thawing is 3-8.

[0018] The application also provides a conductive hydrogel composite foaming material prepared by the preparation method, which comprises an open-cell foaming material and a polyvinyl alcohol-phytic acid hydrogel filled in the pores of the open-cell foaming material in situ.

[0019] The application provides a preparation method of a conductive hydrogel composite foamed material, comprising: mixing polyvinyl alcohol and phytic acid in water to perform a pre-crosslinking reaction to obtain a conductive hydrogel precursor; and filling the conductive hydrogel precursor into pores of an open-cell foamed material, and then performing a cyclic freezing and thawing to obtain the conductive hydrogel composite foamed material; the mass ratio of the polyvinyl alcohol to the phytic acid is (0.2-1):1; the pre-crosslinking reaction is performed at a temperature of 50-150°C for 0.5-5h; the cyclic freezing and thawing is performed at a freezing temperature of-40--5°C and a thawing temperature of 5-40°C; and the cyclic freezing and thawing is performed for 2-10 cycles, and each cycle is performed for 5-10h. The strong acidity of the phytic acid is used to ionize a large amount of hydrogen ions in the hydrogel to form a proton conductive channel; a large amount of hydroxyl groups on the polyvinyl alcohol chain are used to form hydrogen bonds with the phosphorus of the phytic acid, and the hydroxyl groups contained in the phytic acid also form a large amount of hydrogen bonds with the polyvinyl alcohol, so that the crystallinity of the polyvinyl alcohol is reduced, a hydrogen bond network is formed, the mechanical properties of the hydrogel are improved, and the hydrogen ions can also migrate on the hydrogen bond network to improve the conductive properties of the hydrogel; by limiting the mass ratio of the polyvinyl alcohol to the phytic acid, the strength of the hydrogen bond network can be improved; by limiting the temperature and time of the pre-crosslinking, the polyvinyl alcohol and the phytic acid can be fully reacted to improve the mechanical properties of the material; by filling the conductive hydrogel precursor into the pores of the foamed material, the conductive hydrogel is formed in the pores of the foamed material, the in-situ generated conductive hydrogel can be closely combined with the foamed material to improve the stability of the material; the good toughness and conductivity of the conductive hydrogel are used to improve the mechanical properties and conductive properties of the composite material; and by limiting the parameters of the freezing and thawing, the conductive hydrogel is fully shaped in the pores of the foamed material, the strength of the physical crosslinking network and the hydrogen bond network is improved, the hydrogel with a stable structure is formed, and the mechanical properties and conductive properties of the material are improved. The results of the examples show that the conductive hydrogel composite foamed material prepared by using the preparation method provided by the application has a tensile modulus of 59.6-82.1kPa, an elongation at break of 6.82-8.64%, a tensile strength of 155.1-223.8kPa, a compressive modulus of 121.4-162.5kPa, a compaction strength of 55.2-75.6kPa, and an electrical conductivity of 9.1x10 -2 -1.8x10 -1 S / m. DETAILED DESCRIPTION

[0020] All raw materials of the application have no particular restrictions on their sources, and can be purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0021] All raw materials of the application have no particular restrictions on their purity, and the application preferably uses industrial pure raw materials.

[0022] The application provides a preparation method of a conductive hydrogel composite foamed material, comprising: mixing polyvinyl alcohol and phytic acid in water to perform a pre-crosslinking reaction to obtain a conductive hydrogel precursor; and filling the conductive hydrogel precursor into the pores of an open-cell foamed material and then performing a cyclic freezing and thawing to obtain the conductive hydrogel composite foamed material.

[0023] The mass ratio of the polyvinyl alcohol to the phytic acid is (0.2-1):1.

[0024] The pre-crosslinking reaction is performed at a temperature of 50-150 DEG C and for 0.5-5 h.

[0025] The freezing temperature of the cyclic freezing and thawing is -40 to -5 DEG C and the thawing temperature is 5-40 DEG C; the cyclic freezing and thawing is performed for 2-10 cycles, and each freezing and thawing is performed for 5-10 h.

[0026] The application mixes polyvinyl alcohol and phytic acid in water to perform a pre-crosslinking reaction to obtain a conductive hydrogel precursor.

[0027] As an embodiment of the application, the molecular weight of the polyvinyl alcohol can be 10-100 W. In the embodiment of the application, the molecular weight of the polyvinyl alcohol is 44.05256 W.

[0028] As an embodiment of the application, the mass ratio of the water to the polyvinyl alcohol can be (2-10):1. In the embodiment of the application, the mass ratio of the water to the polyvinyl alcohol is 5:1.

[0029] In the application, the mass ratio of the polyvinyl alcohol to the phytic acid is (0.2-1):1, preferably (0.2-0.75):1; as an embodiment of the application, the mass ratio of the polyvinyl alcohol to the phytic acid can be 2:9, 1:3, 2:3, 3:4 or 1:1. The mass ratio of the polyvinyl alcohol to the phytic acid in the above range can improve the strength of the hydrogen bond network.

[0030] The application does not particularly limit the specific manner of the mixing, as long as the raw materials can be uniformly mixed. In the embodiment of the application, the mixing is performed by magnetic stirring.

[0031] In the application, the pre-crosslinking reaction is performed at a temperature of 50-150 DEG C, preferably 80-120 DEG C; as an embodiment of the application, the pre-crosslinking reaction can be performed at a temperature of 60 DEG C, 70 DEG C, 85 DEG C, 90 DEG C, 100 DEG C, 125 DEG C or 145 DEG C. The pre-crosslinking reaction is performed at a temperature in the above range, which can make the polyvinyl alcohol and the phytic acid form a hydrogen bond network, and is beneficial to improving the mechanical properties of the material.

[0032] In the present application, the pre-crosslinking reaction time is 0.5-5h, preferably 1-3h; as an embodiment of the present application, the pre-crosslinking reaction time can be 1h, 1.5h, 2h, 2.5h or 3h. The pre-crosslinking reaction time in the above range can form a hydrogen bond network between polyvinyl alcohol and phytic acid, which is beneficial to improve the mechanical properties of the material.

[0033] The present application does not have special limitations on the device for the pre-crosslinking reaction, as long as it can normally perform the pre-crosslinking reaction. In the examples of the present application, the raw materials are placed in a beaker and the pre-crosslinking reaction is performed on a magnetic heating table.

[0034] After obtaining the conductive hydrogel precursor, the present application fills the conductive hydrogel precursor into the pores of the open-cell foam material, performs cyclic freezing and thawing to obtain a conductive hydrogel composite foam material.

[0035] In the present application, the open-cell foam material preferably includes one or more of open-cell polyurethane foam material, open-cell polyester elastomer foam material and nylon elastomer open-cell foam material. In the examples of the present application, the open-cell foam material is polyurethane open-cell foam material (PU) or wood fiber sponge. The above-mentioned materials have good porosity, which is beneficial to the filling of the conductive hydrogel and further improves the mechanical properties of the material.

[0036] The present application does not have special limitations on the specific way of filling, as long as the conductive hydrogel precursor can be filled into the pores of the open-cell foam material.

[0037] In the present application, the freezing temperature of the cyclic freezing and thawing is -40 to -5℃, preferably -30 to -15℃; as an embodiment of the present application, the freezing temperature of the cyclic freezing and thawing can be -40℃, -30℃, -20℃, -10℃ or -5℃. In the present application, the thawing temperature of the cyclic freezing and thawing is 5-40℃, preferably 15-30℃; as an embodiment of the present application, the thawing temperature of the cyclic freezing and thawing can be 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ or 40℃. The freezing and thawing temperature of the cyclic freezing and thawing in the above range can make the hydrogel fully set in the pores of the foam material, and improve the strength of the physical crosslinking network and the hydrogen bond network.

[0038] In the present application, the number of cycles of the cyclic freezing and thawing is 2-10, preferably 3-8; as an embodiment of the present application, the number of cycles of the cyclic freezing and thawing can be 3, 5, 7 or 9. The number of cycles of the cyclic freezing and thawing in the above range can improve the strength of the gel physical crosslinking network and the hydrogen bond network.

[0039] In the present application, the time for each freeze-thaw is 5-10h, preferably 6-8h; the time for each freeze-thaw within the above range can make the gel structure more compact and improve the mechanical properties of the material.

[0040] In the present application, the time ratio of freezing to thawing in each freeze-thaw is independently preferably 2:(1-2), more preferably 2:1. In the present application, the freezing time is the placement time of the material at the freezing temperature; the thawing time is the placement time of the material at the thawing temperature. The time ratio of freezing to thawing within the above range is conducive to the physical crosslinking of the gel and further improves the mechanical properties of the material.

[0041] The freezing device in the present application is not particularly limited as long as it can reach the required freezing temperature. In the embodiments of the present application, a refrigerator is used for freezing.

[0042] The present application utilizes the strong acidity of phytic acid to ionize a large number of hydrogen ions in the hydrogel to form proton-conducting channels; utilizes a large number of hydroxyl groups on the polyvinyl alcohol chain to form hydrogen bonds with the phosphorus of phytic acid, and the hydroxyl groups contained in phytic acid also form a large number of hydrogen bonds with polyvinyl alcohol to reduce the crystallinity of polyvinyl alcohol, form a hydrogen bond network, and improve the mechanical properties of the hydrogel; hydrogen ions can also migrate on the hydrogen bond network to improve the conductivity of the hydrogel; by limiting the mass ratio of polyvinyl alcohol to phytic acid, the strength of the hydrogen bond network can be improved; by limiting the temperature and time of pre-crosslinking, polyvinyl alcohol and phytic acid can be fully reacted to improve the mechanical properties of the material; by filling the electrically conductive hydrogel precursor in the pores of the foamed material, an electrically conductive hydrogel is formed in the pores of the foamed material; the in-situ generated electrically conductive hydrogel can be tightly combined with the foamed material to improve the stability of the material; the good toughness and conductivity of the electrically conductive hydrogel improve the mechanical properties and conductivity of the composite material; by limiting the freeze-thaw parameters, the electrically conductive hydrogel is fully shaped in the pores of the foamed material to improve the strength of the physical crosslinking network and the hydrogen bond network, form a hydrogel with a stable structure, and improve the mechanical properties and conductivity of the material.

[0043] The present application also provides an electrically conductive hydrogel composite foamed material prepared by the preparation method of the above technical solution, which comprises an open-cell foamed material and a polyvinyl alcohol-phytic acid hydrogel in-situ filled in the pores of the open-cell foamed material.

[0044] The electrically conductive hydrogel composite foamed material provided by the present application comprises an open-cell foamed material, which is preferably the open-cell foamed material of the above technical solution and will not be described here.

[0045] The electrically conductive hydrogel composite foamed material provided by the present application comprises a polyvinyl alcohol-phytic acid hydrogel in-situ filled in the pores of the open-cell foamed material.

[0046] The conductive hydrogel composite foamed material has good conductivity and better mechanical properties, can meet more application requirements, and expands the application range of the material.

[0047] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0048] Embodiment 1

[0049] A preparation method of the conductive hydrogel composite foamed material, and the specific process is as follows:

[0050] The commercially available polyvinyl alcohol (molecular weight 44.05256W) and phytic acid are placed in a beaker in a mass ratio of 2:3, and water in an equal mass of polyvinyl alcohol is added, and the pre-crosslinking reaction is carried out on a magnetic stirring heating table at a temperature of 95 DEG C for 2h, to obtain a conductive hydrogel precursor, and the open-cell polyurethane foamed material (PU, Samsung Water Treatment Co., Ltd.) is placed in the conductive hydrogel precursor, and the conductive hydrogel precursor is filled into the PU.

[0051] The foamed material filled with the conductive hydrogel precursor is placed in a refrigerator, the freezing temperature is-30 DEG C, the thawing temperature is 25 DEG C, and the conductive hydrogel composite foamed material is obtained by the way of cyclic freezing and thawing, the time of each freezing and thawing is 8h, the time ratio of freezing and thawing is 2:1, and the cycle number of cyclic freezing and thawing is 3 times.

[0052] Embodiment 2

[0053] A preparation method of the conductive hydrogel composite foamed material, and the process is the same as that in embodiment 1, except that the mass ratio of polyvinyl alcohol to phytic acid is 1:3.

[0054] Embodiment 3

[0055] A preparation method of the conductive hydrogel composite foamed material, and the process is the same as that in embodiment 1, except that the mass ratio of polyvinyl alcohol to phytic acid is 2:9.

[0056] Embodiment 4

[0057] A preparation method of the conductive hydrogel composite foamed material, and the process is the same as that in embodiment 2, except that the temperature of the pre-crosslinking reaction is 90 DEG C.

[0058] Embodiment 5

[0059] A method for preparing a conductive hydrogel composite foam material, the process is the same as example 2, except that the pre-crosslinking reaction time is 1.5 h.

[0060] Example 6

[0061] A method for preparing a conductive hydrogel composite foam material, the process is the same as example 2, except that the freezing temperature is -20℃.

[0062] Example 7

[0063] A method for preparing a conductive hydrogel composite foam material, the process is the same as example 2, except that the thawing temperature is 20℃.

[0064] Example 8

[0065] A method for preparing a conductive hydrogel composite foam material, the process is the same as example 2, except that the time for each freeze-thaw cycle is 6 h.

[0066] Example 9

[0067] A method for preparing a conductive hydrogel composite foam material, the process is the same as example 2, except that an equal mass of wood fiber sponge is used to replace PU, and the number of freeze-thaw cycles is 5.

[0068] Comparative Example 1

[0069] A method for preparing a conductive hydrogel composite foam material, the process is the same as example 2, except that no phytic acid is added.

[0070] Comparative Example 2

[0071] A method for preparing a conductive hydrogel composite foam material, the process is the same as example 2, except that the mass ratio of polyvinyl alcohol to phytic acid is 5:1.

[0072] Comparative Example 3

[0073] A method for preparing a conductive hydrogel composite foam material, the process is the same as example 2, except that the pre-crosslinking reaction time is 10 min.

[0074] Comparative Example 4

[0075] A method for preparing a conductive hydrogel composite foam material, the process is the same as example 2, except that the freezing temperature is 0℃.

[0076] Comparative Example 5

[0077] A method for preparing a conductive hydrogel composite foam material, the process is the same as example 2, except that the time for each freeze-thaw cycle is 2 h.

[0078] Comparative Example 6

[0079] A method for preparing the conductive hydrogel composite foam material, the process is the same as example 2, the difference is that the number of cycles of freeze-thaw cycles is 1.

[0080] The tensile modulus, elongation at break and tensile strength of the conductive hydrogel composite foam materials prepared from PU and examples 1-9 and comparative examples 1-6 were tested using a universal testing machine according to the method of GB / T 1040-2006, and the results are recorded in Table 1.

[0081] Table 1 tensile property test record table of different materials

[0082]

[0083]

[0084] The compressive modulus and compressive strength of the conductive hydrogel composite foam materials prepared from PU and examples 1-9 and comparative examples 1-6 were tested using a universal testing machine according to the method of GB / T 1041-2008, and the results are recorded in Table 2.

[0085] Table 2 compressive modulus and compressive strength record table of different materials

[0086] / Compression modulus / kPa Compression modulus increase / times Compression strength / kPa Compression strength increase / times PU 5.8 / 2.0 / Example 1 122.1 20.1 55.2 26.6 Example 2 162.5 27.0 73.3 35.7 Example 3 138.7 22.9 56.1 27.1 Example 4 134.1 22.1 65.2 31.6 Example 5 121.4 19.9 57.9 28.0 Example 6 146.9 24.3 62.3 30.2 Example 7 149.6 24.7 66.7 32.4 Example 8 135.5 22.4 61.7 29.9 Example 9 157.9 26.2 75.6 36.8 Comparative Example 1 30.8 4.3 6.8 2.4 Comparative Example 2 32.4 4.6 20.3 9.2 Comparative Example 3 36.8 5.3 16.2 7.1 Comparative Example 4 41.4 6.1 14.4 6.2 Comparative Example 5 44.9 6.7 9.0 3.5 Comparative Example 6 58.4 9.1 18.6 8.3

[0087] The conductivity of the conductive hydrogel composite foam materials prepared from PU and examples 1-9 and comparative examples 1-6 was tested using a high-precision bridge according to the method of GB / T 1410, and the results are recorded in Table 3.

[0088] Table 3 conductivity record table of different materials

[0089]

[0090]

[0091] As can be seen from Tables 1-3, the materials prepared in examples 1-9 have high strength and toughness, and high conductivity, and the performance is significantly improved compared to PU.

[0092] In comparative example 1, since no phytic acid is added, the polyvinyl alcohol forms a gel only by physical crosslinking, without a hydrogen bond network, and the mechanical properties and conductive properties of the material are not significantly improved.

[0093] In comparative example 2, since the content of added phytic acid is too low, the hydrogen bond network formed by polyvinyl alcohol and phytic acid is less, resulting in that the mechanical properties and conductive properties of the final prepared foam material are not significantly improved.

[0094] Comparative Example 3: Due to the too short pre-crosslinking reaction time, the reaction degree of polyvinyl alcohol and phytic acid is too low, and the hydrogen bond network is not fully formed, resulting in that the mechanical and conductive properties of the final prepared foamed material are not significantly improved.

[0095] Comparative Example 4: Due to the too high freezing temperature in the cycle freezing and thawing process, the conductive hydrogel precursor filled into the open-cell polyurethane foamed material is poorly shaped, and the strength of the material crosslinking network and hydrogen bond network is poor, resulting in that the mechanical and conductive properties of the final prepared foamed material are not significantly improved.

[0096] Comparative Example 5: Due to the too short cycle freezing and thawing process time, the conductive hydrogel precursor filled into the open-cell polyurethane foamed material is poorly shaped, and the strength of the material crosslinking network and hydrogen bond network is poor, resulting in that the mechanical and conductive properties of the final prepared foamed material are not significantly improved.

[0097] Comparative Example 6: Due to the too few cycle freezing and thawing times, the conductive hydrogel precursor filled into the open-cell polyurethane foamed material is poorly shaped, and the strength of the material crosslinking network and hydrogen bond network is poor, resulting in that the mechanical and conductive properties of the final prepared foamed material are not significantly improved.

[0098] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method of making an electrically conductive hydrogel composite foam material, comprising: The pre-crosslinking reaction is performed after mixing polyvinyl alcohol and phytic acid in water to obtain a conductive hydrogel precursor; The conductive hydrogel precursor is filled into the pores of the open-cell foam material, and then subjected to cyclic freezing and thawing to obtain a conductive hydrogel composite foam material; The mass ratio of the polyvinyl alcohol to the phytic acid is (0.2-1):

1. The pre-crosslinking reaction is performed at a temperature of 50-150℃ for 0.5-5h. The cyclic freezing and thawing is performed at a freezing temperature of-40--5℃ and a thawing temperature of 5-40℃, and the cycle is repeated for 2-10 times, with each freezing and thawing lasting for 5-10h.

2. The production method according to claim 1, characterized by, The open-cell foam material comprises one or more of open-cell polyurethane foam material, open-cell polyester elastomer foam material and nylon elastomer open-cell foam material.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the polyvinyl alcohol to the phytic acid is (0.2-0.75):

1.

4. The method of claim 1, wherein, The pre-crosslinking reaction is performed at a temperature of 80-120℃.

5. The production method according to claim 1 or 4, characterized by, The pre-crosslinking reaction is performed for 1-3h.

6. The method of claim 1, wherein, The cyclic freezing and thawing is performed at a freezing temperature of-30--15℃.

7. The preparation method according to claim 1, characterized in that, The cyclic freezing and thawing is performed at a thawing temperature of 15-30℃.

8. The production method according to claim 1, 6 or 7, characterized by, The ratio of the freezing time to the thawing time in each cycle is 2:(1-2).

9. The method of claim 1, wherein, The cyclic freezing and thawing is repeated for 3-8 times.

10. The conductive hydrogel composite foam material prepared by the method of any one of claims 1-9, comprising an open-cell foam material and a polyvinyl alcohol-phytic acid hydrogel in situ filled in the pores of the open-cell foam material.

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