CN111499999B - A kind of polyvinyl alcohol sponge with high elongation rate and preparation method thereof - Google Patents

Abstract

The invention discloses a polyvinyl alcohol sponge with high elongation rate and a preparation method thereof. The method comprises: after mixing polyvinyl alcohol, cellulose, carbonate and deionized water, stirring under closed conditions until the dissolution is complete, to obtain a homogeneous polyvinyl alcohol solution; adding the mixture of emulsifier and ester to the polyvinyl alcohol In the solution, stir until the reaction is complete to obtain a white viscous solution; after adding a foaming agent to the white viscous solution, use a strong stirrer to stir until bubbles of uniform size are generated in the solution to obtain a foamed solution; After foaming, the solution is poured into a mold, and after freezing and thawing, a polyvinyl alcohol sponge with high elongation rate is obtained. Compared with the existing production process of polyvinyl alcohol sponge, the freeze-thaw method used in this method has the advantages of easy control, good environmental protection, less waste of resources, and avoiding the harm of formaldehyde to human health.

Description

A kind of polyvinyl alcohol sponge with high elongation rate and preparation method thereof

technical field

The invention belongs to the field of polymer materials, in particular to a polyvinyl alcohol sponge with high elongation rate and a preparation method thereof.

Background technique

Polyvinyl Alcohol (PVA) sponge is composed of a network structure cross-linked by numerous polymer chains. Polyvinyl alcohol has strong hydrophilicity, so it can absorb and store a large amount of water, and maintain a certain mechanical strength after absorbing water. In addition, polyvinyl alcohol is a polymer material with light weight. It can be made into a porous sponge structure and can also be used in fields such as heat insulation and sound insulation.

Existing polyvinyl alcohol sponges are mainly polyvinyl formal sponges. In terms of resources and environmental protection, starch is generally used as an auxiliary foaming agent for the preparation of polyvinyl formal sponge. After the sponge is solidified and formed, the excess starch is washed away. This preparation method needs to consume a large amount of water, resulting in waste of resources and environmental pollution. In terms of the mechanical properties of the sponge, if the starch in the sponge is not completely washed off, the sponge is easily corroded during use. In addition, during the preparation process, the reaction conditions are difficult to precisely control. If the heating rate is too fast, the acetal is too high, which will cause the sponge to agglomerate and clump together to form a tight material, and it is difficult to form a mesh-like structure well, making it difficult for the reactants to continue to interact. The polyvinyl formal sponge thus obtained has poor tensile properties, the elongation rate is generally 200-300%, and the sponge structure is easily damaged during repeated stretching. In terms of human health, the above preparation method uses formaldehyde, so the product inevitably contains free formaldehyde, which will cause potential health hazards to both the preparation experimenter and the product user.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a polyvinyl alcohol sponge with high elongation rate and a preparation method thereof.

The technical solution of the present invention to solve the technical problem of the method is to provide a method for preparing a polyvinyl alcohol sponge with high elongation rate, which is characterized in that the method comprises the following steps:

(1) after polyvinyl alcohol, cellulose, carbonate are mixed with deionized water, stir to dissolve completely under closed condition, obtain homogeneous polyvinyl alcohol solution;

(2) adding the mixture of emulsifier and esters to the polyvinyl alcohol solution obtained in step 1), stirring until the reaction is complete, to obtain a white viscous solution;

(3) after adding a foaming agent in the white viscous solution obtained in step 2), use a strong stirrer to stir until bubbles of uniform size are generated in the solution, and obtain a solution after foaming;

(4) Pour the foamed solution obtained in step 3) into a mold, and freeze and thaw to obtain a polyvinyl alcohol sponge with a high elongation rate.

In step 1), the reaction temperature is 80-100 ° C; the cellulose is bacterial cellulose; the mass ratio of polyvinyl alcohol, cellulose, calcium carbonate and deionized water is 42-46:2-4:8-12 : 240-260; the molecular weight of polyvinyl alcohol is 135000-300000.

In step 2), the reaction temperature is 70-80 ° C; the emulsifier is OP-10; the ester is dimethyl carbonate; the volume ratio of the emulsifier to the ester is 2-4:4-5, and The mass of the mixture is 16-17% of the sum of the mass of the polyvinyl alcohol solution and the mixture; stirring is performed using a magnetic stirrer or a powerful stirrer equipped with a propeller.

In step 3), the reaction temperature is 30-40° C., and the stirring speed is 1500-2000 r/min. The foaming agent is n-pentane; the mass of the foaming agent is 5-6% of the sum of the mass of the white viscous solution and the foaming agent.

In step 4), freeze-thaw is to freeze the mold with the foamed solution in a freeze dryer at -40°C to -50°C for 4-12 hours, and then thaw at room temperature for 2-3 hours.

A conductive material is added to the raw material in step 1) to obtain a polyvinyl alcohol conductive sponge with high elongation; the conductive material is copper, aluminum, gold, silver, nickel, graphite, acetylene black, graphene, carbon At least one of nanotubes or MXenes.

The technical solution of the present invention to solve the technical problem of the polyvinyl alcohol sponge is to provide a polyvinyl alcohol sponge with high elongation obtained by the preparation method.

Compared with the prior art, the beneficial effects of the present invention are:

(1) Compared with the existing polyvinyl alcohol sponge production process, the freeze-thaw method used in this method has the advantages of easy control, good environmental protection, less waste of resources, and avoiding the harm of formaldehyde to human health.

(2) Compared with the existing production process of polyvinyl alcohol sponge, the sponge prepared by this method has good controllability, mechanical tensile properties can be greater than 300%, and the elongation rate, pore size and resistivity of the polyvinyl alcohol sponge All can be adjusted by changing the preparation parameters. For example, by controlling the content of bacterial cellulose in the formula, the stretch rate of the sponge can be adjusted; by controlling the content of deionized water, the pores of the sponge can be adjusted to obtain sponges with different water holding capacities; adding different amounts to the sponge flexible electrodes with different conductivity can be obtained.

Description of drawings

Fig. 1 is the structural representation of polyvinyl alcohol sponge of the present invention;

Fig. 2 is the electron microscope picture of the embodiment of the present invention 1;

Figure 3 is a stress-strain diagram of Example 3 of the present invention; in the figure, 1 is a pore; 2 is a polyvinyl alcohol skeleton.

Detailed ways

Specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention in detail, and do not limit the protection scope of the claims of the present application.

The invention provides a preparation method (method for short) of a polyvinyl alcohol sponge with high elongation rate, which is characterized in that the method comprises the following steps:

(1) After mixing polyvinyl alcohol (PVA), cellulose, carbonate and deionized water, magnetic stirring at 80-100°C for 1-2h under closed conditions to complete dissolution to obtain a uniform milky white polyethylene alcohol solution;

In step 1), the sealing condition is to use tin foil or fresh-keeping film to seal the container to prevent moisture from evaporating.

In step 1), the carbonate includes calcium carbonate, potassium carbonate or sodium carbonate (preferably calcium carbonate).

In step 1), the cellulose is bacterial cellulose (BC); the mass ratio of polyvinyl alcohol, bacterial cellulose, carbonate and deionized water is 42-46:2-4:8-12:240- 260 (preferably 45:6:10:250); the molecular weight of polyvinyl alcohol is 135000-300000; BC can increase the water retention and tensile properties of polyvinyl alcohol sponge; carbonate can promote polyvinyl alcohol and dimethyl carbonate The reaction rate of the ester.

(2) Cool the polyvinyl alcohol solution obtained in step 1) to 70-80°C (preferably 70°C, 76°C), add the mixture of emulsifier and esters to the polyvinyl alcohol solution at one time, and stir magnetically for 2-3h (preferably 2h) to complete the reaction to obtain a white viscous solution;

In step 2), described emulsifier adopts OP-10, is used for increasing the fusion degree of polyvinyl alcohol and dimethyl carbonate; Described ester is dimethyl carbonate (DMC);

In step 2), the volume ratio of emulsifier and dimethyl carbonate is 2-4:4-5 (preferably 3:5), and the mass of the mixture is 16-17% of the sum of the mass of the polyvinyl alcohol solution and the mixture ; The polycondensation reaction of dimethyl carbonate and polyvinyl alcohol is carried out to build a skeleton for the polyvinyl alcohol sponge.

In step 2), the reaction temperature of polyvinyl alcohol and dimethyl carbonate is too high, and the dimethyl carbonate volatilizes, resulting in too much remaining polyvinyl alcohol; the temperature is too low, and the reaction is insufficient. In the reaction process of dimethyl carbonate and polyvinyl alcohol, it is more preferable to use a strong stirrer equipped with a propeller for stirring, so as to avoid insufficient reaction caused by incomplete stirring.

(3) the white viscous solution obtained in step 2) is cooled to 30-40°C (preferably 30°C), after adding the foaming agent, use a powerful stirrer equipped with a propeller to quickly and vigorously stir until the solution is uniform in size the bubbles to obtain the foamed solution;

In step 3), the foaming agent is n-pentane; the quality of the foaming agent is 5-6% of the sum of the mass of the white viscous solution and the foaming agent, and the foaming temperature is between 33-38 ° C. between.

In step 3), the stirring rotation speed is 1500-2000 r/min, and the size of the rotation speed will affect the size and uniformity of the mesh structure of the sponge.

(4) Pour the foamed solution obtained in step 3) into a mold, and freeze and thaw for 2-4 times (preferably 3 times) to obtain a polyvinyl alcohol sponge with a high elongation rate.

The specific process of freezing and thawing is to freeze the mold with the foamed solution in a freeze dryer at -40°C to -50°C for 4-12h (preferably 7h), and then thaw it at room temperature for 2-3h (preferably 2h); The characteristic of freezing and thawing is that the temperature is easy to control; freezing is to make the polyvinyl carbonate polymer generated by the reaction of polyvinyl alcohol and dimethyl carbonate physically cross-linked; thawing is to test whether the polyvinyl carbonate polymer has completely occurred. Physical cross-linking; multiple freeze-thaw cycles are to ensure complete physical cross-linking of the polyvinyl carbonate polymer.

Preferably, a conductive substance is added to the raw material in step 1), and finally a polyvinyl alcohol conductive foam with high elongation can be obtained; the conductive substance is copper, aluminum, gold, silver, nickel, graphite, acetylene black, At least one of graphene, carbon nanotube (CNT) or MXene; the added amount of the conductive substance is related to the conductivity.

The present invention also provides a polyvinyl alcohol sponge with high elongation obtained by the preparation method.

It can be seen from Figure 1 that polyvinyl alcohol and dimethyl carbonate undergo an esterification reaction, and then a large number of pores are generated by foaming with a foaming agent, which can provide space for storing moisture.

In the following examples and comparative examples, the pore diameter was measured by metallographic microscope WYJ-55XA. The elongation rate was measured by Liangong universal testing machine CMT-1 according to the standard GB/T 528-2009, and all samples were cut into dumbbell shapes of 5mm×15mm×2mm. The resistivity was measured with a lattice JG2511C resistivity four-probe tester.

Example 1

(1) Place 10g of polyvinyl alcohol (molecular weight 145000), 0.6g of bacterial cellulose, 3g of calcium carbonate and 100ml of deionized water in a beaker, place a stirring bar of appropriate size, then seal it with tin foil, and stir magnetically at 95°C Stir and dissolve in a water bath for 1.5h to obtain a uniform milky white polyvinyl alcohol solution;

(2) Cool the polyvinyl alcohol solution to 76°C, pour the mixed 10ml emulsifier OP-10 and 14ml dimethyl carbonate into the beaker containing the polyvinyl alcohol solution at one time, and stir for 2h until the solution reaction is White and viscous, remove the magnetic stirrer;

(3) the white viscous solution was cooled to 36 ℃, 12ml of foaming agent n-pentane was added, and a strong stirrer was used to stir at a rotating speed of 1500r/min until bubbles of uniform size were generated in the solution, and the foamed solution was obtained;

(4) Pour the foamed solution into the mold, and repeat freeze-thaw three times (freeze-thaw is frozen in a freeze dryer at -45°C for 7 hours, and then thawed at room temperature for 2 hours) to obtain a pore diameter of 12.64 -18.04 μm, polyvinyl alcohol sponge with 318% elongation.

As can be seen from Figure 2, the sponge prepared in Example 1 is consistent with the structural representation of the sponge (Figure 1), and contains a polyvinyl alcohol sponge with a porous structure;

Comparative Example 1

(1) Place 10g of polyvinyl alcohol (molecular weight 145000), 0g of bacterial cellulose, 3g of calcium carbonate and 100ml of deionized water in a beaker, place a stirring bar of appropriate size, then seal it with tin foil, and magnetically stir the water bath at 95°C Stir and dissolve in the pot for 1.5h to obtain a uniform milky white polyvinyl alcohol solution;

(2) Cool the polyvinyl alcohol solution to 76°C, pour the mixed 10ml emulsifier OP-10 and 14ml dimethyl carbonate into the beaker containing the polyvinyl alcohol solution at one time, and stir for 2h until the solution reaction is White and viscous, remove the magnetic stirrer;

(3) the white viscous solution was cooled to 36 ℃, 12ml of foaming agent n-pentane was added, and a strong stirrer was used to stir at a rotating speed of 1500r/min until bubbles of uniform size were generated in the solution, and the foamed solution was obtained;

(4) Pour the foamed solution into the mold, and repeat freeze-thaw three times (freeze-thaw is frozen in a freeze dryer at -45°C for 7 hours, and then thawed at room temperature for 2 hours) to obtain a pore diameter of 12.64 -18.04 μm, 180% elongation polyvinyl alcohol sponge.

Comparative Example 2

(1) Place 10g polyvinyl alcohol (molecular weight 145000), 0.3g bacterial cellulose, 3g calcium carbonate and 100ml deionized water in a beaker, place a stirring bar of appropriate size, then seal with tin foil, and stir magnetically at 95°C Stir and dissolve in a water bath for 1.5h to obtain a uniform milky white polyvinyl alcohol solution;

(2) Cool the polyvinyl alcohol solution to 76°C, pour the mixed 10ml emulsifier OP-10 and 14ml dimethyl carbonate into the beaker containing the polyvinyl alcohol solution at one time, and stir for 2h until the solution reaction is White and viscous, remove the magnetic stirrer;

(3) the white viscous solution was cooled to 36 ℃, 12ml of foaming agent n-pentane was added, and a strong stirrer was used to stir at a rotating speed of 1500r/min until bubbles of uniform size were generated in the solution, and the foamed solution was obtained;

(4) Pour the foamed solution into the mold, and repeat freeze-thaw three times (freeze-thaw is frozen in a freeze dryer at -45°C for 7 hours, and then thawed at room temperature for 2 hours) to obtain a pore diameter of 12.64 -18.04 μm, 260% elongation polyvinyl alcohol sponge.

Comparative Example 3

(1) Put 10g of polyvinyl alcohol (molecular weight 145000), 0.9g of bacterial cellulose, 3g of calcium carbonate and 100ml of deionized water in a beaker, place a stirring bar of appropriate size, then seal it with tin foil, and stir magnetically at 95°C Stir and dissolve in a water bath for 1.5h to obtain a uniform milky white polyvinyl alcohol solution;

(2) Cool the polyvinyl alcohol solution to 76°C, pour the mixed 10ml emulsifier OP-10 and 14ml dimethyl carbonate into the beaker containing the polyvinyl alcohol solution at one time, and stir for 2h until the solution reaction is White and viscous, remove the magnetic stirrer;

(3) the white viscous solution was cooled to 36 ℃, 12ml of foaming agent n-pentane was added, and a strong stirrer was used to stir at a rotating speed of 1500r/min until bubbles of uniform size were generated in the solution, and the foamed solution was obtained;

(4) Pour the foamed solution into the mold, and repeat freeze-thaw three times (freeze-thaw is frozen in a freeze dryer at -45°C for 7 hours, and then thawed at room temperature for 2 hours) to obtain a pore diameter of 12.64 -18.04 μm, 280% elongation polyvinyl alcohol sponge.

By comparing Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3, it can be seen that: the amount of bacterial cellulose can affect the stretch rate of the polyvinyl alcohol sponge, and the bacterial cellulose content is too low to cause polyvinyl alcohol. The strength of the sponge is insufficient, resulting in a small elongation rate; however, if the bacterial cellulose content is too high, the strength of the polyvinyl alcohol sponge is too large, thereby reducing the elongation rate of the polyvinyl alcohol sponge.

Example 2

(1) Place 10g of polyvinyl alcohol (molecular weight 145000), 0.6g of bacterial cellulose, 3g of calcium carbonate and 110ml of deionized water in a beaker, place a stirring bar of appropriate size, then seal it with tin foil, and stir magnetically at 95°C Stir and dissolve in a water bath for 1.5h to obtain a uniform milky white polyvinyl alcohol solution;

(2) Cool the polyvinyl alcohol solution to 76°C, pour the mixed 10ml emulsifier OP-10 and 14ml dimethyl carbonate into the beaker containing the polyvinyl alcohol solution at one time, and stir for 2h until the solution reaction is White and viscous, remove the magnetic stirrer;

(3) the white viscous solution was cooled to 36 ℃, 12ml of foaming agent n-pentane was added, and a strong stirrer was used to stir at a rotating speed of 1500r/min until bubbles of uniform size were generated in the solution, and the foamed solution was obtained;

(4) Pour the foamed solution into the mold, and repeat freeze-thaw three times (freeze-thaw in a freeze dryer at -45°C for 7 hours, and then thaw at room temperature for 2 hours) to obtain a pore diameter of 9.97 - 11.92 μm, 322% elongation polyvinyl alcohol sponge.

Example 3

Place 10g of polyvinyl alcohol (molecular weight 145000), 0.6g of bacterial cellulose, 3g of calcium carbonate and 120ml of deionized water in a beaker, place a stirring bar of appropriate size, then seal it with tin foil, and place it in a magnetic stirring water bath at 95°C. Stir and dissolve for 1.5h to obtain a uniform milky white polyvinyl alcohol solution;

(2) Cool the polyvinyl alcohol solution to 76°C, pour the mixed 10ml emulsifier OP-10 and 14ml dimethyl carbonate into the beaker containing the polyvinyl alcohol solution at one time, and stir for 2h until the solution reaction is White and viscous, remove the magnetic stirrer;

(3) the white viscous solution was cooled to 36 ℃, 12ml of foaming agent n-pentane was added, and a strong stirrer was used to stir at a rotating speed of 1500r/min until bubbles of uniform size were generated in the solution, and the foamed solution was obtained;

(4) Pour the foamed solution into the mold, and repeat freeze-thaw three times (freeze-thaw is frozen in a freeze dryer at -45°C for 7 hours, and then thawed at room temperature for 2 hours) to obtain a pore diameter of 8.68 - 9.17 μm, 332% elongation polyvinyl alcohol sponge.

It can be seen from FIG. 3 that the tensile properties of the polyvinyl alcohol sponge obtained in this example are higher than 300%.

Comparing Example 1, Example 2 and Example 3, it can be seen that: with the increase of the amount of deionized water, the diameter of the pores of the polyvinyl alcohol sponge gradually decreases. From the formation principle of pores, it can be concluded that the amount of deionized water will affect the viscosity of the polyvinyl alcohol solution, which will then affect the fluidity of the system liquid and the strength of the pores, and finally affect the diameter of the pores of the sponge. After many experiments, it is concluded that the amount of deionized water should not exceed a certain range. If it is too large, the strength of the pore wall will be too small, resulting in collapse of bubbles; The pores are uneven.

Example 4

(1) After placing 10g polyvinyl alcohol (molecular weight 145000), 0.6g bacterial cellulose, 3g calcium carbonate, 4ml graphene solution and 100ml deionized water in a beaker, place a stirring bar of appropriate size, and then seal it with tin foil, Stir and dissolve in a magnetic stirring water bath at 95°C for 1.5h to obtain a homogeneous polyvinyl alcohol solution;

(2) Cool the polyvinyl alcohol solution to 76°C, pour the mixed 10ml emulsifier OP-10 and 14ml dimethyl carbonate into the beaker containing the polyvinyl alcohol solution at one time, and stir for 2h until the solution reaction is White and viscous, remove the magnetic stirrer;

(3) the white viscous solution was cooled to 36 ℃, 12ml of foaming agent n-pentane was added, and a strong stirrer was used to stir at a rotating speed of 1500r/min until bubbles of uniform size were generated in the solution, and the foamed solution was obtained;

(4) Pour the foamed solution into the mold, and repeat freeze-thaw three times (freeze and thaw in a freeze-drier at -45°C for 7 hours, and then thaw at room temperature for 2 hours) to obtain a pore diameter of 12.96 -18.75μm, elongation 298%, electrical resistivity 2.68x10 ^-4 Ω·m conductive polyvinyl alcohol sponge.

Example 5

(1) After placing 10g polyvinyl alcohol (molecular weight 145000), 0.6g bacterial cellulose, 3g calcium carbonate, 5ml graphene solution and 100ml deionized water in a beaker, place a stirring bar of appropriate size, and then seal it with tin foil, Stir and dissolve in a magnetic stirring water bath at 95°C for 1.5h to obtain a homogeneous polyvinyl alcohol solution;

(2) Cool the polyvinyl alcohol solution to 76°C, pour the mixed 10ml emulsifier OP-10 and 14ml dimethyl carbonate into the beaker containing the polyvinyl alcohol solution at one time, and stir for 2h until the solution reaction is White and viscous, remove the magnetic stirrer;

(3) the white viscous solution was cooled to 36 ℃, 12ml of foaming agent n-pentane was added, and a strong stirrer was used to stir at a rotating speed of 1500r/min until bubbles of uniform size were generated in the solution, and the foamed solution was obtained;

(4) Pour the foamed solution into the mold, and repeat freeze-thaw three times (freeze and thaw for 7 hours in a freeze dryer at -45°C, and then thaw at room temperature for 2 hours) to obtain a pore diameter of 13.12 -18.95μm, 241% elongation, 1.43x10 ^-4 Ω·m electrical resistivity conductive polyvinyl alcohol sponge.

Example 6

(1) After placing 10g polyvinyl alcohol (molecular weight 145000), 0.6g bacterial cellulose, 3g calcium carbonate, 6ml graphene solution and 100ml deionized water in a beaker, place a stirring bar of appropriate size, and then seal it with tin foil, Stir and dissolve in a magnetic stirring water bath at 95°C for 1.5h to obtain a homogeneous polyvinyl alcohol solution;

(2) Cool the polyvinyl alcohol solution to 76°C, pour 10ml of emulsifier OP-10 and 14ml of dimethyl carbonate mixed in an appropriate amount into the beaker containing the polyvinyl alcohol solution at one time, and stir for 2h until the solution reacts It is white and viscous, take out the magnetic stirring bar;

(3) the white viscous solution is cooled to 36 ℃, 12ml of foaming agent n-pentane is added, and a strong mixer is used to stir at a rotating speed of 1500r/min until bubbles of uniform size are generated in the solution, and the foamed solution is obtained; (4) ) Pour the foamed solution into the mold, and repeat freeze-thaw three times (freeze-thaw in a freeze-drier at -45°C for 7 hours, and then thaw at room temperature for 2 hours) to obtain a pore diameter of 13.31-19.25 A conductive polyvinyl alcohol sponge with μm, elongation rate of 226%, and resistivity of 4.12x10 ^-5 Ω·m.

By comparing Example 4, Example 5 and Example 6, it can be seen that: the content of graphene can affect the conductivity of the conductive sponge, and the higher the content of graphene, the smaller the resistivity; Affecting the pore size and tensile properties of the sponge, adding too much conductive material will reduce the number of cross-linking bonds inside the sponge, thereby greatly reducing the tensile properties. It can be seen that the content of various substances needs to be comprehensively considered when making the polyvinyl alcohol conductive sponge.

Table 1

Table 1 summarizes the data for all of the above examples and comparative examples. To sum up, compared with the traditional polyvinyl alcohol sponge, when the same dosage of polyvinyl alcohol, foaming agent and crosslinking agent is used, the elongation rate of the polyvinyl alcohol sponge prepared by the method provided by the present invention is improved, and the The method is simpler and more environmentally friendly, and the pore diameter, elongation rate and resistivity of the polyvinyl alcohol sponge can be flexibly adjusted according to the use environment.

What is not described in the present invention applies to the prior art.

Claims (9)

1. a preparation method of the polyvinyl alcohol sponge with high elongation is characterized in that the method comprises the steps: 1) after mixing polyvinyl alcohol, cellulose, carbonate and deionized water, stirring under closed conditions to complete dissolution to obtain a uniform polyvinyl alcohol solution; The cellulose is bacterial cellulose; the mass ratio of polyvinyl alcohol, cellulose, carbonate and deionized water is 42-46:2-4:8-12:240-260; the molecular weight of polyvinyl alcohol is 135000 -300000; 2) adding the mixture of emulsifier and esters to the polyvinyl alcohol solution obtained in step 1), stirring until the reaction is complete, to obtain a white viscous solution; 3) After adding a foaming agent to the white viscous solution obtained in step 2), use a strong stirrer to stir until bubbles of uniform size are generated in the solution to obtain a foamed solution; 4) Pour the foamed solution obtained in step 3) into a mold, and freeze-thaw to obtain a polyvinyl alcohol sponge with a high elongation rate. 2 . The method for preparing a polyvinyl alcohol sponge with high elongation rate according to claim 1 , wherein the reaction temperature in step 1) is 80-100° C. 3 . 3. The preparation method of the polyvinyl alcohol sponge with high elongation rate according to claim 1 is characterized in that the reaction temperature of step 2) is 70-80 ℃. 4. the preparation method of the polyvinyl alcohol sponge with high elongation rate according to claim 1, is characterized in that in step 2), described emulsifier adopts OP-10; Described ester is dimethyl carbonate; The volume ratio of emulsifier to ester is 2-4:4-5, and the mass of the mixture is 16-17% of the sum of the mass of the polyvinyl alcohol solution and the mixture; the stirring of step 2) uses magnetic stirring or is equipped with a propeller with a powerful mixer. 5. the preparation method of the polyvinyl alcohol sponge with high elongation rate according to claim 1 is characterized in that the reaction temperature of step 3) is 30-40 ℃, and the stirring speed is 1500-2000r/min. 6. the preparation method of the polyvinyl alcohol sponge with high elongation rate according to claim 1, is characterized in that in step 3), described foaming agent is n-pentane; The quality of foaming agent is white viscous 5-6% of the sum of the mass of the solution and foaming agent. 7. the preparation method of the polyvinyl alcohol sponge with high elongation rate according to claim 1 is characterized in that in step 4), freeze-thaw is to have the mould of foamed solution at -40 ℃ to -50 ℃ After freezing in a freeze dryer for 4-12 hours, thaw at room temperature for 2-3 hours. 8. the preparation method of the polyvinyl alcohol sponge with high elongation rate according to claim 1 is characterized in that adding conductive substance in the raw material of step 1), can make the polyvinyl alcohol conductive material with high elongation rate Sponge; the conductive substance is at least one of copper, aluminum, gold, silver, nickel, graphite, acetylene black, graphene, carbon nanotubes or MXene. 9. A polyvinyl alcohol sponge with high elongation obtained by the preparation method of any one of claims 1-8.

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