A non-polarized cotton cellulose / PVDF composite piezoelectric fabric and its preparation method and application

Abstract

A method for preparing a non-polarized cotton cellulose / PVDF composite piezoelectric fabric comprises: placing cotton cellulose in a constant temperature oven and drying it to constant weight, adding DMAc solvent for activation treatment; dissolving cotton cellulose in a LiCl / DMAc system to obtain a cotton cellulose solution; dissolving PVDF in a DMAc solvent to obtain a PVDF solution; blending the cotton cellulose solution and the PVDF solution under mechanical stirring, and subjecting the obtained blended solution to high-pressure degassing treatment to obtain a cotton cellulose / PVDF composite spinning solution; extruding the cotton cellulose / PVDF composite spinning solution from a spinneret, and immersing it in a coagulation bath to coagulate and form the fiber through the double diffusion effect of the solvent, and then washing and drying to obtain a cotton cellulose / PVDF composite piezoelectric fiber; weaving the cotton cellulose / PVDF composite piezoelectric fiber by warp and weft weaving to obtain a non-polarized cotton cellulose / PVDF composite piezoelectric fabric. The invention uses waste cotton pulp (cotton cellulose) as a raw material, adopts a pre-activation process and then dissolves it in a LiCl / DMAc system, is simple to operate, and realizes the reuse of waste cotton.

Description

Technical Field

[0001] The present invention relates to the field of wearable fabrics and intelligent sensing, and in particular to a non-polarized cotton cellulose / PVDF composite piezoelectric fabric and a preparation method and application thereof. Background Art

[0002] New electronic fabric technology is promoting innovative applications in clothing, and the sensory experience of telemedicine, temperature regulation, reality and even the metaverse may usher in a huge change. Smart fabrics (also known as electronic fabrics) refer to fibers and fabrics embedded with electronic devices or electronic functions, which have the characteristics of automatic heating and cooling, data collection and transmission, power generation, tactile sensing, etc.

[0003] Traditional sensors usually have problems such as large mass, rigidity and battery replacement. The development of self-powered sensing fabrics using the piezoelectric effect solves the problems of traditional wearable electronic devices relying on external power supply, single function and low sensitivity, and provides a new solution for realizing multifunctional integrated wearable devices. In addition, most piezoelectric materials need to be polarized by an external high-voltage electric field to induce the transformation of the non-piezoelectric phase in the piezoelectric material to the piezoelectric phase in order to produce the piezoelectric effect, which will inevitably cause energy loss and limit the application, so it needs further improvement. Summary of the invention

[0004] Based on this, the present invention provides a non-polarized cotton cellulose / PVDF composite piezoelectric fabric and its preparation method and application, which utilizes the stretching force in the wet spinning process to promote the transformation of the non-piezoelectric phase in the piezoelectric material PVDF to the piezoelectric phase. In this way, there is no need for external electric field polarization to produce a piezoelectric effect, thereby solving the technical problem in the prior art that self-powered sensing materials using the piezoelectric effect require external electric field polarization, resulting in energy loss.

[0005] To achieve the above object, the present invention provides a method for preparing a non-polarized cotton cellulose / PVDF composite piezoelectric fabric, which comprises the following steps:

[0006] S1, drying cotton cellulose with a degree of polymerization of 500 to 650 in a 50°C constant temperature oven to constant weight, and adding DMAc solvent for activation treatment;

[0007] S2, dissolving the cotton cellulose treated in step S1 in a LiCl / DMAc system to obtain a cotton cellulose solution; preferably, the mass fraction of LiCl in DMAc is 10%, and the activated cotton cellulose is dissolved in the LiCl / DMAc system by high-speed mechanical stirring, with a rotation speed of ≥1500rpm and a stirring time of 60 to 90min. After the solution is dissolved, the solution is placed in a constant temperature oven at 25°C and allowed to stand for 12h for standby use;

[0008] S3, dissolving PVDF with a molecular weight of 400,000 to 600,000 in DMAc solvent to obtain a PVDF solution;

[0009] S4, blending the cotton cellulose solution and the PVDF solution under mechanical stirring at a mass ratio of cotton cellulose to PVDF of 7:10-9:10, and subjecting the obtained blended solution to high-pressure degassing to obtain a cotton cellulose / PVDF composite spinning solution;

[0010] S5, the cotton cellulose / PVDF composite spinning solution is heated to 25-30°C and the spinning pressure is 50-100 kg / cm 3 , extruded from the spinneret at a spinning speed of 4 to 5 m / min, and immersed in a coagulation bath to coagulate the fiber through the double diffusion of the solvent, and then washed and dried to obtain the cotton cellulose / PVDF composite piezoelectric fiber; preferably, the fiber baths used for the coagulation bath are sequentially arranged with 5 baths, namely: 1#, 2#, 3#, 4# baths are water at a temperature of 40°C, and 5# baths are methanol at room temperature; of course, the number of baths can be adjusted according to actual needs, and at least one bath contains water, and at least one bath contains methanol;

[0011] S6. Weaving the cotton cellulose / PVDF composite piezoelectric fibers by warp and weft weaving method to obtain non-polarized cotton cellulose / PVDF composite piezoelectric fabric.

[0012] As a further preferred technical solution of the present invention, in step S1, the cotton cellulose activation treatment temperature is 50-70°C, and the activation treatment time is 6-12 hours. The activation treatment can reduce the dissolution temperature of cotton cellulose in the LiCl / DMAc system in the subsequent steps, and also improve the dissolution effect of cellulose and the uniformity in the solvent system.

[0013] As a further preferred technical solution of the present invention, the cotton cellulose activated by DMAc in step S1 is placed in a vacuum oven at 50-60° C. for drying.

[0014] As a further preferred technical solution of the present invention, in step S2, the solid content of LiCl in the LiCl / DMAc system is 6% to 10%, and the dissolution temperature is 50°C.

[0015] As a further preferred technical solution of the present invention, in step S4, the concentration of the cotton cellulose solution is 3% to 4%, and the concentration of the PVDF solution is 20%.

[0016] As a further preferred technical solution of the present invention, in step S4, the mechanical stirring speed is 1000-1500 rpm, the stirring time is 30 min, and the degassing pressure is 0.4-0.6 MPa.

[0017] As a further preferred technical solution of the present invention, in step S5, the specification of the spinneret is 20 holes×0.2 mm, the component of the coagulation bath is water, and the temperature of the coagulation bath is 25-60°C.

[0018] As a further preferred technical solution of the present invention, in step S6, the fiber bundles of the cotton cellulose / PVDF composite piezoelectric fibers are cut into 5 m sections before weaving, and then twisted.

[0019] According to another embodiment of the present invention, the present invention further provides a non-polarized cotton cellulose / PVDF composite piezoelectric fabric, which is prepared by the above-mentioned preparation method of the non-polarized cotton cellulose / PVDF composite piezoelectric fabric.

[0020] The non-polarized cotton cellulose / PVDF composite piezoelectric fabric and the preparation method thereof of the present invention can achieve the following beneficial effects by adopting the above technical scheme:

[0021] (1) The present invention uses waste cotton pulp (cotton cellulose) as raw material, adopts a pre-activation process and then dissolves it in a LiCl / DMAc system, which is not only simple to operate but also realizes the reuse of waste cotton.

[0022] (2) The cotton cellulose / PVDF composite spinning solution prepared by the present invention has good spinnability. The coagulation bath is water and methanol, wherein water is a green and pollution-free solvent and methanol can be reused.

[0023] (3) The non-polarized cotton cellulose / PVDF composite piezoelectric fabric prepared by the present invention has excellent piezoelectric sensing performance. Its peak open circuit voltage and peak short circuit current can reach 10V and 1μA respectively, and it remains stable after 3000 cycle tests, meeting the needs of self-powered sensing, thereby reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0025] Figure 1 This is the process flow chart of wet spinning of composite piezoelectric fibers.

[0026] Figure 2 This is a real picture of cotton cellulose / PVDF composite piezoelectric fabric.

[0027] Figure 3 This is the infrared spectrum of cotton cellulose / PVDF composite piezoelectric fabric.

[0028] Figure 4 This is the X-ray diffraction spectrum of cotton cellulose / PVDF composite piezoelectric fabric.

[0029] Figure 5The open circuit voltage (a) and short circuit current (b) test results of the composite piezoelectric fabric with cotton cellulose: PVDF = 8:10 (mass ratio).

[0030] Figure 6 The composite piezoelectric fabric with cotton cellulose: PVDF = 8:10 (mass ratio) was tested after 3000 cycles.

[0031] Figure 7 Fiber breaking strength at different ratios of cotton cellulose and PVDF.

[0032] Figure 8 is the open circuit voltage of piezoelectric fabric under 10N force under different spinning pressures

[0033] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0034] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0035] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0036] Example 1

[0037] (1) Weigh 3.6 g of absolutely dry waste cotton pulp (cotton cellulose) with a degree of polymerization of 543 and place it in a 250 ml beaker, add 30 g of N,N-dimethylacetamide (DMAc) solvent, and activate it at 60°C for 6 h. After the activation, remove the residual DMAc solvent in the pulp and recover the DMAc solvent. Then, place the activated cotton pulp in a vacuum oven at 60°C and dry it to constant weight.

[0038] (2) 3.6 g of the activated waste cotton pulp in step (1) was dissolved in 86.4 g of LiCl / DMAc co-solvent, wherein the mass fraction of LiCl was 8%, and mechanically stirred at a speed of 1500 rpm at room temperature for 40 min to obtain a cellulose solution with a mass fraction of 4%; 2.52 g of polyvinylidene fluoride (PVDF) with a molecular weight of 500,000 was weighed and added to 10.08 g of DMAc, and stirred at 50° C. for 8 h to obtain a PVDF solution with a mass fraction of 20%.

[0039] (3) The cellulose solution and PVDF solution prepared in step (2) are mixed evenly by mechanical stirring and subjected to high-pressure degassing treatment, wherein the cotton cellulose:PVDF=7:10 (mass ratio), and then the cotton cellulose / PVDF composite piezoelectric fiber is prepared by wet spinning technology, wherein 5 coagulation bath tanks for spinning are set, namely: 1#, 2#, 3#, 4# tanks are water at a temperature of 40°C, and 5# tank is methanol at room temperature; the spinning cap specification is 20 holes×0.2mm, and the spinning pressure is 75kg / cm 2 The spinning speed is 5m / min. The process flow of wet spinning technology is as follows Figure 1 shown.

[0040] (4) The obtained fiber bundle is cut into sections of 5 m each and twisted, and then manually woven into a fabric using a warp and weft weaving method, to obtain a fabric such as Figure 2 Non-polarized cotton cellulose / PVDF composite piezoelectric fabric.

[0041] The piezoelectric sensing test was carried out on the composite piezoelectric fabric prepared by wet spinning in Example 1. Under a cyclic pressure of 10N, its open circuit voltage and short circuit current were measured to be 4V and 0.5μA respectively. Then, its structure was characterized as follows: Figure 3 and Figure 4 As shown, compared with the original PVDF, the non-piezoelectric α phase of PVDF in the cotton cellulose / PVDF piezoelectric fabric formed by wet spinning almost disappears, while the piezoelectric β phase content is greatly increased.

[0042] As a control group of Example 1, the same preparation method as Example 1 was adopted, except that the last coagulation bath in the wet spinning process was replaced by ethanol from methanol, and the spinnability of the fiber was deteriorated.

[0043] Example 2

[0044] (1) Weigh 3.6 g of absolutely dry waste cotton pulp with a degree of polymerization of 543 and place it in a 250 ml beaker, add 30 g of DMAc solvent, and activate it at 60°C for 6 h. After the activation, remove the residual DMAc solvent in the pulp and recover the DMAc solvent. Then, place the activated cotton pulp in a vacuum oven at 60°C and dry it to constant weight.

[0045] (2) 3.6 g of the activated waste cotton pulp in step (1) was dissolved in 86.4 g of LiCl / DMAc co-solvent, wherein the mass fraction of LiCl was 8%, and mechanically stirred at a rotation speed of 1500 rpm at room temperature for 40 min to obtain a cellulose solution with a mass fraction of 4%; 2.88 g of PVDF with a molecular weight of 500,000 was weighed and added to 11.52 g of DMAc, and stirred at 50° C. for 8 h to obtain a PVDF solution with a mass fraction of 20%.

[0046] (3) The solution prepared in step (2) is mixed evenly by mechanical stirring and subjected to high-pressure degassing treatment, cotton cellulose: PVDF = 8:10 (mass ratio), and then the cotton cellulose / PVDF composite piezoelectric fiber is prepared by wet spinning technology, and the process is as follows: 5 bath tanks for the coagulation bath used for spinning are set, namely: 1#, 2#, 3#, 4# tanks are water, the temperature is 40°C, 5# tank is methanol, the temperature is room temperature; the spinneret used for spinning has a specification of 20 holes × 0.2 mm, and the spinning pressure is 75 kg / cm 2 , the spinning speed is 5m / min.

[0047] (4) The obtained fiber bundles were cut into sections of 5 m each and twisted, and then manually woven into a fabric using a warp and weft weaving method, namely, a non-polarized cotton cellulose / PVDF composite piezoelectric fabric.

[0048] The piezoelectric sensing test was performed on the composite piezoelectric fabric obtained by wet spinning in Example 2. Figure 5 The open circuit voltage and short circuit current measured under 10N cycle pressure were 7V and 0.7μA, respectively, which were higher than the open circuit voltage and short circuit current generated under the same pressure in Example 1. Figure 6 As shown in Figure 2, it remains stable after 3000 cycles of testing. Next, its structure is characterized, as shown in Figure 2. Figure 3 and Figure 4 As shown, compared with the original PVDF, the non-piezoelectric α phase of PVDF in the cotton cellulose / PVDF piezoelectric fabric formed by wet spinning almost disappears, while the piezoelectric β phase content is greatly increased. Compared with the fabric in Example 1, the piezoelectric β phase content of the composite piezoelectric fabric is higher.

[0049] As a control group of Example 2, the same preparation method as Example 2 was adopted, except that the temperature of the coagulation bath water was set to 60°C and 80°C, respectively. The content of the piezoelectric β phase in the prepared composite piezoelectric fiber remained almost unchanged. From the perspective of energy saving and double diffusion of the solvent in the coagulation bath, a temperature of the coagulation bath water of 40°C was more appropriate, with lower energy consumption and more suitable for industrial production.

[0050] Example 3

[0051] (1) Weigh 3.6 g of absolutely dry waste cotton pulp with a degree of polymerization of 543 and place it in a 250 ml beaker, add 30 g of DMAc solvent, and activate it at 60°C for 6 h. After the activation, remove the residual DMAc solvent in the pulp and recover the DMAc solvent. Then, place the activated cotton pulp in a vacuum oven at 60°C and dry it to constant weight.

[0052] (2) 3.6 g of the activated waste cotton pulp in step (1) was dissolved in 86.4 g of LiCl / DMAc co-solvent, wherein the mass fraction of LiCl was 8%, and mechanically stirred at a speed of 1500 rpm at room temperature for 40 min to obtain a cellulose solution with a mass fraction of 4%; 3.24 g of PVDF with a molecular weight of 500,000 was weighed and added to 12.96 g of DMAc, and stirred at 50° C. for 8 h to obtain a PVDF solution with a mass fraction of 20%.

[0053] (3) The solution prepared in step (2) is mixed evenly by mechanical stirring and subjected to high-pressure degassing treatment, cotton cellulose: PVDF = 9:10 (mass ratio), and then the cotton cellulose / PVDF composite piezoelectric fiber is prepared by wet spinning technology, and the process is as follows: 5 bath tanks for the coagulation bath used for spinning are set, namely: 1#, 2#, 3#, 4# tanks are water, the temperature is 40°C, 5# tank is methanol, the temperature is room temperature; the spinneret used for spinning has a specification of 20 holes × 0.2 mm, and the spinning pressure is 75 kg / cm 2 , the spinning speed is 5m / min.

[0054] (4) The obtained fiber bundles were cut into sections of 5 m each and twisted, and then manually woven into a fabric using a warp and weft weaving method, namely, a non-polarized cotton cellulose / PVDF composite piezoelectric fabric.

[0055] The piezoelectric sensing test was performed on the composite piezoelectric fabric prepared by wet spinning in Example 3. The open circuit voltage and short circuit current were measured to be 10V and 1μA respectively under a cyclic pressure of 10N, which were higher than the open circuit voltage and short circuit current generated under the same pressure in Example 2. Next, the structure was characterized, as shown in FIG. Figure 3 and Figure 4 As shown in the figure, compared with the original PVDF, the non-piezoelectric α phase of PVDF in the wet-spinning cotton cellulose / PVDF piezoelectric fabric almost disappears, while the piezoelectric β phase content is greatly increased. Compared with the fabric in Example 2, the piezoelectric β phase content of the composite piezoelectric fabric is higher. It can be seen that the content of the piezoelectric β phase increases with the increase of the PVDF content, as shown in FIG. Figure 7 As shown, it can be seen that with the further increase of PVDF content, the breaking strength of the piezoelectric fiber will decrease.

[0056] As a control group of Example 3, the same preparation method as Example 3 was used, except that the spinning pressure was changed to 110 kg / cm 3 The open circuit voltage and open circuit current of the prepared piezoelectric fabric are only half of the original ones, 5V and 0.5μA respectively. Figure 8The open circuit voltage of the piezoelectric fabric under 10N force under different spinning pressures is shown in the figure. It can be seen that with the increase of spinning pressure, the open circuit voltage and short circuit current of the fabric first increase and then decrease, and when the spinning pressure is 75kg / cm 3 When the open circuit voltage and short circuit current of the fabric reach the maximum values ​​of 10 V and 1 μA, respectively. Therefore, the piezoelectric fabric of the present invention can generate considerable voltage and current without external high voltage electric field polarization, so that the piezoelectric fabric can be used as a self-powered sensing material without external electric field polarization.

[0057] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a non-polarized cotton cellulose / PVDF composite piezoelectric fabric, characterized in that: The following steps are involved: S1, drying cotton cellulose with a degree of polymerization of 500 to 650 in a constant temperature oven to constant weight, and adding DMAc solvent for activation treatment; S2, dissolving the cotton cellulose treated in step S1 in a LiCl / DMAc system to obtain a cotton cellulose solution; S3, dissolving PVDF with a molecular weight of 400,000 to 600,000 in DMAc solvent to obtain a PVDF solution; S4, blending the cotton cellulose solution and the PVDF solution under mechanical stirring at a mass ratio of cotton cellulose to PVDF of 7:10-9:10, and subjecting the obtained blended solution to high-pressure degassing to obtain a cotton cellulose / PVDF composite spinning solution; S5, the cotton cellulose / PVDF composite spinning solution is heated to 25-30°C and the spinning pressure is 50-100 kg / cm 3 , extruding from a spinning cap at a spinning speed of 4 to 5 m / min, and immersing in a coagulation bath to coagulate the fiber through the double diffusion of the solvent, and then washing and drying to obtain a cotton cellulose / PVDF composite piezoelectric fiber, wherein there are multiple coagulation baths, at least one of which has water as the bath liquid, and at least one of which has methanol as the bath liquid, and the fiber extruded from the spinning cap passes through multiple coagulation baths in sequence; S6. Weaving the cotton cellulose / PVDF composite piezoelectric fibers by warp and weft weaving method to obtain non-polarized cotton cellulose / PVDF composite piezoelectric fabric.

2. The method for preparing the non-polarized cotton cellulose / PVDF composite piezoelectric fabric according to claim 1, characterized in that: In step S1, the cotton cellulose activation treatment temperature is 50-70° C., and the activation treatment time is 6-12 hours.

3. The method for preparing the non-polarized cotton cellulose / PVDF composite piezoelectric fabric according to claim 1, characterized in that: The cotton cellulose activated by DMAc in step S1 is placed in a vacuum oven at 50-60° C. and dried.

4. The method for preparing the non-polarized cotton cellulose / PVDF composite piezoelectric fabric according to claim 1, characterized in that: In step S2, the solid content of LiCl in the LiCl / DMAc system is 6% to 10%, and the dissolution temperature is 50°C.

5. The method for preparing the non-polarized cotton cellulose / PVDF composite piezoelectric fabric according to claim 1, characterized in that: In step S4, the concentration of the cotton cellulose solution is 3% to 4%, and the concentration of the PVDF solution is 20%.

6. The method for preparing the non-polarized cotton cellulose / PVDF composite piezoelectric fabric according to claim 1, characterized in that: In step S4, the mechanical stirring speed is 1000-1500 rpm, the stirring time is 30 min, and the degassing pressure is 0.4-0.6 MPa.

7. The method for preparing the non-polarized cotton cellulose / PVDF composite piezoelectric fabric according to claim 1, characterized in that: In step S5, the specification of the spinneret is 20 holes×0.2 mm, the component of the coagulation bath is water, and the temperature of the coagulation bath is 25-60°C.

8. The method for preparing the non-polarized cotton cellulose / PVDF composite piezoelectric fabric according to claim 1, characterized in that: In step S6, the fiber bundles of the cotton cellulose / PVDF composite piezoelectric fibers are cut into 5-meter sections before weaving, and then twisted.

9. A non-polarized cotton cellulose / PVDF composite piezoelectric fabric, characterized in that: The non-polarized cotton cellulose / PVDF composite piezoelectric fabric is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the non-polarized cotton cellulose / PVDF composite piezoelectric fabric according to claim 9 in self-powered sensing.

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