TWI780437B - Yarn and fabric - Google Patents

Abstract

Yarns (1, 2) are provided with fibers (10) that generate a potential on the surface by external energy, and the above-mentioned surface is generated with a potential of 0.1 V or more by measuring under the following conditions (a) to (d): (a) Stretch the above-mentioned yarns (1, 2) by a predetermined amount in the uniaxial direction; (b) Coating the above-mentioned fibers (10) on a core material composed of conductive fibers; (c) grounding said core material; (d) The surface potential of the above-mentioned fiber (10) was measured using an electrostatic force microscope.

Description

Yarn and Fabric

The present invention relates to yarns and fabrics that generate charges.

For example, Patent Document 1 discloses a yarn and fabric including a charge-generating fiber that generates charges using external energy. The yarn and fabric of Patent Document 1 exert an antibacterial effect by utilizing the electric charges generated. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent No. 2018-90950

[Problem to be Solved by the Invention]

However, the charge-generating fiber of Patent Document 1 does not disclose to what extent electric potential is generated on the surface of the fiber. If the generated potential is too low, the desired effect may not be produced.

Therefore, the object of the present invention is to provide a yarn and a cloth that exhibit desired effects. [Technical means to solve the problem]

The yarn of the present invention is provided with fibers whose surface is potential-generated by external energy, and the above-mentioned surface is made to generate a potential of 0.1 V or more by measuring under the following conditions (a) to (d): (a) Stretch the above-mentioned yarn by a predetermined amount in the uniaxial direction; (b) covering the above-mentioned fibers on a core material composed of conductive fibers; (c) grounding said core material; (d) The surface potential of the above-mentioned fibers was measured using an electrostatic force microscope.

Fibers that use external energy to generate potential on the surface include materials with piezoelectric effects (such as polylactic acid, materials with photoelectric effects, and materials with pyroelectric effects (such as PVDF: Polyvinylidene Difluoride)) , or substances that use chemical changes to generate charges, etc. The yarn of the present invention exerts an antibacterial effect by utilizing the potential generated. In addition, the yarn of the present invention can also charge a substance by generating a predetermined potential under the above-mentioned conditions. Alternatively, the yarn of the present invention can adsorb substances by generating a predetermined potential under the above conditions. [Effect of Invention]

According to the present invention, desired effects such as antibacterial, electrification, or adsorption can be exerted by generating a predetermined potential under predetermined conditions.

Embodiments of the present invention will be described below. Fig. 1 (A) is a partial exploded view showing the composition of the yarn 1, and Fig. 1 (B) is a sectional view of line A-A of Fig. 1 (A).

The yarn 1 is a multifilament yarn formed by twisting a plurality of fibers 10 . Fiber 10 is a fiber with a circular cross section. The yarn 1 is a left-handed yarn obtained by twisting a plurality of fibers 10 left-handedly (hereinafter referred to as Z yarn).

The fiber 10 is made of, for example, a piezoelectric polymer. The fiber 10 is manufactured, for example, by extruding a piezoelectric polymer and forming a fiber. Alternatively, the fiber 10 is produced by a method such as a method of melt-spinning a piezoelectric polymer to form fibers (for example, a spinning-extending method including a spinning step and an extending step; a linking spinning step and The straight stretching method of the extension step; the POY-DTY method of the false twisting step at the same time; or the ultra-high-speed spinning method of high speed, etc.); the use of dry or wet spinning (for example, including: if the polymer used as raw material Dissolved in a solvent and then extruded from a nozzle to form a phase separation method or a dry-wet spinning method; a gel spinning method in which the fiber is uniformly formed into a gel in a state containing a solvent; or using a liquid crystal solution or melt to form a fiber A method of fiberizing piezoelectric polymers, such as liquid crystal spinning, or a method of using electrospinning to fiberize piezoelectric polymers. Furthermore, the cross-sectional shape of the fiber 10 is not limited to a circle.

Piezoelectric polymers include those having pyroelectricity and those not having pyroelectricity, but all of them can be used. For example, PVDF has pyroelectricity, and it is also polarized by temperature changes, generating potential on the surface of the fiber. Piezoelectric materials with pyroelectric properties such as PVDF are also polarized by the heat energy of the human body. In this case, the thermal energy of the human body is energy from the outside.

In addition, polylactic acid (PLA: Polylactic Acid) is a piezoelectric polymer that does not have pyroelectricity. Polylactic acid generates piezoelectricity by uniaxial stretching. As polylactic acid, according to the crystal structure, there are poly-L-lactic acid obtained by polymerizing L-lactic acid and L-lactide, poly-D-lactic acid obtained by polymerizing D-lactic acid and D-lactide, and further, polylactic acid obtained by polymerizing D-lactic acid and D-lactide. Stereocomplex (stereocomplex) polylactic acid, etc., which are composed of a hybrid structure, can be used as long as it exhibits piezoelectricity. From the viewpoint of the level of piezoelectricity, it is preferable to use poly-L-lactic acid or poly-D-lactic acid. The polarity of polarization of poly-L-lactic acid and poly-D-lactic acid is opposite to each other for the same deformation.

When polylactic acid is uniaxially stretched and its molecules are oriented, it exhibits piezoelectricity. The crystallinity of polylactic acid can be increased by further applying heat treatment, thereby increasing the piezoelectric constant. Polylactic acid produces piezoelectricity due to the orientation treatment of extended molecules, so it does not require polarization treatment like other piezoelectric polymers such as PVDF or piezoelectric ceramics.

The piezoelectric constant of uniaxially stretched polylactic acid is about 5-30 pC/N, which is a very high piezoelectric constant among polymers. Furthermore, the piezoelectric constant of polylactic acid does not change over time and is extremely stable.

In the fiber 10 comprising uniaxially stretched polylactic acid, the thickness direction is defined as the first axis, the stretching direction 900 is defined as the third axis, and the direction perpendicular to both the first axis and the third axis is defined as the second axis. For 2 axes, it has tensor components such as d ₁₄ and d ₂₅ as the piezoelectric strain constant. Therefore, when the fiber 10 made of uniaxially stretched polylactic acid undergoes shear deformation in a direction intersecting the direction of uniaxial stretching, a potential is generated.

In FIG. 1(A), the extending direction 900 of each fiber 10 is consistent with the axial direction of each fiber 10 . By twisting a plurality of fibers 10 , the extending direction 900 of the fibers 10 becomes inclined with respect to the axial direction of the yarn 1 .

When tension is applied to the yarn 1 of the Z yarn to stretch it, the fiber 10 is strained in the axial direction of the yarn 1 and sheared in the axial direction of the yarn 1 . Therefore, a positive potential is generated on the surface of the fiber 10 and a negative potential is generated on the inside. Furthermore, in the case of a right-handed yarn (hereinafter referred to as S yarn) formed by twisting the fiber 10 to the right as shown in FIG. 2 , when stretched, the surface of the fiber 10 generates a negative potential. , a positive potential is generated inside.

Therefore, a positive potential is generated on the surface of the yarn 1, and a negative potential is generated on the inside. Negative potential is generated on the surface of yarn 2, and positive potential is generated on the inside. However, the twist angle of the fiber 10 differs depending on the location, and the thickness of the yarn 1 and the yarn 2 is not uniform as a whole. As a result, fibers 10 generally cannot generate a uniform surface potential.

Fig. 3 shows the simulation results of the potential when a 2% displacement is applied to the yarn 1 in the axial direction. However, in this simulation result, it is assumed that the fibers 10 slide against each other when the yarn 1 is displaced in the axial direction. In this simulation result, by applying a 2% displacement to the axial direction, the average value of the twist angle changes from 6.5° to 5.5°.

As shown in the simulation results of FIG. 3 , the fiber 10 has a portion where a positive potential is generated and a portion where a negative potential is generated. The yarn 1 respectively forms electric fields between the parts generating positive potential and the parts generating negative potential.

Fig. 4(A) shows the simulation results of the electric field in a certain section of the yarn 1 as the Z yarn. Fig. 4(B) shows the simulation results of the electric field in a certain section of the yarn 2 as the S yarn. As shown by these simulation results, it can be seen that each of the yarn 1 and the yarn 2 alone also has a portion generating an electric field of several MV/m.

In this way, the yarn of the present invention has a plurality of fibers 10 that generate electric potential on the surface using external energy, and an electric field is generated between the plurality of fibers 10 when a displacement is applied.

More specifically, the fiber 10 has a positive potential portion and a negative potential portion (a portion with a different potential), and an electric field is generated between the positive portion and the negative portion of the plurality of fibers 10 .

In addition, the extending direction 900 of the fiber 10 only needs to intersect at least the axial direction of the yarn. Preferably, the average twist angle is 10° to 50°. More preferably, the average twist angle is 20° to 40°.

Of course, an electric field is also generated between the yarn 1 and other substances, between the yarn 2 and other substances, or between the yarn 1 and the yarn 2 . Fig. 5 is a cross-sectional view showing the state of the electric field when the yarn 1 and the yarn 2 are brought close to each other. In a single yarn, when tension is applied in the axial direction, the surface becomes a positive potential and the inside becomes a negative potential. In the two yarns, when tension is applied in the axial direction, the surface becomes negative potential and the inside becomes positive potential.

When these yarns 1 and 2 are close to each other, the adjacent parts (surfaces) tend to have the same potential. In this case, the portion close to the yarn 1 and the yarn 2 becomes 0 V, and the negative potential inside the yarn 1 is further lowered in order to maintain the original potential difference. Likewise, the positive potential inside the yarn 2 further becomes higher.

In the cross-section of the yarn 1, an electric field is mainly formed from the outside of the yarn 1 toward the inside, and in the cross-section of the yarn 2, an electric field is mainly formed from the inside to the outside. When the yarn 1 and the yarn 2 are brought close together, these electric fields are leaked into the air and synthesized, and an electric field is formed between the yarn 1 and the yarn 2 by utilizing the potential difference between the yarn 1 and the yarn 2.

Also, when the yarn 1 is close to an object having a predetermined potential such as a human body, an electric field is also generated between the yarn 1 and the approaching object. When the yarn 2 is close to an object with a predetermined potential such as a human body, an electric field is also generated between the yarn 2 and the approaching object.

Such an electric field, for example, exerts an antibacterial effect of inhibiting the proliferation of viruses, bacteria, fungi, archaea, or microorganisms such as mites and fleas.

Furthermore, when the yarn 1 or the yarn 2 contains water containing an electrolyte, an electric current flows through the water. The yarn 1 or the yarn 2 may also directly exert an antibacterial effect or a bactericidal effect by this electric current. Alternatively, there are free radical-containing substances or substances containing free radicals produced by using active oxygen-containing substances that change the oxygen contained in moisture due to the action of electric current or voltage, and then interact with additives contained in fibers or act as catalysts. Other antibacterial chemical species (amine derivatives, etc.) indirectly exert antibacterial or bactericidal effects. Or there is a situation where oxygen free radicals are generated in the cells of bacteria according to the pressure environment formed by the existence of electric field or current. With regard to free radicals, the generation of superoxide anion free radicals (active oxygen) or hydroxyl free radicals can be conceived.

The effect of antibacterial materials such as conventional medicines is not long-lasting. In addition, known antibacterial materials may also cause allergic reactions due to drugs and the like. On the other hand, the duration of the antibacterial effect of the yarn of this embodiment is longer than the antibacterial effect of chemicals and the like. In addition, the possibility of an allergic reaction to the yarn of this embodiment is lower than that of a drug. Furthermore, as mentioned above, the piezoelectric constant of polylactic acid does not change over time and is extremely stable, so the antibacterial effect of the yarn can also be stably exhibited for a long time.

In addition, yarn 1 or yarn 2 can use the generated potential to charge other substances. Alternatively, the yarn 1 or the yarn 2 can adsorb substances by means of the generated potential. For example, a positive potential is generated on the surface of the yarn 1, so substances with a negative potential can be adsorbed. A negative potential is generated on the surface of the yarn 2, so substances with a positive potential can be adsorbed.

The yarn 1 or the yarn 2 can also efficiently absorb substances by constituting a filter element. This type of filter is suitable for masks or air purifiers. Also, as the front-stage pre-filter, the material is positively or negatively charged by yarn 1 or yarn 2, and as the rear-stage filter, use yarn 1 or yarn 2 that generates a potential of opposite polarity, thereby more efficiently Adsorbed substances are also possible. As the front stage pre-filter, the material is positively or negatively charged by yarn 1 or yarn 2, and as the rear stage filter, an electret filter with opposite polarity potential can also be used.

Here, if the electric potential generated on the surface of the yarn 1 or the yarn 2 is too low, the various desired effects mentioned above may not be produced. However, the yarn of the present invention is characterized in that it has fibers that generate potential on the surface using energy from the outside, and the surface of the yarn is generated by 0.1 V or more by measuring under the following conditions (a) to (d). The potential. The yarn of the present invention can exert the desired effect by generating the prescribed potential under such conditions: (a) Stretch the above-mentioned yarn by a predetermined amount in the uniaxial direction; (b) covering the above-mentioned fibers on a core material composed of conductive fibers; (c) grounding said core material; (d) The surface potential of the above-mentioned yarns was measured using an electrostatic force microscope.

Furthermore, as the predetermined amount of (a) above, the strain of the yarn is preferably 0.1% or more. More preferably a strain of 0.5% or more. The surface potential is preferably at least 0.3 V, more preferably at least 1.0 V.

The thickness of the yarn (single fiber fineness) is preferably 0.005-10 dtex. If the fineness of single fibers becomes small, the number of long fibers becomes too large, and fluffing tends to occur. On the other hand, if the single fiber fineness is large and the number of long fibers is too small, the hand feeling will be damaged. In addition, the single fiber fineness mentioned here refers to the single fiber fineness of one twisted yarn. Even in the case of further doubling twisted yarns, it refers to the single fiber fineness of one twisted yarn before doubling.

Furthermore, the fiber strength of the yarn is preferably 1 to 5 cN/dtex. In this way, even if the yarn undergoes greater deformation in order to generate a higher potential, it can withstand without breaking. The fiber strength is more preferably 2 to 10 cN/dtex, further preferably 3 to 10 cN/dtex, most preferably 3.5 to 10 cN/dtex. According to the same purpose, the elongation of the yarn is preferably 10-50%.

Also, the crystallinity of polylactic acid is preferably 15 to 55%. Thereby, the piezoelectricity derived from the polylactic acid crystal becomes higher, and the polarization utilizing the piezoelectricity of the polylactic acid can be generated more effectively.

Examples are described below. The yarns of Examples 1-3 are twisted yarns using polylactic acid with a crystallinity of 45%, a crystal size of 12 nm, and a degree of orientation of 79%, and 84 dtex-24 long fibers. The yarns of Examples 1-3 are formed by coating long fibers of polylactic acid on a core material made of conductive fibers. Also, the core material is grounded. Therefore, the potential inside the yarns of Examples 1 to 3 was 0 V.

The number of twists in Example 1 is 500 T/m, the number of twists in Example 2 is 1150 T/m, and the number of twists in Example 3 is 3000 T/m. When the number of twists is 500 T/m, the average twist angle is 10°, and when the number of twists is 1150 T/m, the average value of twist angles is 28°. In the case of 3000 T/m, the average twist angle is 47°.

Table 1 shows that the two ends of the yarns of Examples 1-3 are clamped with rigid jigs, and the 40 mm yarns are stretched to 40.2 mm. After removing static electricity with an ionizer, stretch 0.5% in the axial direction (from 40.2 mm to 40.4 mm), the results of measuring the surface potential of the yarn using an electrostatic force microscope. The values of the potentials shown in Table 1 are positive or negative peak values.

[Table 1] 40.2 → 40.4 mm (0.5%) stretch twist direction 500 times 1150 times 3000 times S -0.15V -1.22V -0.35 V Z 0.12V 0.96V 0.40V

As shown in Table 1, the S yarn of Example 1 generated a potential of -0.15 V. The Z yarn of Example 1 produced a potential of 0.12 V. The S yarn of Example 2 produced a potential of -1.22 V. The Z yarn of Example 2 produced a potential of 0.96 V. The S yarn of Example 3 produced a potential of -0.35 V. The Z yarn of Example 3 produced a potential of 0.40 V.

Table 2 shows the results of measuring the surface potential of the yarn using an electrostatic force microscope when the yarn is stretched and stretched by 0.25% in the axial direction (between 40.4 mm and 40.5 mm) after being measured under the conditions in Table 1 above. The S yarn has a negative potential on its surface when stretched, and a positive potential on its surface when it shrinks. When the Z yarn is stretched, the surface generates a positive potential, and when it shrinks, the surface generates a negative potential. Therefore, when the yarn is stretched, positive and negative potentials are alternately generated. The value of the surface potential shown in Table 2 is the difference between the minimum value and the maximum value (peak-to-peak value difference).

[Table 2] 40.4→40.5 mm (0.25%) telescopic twist direction 500 times 1150 times 3000 times S 0.28V 2.83V 0.80V Z 0.33V 2.42V 0.75V

As shown in Table 1, the S yarn of Example 1 generated a potential of 0.28 V. The Z yarn of Example 1 produced a potential of 0.33 V. The S yarn of Example 2 produced a potential of 2.83 V. The Z yarn of Example 2 produced a potential of 2.42 V. The S yarn of Example 3 generated a potential of 0.80 V. The Z yarn of Example 3 produced a potential of 0.75 V.

From the results in Table 1 and Table 2, it can be confirmed that when the number of twists is 500 to 3000 Tm, a potential of about 0.1 V or more is generated on the surface of the yarn. In these examples, it was confirmed that the antibacterial effect was produced. Therefore, the yarn of the present invention can exert a desired effect by generating a predetermined potential (0.1 V or more) under the conditions of (a) to (d) above.

According to the measurement results of these examples, it can be said that the average value of the twist angle is preferably 10-50°. Also, in the above measurement results, the highest potential was generated when the twist angle was 30°, so it can be said that the average value of the twist angle is more preferably 20 to 40°.

The yarn of the present invention can be used in combination with various twisted yarns as needed. For example, twisted yarn of S twist mainly using poly-L-lactic acid and twisted yarn of Z twist mainly using poly-L-lactic acid can be used. When these yarns are brought close to each other, the electric field between the fibers becomes larger, and the antibacterial property becomes higher.

The case of using twisted yarn with S twist mainly using poly-L-lactic acid and twisted yarn with S-twist mainly using poly-D-lactic acid, and using twisted yarn with Z-twist mainly using poly-L-lactic acid and poly-D-lactic acid The Z-twist twisted yarn, the S-twist twisted yarn using poly-D-lactic acid, and the Z-twisted twisted yarn mainly using poly-D-lactic acid are the same.

These twisted yarns may be used after doubling, or any two twisted yarns among the above-mentioned twisted yarns may be used together as yarns constituting the fabric. The fabric of the present invention is composed of, for example, the above-mentioned yarn 1 or yarn 2 . Furthermore, in the present invention, cloth refers to fiber products such as woven fabrics, knitted fabrics, jogging fabrics, non-woven fabrics, and lace.

Each yarn constituting the cloth can generate a potential of 0.1 V or more on the surface under the above conditions (a)~(d), but the cloth itself of the present invention can also be measured under the following conditions (a)~(d) And make the surface of the cloth generate a potential of 0.1 V or more. The fabric of the present invention can also produce the desired effect by generating the prescribed potential under such conditions: (a) Stretch the above cloth by a predetermined amount in the uniaxial direction; (b) covering the above-mentioned fibers on a core material composed of conductive fibers; (c) grounding said core material; (d) The surface potential of the above-mentioned fabrics was measured using an electrostatic force microscope.

As in the case of the yarn, as the predetermined amount of (a) above, the strain of the fabric is preferably 0.1% or more. More preferably a strain of 0.5% or more. The surface potential is preferably at least 0.3 V, more preferably at least 1.0 V.

The parameters of the fibers constituting the fabric are the same as those of the above yarns. That is, the fiber thickness (single fiber fineness) is preferably 0.005 to 10 dtex. Furthermore, the fiber strength is preferably 1 to 5 cN/dtex. The fiber strength is more preferably 2 to 10 cN/dtex, further preferably 3 to 10 cN/dtex, most preferably 3.5 to 10 cN/dtex. The elongation of the fiber is preferably 10-50%. The crystallinity of polylactic acid is preferably 15-55%.

When the fibers constituting the fabric are twisted yarns, the average twist angle of the twisted yarn is preferably 10-50°, more preferably 20-40°.

Preferably, the weight per unit area of the fabric is 20-200 g/m ² , and the porosity is 50-95%. In addition, in the case of using cloth as a filter, in order to improve the capture performance and capture stability, it is preferable to set the capture rate of 0.3 μm particles at a wind speed of 5.1 cm/sec or higher to 40% or higher, and the pressure loss does not reach 250 Pa filter.

The cloth of the present invention can be applied to various products such as clothing and medical supplies. For example, the fabric of the present invention can be applied to underwear (especially socks), towels, insoles of shoes and boots, all sportswear, hats, bedding (including quilts, mattresses, sheets, pillows, pillowcases, etc.), toothbrushes, Dental floss, various types of filters (filters for water purifiers, air conditioners or air purifiers, etc.), dolls, pet-related products (mats for pets, pet clothes, linings for pet clothes), various mat products (feet , hand, or toilet seat, etc.), curtains, kitchen supplies (sponges or rags, etc.), seats (seats for automobiles, electric multiple vehicles, or airplanes, etc.), cushioning materials for motorcycle helmets and their exterior materials, sofas , bandages, gauze, masks, sutures, clothes for doctors and patients, protective gear, sanitary products, sporting goods (clothes and glove lining, or arm guards used in martial arts, etc.), or packaging materials, etc.

Clothing materials, especially socks (or protective gear), must expand and contract along the joints due to walking and other actions, so polarization will occur at a high frequency. In addition, although socks absorb moisture such as sweat and become a hotbed for bacterial proliferation, the fabric of the present invention can inhibit the proliferation of bacteria, so it has a significant effect as a bacterial countermeasure.

Furthermore, the yarn of the present invention can be either a non-twisted yarn or a false twisted yarn. The yarns constituting the cloth of the present invention may also be untwisted yarns or false twisted yarns. As long as the fiber is provided with a surface potential generated by external energy, and a potential of 0.1 V or more is generated under the above conditions, various desired effects such as an antibacterial effect can be exhibited.

It should be considered that description of this embodiment is an illustration in every respect, and it does not restrict|limit. The scope of the present invention is not shown by the above-mentioned embodiments, but by the claims. Furthermore, the scope of the present invention includes all modifications within the meaning and range equivalent to the claims.

1, 2: Yarn 10: fiber 900: Extension direction

[Fig. 1] Fig. 1(A) is a partially exploded view showing the constitution of the yarn 1, and Fig. 1(B) is a cross-sectional view along line A-A of Fig. 1(A). [ Fig. 2 ] is a partially exploded view showing the structure of the yarn 2 . [ Fig. 3 ] shows the simulation results of the potential when a 2% displacement is applied to the yarn 1 in the axial direction. [Fig. 4] Fig. 4(A) shows the simulation result of the electric field of a certain section of the Z yarn, that is, yarn 1, and Fig. 4(B) shows the simulation result of the electric field of a certain section of the S yarn, that is, yarn 2 result. [ Fig. 5 ] is a cross-sectional view showing the state of the electric field when the yarn 1 and the yarn 2 are brought close to each other.

1: Yarn

10: fiber

900: Extension direction

Claims (8)

A kind of yarn, it has the fiber that utilizes the energy from the outside to make the surface electric potential, and above-mentioned fiber is twisted, by measuring under the following conditions (a)~(f), make above-mentioned surface generate electric potential of 0.1V or more Potential: (a) Stretch the above-mentioned yarn by a predetermined amount in the uniaxial direction; (b) Cover the above-mentioned fiber on the core material composed of conductive fibers; (c) Ground the above-mentioned core material; (d) Use static electricity The surface potential of the above-mentioned yarns was measured by a force microscope; (e) the degree of crystallinity was 15-55%; (f) the number of times of twisting was 1150-3000T/m. The yarn according to claim 1, wherein the strain of the yarn is 0.1% or more as the predetermined amount. Such as the yarn of claim 1 or 2, its thickness is 0.005~10dtex. The yarn according to claim 1 or 2, wherein said fiber comprises polylactic acid. The yarn according to claim 3, wherein said fiber comprises polylactic acid. Such as the yarn of claim 1, wherein the average twist angle is 10-50°. Such as the yarn of claim 1 or 2, it satisfies the following necessary conditions (A)~(B): (A) fiber strength is 1~5cN/dtex; (B) elongation is 10~50%. A fabric comprising fibers whose surface is potential-generated by energy from the outside, wherein the fibers are twisted, A potential of 0.1 V or more is generated on the above-mentioned surface by performing measurements under the following conditions (a) to (f): (a) stretching the above-mentioned cloth by a predetermined amount in the uniaxial direction; (c) ground the above core material; (d) measure the surface potential of the above cloth using an electrostatic force microscope; (e) the degree of crystallinity is 15-55%; (f) the number of times of twisting is 1150~3000T/m.

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