A method for preparing highly electroactive nano-coated natural wool fabric

Abstract

This invention discloses a method for preparing a highly electroactive nano-coated natural wool fabric, comprising the following steps: a polyamine hyperbranched polymer undergoes self-crosslinking of its branches under the action of an acid anhydride to generate a reinforced polyamine hyperbranched polymer; barium titanate nanoparticles are modified by the reinforced polyamine hyperbranched polymer; the surface of the natural wool fabric is etched using low-temperature plasma; a polyhydroxy hyperbranched polymer is dissolved in an organic solvent and reacts with the surface-etched modified fabric to obtain a hydroxy polymer-modified fabric; the hydroxy polymer-modified fabric is then immersed in an amino polymer-modified barium titanate solution to obtain a highly electroactive nano-coated natural wool fabric. The highly electroactive nano-coated natural wool fabric prepared by this invention exhibits uniform dispersion and high distribution density of nanomaterials on its surface, stable physicochemical structure, and strong dielectric properties, making it applicable to wearable flexible nanogenerators, distributed micro / nano energy harvesting, and other fields.

Description

Technical Field

[0001] This invention relates to a method for preparing a nano-coated composite material, and more particularly to a method for preparing a highly electroactive nano-coated natural wool fabric. Background Technology

[0002] Barium titanate (BaTiO3) nanoparticles possess high surface energy and excellent dielectric properties, showing great potential for applications in capacitance, piezoelectricity, and sensing. Modifying natural fiber materials with BaTiO3 can enhance the triboelectric activity of the fiber surface and improve nano-power generation performance. However, nanoparticles are prone to agglomeration and deposition, which can reduce performance and lead to a decline in triboelectric properties. Furthermore, agglomerated particles are easily detached and difficult to recycle, potentially causing material waste and nano-contamination, affecting the performance stability and safety of functional natural fiber materials during use. Summary of the Invention

[0003] To address the aforementioned deficiencies in the prior art, the present invention aims to provide a method for preparing a highly electroactive nano-coated natural wool fabric, with the goal of solving the problems of uniform distribution and adhesion of barium titanate nanoparticles on the surface of natural wool fibers, thereby improving the electrical properties and stability of the wool fabric.

[0004] The technical solution of this invention is as follows: A method for preparing a highly electroactive nano-coated natural wool fabric, comprising the following steps:

[0005] S1. Dissolve the polyamino hyperbranched polymer in an organic solvent to prepare a 10-25 wt% solution, add acid anhydride and stir continuously at 100-200°C to allow the internal branches of the polyamino hyperbranched polymer to self-crosslink and generate a reinforced polyamino hyperbranched polymer. The molar ratio of the polyamino hyperbranched polymer to the acid anhydride is 8-15:1.

[0006] S2. The reinforced polyamino hyperbranched polymer is dissolved in an organic solvent to prepare a 10-15 wt% solution. The barium titanate nanoparticles are dispersed in the solution in this step at a concentration of 0.1-1.0 wt%. The mixture is continuously refluxed and stirred at 30-100°C. After washing and drying, the amino polymer modified barium titanate is obtained.

[0007] S3. Low-temperature plasma is used to etch the surface of natural wool fabrics to obtain pre-modified fabrics.

[0008] S4. Dissolve the polyhydroxy hyperbranched polymer in an organic solvent to prepare an 8-20 wt% solution. Immerse the pre-modified fabric in the solution at a mass ratio of 1:15-20 (pre-modified fabric to solution). Reflux and stir continuously at 30-100°C. After washing and drying, obtain the hydroxy polymer-modified fabric.

[0009] S5. Disperse the amino polymer-modified barium titanate in an organic solvent to prepare a 0.5-2.0 wt% solution. Immerse the pre-modified fabric in the solution at a mass ratio of 1:10-50 (pre-modified fabric to solution). Stir continuously at 30-100°C. After washing and drying, obtain a highly electroactive nano-coated natural wool fabric.

[0010] The polyhydroxy hyperbranched polymer is obtained by reacting one of the monomers containing double bonds and carboxyl or ester groups with a polyhydroxy monomer and an organic acid; the polyamino hyperbranched polymer is obtained by copolymerizing one of the monomers containing double bonds and ester or carbonyl groups with an acid anhydride and a polyamino monomer.

[0011] Further, the monomer containing a double bond and a carboxyl or ester group is methyl acrylate, ethyl acrylate, methyl methacrylate, acrylic acid, or methacrylic acid; the polyhydroxy monomer is iminodiethanol, trimethylolpropane, or trimethylolpropane; the organic acid is dodecylbenzenesulfonic acid, m-toluenesulfonic acid, o-toluenesulfonic acid, or p-toluenesulfonic acid; the monomer containing a double bond and an ester or carbonyl group is methyl acrylate, ethyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, or allyl acetate; the acid anhydride is succinic anhydride, phthalic anhydride, cyclobutyric anhydride, or acetic propionic anhydride; and the polyamino monomer is ethylenediamine, diethylenetriamine, triethylenetetramine, tetravinylpentamine, or pentavinylhexamine.

[0012] Furthermore, the molecular structural formula of the polyamino hyperbranched polymer is as follows:

[0013]

[0014] The molecular structural formula of the polyhydroxy hyperbranched polymer is:

[0015]

[0016] Further, the acid anhydride is one or more of methyl succinic anhydride, acetic propionic anhydride, succinic anhydride, acetic propionic anhydride, and acetic propionyl thioanhydride.

[0017] Furthermore, when using low-temperature plasma to etch the surface of natural wool fabrics, at least two gas atmospheres are selected to perform the surface etching sequentially.

[0018] Furthermore, the gas atmosphere used when etching the surface of natural wool fabric with low-temperature plasma is air, nitrogen, oxygen, ammonia, or argon.

[0019] Furthermore, the low-temperature plasma power used for surface etching of natural wool fabrics is 20-300W, for example, 20W, 50W, 80W, 100W, 150W, 200W, 250W or 300W, and the processing time is 1-20min, for example, 1min, 3min, 5min, 8min, 10min, 15min or 20min.

[0020] Furthermore, the barium titanate nanoparticles have a particle size of 50–500 nm, for example, 50 nm, 100 nm, 200 nm, 300 nm or 500 nm.

[0021] Furthermore, the organic solvent is one or more selected from methanol, acetone, anhydrous ethanol, isopropanol, methyl ethyl ketone, toluene, and cyclohexane.

[0022] Furthermore, the natural wool fabric is a camel hair, alpaca hair, rabbit hair, sheep wool, or cashmere fabric.

[0023] The advantages of this invention compared to the prior art are:

[0024] A "macromolecule branched self-crosslinking reinforcement" strategy was employed to design and synthesize hyperbranched polymers with enhanced structures, improving polymer modification capabilities and assembly stability. A "cooperative pairing-induced assembly fixation" strategy was used to modify wool fibers and barium titanate nanoparticles with differentiated hyperbranched polymers, achieving cooperative pairing assembly of barium titanate on the fiber surface. The cavity structure of the hyperbranched polymers, containing numerous active sites, effectively controls the nanoparticles, creating electrostatic repulsion between particles and achieving quasi-monolayer uniform dispersion. The differentiated surface properties of the two hyperbranched polymers facilitated pairing attraction assembly, with strong hydrogen bonding from high-density active groups, resulting in stable assembly of nanoparticles on the fiber surface. Precise activation of the natural wool fabric was achieved using low-temperature plasma treatment. Multi-atmosphere etching effectively introduced active functional groups into the fiber surface, enhancing chemical adhesion, weakening the barrier effect of the scale layer, increasing the fiber specific surface area, and significantly increasing attachment sites. The resulting fabric surface nanomaterials exhibited uniform dispersion, high distribution density, stable physicochemical structure, and strong dielectric properties.

[0025] The preparation conditions of this invention are mild, the process is simple and the cycle is short. The natural wool fiber material used is abundant and the cost is low. It is easy to realize large-scale industrial production and has broad application prospects. It can be applied to wearable flexible nanogenerators, distributed micro-nano energy harvesting and other fields. Attached Figure Description

[0026] Figure 1 This is a scanning electron microscope image of the highly electroactive nano-coated wool fiber material prepared in Example 2 of the present invention.

[0027] Figure 2 The graph shows a comparison of the contact separation triboelectric output voltage of the highly electroactive nano-coated natural wool fabric prepared in Example 2 of this invention and ordinary wool fabric.

[0028] Figure 3 The graph shows a comparison of the contact separation triboelectric output current of the highly electroactive nano-coated natural wool fabric prepared in Example 2 of this invention and ordinary wool fabric. Detailed Implementation

[0029] The present invention will be further described below with reference to embodiments, but these are not intended to limit the scope of the invention.

[0030] The molecular structural formula of the polyamino hyperbranched polymer used in the following examples is as follows:

[0031]

[0032] The molecular structural formula of the polyhydroxy hyperbranched polymer is:

[0033]

[0034] However, it should be noted that the preparation method of the polyamino hyperbranched polymer in this invention can be referred to in the literature Zhang Feng, Chen Yuyue, Lin Hong, et al. Synthesis of an amino-terminated hyperbranched polymer and its application in reactive dyeing on cotton as a salt-free dyeing auxiliary[J]. Coloration technology, 2007, 123(6):351-357. The preparation method of the polyhydroxy hyperbranched polymer can be referred to in the literature Xu S, Chen S, Zhang F, et al. Preparation and controlled coating of hydroxyl-modified silver nanoparticles on silk fibers through intermolecular interaction-induced self-assembly[J]. Materials & Design, 2016:107-118.

[0035] Example 1:

[0036] The polyamino hyperbranched polymer was dissolved in anhydrous ethanol, and succinic anhydride was added to a 10 wt% polyamino hyperbranched polymer solution. The mixture was stirred continuously at 120 °C for 6 h to induce self-crosslinking of the internal branches of the polymer macromolecules, forming a multi-cavity network structure, thus obtaining a reinforced polyamino hyperbranched polymer. The molar ratio of polyamino hyperbranched polymer to succinic anhydride was controlled at 10:1.

[0037] The reinforced polyamino hyperbranched polymer was dissolved in anhydrous ethanol to prepare a 10 wt% reinforced polyamino hyperbranched polymer solution. Barium titanate nanoparticles with a particle size of 100 nm were dispersed in the above solution, and the concentration of barium titanate nanoparticles was controlled at 0.1 wt%. The mixture was continuously refluxed and stirred at 50 °C for 3 h. After repeated centrifugation, washing and vacuum drying, amino polymer modified barium titanate was obtained.

[0038] Natural cashmere fabric was etched with high specific surface area for 5 minutes using an oxygen atmosphere and a 50W low-temperature plasma to generate activated groups and obtain a pre-modified fabric.

[0039] The pre-modified fabric was immersed in an 8 wt% ethanol solution of a polyhydroxy hyperbranched polymer, with a pre-modified fabric to solution mass ratio of 1:20. The mixture was continuously refluxed and stirred at 60°C for 3 hours. After filtration, washing, and vacuum drying, the hydroxy polymer-modified fabric was obtained.

[0040] Aminopolymer-modified barium titanate nanoparticles were dispersed in acetone to prepare an aminopolymer-modified barium titanate concentration of 0.5wt%. Hydroxypolymer-modified fabric was immersed in the above solution with a mass ratio of hydroxypolymer-modified fabric to solution of 1:50. The mixture was stirred and reacted at 50°C for 5 hours, filtered, washed, and vacuum dried to obtain a highly electroactive nanocoated natural wool fabric.

[0041] Example 2:

[0042] The polyamino hyperbranched polymer was dissolved in methanol, and methylsuccinic anhydride was added to a 15 wt% polyamino hyperbranched polymer solution. The mixture was stirred continuously at 120 °C for 6 h to allow the internal branches of the polymer macromolecules to self-crosslink, forming a multi-cavity network structure, thus obtaining a reinforced polyamino hyperbranched polymer. The molar ratio of polyamino hyperbranched polymer to methylsuccinic anhydride was controlled at 8:1.

[0043] A 15wt% solution of a reinforced polyamino hyperbranched polymer was prepared by dissolving a reinforced polyamino hyperbranched polymer in methanol. Barium titanate nanoparticles with a particle size of 200 nm were dispersed in the solution, and the concentration of barium titanate nanoparticles was controlled at 0.3wt%. The solution was continuously refluxed and stirred at 60°C for 3 hours. After repeated centrifugation, washing, and vacuum drying, amino polymer-modified barium titanate was obtained.

[0044] Natural camel hair fabric was etched with high specific surface area for 3 min and 5 min using argon and oxygen atmospheres and low-temperature plasma with power of 50W and 50W respectively to generate activated groups and obtain pre-modified fabric.

[0045] The pre-modified fabric was immersed in a 10 wt% ethanol solution of a polyhydroxy hyperbranched polymer with a bath ratio of 1:20. The mixture was continuously refluxed and stirred at 60°C for 3 hours. After filtration, washing, and vacuum drying, the hydroxy polymer-modified fabric was obtained.

[0046] Aminopolymer-modified barium titanate nanoparticles were dispersed in acetone to prepare a solution with an aminopolymer-modified barium titanate concentration of 1 wt%. Hydroxylpolymer-modified fabric was then immersed in the solution at a mass ratio of 1:30. The mixture was stirred at 60°C for 3 hours, filtered, washed, and vacuum dried to obtain a highly electroactive nanocoated natural wool fabric. The scanning electron microscope image of the fibers is shown below. Figure 1 As shown.

[0047] Example 3:

[0048] The polyamino hyperbranched polymer was dissolved in isopropanol, and ethyl propionic anhydride was added to a 20 wt% polyamino hyperbranched polymer solution. The mixture was stirred continuously at 120 °C for 6 h to allow the internal branches of the polymer macromolecules to self-crosslink, forming a multi-cavity network structure, thus obtaining a reinforced polyamino hyperbranched polymer. The molar ratio of polyamino hyperbranched polymer to methyl succinic anhydride was controlled at 12:1.

[0049] A 10 wt% solution of a reinforced polyamino hyperbranched polymer was prepared by dissolving a reinforced polyamino hyperbranched polymer in isopropanol. Barium titanate nanoparticles with a particle size of 300 nm were dispersed in the solution, and the concentration of barium titanate nanoparticles was controlled at 0.5 wt%. The mixture was continuously refluxed and stirred at 80 °C for 3 h. After repeated centrifugation, washing, and vacuum drying, amino polymer-modified barium titanate was obtained.

[0050] Natural sheep wool fabrics were etched with high specific surface area for 3 minutes at 3 minutes using nitrogen and oxygen atmospheres and low-temperature plasma with power of 100W and 100W respectively to generate activated groups and obtain pre-modified fabrics.

[0051] The pre-modified fabric was immersed in a 20wt% ethanol solution of a polyhydroxy hyperbranched polymer, with a pre-modified fabric to solution mass ratio of 1:20. The mixture was continuously refluxed and stirred at 60℃ for 3 hours. After filtration, washing, and vacuum drying, the hydroxy polymer-modified fabric was obtained.

[0052] Aminopolymer-modified barium titanate nanoparticles were dispersed in acetone to prepare an aminopolymer-modified barium titanate concentration of 1.5 wt%. Hydroxypolymer-modified fabric was immersed in the above solution with a mass ratio of hydroxypolymer-modified fabric to solution of 1:20. The mixture was stirred and reacted at 60°C for 3 hours, filtered, washed, and vacuum dried to obtain a highly electroactive nanocoated natural wool fabric.

[0053] Example 4:

[0054] The polyamino hyperbranched polymer was dissolved in toluene, and acetic acid propionic anhydride was added to a 25 wt% polyamino hyperbranched polymer solution. The mixture was stirred continuously at 150 °C for 6 h to allow the internal branches of the polymer macromolecules to self-crosslink, forming a multi-cavity network structure, thus obtaining a reinforced polyamino hyperbranched polymer. The molar ratio of polyamino hyperbranched polymer to methyl succinic anhydride was controlled at 10:1.

[0055] A 10 wt% solution of a reinforced polyamino hyperbranched polymer was prepared by dissolving a reinforced polyamino hyperbranched polymer in toluene. Barium titanate nanoparticles with a particle size of 100 nm were dispersed in the solution, and the concentration of barium titanate nanoparticles was controlled at 0.2 wt%. The solution was continuously refluxed and stirred at 80 °C for 3 h. After repeated centrifugation, washing, and vacuum drying, amino polymer-modified barium titanate was obtained.

[0056] Natural sheep wool fabrics were subjected to high specific surface area etching for 3 min, 3 min, and 5 min respectively using argon, nitrogen, oxygen atmospheres and low temperature plasmas with power of 20W, 50W, and 80W to generate activated groups and obtain pre-modified fabrics.

[0057] The pre-modified fabric was immersed in a 10 wt% anhydrous ethanol solution of a polyhydroxy hyperbranched polymer, with a pre-modified fabric to solution mass ratio of 1:15. The mixture was continuously refluxed and stirred at 60°C for 3 hours. After filtration, washing, and vacuum drying, the hydroxy polymer-modified fabric was obtained.

[0058] Aminopolymer-modified barium titanate nanoparticles were dispersed in acetone to prepare an aminopolymer-modified barium titanate concentration of 1 wt%. Hydroxypolymer-modified fabric was immersed in the above solution with a mass ratio of hydroxypolymer-modified fabric to solution of 1:10. The mixture was stirred and reacted at 50°C for 3 hours, filtered, washed, and vacuum dried to obtain a highly electroactive nanocoated natural wool fabric.

[0059] Example 5:

[0060] The polyamino hyperbranched polymer was dissolved in anhydrous ethanol, and acetic acid propylthioic anhydride was added to a 20 wt% polyamino hyperbranched polymer solution. The mixture was stirred continuously at 180 °C for 6 h to allow the internal branches of the polymer macromolecules to self-crosslink, forming a multi-cavity network structure, thus obtaining a reinforced polyamino hyperbranched polymer. The molar ratio of polyamino hyperbranched polymer to methyl succinic anhydride was controlled at 15:1.

[0061] A 15 wt% solution of a reinforced polyamino hyperbranched polymer was prepared by dissolving the reinforced polyamino hyperbranched polymer in anhydrous ethanol. Barium titanate nanoparticles with a particle size of 200 nm were dispersed in the solution, and the concentration of barium titanate nanoparticles was controlled at 0.8 wt%. The mixture was continuously refluxed and stirred at 60 °C for 5 h. After repeated centrifugation, washing, and vacuum drying, amino polymer-modified barium titanate was obtained.

[0062] Natural alpaca wool fabrics were etched with high specific surface area for 3 min, 3 min, and 5 min respectively using argon, air, oxygen atmospheres and low-temperature plasma with power of 20W, 50W, and 100W to generate activated groups and obtain pre-modified fabrics.

[0063] The pre-modified fabric was immersed in a 10 wt% anhydrous ethanol solution of a polyhydroxy hyperbranched polymer, with a pre-modified fabric to solution mass ratio of 1:20. The mixture was continuously refluxed and stirred at 60°C for 3 hours. After filtration, washing, and vacuum drying, the hydroxy polymer-modified fabric was obtained.

[0064] Aminopolymer-modified barium titanate nanoparticles were dispersed in anhydrous ethanol to prepare an aminopolymer-modified barium titanate concentration of 1wt%. Hydroxypolymer-modified fabric was immersed in the above solution with a mass ratio of hydroxypolymer-modified fabric to solution of 1:10. The mixture was stirred and reacted at 60°C for 3 hours, filtered, washed, and vacuum dried to obtain a highly electroactive nanocoated natural wool fabric.

[0065] The triboelectric output performance of the highly electroactive nano-coated natural wool fabric prepared in Example 2 was compared with that of ordinary natural wool fabric. Specifically, a contact / triboelectric power generation device was constructed using wool fabric as the triboelectric positive material, silicone rubber as the triboelectric negative material, and a conductive film / fabric as the flexible electrode. Electrostatic voltage output was tested at an ambient humidity of 70%, and the results are as follows: Figure 2 , 3 As shown, it can be seen that in a high humidity environment that is not conducive to electrical output, the output voltage and current of nano-coated wool fabrics are significantly enhanced compared to ordinary wool fabrics.

[0066] The performance test results of the example are as follows:

[0067]

[0068] The experimental results show that each embodiment improved the surface electrical properties of natural wool fabrics through nano-modification and solved the problems of uniform distribution and adhesion strength.

Claims

1. A method for preparing a highly electroactive nano-coated natural wool fabric, characterized in that, Includes the following steps: S1. Dissolve the polyamino hyperbranched polymer in an organic solvent to prepare a 10-25 wt% solution, add acid anhydride and stir continuously at 100-200°C to allow the internal branches of the polyamino hyperbranched polymer to self-crosslink and generate a reinforced polyamino hyperbranched polymer with a multi-cavity network structure. The molar ratio of the polyamino hyperbranched polymer to the acid anhydride is 8-15:

1. S2. The reinforced polyamino hyperbranched polymer is dissolved in an organic solvent to prepare a 10-15 wt% solution. The barium titanate nanoparticles are dispersed in the solution in this step at a concentration of 0.1-1.0 wt%. The reaction is carried out under continuous reflux and stirring at 30-100℃. After washing and drying, the amino polymer modified barium titanate is obtained. S3. Low-temperature plasma is used to etch the surface of natural wool fabrics to obtain pre-modified fabrics. S4. Dissolve the polyhydroxy hyperbranched polymer in an organic solvent to prepare an 8-20 wt% solution. Immerse the pre-modified fabric in the solution at a mass ratio of 1:15-20 (pre-modified fabric to solution). Reflux and stir continuously at 30-100°C. After washing and drying, obtain the hydroxy polymer-modified fabric. S5. Disperse the amino polymer-modified barium titanate in an organic solvent to prepare a 0.5-2.0 wt% solution. Immerse the hydroxy polymer-modified fabric in the solution at a mass ratio of 1:10-50. Stir continuously at 30-100℃. After washing and drying, obtain a natural wool fabric with a highly electroactive nano-coating. The polyhydroxy hyperbranched polymer is obtained by reacting one of the monomers containing double bonds and carboxyl or ester groups with a polyhydroxy monomer and an organic acid; the polyamino hyperbranched polymer is obtained by copolymerizing one of the monomers containing double bonds and ester or carbonyl groups with an acid anhydride and a polyamino monomer.

2. The method for preparing highly electroactive nano-coated natural wool fabric according to claim 1, characterized in that, The monomer containing a double bond and a carboxyl or ester group is methyl acrylate, ethyl acrylate, methyl methacrylate, acrylic acid, or methacrylic acid; the polyhydroxy monomer is iminodiethanol, trimethylolethane, or trimethylolpropane; the organic acid is dodecylbenzenesulfonic acid, m-toluenesulfonic acid, o-toluenesulfonic acid, or p-toluenesulfonic acid; the monomer containing a double bond and an ester or carbonyl group is methyl acrylate, ethyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, or allyl acetate; the acid anhydride is succinic anhydride, phthalic anhydride, cyclobutyric anhydride, or acetic propionic anhydride; and the polyamino monomer is ethylenediamine, diethylenetriamine, triethylenetetramine, tetravinylpentamine, or pentavinylhexamine.

3. The method for preparing highly electroactive nano-coated natural wool fabric according to claim 1 or 2, characterized in that, The molecular structural formula of the polyamino hyperbranched polymer is: The molecular structural formula of the polyhydroxy hyperbranched polymer is: .

4. The method for preparing highly electroactive nano-coated natural wool fabric according to claim 1, characterized in that, The acid anhydride is one or more of methyl succinic anhydride, ethyl propionic anhydride, succinic anhydride, acetic propionic anhydride, and acetic propionyl thioanhydride.

5. The method for preparing highly electroactive nano-coated natural wool fabric according to claim 1, characterized in that, When using low-temperature plasma to etch the surface of natural wool fabrics, at least two gas atmospheres are selected for sequential surface etching.

6. The method for preparing highly electroactive nano-coated natural wool fabric according to claim 5, characterized in that, The gas atmosphere used when etching the surface of natural wool fabric with low-temperature plasma is air, nitrogen, oxygen, ammonia, or argon.

7. The method for preparing highly electroactive nano-coated natural wool fabric according to claim 6, characterized in that, The low-temperature plasma power used for surface etching of natural wool fabrics is 20-300W, and the processing time is 1-20min.

8. The method for preparing highly electroactive nano-coated natural wool fabric according to claim 1, characterized in that, The barium titanate nanoparticles have a particle size of 50–500 nm.

9. The method for preparing highly electroactive nano-coated natural wool fabric according to claim 1, characterized in that, The organic solvent is one or more of methanol, acetone, anhydrous ethanol, isopropanol, methyl ethyl ketone, toluene, and cyclohexane.

10. The method for preparing highly electroactive nano-coated natural wool fabric according to claim 1, characterized in that, The natural wool fabric is made of camel hair, alpaca hair, rabbit hair, sheep wool, or cashmere.

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