Oil-resistant easy-to-clean anti-static special fabric containing nano coating and preparation method of oil-resistant easy-to-clean anti-static special fabric

Abstract

The invention belongs to the technical field of functional textile materials, and provides a gradient nano composite functional layer structure aiming at the problems of single function, poor coating adhesive force, serious process pollution and the like in the prior art. Comprising an antistatic bottom layer (a carbon nanotube / polypyrrole conductive network), an oil-stain-resistant middle layer (fluorosilicone modified nano SiO) and an easy-to-clean surface layer (a TiO-graphene quantum dot photocatalytic material), and high adhesive force and environmental friendliness of the coating are realized by combining a plasma activated substrate with a low-temperature gradient curing process. The embodiment shows that the initial surface resistivity of the fabric is smaller than or equal to 8.3 * 10 omega / sq, the initial surface resistivity is still smaller than or equal to 9.1 * 10 omega / sq after 50 times of washing, the oil-resistant contact angle is larger than or equal to 154 degrees, the oil stain photocatalytic decomposition rate is larger than or equal to 93%, VOC emission is smaller than or equal to 12 g / L, and the fabric is remarkably superior to a traditional solvent type process (VOC is 320 g / L). The conductive sutures can be widely applied to petrochemical engineering protective clothing, medical operating gowns and electronic clean room work clothes, particularly, through the design of the conductive sutures, the seam resistance is smaller than or equal to 8.5 * 10 omega / cm, the overall electrostatic discharge time is smaller than or equal to 0.3 s, and the comprehensive performance reaches the industry leading level.

Description

Technical Field

[0001] This invention belongs to the field of functional textile materials technology, and specifically discloses a special fabric with a nano-coating that is oil-resistant, easy to clean, and antistatic, as well as its preparation method. Background Technology

[0002] With the increasing demands of industrial production and special protection, functional textiles are being used more and more widely in areas such as oil resistance, easy stain removal, and antistatic properties. However, most existing fabrics suffer from problems such as limited functionality, insufficient durability, or complex manufacturing processes. For example, traditional antistatic fabrics are often achieved by blending conductive fibers or spraying antistatic agents onto the surface, but these methods suffer from drawbacks such as the degradation of antistatic properties with each wash and insufficient oil resistance.

[0003] Taking patent CN106010094A (An antistatic coating and its preparation method) as an example, its technical solution involves compounding epoxy resin, acrylic resin, and nano-antistatic fillers (such as nano-nickel powder, carbon nanotubes, etc.) to form a conductive network to reduce volume resistivity. While this coating has some effect in the field of electronic device protection, its application in textiles has the following drawbacks:

[0004] Functional limitation: This coating only focuses on antistatic properties and does not integrate anti-oil and easy-to-clean functions, thus failing to meet the multiple requirements under complex working conditions;

[0005] Insufficient coating adhesion: The coating has weak adhesion to the textile substrate and is prone to peeling off after repeated washing, leading to functional failure.

[0006] Poor environmental adaptability: The solvent system in the coating (such as isopropanol, butyl acetate) may damage the fibers, and the high-temperature curing process is not suitable for heat-sensitive textile substrates;

[0007] Uneven nano-dispersion: Nanofillers are prone to agglomeration, which affects the continuity of the conductive path and leads to a decrease in local electrostatic shielding efficiency.

[0008] To address the aforementioned issues, there is an urgent need to develop a fabric that integrates oil resistance, easy stain removal, and durable antistatic properties, and to optimize the bonding process between the coating and the substrate. While existing nano-coating technologies (such as electrospinning and solvent-free coating) can improve functionality, they suffer from problems such as fiber fragility, high cost, or poor adhesion to the substrate. Furthermore, the layering of single-functional coatings can easily lead to a heavy fabric with poor breathability, making it difficult to meet the comfort requirements of special protective clothing. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention discloses a special fabric with a nano-coating that is oil-resistant, easy to clean, and antistatic, and its preparation method. By constructing a gradient coating using composite nanomaterials, the synergistic effect of oil resistance, easy cleaning, and antistatic functions is achieved. Plasma activation combined with chemical grafting technology is used to enhance the interfacial bonding strength between the coating and the polyester substrate. An aqueous nano-dispersion system is used to avoid damage to the fibers by organic solvents, and low-temperature cross-linking curing reduces energy consumption.

[0010] This invention includes the following technical solutions:

[0011] A special oil-resistant, stain-resistant, and antistatic fabric with a nano-coating, comprising:

[0012] Polyester substrate layer (1) and nanocomposite functional layer (2) bonded to the surface of substrate layer;

[0013] The nanocomposite functional layer (2) comprises, from the inside out:

[0014] a) Antistatic underlayer (21) containing 5%-15% carbon nanotube / polypyrrole composite conductive agent by mass fraction;

[0015] b) An oil-resistant intermediate layer (22) containing 10%-20% by mass of fluorosilicone modified nano-silica particles;

[0016] c) Easy-to-clean surface (23), containing 3%-8% by mass of titanium dioxide-graphene quantum dot composite photocatalytic material;

[0017] The nanocomposite functional layer (2) is bonded to the polyester substrate layer (1) after plasma pretreatment and a padding-drying-curing process.

[0018] Furthermore, the aforementioned special fabric, the antistatic underlayer (21) also contains 0.5%-2% by mass of nano-silver particles with a particle size of 20-50nm.

[0019] Furthermore, in the aforementioned special fabric, the fluorosilicone modified nano-silica particles have a contact angle ≥150° and a surface energy ≤10mN / m.

[0020] Furthermore, the aforementioned special fabric has an oil decomposition efficiency of ≥90% under sunlight irradiation of the easily degreased surface layer (23).

[0021] Furthermore, the aforementioned special fabric, after 50 standard washes, still has a surface resistivity of ≤10. 6 Ω / sq.

[0022] This invention also discloses a method for preparing the above-mentioned special fabric, comprising the following steps:

[0023] S1. The polyester substrate layer (1) is subjected to plasma activation treatment with a power of 50-100W and a treatment time of 3-10min;

[0024] S2. Preparation of coating solution for nanocomposite functional layer (2):

[0025] Antistatic underlayer (21) coating liquid: Carbon nanotubes and polypyrrole are dispersed in an aqueous polyurethane emulsion at a mass ratio of 1:2-1:5. Optionally, 0.5%-2wt% of nano silver particles with a particle size of 20-50nm are added.

[0026] Oil-resistant intermediate layer (22) coating liquid: Fluorosilicone modified nano-SiO2 and epoxy modified organosilicon resin are mixed at a ratio of 1:3-1:6;

[0027] Easy-to-clean surface coating solution (23): TiO2-graphene quantum dot composite and fluorocarbon surfactant are compounded in a ratio of 1:1-1:3;

[0028] S3. Three functional layers are coated sequentially using a three-roller coater, with the coating amount of each layer controlled at 10-30 g / m². 2 ;

[0029] S4. Gradient curing: Pre-bake the bottom layer at 80-100℃ for 5 minutes, cure the middle layer at 120-140℃ for 8 minutes, and finally cure the top layer at 150-170℃ for 3 minutes.

[0030] Furthermore, in the above preparation method, the plasma treatment gas in step S1 is a mixture of argon and oxygen in a volume ratio of 4:1 to 6:1.

[0031] Furthermore, in the above preparation method, the roller speed ratio of the coating machine in step S3 is 1:1.2:1.5, and the pressure is 0.2-0.5MPa.

[0032] The present invention also discloses the application of the above-mentioned special fabrics in petrochemical protective clothing, medical surgical gowns or electronic cleanroom work clothes.

[0033] Furthermore, in the above application, the seams of the petrochemical protective clothing are sewn with conductive yarn, and the seam resistance is ≤10 ohms. 3 Ω / cm.

[0034] Compared with the prior art, the present invention has the following outstanding advantages:

[0035] This invention achieves a synergistic effect of anti-oil, easy-to-clean, and long-lasting antistatic functions through the gradient design and process innovation of multi-layer nano-coatings, specifically manifested as follows:

[0036] 1. Multifunctional Integration Breakthrough: Traditional antistatic fabrics (such as CN106010094A) rely on only a single conductive layer, while the antistatic bottom layer (carbon nanotubes / polypyrrole), the oil-resistant intermediate layer (fluorosilicone-modified nano-SiO2), and the easy-to-clean surface layer (TiO2-graphene quantum dots) of this invention form complementary functions, and the antistatic performance remains stable at 10 after 50 washes. 6 With a strength of less than Ω / sq (Test Example 1), it also possesses superhydrophobicity (contact angle ≥150°) and high efficiency in photocatalytic decomposition (oil decomposition rate ≥90%), thus solving the problem of limited functionality.

[0037] 2. Improved environmental friendliness and durability of the process: Plasma activation pretreatment (argon / oxygen mixed gas) is used to enhance coating adhesion (ISO 2409 Class 1). Combined with a water-based coating system and low-temperature gradient curing (80-170℃), it avoids fiber melting damage caused by traditional high-temperature solvent processes (such as Comparative Example 3), and VOC emissions are reduced by 97% (12g / L vs 320g / L).

[0038] 3. Optimized for application scenarios: Through conductive seam design (seam resistance ≤ 10 ohms) 3 By adjusting the electrostatic discharge time (Ω / cm) and photocatalytic activity, the electrostatic discharge time of the protective clothing in the high electrostatic environment of petrochemical industry was shortened to 0.3s (Test Example 4), which is 67% better than commercially available products (0.9s). At the same time, the surface photocatalytic material can decompose more than 90% of oil stains under sunlight, reducing the use of chemical cleaning agents, thus combining economy and environmental friendliness. In addition, the introduction of nano-silver particles (Example 2) further reduced the surface resistivity to 10. 4 With an Ω / sq rating, this invention expands its application potential in precision electronics manufacturing. From structural design and process innovation to end-use applications, it forms a complete technological closed loop, significantly enhancing the technological competitiveness of special protective fabrics. Attached Figure Description

[0039] Figure 1 Comparison of contact angle (°) in oil resistance and easy-to-clean properties tests;

[0040] Figure 2 Comparison of oleic acid decomposition rate (%) in oil stain resistance and easy stain removal performance tests;

[0041] Figure 3 Comparison of VOC emissions (g / L) in environmental protection tests. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Table 1 Raw Material List

[0044]

[0045]

[0046] Table 2 Equipment and Instrument List

[0047]

[0048] Example 1

[0049] Basic Solution

[0050] 1. Substrate: 150D polyester woven fabric (180g / m²) 2 )

[0051] Pretreatment: Argon / oxygen mixed gas (volume ratio 5:1), plasma power 80W, treatment time 6min

[0052] 2. Composition of the coating solution:

[0053] Antistatic base layer: Carbon nanotubes (CNTs): polypyrrole = 1:3, dispersed in an aqueous polyurethane emulsion, solid content 12%.

[0054] Oil-resistant intermediate layer: Fluorosilicone modified nano-SiO2 (contact angle 152°): Epoxy modified silicone resin = 1:4 Easy-to-clean surface layer: TiO2-graphene quantum dots (mass ratio 2:1): Fluorocarbon surfactant = 1:2

[0055] 3. Coating process: Three-roller coater (roller speed ratio 1:1.2:1.5, pressure 0.3MPa), single-layer coating amount 20g / m² 2

[0056] 4. Curing process: Pre-bake the bottom layer at 90℃ for 5 minutes → cure the middle layer at 130℃ for 8 minutes → cure the top layer at 160℃ for 3 minutes.

[0057] Example 2

[0058] Optimize the antistatic layer

[0059] Based on Example 1:

[0060] The antistatic base layer contains 1 wt% nano-silver particles (average particle size 30 nm).

[0061] The plasma treatment time has been extended to 8 minutes.

[0062] Example 3

[0063] Improve oil resistance

[0064] Based on Example 1:

[0065] The content of fluorine-silicon modified nano-SiO2 in the anti-oil intermediate layer has been increased to 18%.

[0066] The coating machine pressure was adjusted to 0.4 MPa.

[0067] Example 4

[0068] Optimize low-temperature curing process

[0069] Based on Example 1:

[0070] The curing temperature gradient is adjusted as follows: bottom layer 85℃ / 5min → middle layer 125℃ / 10min → top layer 155℃ / 5min

[0071] Example 5

[0072] Superhydrophobic design

[0073] Based on Example 1:

[0074] The oil-resistant interlayer has been replaced with perfluoroalkyl-modified nano-ZnO (contact angle 158°).

[0075] The plasma treatment gas ratio was adjusted to argon:oxygen = 6:1.

[0076] Comparative Example 1

[0077] Single functional layer

[0078] Only an antistatic undercoat (CNT / polypyrrole composite liquid, same as in Example 1) is applied, without an anti-oil and easy-to-clean layer.

[0079] Comparative Example 2

[0080] Plasma-free processing

[0081] The plasma activation step is omitted, and the three functional layers are directly coated. The rest is the same as in Example 1.

[0082] Comparative Example 3

[0083] Organic solvent system

[0084] Replace the coating solution solvent with isopropanol / butyl acetate (volume ratio 3:1).

[0085] The curing temperature was increased to 180°C. Everything else was the same as in Example 1.

[0086] Test Example 1

[0087] Antistatic performance test

[0088] 1. Test objective: To verify the initial antistatic properties of the fabric and its durability after washing.

[0089] 2. Testing Method:

[0090] Surface resistivity: Measured according to ASTM D257 standard using a resistance tester (Keythley 6517B) at 25°C and 50% humidity.

[0091] Washing durability: Wash according to AATCC 61-2013 2A program (simulate 50 household washes), air dry and test resistivity.

[0092] 3. Test Groups:

[0093] Example 1: Basic Three-Layer Coating Process

[0094] Example 2: Optimized antistatic layer containing nano-silver

[0095] Comparative Example 1: Antistatic base layer only (no anti-oil / easy-cleaning layer)

[0096] Comparative Example 2: Process of Example 1 without plasma treatment

[0097] The results are shown in Table 3.

[0098] Table 3 Antistatic Performance Test

[0099] sample Initial surface resistivity (Ω / sq) Surface resistivity (Ω / sq) after 50 washes Example 1 <![CDATA[8.3×10 5 ]]> <![CDATA[9.1×10 5 ]]> Example 2 <![CDATA[2.7×10 4 ]]> <![CDATA[3.5×10 4 ]]> Comparative Example 1 <![CDATA[1.2×10 6 ]]> <![CDATA[8.9×10 7 ]]> Comparative Example 2 <![CDATA[5.4×10 6 ]]> <![CDATA[2.1×10 8 ]]>

[0100] Results analysis:

[0101] The resistivity of Example 1 is stable at 10. 6 Below Ω / sq indicates a synergistic effect of the three-layer structure on electrostatic dissipation;

[0102] Example 2: Due to the addition of nano-silver particles, the resistivity was reduced to 10. 4 Ω / sq, demonstrating the synergistic effect;

[0103] The resistivity of Comparative Example 1 (single functional layer) and Comparative Example 2 (no plasma treatment) increased significantly, indicating that plasma activation and multilayer structure have a key impact on durability.

[0104] Test Example 2

[0105] Oil and stain resistance and easy stain removal performance test

[0106] Test objective: To evaluate the fabric's hydrophobicity and photocatalytic ability to decompose oil stains, supporting claims 4, 5, and 9.

[0107] Test method:

[0108] Contact angle test: According to AATCC 118 standard, the static contact angle was measured using a contact angle measuring instrument (Dataphysics OCA20) with 5μL of soybean oil added.

[0109] Photocatalytic decomposition rate: According to ASTM D6547 standard, the coating oleic acid (0.1g / m³) 2 After UV irradiation (365nm, 100W / m) 2 Calculate the quality loss rate after 4 hours.

[0110] Test Groups:

[0111] Example 3: Intermediate layer with high fluorine-silicon modified nano-SiO2 content

[0112] Example 5: Perfluoroalkyl-modified ZnO interlayer

[0113] Comparative Example 3: Coatings based on organic solvent systems

[0114] Blank substrate: Untreated polyester fabric.

[0115] The results are shown in Table 4 and Figure 1 and Figure 2 .

[0116] Table 4. Oil and stain resistance and easy-to-clean performance test

[0117] sample Contact angle (°) Oleic acid decomposition rate (%) Example 3 154 93 Example 5 159 88 Comparative Example 3 142 65 Blank substrate 78 0

[0118] Results analysis:

[0119] The contact angles of Examples 3 and 5 are both >150°, meeting the superhydrophobic standard (right 4), and the oleic acid decomposition rate is >85%;

[0120] Comparative Example 3 showed a significant decrease in hydrophobicity and decomposition rate due to solvent damage to the fibers.

[0121] Example 5 showed a higher contact angle but a slightly lower decomposition rate, which may be related to the weaker photocatalytic activity of ZnO compared to TiO2.

[0122] Test Example 3

[0123] Coating adhesion and environmental performance testing

[0124] Test objective: To verify the advantages of plasma treatment in improving bonding strength and its environmentally friendly process.

[0125] Test method:

[0126] Adhesion test: Evaluate the area of ​​coating peeling according to ISO 2409 cross-cut test (1 mm spacing) (Grade 0: no peeling; Grade 5: >65% peeling).

[0127] VOC emissions: The total amount of volatile organic compounds in the coating solution shall be determined by gas chromatography in accordance with GB / T 23986-2009.

[0128] Test Groups:

[0129] Example 1: Standard plasma + aqueous system

[0130] Comparative Example 2: Plasma-free treatment

[0131] Comparative Example 3: Organic Solvent System

[0132] The results are shown in Table 5 and Figure 3

[0133] Table 5 Coating Adhesion and Environmental Friendliness Tests

[0134] sample Adhesion rating VOC emissions (g / L) Example 1 Level 1 12 Comparative Example 2 Level 4 15 Comparative Example 3 Level 2 320

[0135] Results analysis:

[0136] The Grade 1 adhesion in Example 1 demonstrates that plasma activation significantly enhances interfacial bonding.

[0137] The high VOC (320 g / L) content in Comparative Example 3, which melts with the substrate, demonstrates the destructive effects of the solvent system on environmental friendliness and fiber structure.

[0138] The low VOC (12g / L) of Example 1 meets environmental protection requirements.

[0139] Test Example 4

[0140] Application scenario simulation test (conductivity of protective clothing seams)

[0141] Test objective: To verify the overall antistatic properties of the fabric after it is made into protective clothing, supporting claims 9 and 10.

[0142] Test method:

[0143] Seam resistance test: According to ISO 3801 standard, use conductive yarn to sew the fabric and measure the line resistance at the seam (length 10cm).

[0144] Actual protective effect: Simulating a petrochemical environment (30% humidity, 15kV electrostatic voltage), the static discharge time of the human body after wearing the protective gear was tested (target ≤0.5s).

[0145] Test Groups:

[0146] Example 2: Fabric + Conductive Sewing Thread: Sewing Thread Resistance ≤ 103 Ω / cm

[0147] Example 2: Fabric + Ordinary Thread: Thread resistance > 10 12 Ω / cm

[0148] Commercially available antistatic clothing conforms to GB 12014-2019 standard.

[0149] The results are shown in Table 6.

[0150] Table 6. Conductivity Test of Seams in Protective Clothing

[0151] sample Joint resistance (Ω / cm) Static electricity discharge time (s) Example 2 + Conductive Thread <![CDATA[8.5×10 2 ]]> 0.3 Example 2 + Ordinary sutures <![CDATA[3.2×10 13 ]]> 5.8 Commercially available antistatic clothing <![CDATA[1.1×10 3 ]]> 0.9

[0152] Results analysis:

[0153] Example 2 + Joint resistance of conductive thread (≤10) 3 Both the Ω / cm and the discharge time (0.3s) are superior to commercially available products, proving the necessity of the seam design;

[0154] Ordinary stitching leads to static electricity buildup (discharge time 5.8s), highlighting the crucial role of conductive stitching in the overall protective design;

[0155] Example 2: The synergistic properties of the fabric make it suitable for demanding scenarios (such as electronic cleanrooms).

[0156] Summary of Implementation Examples and Verification of Invention Effects:

[0157] Through systematic verification using four test cases, the core advantages of this invention have been fully demonstrated:

[0158] 1. Multifunctional integration: Simultaneously achieves antistatic properties (≤10). 6 Ω / sq), superhydrophobic (contact angle ≥150°) and photocatalytic decontamination (decomposition rate ≥85%);

[0159] 2. Process innovation: Plasma activation combined with low-temperature curing process ensures coating adhesion (Level 1) and substrate integrity;

[0160] 3. Application reliability: The conductive seam design ensures that the overall electrostatic discharge time of the protective clothing is ≤0.5s, far exceeding the industry standard (GB 12014-2019 requires ≤1.0s).

[0161] It is worth noting that the above description of the embodiments focuses on illustrating the technical solution of the present invention, rather than precisely defining its scope of protection. Those skilled in the art should understand that appropriate adjustments and optimizations can be made based on the technical details disclosed in the embodiments of the present invention, or equivalent substitutions can be implemented for individual or even all technical elements. Such adjustments and substitutions will not deviate from the core essence of the technical solution of the present invention and should be included within the technical protection scope of the embodiments of the present invention. In short, the protection of the present invention should not be limited to the concrete presentation of the above embodiments, but broadly covers all equivalent changes and improvements that do not depart from its basic concept. In summary, the protection definition of the present invention should be based on the statement of the claims, and the above embodiments are only used as a reference guide for understanding the present invention.

Claims

1. A special oil-resistant, easy-to-clean, and antistatic fabric with a nano-coating, characterized in that, include: Polyester substrate layer (1) and nanocomposite functional layer (2) bonded to the surface of substrate layer; The nanocomposite functional layer (2) comprises, from the inside out: a) Antistatic underlayer (21), containing 5%-15% by mass of carbon nanotube / polypyrrole composite conductive agent; b) An oil-resistant intermediate layer (22) comprising 10%-20% by mass of fluorosilicone modified nano-silica particles; c) Easy-to-clean surface (23), containing 3%-8% by mass of titanium dioxide-graphene quantum dot composite photocatalytic material; The nanocomposite functional layer (2) is bonded to the polyester substrate layer (1) after plasma pretreatment and a padding-drying-curing process.

2. The special fabric according to claim 1, characterized in that, The antistatic bottom layer (21) also contains 0.5%-2% by mass of nano-silver particles with a particle size of 20-50nm.

3. The special fabric according to claim 1, characterized in that, The fluorosilicone modified nano-silica particles have a contact angle ≥150° and a surface energy ≤10mN / m.

4. The special fabric according to claim 1, characterized in that, The decomposition efficiency of the easily degreased surface layer (23) on oil stains under sunlight is ≥90%.

5. The special fabric according to claim 1, characterized in that, The surface resistivity of the fabric remains ≤10 after 50 standard washes. 6 Ω / sq.

6. The method for preparing the special fabric according to any one of claims 1-5, characterized in that, Includes the following steps: S1. The polyester substrate layer (1) is subjected to plasma activation treatment with a power of 50-100W and a treatment time of 3-10min; S2. Preparation of coating solution for nanocomposite functional layer (2): Antistatic underlayer (21) coating liquid: Carbon nanotubes and polypyrrole are dispersed in an aqueous polyurethane emulsion at a mass ratio of 1:2-1:

5. Optionally, 0.5%-2wt% of nano silver particles with a particle size of 20-50nm are added. Oil-resistant intermediate layer (22) coating liquid: Fluorosilicone modified nano-SiO2 and epoxy modified organosilicon resin are mixed at a ratio of 1:3-1:6; Easy-to-clean surface coating solution (23): TiO2-graphene quantum dot composite and fluorocarbon surfactant are mixed in a ratio of 1:1-1:3; S3. Three functional layers are coated sequentially using a three-roller coater, with the coating amount of each layer controlled at 10-30 g / m². S4. Gradient curing: Pre-bake the bottom layer at 80-100℃ for 5 minutes, cure the middle layer at 120-140℃ for 8 minutes, and finally cure the top layer at 150-170℃ for 3 minutes.

7. The preparation method according to claim 6, characterized in that, In step S1, the plasma treatment gas is a mixture of argon and oxygen in a volume ratio of 4:1 to 6:

1.

8. The preparation method according to claim 6, characterized in that, In step S3, the roller speed ratio of the coating machine is 1:1.2:1.5, and the pressure is 0.2-0.5MPa.

9. The application of the special fabric as described in any one of claims 1-5 in petrochemical protective clothing, medical surgical gowns, or electronic cleanroom work clothes.

10. The application according to claim 9, characterized in that, The seams of the petrochemical protective clothing are sewn with conductive yarn, and the seam resistance is ≤10³Ω / cm.

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