Preparation method of an impact-resistant buoyant plate

Abstract

The invention discloses a method for preparing an impact-resistant buoyancy plate. The method comprises the following steps: laying glass fiber cloth on a demoulding cloth, uniformly coating the glass fiber cloth with glass fiber reinforced plastic resin to impregnate the glass fiber cloth, repeating the operations of laying the glass fiber cloth and coating the glass fiber reinforced plastic resin, curing and demoulding to obtain a glass fiber reinforced plastic plate; cutting glass fiber reinforced plastic grating bars according to design dimensions, splicing them together to obtain a glass fiber reinforced plastic grating; placing the glass fiber reinforced plastic grating in a mold, adding a main raw material of a buoyancy material, curing and demoulding to obtain a main body of the buoyancy material; covering the surface of the main body of the buoyancy material with a glass fiber reinforced plastic skin by a vacuum infusion method; the glass fiber reinforced plastic skin is composited with glass fiber cloth and glass fiber reinforced plastic resin; compared with conventional impact-resistant materials, the addition of the glass fiber reinforced plastic grating and the glass fiber reinforced plastic skin to the formula can effectively improve the performance of the buoyancy material, especially in terms of impact resistance. The added glass fiber reinforced plastic grating and the glass fiber reinforced plastic skin can effectively prevent the expansion of surface and internal cracks while resisting impact force.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and particularly relates to a method for preparing an impact-resistant buoyancy plate. Background Art

[0002] Buoyancy materials are closed-cell composite foams made by uniformly dispersing fillers such as hollow glass microspheres, hollow plastic microspheres, and hollow metal microspheres into a polymer matrix (resin, etc.) through a specific preparation process. They possess excellent properties such as high strength, low density, and low water absorption. Their laminated design enables efficient energy absorption and transfer, making them a key material for deep-sea unmanned or manned submersibles.

[0003] FRP is a composite material reinforced with glass fiber. Its advantages include light weight, high strength, and corrosion resistance. It is widely used in transportation, construction, electronics, aerospace, and other fields, making it an ideal material for manufacturing buoyancy panels. In recent years, with the rise of transportation, composite materials have gained increasing attention as a key component in the manufacture of automobile, train, and ship bodies and components, as well as aircraft. It is reported that many countries around the world have conducted extensive research on deep-sea buoyancy materials, and the high-strength buoyancy materials they have developed are widely used in civilian, commercial, and military fields.

[0004] In deep-sea applications, hollow glass microspheres and epoxy resin composites are often the only option to ensure high compressive strength and maximum safety and reliability. These composites leverage the high strength and adhesion of epoxy resin and the lightweight, hollow, and thermally insulating properties of glass microspheres. These composites play a crucial role in ensuring submersible buoyancy, increasing payload, and reducing overall dimensions, particularly in improving underwater performance and safety in deep-sea submersibles. Buoyancy materials, which must remain submerged in water for extended periods of time, require low density, low water absorption, excellent pressure resistance, and impact resistance.

[0005] In recent years, this new composite material has been increasingly used in energy-absorbing and cushioning devices for automobiles and road bridges due to its low density, high specific energy absorption, and thermal insulation. The addition of hollow microspheres to the resin matrix allows for better absorption of external impacts through the crushing effect of the hollow microspheres, meeting both the basic requirements of automotive energy-absorbing materials and the need for lightweight vehicles. It also provides effective thermal insulation, facilitating battery thermal management in electric vehicles. However, after the resin matrix undergoes a cross-linking reaction with the curing agent, the three-dimensional network structure formed within it has poor toughness and insufficient impact resistance. This can lead to propagating cracks along the buoyancy material sheet before the hollow microspheres are completely crushed, resulting in overall material failure. Summary of the Invention

[0006] In order to solve the problem that conventional buoyancy materials have insufficient impact resistance, the present invention provides a method for preparing a high-performance impact-resistant buoyancy plate.

[0007] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0008] A method for preparing an impact-resistant buoyancy plate comprises the following steps:

[0009] (1) Laying glass fiber cloth on the demoulding cloth, evenly coating the glass fiber cloth with glass fiber reinforced plastic resin to impregnate the glass fiber cloth, repeating the operation of laying the glass fiber cloth and coating the glass fiber reinforced plastic resin, curing and demoulding to obtain a glass fiber reinforced plastic plate; cutting the glass fiber reinforced plastic grille bars according to the designed size, and splicing them together to obtain a glass fiber reinforced plastic grille;

[0010] (2) placing the glass fiber reinforced plastic grid in a mold, adding the raw material of the buoyancy material body, and demoulding after solidification to obtain the buoyancy material body;

[0011] (3) The surface of the buoyancy material body is covered with a fiberglass skin by vacuum infusion; the fiberglass skin is made of a composite of glass fiber cloth and fiberglass resin.

[0012] According to the above solution, the thickness of the fiberglass reinforced plastic grille is 0.5-2 mm, the thickness of the buoyancy material body is 3-8 mm, and the thickness of the fiberglass reinforced plastic skin is 0.4-5 mm.

[0013] According to the above scheme, in step 1, the curing temperature is 25-30°C and the curing time is 3-5 hours.

[0014] According to the above scheme, in step 2, the curing temperature is 20-25°C and the curing time is 24-72 hours.

[0015] According to the above solution, the glass fiber cloth adopts model SW220C-100B.

[0016] According to the above scheme, the main raw materials of the buoyancy material are calculated by weight: 100 parts of vinyl resin, 0.2-0.6 parts of diluent, 1-3 parts of coupling agent, 20-30 parts of glass microbead powder, 0.2-0.6 parts of accelerator, 0.5-1 parts of defoaming agent, 0.5-1 parts of deaerator, 2-2.5 parts of dispersant, and 0.5-1.5 parts of curing agent.

[0017] According to the above scheme, the vinyl resin is one or two of E22-901 resin, 3201 resin, 820(A) resin, and 820(m) resin.

[0018] According to the above scheme, the diluent is one or two of S06 diluent, UE6H diluent, and vinyltoluene.

[0019] According to the above solution, the coupling agent is one or two of KH-560 coupling agent, KH-570 coupling agent, and A-187 silane coupling agent.

[0020] According to the above solution, the glass microbead powder is one or two of K1 glass microbead powder (particle size 22-200 μm), H20 glass microbead powder (particle size 22-200 μm), and H15 glass microbead powder (particle size 22-200 μm).

[0021] According to the above scheme, the accelerator is one or two of the LDB accelerator, LDA accelerator and E5 accelerator.

[0022] According to the above solution, the defoaming agent is one or both of tributyl phosphate defoaming agent and BYK-A530 defoaming agent.

[0023] According to the above solution, the deaerator is one or both of BYK-A560 deaerator and BYK-A570 deaerator.

[0024] According to the above solution, the dispersant is one or both of 908 dispersant and BYK-W9010 dispersant.

[0025] According to the above solution, the curing agent is one or two of LC curing agent, K90 curing agent, and L liquid curing agent.

[0026] According to the above scheme, the fiberglass resin raw materials are calculated by weight: 100 parts of vinyl resin, 2 to 4 parts of curing agent, 0.1 to 4 parts of accelerator, 0.5 to 1 part of coupling agent, 8 to 12 parts of flame retardant, 0 to 5 parts of diluent and 0.2 to 0.5 parts of solid filler white carbon black.

[0027] According to the above scheme, the vinyl resin is one or two of E22-901 resin, 3201 resin, 820(A) resin, and 820(m) resin.

[0028] According to the above scheme, the diluent is one or two of styrene diluent, SO6 diluent, UE6H diluent and vinyl toluene.

[0029] According to the above solution, the coupling agent is one or two of KH-560 coupling agent, KH-570 coupling agent, and A-187 silane coupling agent.

[0030] According to the above scheme, the accelerator is one or two of the LDB accelerator, LDA accelerator, E5 accelerator and E4 accelerator.

[0031] According to the above solution, the curing agent is one or two of LC curing agent, K90 curing agent, and L liquid curing agent.

[0032] According to the above solution, the flame retardant is one or two of FR-685 flame retardant, FR-2025 flame retardant, and FR-8705 flame retardant;

[0033] According to the above scheme, the solid filler is white carbon black, with a silicon dioxide content of 90-98% and a specific surface area of 161-800m 2 / g.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The invention has simple process, low cost and is suitable for large-scale industrial production.

[0036] Compared with conventional impact-resistant materials, the addition of FRP grating and FRP skin to the formula can effectively improve the performance of buoyancy materials, especially in terms of impact resistance. The added FRP grating and FRP skin can effectively prevent the expansion of surface and internal cracks while resisting impact force.

[0037] During the design and manufacturing process, FRP grating buoyancy material panels can be customized according to specific application needs to meet different usage conditions and performance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 : Schematic diagram of the structure of the impact-resistant buoyancy plate of the present invention. DETAILED DESCRIPTION

[0039] The following examples further illustrate the technical solutions of the present invention but are not intended to limit the scope of protection of the present invention.

[0040] A specific embodiment provides a main raw material of a buoyancy material, which comprises the following components in parts by weight: 100 parts of vinyl resin, 0.2-0.6 parts of diluent, 1-3 parts of coupling agent, 20-30 parts of glass microbead powder, 0.5-1.5 parts of curing agent, 0.2-0.6 parts of accelerator, 0.5-1 parts of defoaming agent, 0.5-1 parts of deaerator, and 2-2.5 parts of dispersant;

[0041] A specific embodiment provides a glass fiber reinforced plastic resin raw material, which comprises, by weight: 100 parts of vinyl resin, 2-4 parts of curing agent, 0.1-4 parts of accelerator, 0.5-1 part of coupling agent, 8-12 parts of flame retardant, 0-5 parts of diluent and 0.2-0.5 parts of solid filler white carbon black.

[0042] The specific embodiment also provides an impact-resistant buoyancy plate, the structural diagram of which is shown in the attached figure. Figure 1 , the preparation method is as follows:

[0043] (1) Laying glass fiber cloth on the demoulding cloth, evenly coating the glass fiber cloth with glass fiber reinforced plastic resin to impregnate the glass fiber cloth, repeating the operation of laying the glass fiber cloth and coating the glass fiber reinforced plastic resin, curing and demoulding to obtain a glass fiber reinforced plastic plate; cutting the glass fiber reinforced plastic grille bars according to the designed size, and splicing them together to obtain a glass fiber reinforced plastic grille;

[0044] (2) placing the glass fiber reinforced plastic grid in a mold, adding the raw material of the buoyancy material body, and demoulding after solidification to obtain the buoyancy material body;

[0045] (3) The surface of the buoyancy material body is covered with a fiberglass skin by vacuum infusion; the fiberglass skin is made of a composite of fiberglass cloth and fiberglass resin.

[0046] Unless otherwise specified, all raw materials used in the specific embodiments were commercially available.

[0047] Example 1

[0048] The fiberglass resin raw materials are calculated by weight as follows: 100 parts of vinyl ester resin, 4 parts of curing agent, 2 parts of accelerator, 0.5 parts of coupling agent, 10 parts of flame retardant, 2 parts of diluent and 0.4 parts of solid filler white carbon black.

[0049] Cut 4 pieces of 360*360 high-strength glass fiber cloth, dry the high-strength glass fiber cloth at a temperature of 70-90℃ for 2-4 hours. Wax the mold surface evenly 3 times, with an interval of more than 20 minutes between each time, and then lay the release cloth. Lay the high-strength glass fiber cloth on the release cloth, and then evenly brush the above resin. Rotate the mold when laying the layers, use a scraper to flatten the fiber cloth, and scrape off excess glue to prevent wrinkles and remove bubbles. After the cloth is soaked, lay the second layer of cloth in the same way. The overlap seams between adjacent layers should be staggered evenly in proportion. Lay the molds in sequence according to the above method, lay 4 layers of glass fiber cloth to make the glass fiber reinforced plastic plate, and make 360*5*0.8mm glass fiber reinforced plastic grille bars through mechanical processing. The glass fiber reinforced plastic grille bars are spliced together to form a grille size of 15*15 glass fiber reinforced plastic grille.

[0050] The buoyancy material is prepared by weighing the following raw materials in parts by mass: 100 parts of vinyl ester resin, 28 parts of glass microbead powder, 1.5 parts of coupling agent, 2 parts of dispersant, 0.2 parts of accelerator, 0.5 parts of diluent, 0.5 parts of defoaming agent, 0.5 parts of deaerator, 2 parts of dispersant, and 1.3 parts of curing agent.

[0051] The fiberglass grating is placed in a mold. The main buoyancy material raw materials are stirred evenly and poured into the mold. The material is placed in a vacuum degassing chamber for 20 minutes of vibration degassing before removal. After natural curing, it is demolded and post-cured. The material is heated to 80°C in an oven for 72 hours and naturally cooled before removal. A 0.8mm fiberglass skin is applied to the impact-resistant side of the 360*360*5mm buoyancy material plate through vacuum infusion, and a 0.4mm fiberglass skin is applied to the back.

[0052] Density test was carried out according to GB / T6343-2009, and the density was 900Kg / m 3 ; The compression strength test was carried out in accordance with GB / T8813-2020, and the compression strength was 39MPa; the impact toughness test was carried out in accordance with GB / T1451-2005, and the impact toughness was 7.36KJ / ㎡.

[0053] Example 2

[0054] A method for preparing high-performance impact-resistant buoyancy material

[0055] Preparation of fiberglass grating: Weigh the following raw materials by mass: 100 parts of vinyl ester resin, 2 parts of curing agent, 1 part of accelerator, 0.5 parts of coupling agent, 8 parts of flame retardant, 3 parts of diluent and 0.2 parts of solid filler white carbon black.

[0056] Cut 6 pieces of 360*360 high-strength fiberglass cloth and dry them at a temperature of 70-90°C for 2-4 hours. Apply wax evenly to the mold surface 3 times, leaving at least 20 minutes between each application, and then apply the release cloth. Lay the high-strength fiberglass cloth on the release cloth and evenly brush the above resin. When laying the layers, rotate the mold and use a scraper to flatten the fiberglass cloth and remove excess glue to prevent wrinkles and remove bubbles. After the cloth is thoroughly soaked, lay the second layer of cloth using the same method. The overlaps between adjacent layers should be evenly staggered. Follow the above method to lay the molds in sequence, lay 6 layers of fiberglass cloth to make the fiberglass plate, and then use mechanical processing to produce 360*5*1.2mm fiberglass grating bars. The fiberglass grating bars are spliced together to form a 20*20 fiberglass grating.

[0057] The buoyancy material is prepared by weighing the following raw materials in parts by mass: 100 parts of vinyl ester resin, 1.2 parts of curing agent, 30 parts of glass microbead powder, 1 part of coupling agent, 0.3 parts of accelerator, 0.4 parts of diluent, 0.6 parts of defoaming agent, 0.6 parts of deaerator, and 2.2 parts of dispersant.

[0058] Add the resin to a kneader, followed by the coupling agent, diluent, and glass microbead powder. After stirring thoroughly, add the accelerator, dispersant, degassing agent, and curing agent. Place the fiberglass grating in a mold, stir thoroughly, pour it into the mold, and place it in a vacuum degassing chamber for vibration degassing. Remove it after 20 minutes, allow it to naturally cure, and then demold and post-cure. Heat it to 80°C in an oven for 72 hours, then cool naturally before removing it. Vacuum infuse the impact-resistant side of the 360*360*5mm buoyancy material board with a 2mm fiberglass skin and a 1mm fiberglass skin on the back.

[0059] After the post-curing board is sampled, the density test is carried out according to GB / T6343-2009, and the density is 1010Kg / m 3 ; The compression strength test was carried out in accordance with GB / T8813-2020, and the compression strength was 45MPa; the impact toughness test was carried out in accordance with GB / T1451-2005, and the impact toughness was 8.45KJ / ㎡.

[0060] Example 3

[0061] A method for preparing high-performance impact-resistant buoyancy material

[0062] Preparation of fiberglass grating: Weigh the following raw materials by mass: 100 parts of vinyl ester resin, 3 parts of curing agent, 3 parts of accelerator, 0.7 parts of coupling agent, 11 parts of flame retardant, 4 parts of diluent and 0.5 parts of solid filler white carbon black.

[0063] Cut 4 pieces of 360*360 high-strength glass fiber cloth, dry the high-strength glass fiber cloth at a temperature of 70-90℃ for 2-4 hours. Wax the mold surface evenly 3 times, with an interval of more than 20 minutes between each time, and then lay the release cloth. Lay the high-strength glass fiber cloth on the release cloth, and then evenly brush the above resin. Rotate the mold when laying the layers, use a scraper to flatten the fiber cloth, and scrape off excess glue to prevent wrinkles and remove bubbles. After the cloth is soaked, lay the second layer of cloth in the same way. The overlap seams between adjacent layers should be evenly staggered in proportion. Lay the molds in sequence according to the above method, lay 4 layers of glass fiber cloth to make the glass fiber reinforced plastic plate, and make 360*10*0.8mm glass fiber reinforced plastic grating bars through mechanical processing. The glass fiber reinforced plastic grating bars are spliced together to form a 15*15 glass fiber reinforced plastic grating.

[0064] The buoyancy material is prepared by weighing the following raw materials in parts by mass: 100 parts of vinyl ester resin, 0.8 parts of curing agent, 20 parts of glass microbead powder, 1.6 parts of coupling agent, 0.6 parts of accelerator, 0.6 parts of diluent, 0.9 parts of defoaming agent, 0.9 parts of deaerator, and 2.4 parts of dispersant.

[0065] Add the resin to a kneader, followed by the coupling agent, diluent, and glass microbead powder. After stirring thoroughly, add the accelerator, dispersant, degassing agent, and curing agent. Place the fiberglass grating in a mold, stir thoroughly, pour it into the mold, and place it in a vacuum degassing chamber for vibration degassing. Remove it after 20 minutes, allow it to naturally cure, and then demold and post-cure. Heat it to 80°C in an oven for 72 hours, then cool naturally before removing it. Vacuum infuse the impact-resistant side of the 360*360*10mm buoyancy material plate with a 0.8mm fiberglass skin and the back with a 0.4mm fiberglass skin.

[0066] After the post-curing board is sampled, the density test is carried out according to GB / T6343-2009, and the density is 950Kg / m 3 ; The compression strength test was carried out in accordance with GB / T8813-2020, and the compression strength was 50MPa; the impact toughness test was carried out in accordance with GB / T1451-2005, and the impact toughness was 8.79KJ / ㎡.

[0067] Comparative Example 1

[0068] Example 1 was repeated without adding the fiberglass reinforced plastic grid.

[0069] Density test was carried out according to GB / T6343-2009, and the density was 280Kg / m 3 ; The compression strength test was carried out in accordance with GB / T8813-2020, and the compression strength was 28.62MPa; the impact toughness test was carried out in accordance with GB / T1451-2005, and the impact toughness was 2.32KJ / ㎡.

[0070] Comparative Example 2

[0071] Example 1 was repeated, except that the fiberglass grid was replaced with a PP honeycomb.

[0072] After the post-curing board is sampled, the density test is carried out according to GB / T6343-2009, and the density is 330Kg / m 3 ; The compression strength test was carried out in accordance with GB / T8813-2020, and the compression strength was 34.85MPa; the impact toughness test was carried out in accordance with GB / T1451-2005, and the impact toughness was 2.56KJ / ㎡.

[0073] Comparative Example 3

[0074] Example 1 was repeated, but the upper and lower surfaces of the buoyancy material plate were not covered with fiberglass skin. The post-cured plate was sampled and density tested according to GB / T6343-2009. The density was 450 kg / m 3 ; The compression strength test was carried out in accordance with GB / T8813-2020, and the compression strength was 31.27MPa; the impact toughness test was carried out in accordance with GB / T1451-2005, and the impact toughness was 2.32KJ / ㎡.

[0075] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0076] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A method for preparing an impact-resistant buoyancy plate, characterized in that The following steps are involved: (1) Laying glass fiber cloth on the demoulding cloth, evenly coating the glass fiber cloth with glass fiber reinforced plastic resin to impregnate the glass fiber cloth, repeating the operation of laying the glass fiber cloth and coating the glass fiber reinforced plastic resin, curing and demoulding to obtain the glass fiber reinforced plastic plate; cutting the glass fiber reinforced plastic grille bars according to the designed size, and splicing them together to obtain the glass fiber reinforced plastic grille; (2) placing the glass fiber reinforced plastic grating in a mold, adding the raw materials of the main body of the buoyancy material, and demoulding after solidification to obtain the main body of the buoyancy material; (3) The surface of the buoyancy material body is covered with a fiberglass skin by vacuum infusion; the fiberglass skin is made of a composite of fiberglass cloth and fiberglass resin; The glass fiber reinforced plastic resin raw materials are calculated by weight as follows: 100 parts of vinyl resin, 2-4 parts of curing agent, 0.1-4 parts of accelerator, 0.5-1 parts of coupling agent, 8-12 parts of flame retardant, 0-5 parts of diluent and 0.2-0.5 parts of solid filler white carbon black; The main raw materials of the buoyancy material are calculated by weight: 100 parts of vinyl resin, 0.2-0.6 parts of diluent, 1-3 parts of coupling agent, 20-30 parts of glass microbead powder, 0.2-0.6 parts of accelerator, 0.5-1 parts of defoaming agent, 0.5-1 parts of deaerator, 2-2.5 parts of dispersant, and 0.5-1.5 parts of curing agent; The thickness of the fiberglass reinforced plastic grille is 0.5-2 mm, the thickness of the buoyancy material body is 3-8 mm, and the thickness of the fiberglass reinforced plastic skin is 0.4-5 mm.

2. The method for preparing the impact-resistant buoyancy sheet material according to claim 1, characterized in that In step 1, the curing temperature is 25-30° C. and the curing time is 3-5 hours.

3. The method for preparing the impact-resistant buoyancy sheet material according to claim 1, characterized in that In step 2, the curing temperature is 20-25° C. and the curing time is 24-72 hours.

4. The method for preparing the impact-resistant buoyancy sheet material according to claim 1, characterized in that The glass fiber cloth adopts model SW220C-100B.

5. The method for preparing the impact-resistant buoyancy sheet material according to claim 1, characterized in that The main raw materials of the buoyancy material include: The vinyl resin is one or two of E22-901 vinyl resin, 3201 vinyl resin, 820 (A) vinyl resin, and 820 (m) vinyl resin; The diluent is one or two of S06 diluent, UE6H diluent, and vinyltoluene diluent; The coupling agent is one or two of KH-560 coupling agent, KH-570 coupling agent, and A-187 silane coupling agent; The glass microbead powder is one or two of K1 glass microbead powder with a particle size of 22 to 200 μm, H20 glass microbead powder with a particle size of 22 to 200 μm, and H15 glass microbead powder with a particle size of 22 to 200 μm; The accelerator is one or two of LDB accelerator, LDA accelerator and E5 accelerator; The defoaming agent is one or both of tributyl phosphate defoaming agent and BYK-A530 defoaming agent; The deaerator is one or both of BYK-A560 deaerator and BYK-A570 deaerator; The dispersant is one or both of 908 dispersant and BYK-W9010 dispersant; The curing agent is one or both of LC curing agent and K90 curing agent.

6. The method for preparing the impact-resistant buoyancy sheet material according to claim 1, characterized in that In the glass fiber reinforced plastic resin raw material: The vinyl resin is one or two of E22-901 vinyl resin, 3201 vinyl resin, 820 (A) vinyl resin, and 820 (m) vinyl resin; The diluent is one or two of styrene diluent, SO6 diluent, UE6H diluent, and vinyltoluene diluent; The coupling agent is one or two of KH-560 coupling agent, KH-570 coupling agent, and A-187 silane coupling agent; The accelerator is one or two of LDB accelerator, LDA accelerator, E5 accelerator and E4 accelerator; The curing agent is one or both of LC curing agent and K90 curing agent.

7. The method for preparing the impact-resistant buoyancy sheet material according to claim 1, characterized in that In the glass fiber reinforced plastic resin raw material: The flame retardant is one or two of FR-685 flame retardant, FR-2025 flame retardant, and FR-8705 flame retardant; The solid filler is white carbon black with a silicon dioxide content of 90-98% and a specific surface area of 161-800 m 2 / g.

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