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VERMICULITE添加时间:2018-12-14

              Vermiculite is a kind of layered mineral that contains Mg and degenerates secondarily from hydrated aluminum silicates. It is usually formed by weathering or hydrothermal alteration of biotite or phlogopite. Its name is from Latin vermiculare, to breed worms, for the manner in which it exfoliates when heated. Categorized by stages, vermiculite can be divided into unexpanded vermiculite and expanded vermiculite. Categorized by color, it can be divided into golden and silver (ivory). Vermiculite has excellent properties such as heat insulation, cold-resistance, anti-bacteria, fire prevention, water absorption and sound absorption, etc. When baked for 0.5 ~ 1.0 minutes under 800 ~ 1000 , its volume can be increased rapidly by 8 to 15 times, up to 30 times, with the color changed into gold or silver, producing a loose-textured expanded vermiculite which is not anti-acid and poor in electric performance. The processing process for vermiculite flakes is as follows: after being got rid of sand and impurities, as well as fragmented and screened, etc, vermiculite ore will take on vermiculite flakes that can be divided into No.2 Flake, No.3 Flake, No.4 Flake and No.5 Flake; vermiculite after the expansion process will take on layered flaky shape, with the proportion generally being 100-200kg/ cubic meter ( Due to the huge volume of expanded vermiculite, the transportation cost would be quite huge, so the exported vermiculite is usually types of unexpanded No.2, No.3 or No.4 vermiculite. Categorized by its shapes after expansion, vermiculite flakes can be divided into oblique rotation vermiculite flakes and crop vermiculite flakes.

Physical and Chemical Properties of Vermiculite

Because of different degrees of hydration and oxidation, chemical compositions of vermiculite are not the same. The chemical formula of vermiculite is:

Mg x (H2O)(Mg3—x)(ALSiO3O10)(OH2)

Molecular Formula

SiO2

MgO

AI2O3

Fe2O3

FeO

K2O

H20

CaO

PH

Content (%)

37-42

11-23

9-17

3.5-18

1-3

5-8

7-18

1-2

8-11

Expanded vermiculite

Major Applications

Vermiculite is a hydrate, in blocks or flakes. Its volume will increase by 6-15 times when its water molecules between layers are heated up under high temperature. It is rich in nitrogen, phosphor, potassium, aluminum, iron, magnesium, silicate, etc. Vermiculite has a high charge, so it has a higher capacity of and stronger absorption ability of cation exchange.

Vermiculite ore can rapidly expand by several or tens of times in volume after heated up under high temperature, with the average capacity being 100-130kg/m3 and also tiny air layer, which makes it an excellent building material for heat preservation, sound absorption and cold resistance as well as industrial filler, coatings and refractory material. Besides, the expanded vermiculite is also a good heat insulation material as it is small in thermal conductivity and its capacity is between 50-200kg/m3. Good-quality expanded vermiculite can still be workable up to up to 1100. In addition, expanded vermiculite is good in electric insulation, light in capacity and is cold-resistant, heat-preserving, heat-insulating, sound-absorbing, etc. Therefore, it can be widely used in construction, electric power, petroleum, metallurgy, textile, agriculture, food industries and etc. Applied into the construction industry, it can be used in thermal insulation, sound absorption and coating materials; applied in agriculture, as soil improver and auxiliary of fertilizers, expanded vermiculite is light in terms of weight, absorptive of water and fertilizer, and can be used for 3-5 years without putrefaction. What’s more, it is carrier of animal feed, deodorant, animal drugs and so on. It can also be used as pesticides, fungicides, disinfectant, organic compounds (camphor) and can provide a good media for storing vegetables as well as roots, stems and leaves of other rare plants. Vermiculite has adsorption property for radioactive elements and also can handle some waste water of radioactive elements.

A.    Main Fields and Applications


Fields

Applications

 

Construction

Light Materials

Aggregate of Light Cement Concrete

Heat-Proof Materials

Wall Materials, Fire-Proof Plates and Mortar, Refractory Bricks, Brake Block

Heat Preserving and Insulation Materials; Sound Absorption Materials

Heat-Preserving Materials for Pipelines of Underground and Greenhouse, Inner Packing for Indoor and Tunnel, Wall and Ceiling for Public Places

Metallurgy

Steel Covering Materials, Iron Making, Casting, Drossing

Cladding Material for Steel Frame of High-Rise

Agriculture and Horticulture

Horticulture

Lawn of Golf Ground, Seed Conservative, Soil Modifier, Wetting Agent, Plant Growth Agent, Feed Additives, Gardening Soil Media

Fishing Industry

Bait

 

Others

Adsorbent, Filter Aid, Active Carriers of Chemicals and Fertilizers, Sewage Treatment, Sea Oil Stain Absorption, Cigarette Filter, Regulator of Explosive Density


B. Applications of Different Sizes of Vermiculite


+20

Mesh

2040

Mesh

40-120

Mesh

120270

Mesh

270-1250

Mesh

 Housing Insulation Equipment, Household Refrigeration, Vehicle Silencer, Noise Plaster, Lined Pipe of Safe and Vault, Heat Protection Clothing of Boiler, Long-Handled Spoon of Iron Works, Firebrick, Insulation Cement

Car Insulation Equipment, Aircraft Insulation Equipment, Cold Storage Insulation Equipment, Passenger Carriage Insulation Equipment, Water Cooling Towers of Wall, Steel Annealing, Fire Extinguishers, Filters, Cold Storage

 Linoleum, Roof Panels, Cornices, Referred Gates Board

Wallpaper Print, Outdoor Advertising, Paint, Fire-proof Card Paper of Photographic Soft Wood

Golden and Bronze Printing Ink, Outer Supplements of Paints


Application of Vermiculite in Fire Board

Under certain conditions, with the help of adhesive and chemical additive, granular mineral expanded vermiculite will be adhered together to form the semi-finished board. After that, the semi-finished board will undergo kinds of fine processing by groups of special processing equipments to form the finished board. This technology combines the strong points of organic and inorganic composite hot pressing and inorganic composite adhesive cold or hot pressing.

Vermiculite Fire Board Has the Following Features

1. The inorganic compound formula eliminates the problems of high temperature damage, flue, and poor long-term stability of organic adhesive, with great performance of preventing fire and smoke. It reaches the highest international level (A-15).

2. In technology process, it takes the advantage of the production equipments of man-made panels and mineral wool boards to compose its own special assembly line, which reduces the factors influencing quality to the minimum and makes it easy to control, thus improving production efficiency and pass rate. Besides, vermiculite has a wide application. It can be used to produce fire doors with expanded vermiculite as cores, plant fiber vermiculite flame-resistant plywood, light vermiculite heat-insulation board, light clay brick, polymer film, catalyst and etc.

Expanded vermiculite is porous, light and high in melting point, which makes it most suitable material for high-temperature heat insulation (1000 ℃ or less) and fire insulation. By experiments, the temperature of back surface of 15cm thick cement vermiculite boards is only about 40  after it is burned under high temperature-1000 for 4-5 hours. No heat can be felt with its back surface even if the 7 cm thick vermiculite board is burned for 5 minutes by fire welding flames under 3000  and its front surface is melt. Therefore, expanded vermiculite surpasses all heat preserving materials such as asbestos, diatomite products, etc.

Vermiculite can be used as heat preserving materials for high-temperature facilities, such as the insulating bricks, boards and caps in the smelting industry. Those equipments needing thermal insulation can all use vermiculite boards, vermiculite bricks, cement vermiculite products or asphalt vermiculite products to preserve heat. These facilities include wall, roof, refrigerator, boiler, steam piping, liquid pipeline, water tower, changing furnace, heat exchanger, storage of dangerous goods, annealing, melting furnace, and military enterprises, etc. Tiny air compartments, formed after vermiculite’s expansion, enable the expanded vermiculite become a porous sound insulation material. When the frequency is 2000C / S, the sound-absorbing rate of 5mm thick vermiculite is 63%, 6mm 84%, 8mm 90%.

Expanded vermiculite, paved on the roof, will play a very good heat insulating effect, making the building warm in winter and cool in summer. Using vermiculite bricks into the partition wall of high rise or using vermiculite blocks as partition materials into hotels or entertainment centers, effects of sound absorption, fire proof, heat preservation and so on will be fully displayed and the building will also be reduced of its load.

Vermiculite is great in resisting frost as its capacity and strength keeps the same even after it goes through 40 times of freeze-thaw cycle experiments under -20 . It is porous and has absorption property. It can keep heat and prevent condensation. Besides, it can absorb radiation rays, therefore vermiculite boards can be placed inside laboratory to substitute expensive lead boards to absorb up to 90% of scattered rays. 65mm thick vermiculite is equivalent to 1mm thick lead board.


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