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[ 2010/5/6 10:48:19 ]
 

.what is the unit mesh How to exchange mesh and micron

 

Explanation

 

Sieve diameter (um)14832.4/sieve mesh

 

Unit mesh size is the size of material particles.generally indicated as the maximum length of particles. Mesh represents the sieve size of standard sieve. In Tyler standard sieve, mesh is the sieve number of 2.45 cm(1 inch) length

 

Tyler standard sieve system: the indexing of tayler sieve system is at the base of the size 0.074mm of 200 mesh sieve, multiply or divided by the n-th power (n=1,2,3… …) of the square root of the main module (1.414), to get a mesh size more coarse or fine 200, if the n-th power of the square root of four times(1.1892) of number 2 to multiply or divide 0.074mm, you can get a series of sieve sizes which more detailed indexing

 

The larger the mesh the thinner the particles. Similar to the magnification of the metallurgical structure

 

Sign before the mesth state whether it can leak such numbers of mesh. Negative number means the mesh which can leak the hole, that is, particle size is smaller than the mesh size; while positive number indicate the mesh which can not leak the hole, that is , particle size is larger than the mesh size. For example, the particals are -100 mesh~ +200 mesh, which means those particals can leak the 100 mesh but not 200 mesh, when select this mesh particles, you should put the large mesh(200) under the small mesh(100), and the left in large mesh(200) is -100~200 particles.

 

Mesh is the number of holes, that is, the holes number in per sqrare inch. The larger the mesh, the smaller the aperture. Generally speaking, the mesh × diameter (micron) =15000. For example, the aperture of 400 mesh is 38 microns; the aperture of 500 mesh is 30 microns. Because of the problems of open porosity, and it used different thickness silk when weaving nets, so different countries have different standard. It exists U.S. standard, UK standard and Japanese standard now, the U.S. standard and UK standard have great similarity, but which have big difference from Japanese standard. China is using the U.S standard, so we can use the formula which is given above. It is available to see Tyler standard sieve mesh size at the following table:

 

mesh

μm

mesh

μm

2

8000

100

150

3

6700

115

125

4

4750

120

120

5

4000

125

115

6

3350

130

113

7

2800

140

109

8

2360

150

106

10

1700

160

96

12

1400

170

90

14

1180

175

86

16

1000

180

80

18

880

200

75

20

830

230

62

24

700

240

61

28

600

250

58

30

550

270

53

32

500

300

48

35

425

325

45

40

380

400

38

42

355

500

25

45

325

600

23

48

300

800

18

50

270

1000

13

60

250

1340

10

65

230

2000

6.5

70

212

5000

2.6

80

180

8000

1.6

90

160

10000

1.3

 

We can see that the size of mesh determines the mesh sieve aperture size. The aperture size determines the maximum particle Dmax of sieving powder. So it is possible that 400 mesh polishing powder is very fine. For example, may be it is only 1-2 microns,but it is also entirely possible to be 10 microns, 20 microns. Because the mesh aperture is about 38 microns. The 400 mesh polishing powder D50 we produced may 20 microns. The given pictures are the photo of polishing powder, the ruler is 50 microns.

 

Therefore, it is inappropriate to constant the polishing powder particle size by mesh, the correct way is using particle size( D10, median diameter D50, D90) to represent the particle size, and using mesh size to discount the partical size. If you read the Janpanese standard JIS standard on the abrasive, you will feel it is very scientific. They give request to each number of abrasive D3, D50, D70. and the data is different when use different particle size analyzer principle, which has strict requirements. For example, D50 is a 2 micron powder, D3 roughly 0.9 microns, D97 is 4 mircons. What does that mean? Such as inthe powder 2 microns, the partical size which is less than 0.9 microns and greater than 4 microns can not exceed 3 percent, this is very strict, the most polishing powder ( including foreign) we saw in the market can not meet this requirement, and the fine powder is particular higher than the standard.

 

There is a reason why we use mesh to characterize polishing powder particle size. The old polishing flour mill used the dry grinding and dry sieving process, so it may cause that D50 of 300 mesh flour will be approximately 9 microns and D50 of 500 mesh is 2 microns. This is basically can guide the production and use. However, with the emergence of new producing technology, we require much high precision polishing, so this method should be improved.

 

 

 

Explanation ()

 

1.      mesh is the number of empty sieve eyes in each square inch. 50 mesh refers to 50 holes in per square inch, and 500 mesh is 500 hole. The more mesh the more holes. In addition to express the holes of sieve, it also can be used to represent the partical size which pass the mesh sieve. The higher the mesh the smaller the particle size.

 

2.      powder particle size refers to fine grain. As the shape of partical is complex, it usually expressed as sieve size, settlement size, the equivalent volume particle size and the equivalent surface area size. Sieve size refers to the size the partical can pass the mesh, and represented by the sieve number of 1 inch (25.4mm) mesh sieve, which was known as mesh. Currently it has not a uniform technical standards for partical size at home and abroad. Each enterprise has its own size indicated definition and representation. Different countries and different industries have different standards for sieve size. So it is difficult to unity the meaning of mesh.

 



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