Test method of purified terephthalic acid (PTA) for industrial use—
Part 6: Determination of particle size distribution
1 Scope
This part of GB/T 30921 specifies the air-jet sieve method and laser diffraction method for the determination of particle size distribution of purified terephthalic acid (PTA) for industrial use.
The air-jet sieve method in this part is applicable to the determination of PTA samples with particle size distribution ranging from 10 μm to 4,000 μm; laser diffraction method is applicable to the determination of PTA samples with particle size distribution ranging from 1 μm to 2,000 μm.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 3723 Sampling of chemical products for industrial use—Safety in sampling
GB/T 6679 General rules for sampling solid chemical products
GB/T 6682 Water for analytical laboratory use—Specification and test methods
GB/T 8170 Rules of rounding off for numerical values & expression and judgment of limiting values
GB/T 19077.1 Particle size analysis—Laser diffraction method—Part 1: General principles
3 Air-jet sieve method
3.1 Method summary
Use a group of special sieves to screen the specimens one by one on the air-jet sieve (add 1% carbon black powder to eliminate the generated static electricity), then measure the mass of the specimen remaining on the corresponding special sieve, and calculate the percentage between it and the total mass of the specimen respectively, so as to obtain the particle size and distribution of the specimen.
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3.2 Reagents and materials
3.2.1 Carbon black powder: the particle size is less than 45 μm (325 meshes).
3.2.2 Weighing dishes or aluminum trays.
3.3 Apparatus
3.3.1 Air-jet sieve: consisting of a box containing a special sieve, with a suction port and an air inlet at the bottom, and the adjustable vacuum degree is 1.5 kPa–2.0 kPa.
3.3.2 Special sieve: made of stainless steel; mesh classification: 45 μm (325 meshes), 53 μm (270 meshes), 74 μm (200 meshes), 105 μm (140 meshes), 149 μm (100 meshes), 210 μm (70 meshes), 250 μm (60 meshes), or other set of standard sieves containing 45 μm (325 meshes) and 250 μm (60 meshes) with rubber sealing ring.
3.3.3 Balance: with a sensitivity of 0.1g.
3.4 Sampling
Take samples in accordance with the technical requirements specified in GB/T 3723 and GB/T 6679.
3.5 Procedure
3.5.1 Weigh (25.0 ± 0.1)g specimen in an aluminum tray with a mass of m.
3.5.2 Weigh 0.2g–0.3g carbon black powder in the same tray and mix well with the specimen.
3.5.3 Weigh the mass of special sieve and rubber sealing ring (m1).
3.5.4 Place the weighed special sieve and rubber sealing ring on the air-jet sieve in turn, and push them down slowly so that they just touch the top of the air-jet sieve.
3.5.5 Transfer the weighed specimen in the aluminum tray into a special sieve and cover it with a plastic cover.
