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Cleaning of clean work clothes Clean work clothes are special work clothes with dust-free and antistatic properties suitable for industries such as Electronics, optical instruments, pharmaceuticals, microbial engineering, and precision instruments.
Cleaning of clean work clothes
Clean work clothes are special work clothes with dust-free and antistatic properties suitable for industries such as electronics, optical instruments, pharmaceuticals, microbial engineering, and precision instruments. The fabric is generally a synthetic fiber fabric with woven conductive yarn.
The most important part of the management of clean work clothes is cleaning. Although the fiber itself is a clean fiber that is difficult to get dirty, how to maintain it is an important factor, that is, the method of cleaning. If ordinary washing methods are used, of course, they will be dirty on the contrary. So special methods must be used.
Under normal circumstances, clean work clothes are washed at least once a week, and some high-demand jobs are even washed once a day.
When washing in an ordinary room, dust and bacteria will be attached, and they will be contaminated by detergents. In addition, there is also a risk of dust and microorganisms being attached during packaging and transportation.
Cleanroom work clothes are usually cleaned by professional cleaning companies. The representative cleaning process is shown in Figure 1. The following points should be noted during the cleanroom cleaning process:
Newly sewn cleanroom work clothes can be washed directly, but if oil stains are found on the recycled CleanRoom work clothes, the oil stains should be carefully removed before the washing process.
Before washing, the accessories such as scratches, damages and buckles should be checked. Defective ones should be repaired, replaced or scrapped.
Cleaning, drying and bundling must be carried out in A CleanRoom with a higher cleanliness than the cleanroom where the work clothes are used.
The water used for wet and dry cleaning should be filtered, and the solvent should be distilled and then filtered at the point of use with a filter membrane with a pore size of less than 0.2μm. Filter more than once as needed.
In order to remove water-soluble pollutants, wash with clean water and then use a distilled solvent for the final wash to remove oily pollutants.
The water temperature for wet washing is as follows:
Polyester cloth 60-70C (maximum 70)
Nylon cloth 50-55C (maximum 60)
During the final rinse, antistatic agents can be used to improve the antistatic properties, but the selected antistatic agents should be well bonded to the fibers and free of dust shedding.
Work clothes with buckles should be washed in the buckled state.
Dry in a Clean air circulation system dedicated to washing.
After drying, fold them in A Clean Room dedicated to washing and put them into clean polyester bags or nylon bags. Double-layer packaging or vacuum sealing can be performed as required. The packaging material should preferably be made of materials with good antistatic properties.
Performance test of clean work clothes
1. Purification performance test
The following four methods are used to measure the contaminated particles attached to the inside and outside of the clean work clothes used in the clean room: ASTM F-51 method (microscope method), F-51 revision method (counting method), HELMKE drum method (drum method, equivalent to ASTM test method) and vibration test method (vibration method).
a. ASTM-F-51 method (microscope method)
The test probe is equipped with a filter membrane and is directly connected to the suction metering pump. The Air volume passing through is 28L/min. During the test, air is passed through the test clothes, and the dust particles contained in the air are captured on the test filter membrane. The number of dust particles is observed and counted under a 400x microscope.
Read the number of particles of 0.5-5 and above 5 on the filter membrane. There are 3.08mm grids printed on the filter membrane, and the number of particles in one grid can be read.
b. ASTM-F-51 revised method (counting method)
Air is passed through the test clothing, and the size and number of dust particles are measured with a particle counter.
The sample is placed on a stand with a metal mesh, and a sampler (replaced with a 47mm filter holder) is used for contact suction. The amount of air passing through is 28L/min.
c. Helmke Drum Test
The sample is placed in a rotating drum with an opening on the side and rotated. The dust particles in the drum are sampled and the number of particles is measured with a particle counter to determine the cleanliness level. The size of the rotating drum is 43cm×33cm, and there are 4 blades on the inside of the drum. The drum rotates at 10 rpm.
d. Vibration method
The sample is placed in a small chamber, and particles are generated by vibration and torsion, which are measured with a particle counter. At the same time, particles with large particle sizes (above 25) are captured on the filter membrane and the number of particles is read. The air volume is 3.5 feet/minute (0.099m/mim) and the vibration frequency is 150 times/minute.
At present, there is no national standard in my country for the dust-free performance test of clean work clothes. You can refer to the Japanese Industrial Standard JIS-B-9923 studied by the Special Committee of the Japan Air Cleanliness Association and the American IES Standard RP-CC-003-87-T.
For the evaluation of dust-free performance, each industry can use the Clean room standards specified by the international standard ISO/TC209 in combination with their own cleanliness levels.
2. Antistatic performance test
Antistatic property is an important characteristic of clean work clothes, especially in industries such as microelectronics, where the antistatic performance of clothing is more stringent.
The test method can be based on the National Standard of the People's Republic of China GB/T12703-91 "Test Methods for Electrostatics of Textiles". Since the fabric used for clean work clothes is polyester filament fabric with woven conductive threads, only the friction charging voltage (B method), charge surface density (C method) and friction charging of work clothes (E method) in this standard are suitable for the anti-static performance test of clean work clothes.
a. Friction charging voltage method
The test principle of this method is to make the sample and the standard cloth rub against each other under certain tension conditions, and evaluate the friction charging relationship between the wearer and the outerwear based on the highest voltage and average voltage generated at this time.
The method is to clamp the sample (4 pieces, 2 warps and 2 wefts, size 4cm×8cm) on a rotating drum (outer diameter 150±1mm, width 60±1mm), rub the drum with standard cloth (nylon or polypropylene) at a speed of 400rpm, and test the maximum value (V) of the sample's charged voltage within 1min.
b. Charge surface density method
The sample is rubbed with nylon standard cloth in a specific way under specified conditions.
