Cleaning and performance testing of esd work clothes
1. Cleaning of clean work clothes
Clean work clothes are special work clothes with dust-free and antistatic properties suitable for electronics, optical instruments, pharmacy, microbiological engineering, precision instruments and other industries. The clothing is generally a synthetic fabric with conductive yarns embedded.
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 stain, how to maintain it is an important factor, that is, the method of cleaning. If you use ordinary washing methods, of course, it will be soiled on the contrary. Therefore, a special method must be used. Clean work clothes, from a management perspective, must also be cleaned and packaged in a clean room when cleaning.
Under normal circumstances, clean work clothes are washed at least once a week, and some demanding types of work are even washed once a day.
When cleaning in an ordinary room, dust and dust will be attached, and it will be contaminated by detergent. In addition, there is a risk of dust and microorganisms attaching during the packing and transportation process.
Clean work clothes are generally cleaned in accordance with the * professional cleaning company. The representative cleaning process is shown in Chart 1. The matters that should be paid attention to in the clean room cleaning process are as follows:
(1) The newly sewn clean work clothes can be washed directly, and the recycled clean work clothes found oil stains, the oil stains should be carefully removed before the washing procedure.
(2) Check the accessories such as scratches, damages and buckles before washing, and repair, replace or scrap the defective ones.
(3) The cleaning, drying, and packing must be carried out in a clean room with a higher degree of cleanliness than the clean room where the work clothes are used.
(4) The water used for wet and dry cleaning should be filtered, and the solvent should also be distilled. Use a filter membrane with a pore size of less than 0.2μm at the point of use, and perform more than one filtration as needed.
(5) In order to remove water-soluble contaminants, after washing with water, use a distilled solvent to perform a post-cleaning to remove oily contaminants.
(6) The temperature of the wet washing water is as follows:
Polyester cloth 60-70C (*high 70C)
Nylon cloth 50-55C (*high 60C)
(7) Antistatic agent can be used to improve the antistatic characteristics when rinsing and permeating water after *, but the selected antistatic agent should be well combined with the fiber and no dust will fall off.
(8) Work clothes with buckles should be washed in the buckled state.
(9) Drying is carried out in a clean air circulation system dedicated to washing.
After drying, fold it in a clean room dedicated to washing, and put it into a clean polyester bag or nylon bag. It can be double-layered or vacuum plasticized according to requirements. The packaging material is best to use materials with good antistatic properties. Since the folding process * is easy to generate dust, the folding process must be carried out in a high-grade clean space. For example, the folding and packaging of class 100 clean work clothes should be carried out in a class 10 environment.
2. Performance testing of clean work clothes
2.1 Purification performance test
The pollution particles attached to the inside and outside of the clean work clothes used in the clean room are measured by the following four methods: ASTM F-51 method (microscope method), F-51 repair method (counting method), HELMKE drum method (roller) Method, equivalent to ASTM test method) and vibration test method (vibration method).
(1) ASTM-F-51 method (microscope method)
The test probe is equipped with a filter diaphragm, directly connected to the suction metering pump, and the air volume passing through is 28L/min. During the test, the air is passed through the test cloth, the dust particles contained in the air are captured on the test filter membrane, and the number of dust particles is counted by observation with a 400-fold microscope.
Read the number of particles 0.5-5 and above 5 on the filter membrane. A 3.08mm grid is printed on the filter membrane, and the number of particles in a grid can be read.
(2) ASTM-F-51 revision method (counting method)
Pass air through the test cloth, and measure the size and number of dust particles with a particle counter.
Place the sample on a stand with a metal mesh, and use a sampler (replaced with a 47mm filter holder) to contact and attract, and the amount of air passing through is 28L/min.
(3) Helmke Drum Test
Put the sample into a rotating drum with a side opening and rotate, sample the dust particles from the bucket, and determine the level of cleanliness after measuring the number of particles with a particle counter. The size of the rotating drum is 43cm×33cm, there are 4 blades on the inside of the barrel, and the speed of the barrel is 10 revolutions per minute.
(4) Vibration method
Place the sample in a small chamber, generate particles by vibration and twist, and measure with a particle counter. At the same time, the particles with a large particle size (above 25) are trapped on the filter membrane and the number of particles is read. The air volume is 3.5 feet/minute (0.099m/mim), and the number of vibrations is 150 times/minute.
my country currently does not have a national standard for dust-free performance testing of clean work clothes. You can refer to the Japanese Industrial Standard JIS-B-9923 and the American IES Standard RP-CC-003-87-T studied by the Special Committee of the Japan Air Cleaning Association.
For the evaluation of dust-free performance, each industry can differentiate and use it according to the clean room standard specified in the international standard ISO/TC209, combined with their own cleanliness level.
2.2 Antistatic performance test
Antistatic property is an important feature of clean work clothes, especially in microelectronics and other industries that require more stringent antistatic properties of clothing.