Anti-static work clothes knowledge
1. The generation and harm of static electricity in clothing
In normal production activities, between the clothing worn by the operator and the surface of the external medium (such as worktops, chair surfaces, tools, appliances, etc.), between layers of clothing, underwear and skin, until the soles of the shoes and the ground when walking Between the plateaus, clothing and shoes are charged due to frequent contact, separation and friction, especially when high-insulating chemical fiber clothing is worn. According to the law of charge dissipation on the medium, the electrostatic charge carried by the parts of clothing and shoes gradually dissipates to the entire surface, and when equilibrium is reached, a certain static voltage on the clothing is formed. Of course, because the human body itself is a good conductor, the charging of clothing will cause the skin of the human body to be charged due to electrostatic induction, and a certain static voltage will also be formed. Therefore, for the operator, there are two possible discharge channels; one is the discharge between the fingertip (skin) and the grounding conductor, and the other is the discharge between the work clothes and the grounding conductor. Both of these discharges may cause damage to electrostatic sensitive devices. Although the anti-static wrist strap can eliminate the first type of discharge hazard, it cannot eliminate the second type of discharge hazard. This is because the wrist strap can only eliminate the static electricity on the human skin as a good conductor, and cannot leak the static electricity on the clothes with strong insulation. People often only pay attention to the elimination of human skin static electricity, but neglect or not pay enough attention to eliminate clothing static electricity, which needs to be improved.
It can be seen from the above table that the static voltage value on clothing has greatly exceeded the electrostatic discharge damage threshold of many electrostatic sensitive devices when the human body is performing various activities. Therefore, it may cause damage to the sensitive devices when touching or approaching these components. It should also be pointed out that it is generally believed that wearing pure cotton work clothes can prevent the accumulation of static electricity in the clothing, so it is safe. Actually, this view is one-sided. This is basically the case only when the relative humidity of the air is higher than 50%; and when the relative humidity is relatively low, the charge of pure cotton products increases significantly. Tests have shown that when the relative humidity is lower than 30%, the charge of pure cotton fabric is equivalent to that of polyester; and when the relative humidity is lower than 20%, the charge of cotton fabric will even be higher than that of some chemical fiber fabrics. Therefore, in dry climate areas, we cannot expect to use pure cotton products to eliminate the static electricity hazards of clothing under any circumstances.
Based on the above reasons, in order to effectively prevent the electrostatic discharge hazards of human body static electricity, the operator must wear anti-static work clothes.