Have you ever walked across the room to pet your dog, but got a shock instead? Perhaps you took your hat off on a dry winter’s day and had a “hair-raising” experience! Or, maybe you have made a balloon stick on the wall after rubbing it against your clothes?
Why do these things happen? Is it magic? No, it’s not magic; its static electricity! Static electricity is the result of an imbalance between negative and positive charges in an object. These charges can build up on the surface of an object until they find a way to be released or discharged. This is referred to as an ESD event.
The rubbing of certain materials against one another transfer negative charges, or electrons from one to the other. For example, if you rub your shoe on the carpet, your body collects extra electrons. The electrons cling to your body until they can be released. As you reach and touch your furry friend, you get a shock.
And what about that “hair-raising” experience? As you remove your hat, electrons are transferred from hat to hair, creating that interesting hairdo! Remember, objects with the same charge repel each other. Because they have the same charge, your hair will stand on end. Your hairs are simply trying to get as far away from each other as possible!
While ESD is a great way for science teachers to impress their students, it has harmful consequences in an industrial environment. It can blow out electronics, cause materials to mis-feed, ink to spider, and a host of other maladies.
So how does one go about managing ESD? By developing a working knowledge of the science, doing a process audit, and modify the material that is the source or employ static eliminating equipment.
Basic Principles of Effectively Managing Static
Virtually all materials, sometimes even conductors, can be triboelectrically charged. Knowing that some materials are more prone to static, avoid their use in the manufacturing process. Nylon, PET, and Lexan lead the list of offenders. Can you guess what happens when a PET bottle slides down a nylon chute?
Static can occur throughout the manufacturing, test, shipping, handling, or operational process. Wherever two materials come into contact and rub with one another, there is a potential for a static build up. A great diagnostic tool is a static meter. With it you can find areas of static build up.
The next step is to analyze the materials that are coming into contact with your product. Grounded conductive surfaces are preferable. An alternative is the use of a static eliminator.
Humidity plays an important role in static control. Have you noticed that static is more of a problem in the dry winter months than it is in the humid summer days? The more humidity in the air the more conductive it is. A conductive atmosphere will drain off static charges before they become a problem. Climate control is not always possible so the use of static eliminators is your only option.
Keep in mind that once a static charge is removed it does not stay removed. It will develop again whenever it comes into contact and rubbed with other materials. Static free product packed with static generating materials can become charged before they reach your customer.
Need help? Call one of our application engineers 1-800-903-9247.
Library of Congress – “Everyday mysteries”
ESD Association, Rome, NY –Fundamentals of Electrostatic Discharge