EXAIR published a white paper, Basics of Static Electricity, explaining what causes static electricity; how it is generated; and steps to eliminate it. You can download this paper HERE, and begin to remove the static issues in your plant or process.
In this blog, I would like to expand on the subject about how static can be generated. On a molecular scale, the outer electrons that are orbiting the nucleus can be “stripped” and redistributed from one atom to another. This will cause an electrical charge imbalance called static. An additional electron will create negatively charged static while atoms losing an electron will create a positively charged static. With non-conductive materials like plastic, paper, rubber, glass, etc., the electrons cannot move back to the original atom. There are three common methods of static generation that will cause this phenomenon to occur. I will explain each one in a brief detail below:
Contact – Whenever objects hit each other, electrons can be passed to or received from the surface of another object. The number of electrons being transferred is based on the type of triboelectric material. But, with plastic bottles or trays bumping into each other on conveyor belts, static can be generated relatively easy.
Detachment – when one material is being separated from another material by peeling, electrons may not able to return back to the original molecule. Adhesive tape and protective films are prevalent in generating static charges by detachment because of the larger surface areas. As an example; when the backing material is being removed from labels, the static will cause the labels to be misaligned or cause jams.
Frictional – This is one of the most common reasons for generating large static forces. It is caused by two non-conductive surfaces being rubbed together. The amount of force being applied to the material as it slides back and forth will create higher static charges. As an example, it is noticed when you rub a balloon on your hair. The more times that you rub the balloon against your hair, the stronger the static forces, allowing the balloon to “stick” to the wall. It is also noticed as sheets of material are stacked or running over rollers.
Static tends to propagate. The more contact, detachment, and friction that occurs; the higher the static charge. Even when the static is removed from the surface, static charges can still regenerate by the same mechanisms above. So, controlling the static can be determined by the type of treatment as well as the location for removal.
Another variable that affects static generation is humidity. Most process problems are noticed during the winter months as the ambient air is drier. With a lower relative humidity, static can develop easier and with greater strength. We always refer to winter as static season. You may even notice this when you walk across the carpet and get zapped by touching a door handle.
Production problems can occur like dirty surfaces, tearing, alignment, jamming and shock to staff with static. EXAIR has a number of Static Eliminators to remove these process snags that can cost your company money. You can contact an Application Engineer at EXAIR to discuss any static issues that are occurring.
John Ball
International Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb