3 Types of Static – How Static is Generated

Static, everyone loathes it except for those kids that like to run around shocking their friends. This phenomenon affects not only everyday life with things like frizzy hair and that annoying zap you get when someone touches you but also industry. But what is static and how is it generated?

Static is generated on the atomic level from the exchange of valance electrons on each surface. The energy produced from the friction causes those valance electrons to enter an excited state; when in this excited state they begin to jump back and forth from atom to atom. When this happens, the atoms begin to accumulate either a positive charge if the atom lost electrons or a negative charge if the atom gained electrons.

As the charge accumulates on the surface where the friction occurs if a ground source (i.e., a piece of metal or a person) comes in close proximity to the charged surface an arc is generated between the two surfaces transferring the build-up of electrons and returning the charged surfaces to a neutral state.

But how can these surfaces become charged in the first place?

The most common and well-known way is via friction. Friction generation is when two surfaces rub against each other causing the static to build up on the surfaces. The energy from the two objects being pushed together and rubbing up against each other causes the electrons within the atoms to enter an excited state. When these electrons are in this excited state the valence electrons will jump from atom to another atom; this causes one atom to become positively charged (lost the electron) and the other to become negatively charged (gained the electron). The harder the two surfaces are pushed together and the faster they are rubbed together the more static will be generated.

A second type of static generation is contact static build up, which is when a charge that is built up when two surfaces impact each other and then separate. Much like friction static generation, contact static build up generates the charge on the surfaces from the kinetic energy of the impact. The material of the two objects in question will determine how many electrons are transferred from surface to surface based on the properties of the atoms in the material (Electronegativity, Ionization Energy, and Electron Affinity).

Contact Static Generation

The third type of static generation is detachment static build up. Detachment static build up once again relies on the kinetic energy and the properties of the atoms in the material. When the two surfaces are pulled apart the electrons that are transferring from one molecule to another get stuck with the molecules of one surface, which leaves both surfaces charged. This is seen a lot with plastic protective covers like the ones that come on a new window pane.

Static generation via detachment

No matter how the static is generated EXAIR’s line of Static Eliminators including EXAIR’s New Intellistat that can neutralize a 1000V charge in under one second. Don’t let static cause issues for your production facility, contact EXAIR for a solution. 

Static Eliminators

If you have any questions about compressed air systems or want more information on any of EXAIR’s products, give us a call, we have a team of Application Engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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Eliminating Static in Industrial Processes

Ever wonder what causes that annoying shock you get when you go to grab a plastic or metal piece. That is a phenomenon caused by static electricity. This static is an electrical surface charge that is generated and when two surfaces come in contact with each other and generate an electrical charge from friction, separation, or simple contact. If the material in question is not grounded properly the electrical charge will continue to accumulate until it comes in contact with a proper ground or the path of least resistance to discharge the built up static and return to a neutral state.

Static

Static is generated on the atomic level from the exchange of valance electrons on each surface. The energy produced from the friction, separation or contact cause those valance electrons to enter an excited state; when in this excited state they begin to jump back and forth from atom to atom. When this happens, the atoms begin to accumulate either a positive charge if the atom lost electrons or a negative charge if the atom gained electrons. As the charge accumulates on the surface were the friction occurs if a ground source (i.e. piece of metal or a person) comes in close proximity to the charged surface an arc is generated between the two surfaces returning the originally charged surface to a neutral state.

Static can be harmful to both employees and product in an industrial environment. If a static arc is generated in the presence of either flammable, combustible, or explosive liquids or gasses the arc can cause an ignition of the material. Static can also cause the charged object to stick or cling to various surfaces causing clogs in pipes and issues when trying to separate the material one at a time. This phenomenon is called static cling.

Even though static is very easy to generate it can just as easily be dissipated; EXAIR’s line of static eliminating devices use a high voltage emitter point to generate a small zone of ions which consists of both positive and negative charges to dissipate the static build up on the surface. Also, when the various emitter points and ion bars are coupled with our compressed air products, the air carries the ions much farther and can dissipate static up to 20’ away. The best part is that about the line of our line of static eliminators is that they are shockless; this means that if somebody bumps into it, they won’t get shocked.

Gen 4 Super Ion Air Knife Eliminating Static with Ions

For more information on EXAIR’s Static Eliminators and any of EXAIR‘s Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Cody Biehle
Application Engineer
EXAIR Corporation
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What Causes Static Electricity?

We’ve all been shocked before. And no, I’m not talking about the feeling we all here in Cincinnati felt when the Cincinnati Bengals finally fired Marvin Lewis… I’m referring to the discharge you’ve likely felt on a cold winter day after walking across a carpeted surface and touching a door knob. This electrostatic discharge is a result of static electricity. To understand how this static electricity is generated, let’s first go back to basic chemistry class and talk about the atomic structure of an atom.

hexagon-2307348_1280.png

An atom consists of three basic particles: protons, neutrons, and electrons. The protons (positively charged) and neutrons (neutral charge) form the nucleus. Outside of the nucleus, electrons (negatively charged) are quickly zipping around in orbits at specific distances from the nucleus. These electrons are bound to the nucleus due to electromagnetic force. Opposite charges attract, since the protons in the nucleus carry a positive charge this acts on the negative charge of the electrons and keeps them in orbit. The closer the electron to the nucleus, the stronger the bond and the more energy required to break that electron from its original orbit.

When an atom gains or loses an electron, it affects the balance that occurs within an atom. If an atom gains an electron, it now has more electrons than protons. This results in a negatively charged atom. The opposite can be said if an atom loses an electron, it now carries a positive charge. This charge imbalance is where static electricity comes from. Both positive and negative charges will remain static until contacted by or in close proximity to a conductive or grounded surface.

The strength of this charge will depend on a few different factors: the types of materials, surface area, environmental conditions, etc. will all play a role in the generation of a static charge. The triboelectric series is a scale, listing various different materials and their tendency to become positive or negative. Those at the far end of the spectrum have an increased propensity to gain or lose an electron, while those in the center are more likely to remain balanced. When two materials on opposite ends of the spectrum come into contact with one another, it poses the greatest risk of generating high levels of static electricity. The chart below shows some common materials and where they fall on the tribolectric series.

triboelectric

When materials carry a static charge, a variety of problems can ensue during manufacturing. These can manifest in the form of painful shocks to operators, materials jamming or tearing, sheet feeding problems, discharges causing imperfections in the material appearance, etc. To remove the charge, we need to introduce static eliminating ions to balance it out. EXAIR’s full line of Static Eliminators create an equal number of both positive and negative ions to saturate the surface of the material and neutralize any charge present.

With a wide range of different solutions all available from stock, EXAIR has the solution to your static problems this winter. Give us a call and we’ll be happy to discuss the application and help to identify the best method to mitigating any static issues in your processes. Take advantage of EXAIR’s current promotion (now through the end of March) and receive a free AC Sensor with your Static Eliminator purchase!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD

 

Atom photo courtesy of janjf93 via Pixabay Creative Commons License

How It’s Made: Static Charge

For me, one of the first signs that winter is here takes place at the grocery store. I’ll stop on the way home to pick up a thing or two, and proceed to the automated self-scan…not because I don’t like people, but because they’re the closest to the exit and, while I DO actually like a LOT of people, I REALLY like dinner. Anyway, the drop in humidity that comes with colder temperatures outside leads to what the buried-wire pet containment folks call a “mild correction” when I touch the self-scan terminal.

I won’t rehash my disdain of cold weather (like I did here, herehere, or here) and while those nuisance static shocks aren’t at the top of the list of reasons why, they actually can be quite severe in other cases.  For example, the minor jolt you get from touching a grounded terminal after pushing a rubber-wheeled shopping cart over the vinyl-tiled floor of the produce aisle isn’t near as bad as the shock that a plastic extrusion machine operator gets when he touches a conveyor duct carrying hundreds of pounds of plastic pellets per hour.

Why one is so much worse than the other?  To fully understand the answer to that question, we’ll need to better understand how static charge is generated.  Scientists have been studying the phenomenon since at least the 17th Century, and studies continue to this day of its creation (mainly at universities) and control (right here at EXAIR Corporation.)  Simply put, when two solid surfaces touch each other, the contact can result in electrons in the outer valences of atoms on one surface to “jump ship” and end up in the outer valences of atoms on the other surface.

It’s called the triboelectric effect.  The prefix “tribo” comes from the Greek word “to rub,” and while many common demonstrations of static charge involve rubbing…for example, rubbing a balloon on a wool sweater sleeve and ‘sticking’ it to the wall…mere contact is all it takes – and that’s where we’ll start:

Static charge from simple contact between this injection molded plastic part & the mold caused defects in a subsequent metallic coating process (left,) which were eliminated after an EXAIR Super Ion Air Knife was installed (right.)

Separation of material – lifting the top sheet from a stack, peeling off a protective layer,  or unrolling plastic film, for example – can also cause those weaker-held electrons to leave one surface for another.

Separation of contacting surfaces can generate a considerable static charge. The 16.9kV charge on this roll of film (left) shortened the life of print heads in a downstream process until EXAIR Ionizing Bars (center) dissipated the charge to an inconsequential 0.4kV (right.)

Some processes involve surface contact, and separation.  And more contact, and separation.  And oftentimes, one surface is in relative motion with the other…and that’s what REALLY puts the “tribo” (“to rub,” remember?) in “triboelectric effect.

The constant motion of these plastic jugs on the conveyor (left,) generated (and multiplied) a static charge so great, it resulted in adhesive labels folding or wrinkling while being applied. A pair of EXAIR Super Ion Air Knives (right) solved the problem.

These are just a few examples of the mechanisms behind, and the solutions for, static charge.  For more details, I encourage you to read EXAIR’s Basics Of Static whitepaper (registration required) or watch our recorded Webinar: Understanding Static Electricity.  If you have a static problem you’d like help with, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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