What Is Static Electricity and How Can It Be Neutralized?
An introduction to ION CORD Static Eliminator
What is static electricity?
All matter is made of atoms that have a positively charged nucleus surrounded by negatively charged electrons. Normally the positive and negative charges are exactly equal so there is no net charge. When two surfaces touch, it means that the electrons in their surface atoms have gotten close enough to repel each other. However, when the surfaces of two different materials are separated from each other the atoms of one material will often have a greater attraction for electrons than the other material. When this happens one surface will have a negative charge (more electrons) and the other will be positive (fewer electrons). This charge is called static electricity when it is motionless on a surface. When the charge is on atoms, or groups of atoms called molecules, which are fluid as in a liquid or gas, these charged particles are called ions.
There are powerful forces that occur between charges. Like-charges repel each other and opposite charges are attracted to each other. This is why the natural state for matter is to be neutral, with no net charge. Electrically conductive materials allow electrons to move freely from atom to atom. Pure water is a very poor conductor but a little dissolved salt or other material creates ions that can move to allow an electric current to flow.
Static is often a major problem on machinery that processes non-conductive materials. Printing presses, slitters, and rewind machines that process paper and plastic films are notorious for generating static that can result in sparks that are several feet long. The Van deGraaff Generator (http://chem.ch.huji.ac.il/~eugeniik/history/graaff.html) operates on the same principles to generate millions of volts. Pouring gasoline or other non-conductive liquid from one container to another will create static charge. What can be done about the problem?
How can static problems be eliminated?
There are several approaches that can be used. The best choice depends on the situation.
- Grounding. If the charged object is conductive and stationary it should be connected by a wire to an earth ground. This is usually the metal frame of a machine, a cold water pipe, or something similar. The earth is such a massive object that it can absorb a lot of charge without a measurable imbalance. But the “earth” does need to have some conductivity from moisture in it or other mechanism. “Grounding” is used in the electrical service in most buildings which are connected at one point to a metal rod driven into the ground. Workers who assemble electronic components often wear a grounding strap on the wrist or ankle that prevents a charge buildup on their body that could damage the electronics. This is somewhat inconvenient but effective. Non-conductive materials cannot be grounded.
- Anti-static sprays. Static on non-conductive surfaces can be removed by making the surface conductive to ground. Anti-static sprays and additives work this way by attracting moisture from the air and making the surface slightly conductive. There still must be a path to ground or to the oppositely charged surface, however. Anti-static sprays do wear-off and are sensitive to humidity levels in the air.
- Passive neutralizers. This category includes ION CORD and is often referred to as inductive neutralizers. The electric field created by the static electricity is used to induce a charge concentration on a sharp point of conductive material. The sharp point causes the electric field to become very concentrated right at the tip. The field will easily become concentrated enough to start stripping electrons off of air molecules, creating both negatively charged and positively charged molecules, which are called ions. The negative ions are strongly attracted to the positive side of the electric field, while positive ions move the opposite direction. The advantage of ION CORD, besides its low cost, is that it will automatically generate the correct polarity and quantity of ions to neutralize the static. This makes it ideal for use on high speed machinery such as slitters and printing presses. Although ION CORD will usually reduce static to unnoticeable levels it cannot reduce static completely to zero because the static charge is what makes it work.
- Powered static neutralizers. Powered ion-generators can be very effective but they are expensive and selecting the correct one of the many different types can be very complicated. These generate charged air molecules (ions) by applying a high voltage to a sharp needle or wire, just like ION CORD, but use an external power supply. Powered neutralizers can be powered by D.C. (direct current) or A.C. (alternating current). A D.C. unit will generate either positive or negative ions at one point, or positive ions at one point and negative at another point. An AC unit will generate positive ions for a fraction of a second and then negative ions for a fraction of a second. Ions of the correct polarity are attracted to the static charge and those with the wrong polarity are repelled and eventually go to an earth ground or combine with “good” ions. Thus the efficiency of AC units is low. Powered neutralizers always operate at full power and generate more ions than needed or they will not be effective. There are some computer controlled units that will address these problems but they are, of course, very expensive and, in most cases, no more effective in solving static problems than ION CORD.
- Radioactive static neutralizers. These are generally used with laboratory analytical balances where very sensitive weight measurements can be affected by static charges. These contain an encapsulated radioactive material that is an alpha particle emitter. Alpha particles cannot penetrate through a sheet of paper so the radiation is relatively safe unless you ingest the material. The alpha particles ionize air molecules as they pass, generating both positive and negative ions. The power of these neutralizers is very low but they are very small and they will, in time, bring static charge to zero. These are government regulated so they are usually leased rather than owned. They also have to be replaced at least once a year.
What makes ION CORD Unique?
- ION CORD is made from 100% carbon fiber which means that it is inert to almost all chemicals, sunlight, and can be used at very high temperatures (600F in air or 3000F in a non-oxidizing atmosphere).
- There are over 24,000 filaments in ION CORD that are about 5 micron (0.0002”) in diameter. A small percentage of these filaments are broken and protrude from the cord in all directions. These are effectively far sharper than any metal needle. These filaments cannot get dull, as will a metal needle due to the corrosive effects of ions.
- ION CORD will not create sparks (it prevents them by neutralizing the static). It can be used in flammable atmospheres.
- It is the often the most effective and economical solution to a static problem.
- It can be fit into almost any location on a machine. It is less than 0.060” in diameter. The individual filaments are almost invisible and may protrude 0.5” from the cord.
- ION CORD is available in 20 ft., 100 ft. packages and larger bulk spools.
How is ION CORD Used?
Static problems can be very mysterious and difficult to understand without a good understanding of electricity. Here are some pointers on how to use it correctly, but generally if you place ION CORD near where you observe a problem with static the problem will be solved. Trying a few different locations will find the best location.
- ION CORD must be grounded by connecting to a metal frame or other earth ground so that the static it collects can be dissipated.
- Static is generated when two surfaces in contact with each other are separated. ION CORD should be placed on that side of a sheet. If you place it on the opposite side it will give that side an opposite charge and the static will appear to be gone but you may or may not see other strange static problems later in your process.
- ION CORD can touch the surface but does not have to in order to work. It can work as far as several feet from the static but is more effective the closer it is. The ions it generates must actually create a breeze toward the static charge. External drafts can help or hinder this effect.
- ION CORD will be attracted to a static charge so it should be kept taught or it will start to swing. This is because it becomes more effective as it gets closer to the charge and so the charge is reduced so the attraction decreases.
- ION CORD is very low stretch and very strong. Although it is easily cut with a knife or scissors the carbon filaments are stronger than steel. If the cord accidentally wraps around a roller or is caught in a nip point it could result in damage or injury.
- ION CORD is electrically conductive so it should be kept away from exposed power lines. Loose filaments that break free of the cord can drift in the air, so care should be taken to avoid unnecessary abrasion to the cord.
- ION CORD does tend to unravel at cut ends. This can be prevented by tying at knot in the end prior to cutting or by applying a drop of adhesive to the cord. Cyanoacrylate (Super Glue) or epoxy works well.
- The filaments in bare ION CORD are easily crushed by clamping pressure, which may cut the cord. If you wish to crimp a termination onto the cord or clamp it under a screw, apply a drop of adhesive to the cord at that point and let it harden first.
- A small spring or length of shock cord at one end of the ION CORD is effective at maintaining a constant tension.
- Ion cord is not effective at removing static that is already sticking two things together. In such a case two opposite charges are very close together and there is no electric field to energize ION CORD.
- ION CORD is grounded and other grounded objects such as machine frames or conductive rollers near the cord will reduce its effectiveness.
- Charged dust particles will be attracted to ION CORD. The cord can be cleaned by simply wiping it or if necessary can be cleaned with soap and water or solvents. Burn-off with a propane torch is also possible with appropriate safety precautions.
- ION CORD can be wrapped around a bar or wire for support if necessary.