Root Cause and Novel Solutions to Static Electricity

Static electricity has long been recognized as a serious workplace hazard, exposing employees to electric shock, fires, and explosions. Static buildup on process rollers is most common in dry area applications such as slitting, sheeting, coating, and die cutting.

The good news is that with the proper technology, the static buildup can be avoided in most applications, improving safety and reducing incident rates. This article will discuss the root causes of static buildup and present unique technology solutions to prevent static charge buildup on process rollers

Static electricity is static because it does not move through wires; however, if enough builds up, it will jump from one object to another. The video below shows an example of static discharge on a conveyor belt.

Root Cause of Static Discharge

To understand the fundamentals of static discharge we must explore materials at the atomic level. All atoms have a positive central core surrounded by a fuzzy “cloud” of negatively charged electrons. If we put two different materials in contact, and one material attracts electrons more than the other, the electrons will transfer from one material to the other creating a charge.

Therefore, the more we rub things together, the more we increase the chances that atoms will take part in this electron-swap which creates a static charge. In the example below, if we contact an acrylic rod and felt cloth together, the rod will give up electrons to the cloth resulting in a positively charged rod and negatively charged cloth.

The willingness of a particular material to donate electrons is defined by the Triboelectric Effect. The further apart two materials are in the series, the more static electricity will build up when you rub them together. If two materials are very close in the series, it’s hard to get them to build up any charge at all no matter how hard you rub them.

Triboelectric Series

+ Air
+ Glass
+ Quartz
+ Nylon
+ Wool
+ Lead
+ Aluminum
0 Paper
0 Cotton
0 Steel
− Hard rubber
− Copper
− Silver
− Gold
− Platinum
− Polypropylene
− Polyvinylchloride
− Fluoropolymers 
− Silicone rubber

As shown in this series, rubber and Fluoropolymers tend to gain electrons, while paper and other non-woven materials tend to give electrons. This is the reason that rubber or fluoropolymer covered process rollers often build up a charge in a manufacturing process where these materials are in repeated contact.

However, the question remains as to what causes the static charge to build up and suddenly discharge as an electric shock? The answer is found in how easily electrons move around within a particular material. In a conductor, electrons move freely about throughout the entire body. Therefore, a charged conductor can be neutralized simply by connecting it to earth ground, since the ground is virtually an infinite source and receptacle for electrons.

An insulator reacts much differently because electrons do not flow freely through the material. In other words, the built-up charge is “static”, and the material cannot be neutralized by simply grounding it to earth. Because of this, an insulator retains the static charge on its surface until a discharge source presents itself and the electrons “jump” from one material to the other resulting in an electric arc.

Solutions to Static Buildup

Most fluoropolymer roller covers are insulators and easily gain electrons from repeated contact with webs and non-woven materials and are especially susceptible to static buildup in dry areas.

Fortunately, Fluoron engineers have designed a way to eliminate this problem through the use of graphite fillers. In graphite, electrons which are not contained in the planar layer, are loosely bound and available for conduction of electricityTherefore, carbon black addition to fluoropolymers is sufficient to cause a significant and abrupt increase in electrical conductivity. As the loading of the carbon black in the compound increases, the plastic compound remains initially insulating, as the loading increases the conductivity passes through a sharp and abrupt rise over a very narrow black concentration (loading) range. Further increases in loading past this threshold cause little increase in the conductivity. This narrow range is known as the percolation threshold.

Percolation Threshold

Fluoron’s Fluoro-Stat 102 Heat Shrinkable Fluoropolymer Roller Covers are made from abrasion resistant PTFE and are engineered specifically for areas that are susceptible to static buildup. They have the additional advantage of having 10X the wear life of traditional FEP fluoropolymer covers.

Through the use of optimized graphite loading levels and a proprietary conductive underlayer, Fluoron has been providing anti-static, non-stick and corrosion resistant solutions on process rollers for over 30 years.

Our anti-static heat shrinkable sleeves are available for rollers over 5” in diameter and any face length. Our expert technicians are available 365 days a year to install them at our facility or yours.

Not sure which solution is right for you? Please contact one of our technical experts today to discuss your process issues. We can provide recommendations and free sample coupons for you to test out our products in your process.

You might also be interested in reading our article How To Get Out of a Sticky Situation, detailing buildup on process rollers and other equipment.

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