Contamination Caused by Static Electricity in Plastic Products and Its Solution

One of the major issues encountered in food packaging production, in facilities that manufacture food, during food filling operations, at points of sale, and even while the product is being used by the consumer, is contamination caused by static electricity (such as dirt, dust, lint, etc.). A product that becomes statically charged at any stage will attract all contaminants around it—dust, dirt, and lint—like a magnet. These problems can be observed both in contaminants present on the product itself and in the reduced appeal of displayed packaging that loses its visual attractiveness due to dust.

In production facilities, static electricity can lead to many additional problems. For example, it may cause gas, liquid, and dust explosions.

It may also lead to static shocks affecting personnel. Although these shocks are very short and not fatal, they can distract employees and lead to secondary accidents. Furthermore, static electricity hinders the smooth flow of products on production lines, slows machine speed, disrupts automation systems, and can damage machine components, particularly electronic boards. Therefore, static electricity is a fundamental production parameter that must be well understood and properly controlled.

When two materials rub against each other, they become charged based on their triboelectric properties. We refer to this as “static charge.” High temperatures, pressure, and friction generated during molding produce static electricity, which then attracts oppositely charged dust particles in the air, causing dirt and dust accumulation on the product.

Static electricity varies depending on many factors. For example, the type of material exposed to static (the raw material used in production) affects the magnitude of the charge. Repeated operations (such as friction) increase static build-up. Likewise, when multiple statically charged pieces are stacked or assembled, the overall static level increases—similar to how stacked batteries amplify voltage.

If the material we produce is conductive, we can eliminate the static charge simply by grounding it. Using conductive material for all tables on which the product is dropped or processed and connecting them to the facility’s grounding line will solve the issue. Another solution, depending on the product's shape and features, is to use a metal brush. When the conductive bristles of the brush are grounded, any product touching or approaching the bristles will discharge its static load.

The product does not even need to touch the bristles. Proximity alone is sufficient. Similar to a lightning rod, the brush works by "inducing" the discharge of electric charge.

However, the most common challenge is removing static electricity from insulating materials rather than conductive ones. Insulating materials do not allow charges to move across them. Thus, these charges remain trapped and cannot be eliminated through grounding. The charges on an insulating surface can neutralize only through random atomic or molecular movements, which may take a long time. Most commercially available antistatic additives help shorten this duration, but they do not provide a complete solution for contamination that occurs immediately after production.

By placing opposite charges near a statically charged insulating product, each can be turned into an electrical dipole, and the effectiveness distance of the electric field they generate can be reduced almost to zero. One method to achieve this is to ionize the air around the material. Air naturally contains some ions. One method of ionizing air is through radioactive materials. However, the most common method is using electric fields.

When a high voltage is applied between two sharp conductive tips, ionization occurs. Air ionization devices, also known as “ion generators,” operate using this principle. These devices do not create ions themselves; rather, they mobilize existing ions in the air and increase their quantity. Once the ions reach the surface of the insulating material, they combine with the surface charges and neutralize them.

However, in dusty environments, these devices may cause dust to move with the airflow and settle on the material. In such cases, directing ionized air onto the material with an air gun can simultaneously remove static and clean the surface.

Another important factor in static elimination is humidity. It is well known that humid air containing water vapor is more conductive than dry air. As humid air contains more ion pairs, part of the static charge is naturally neutralized. Humidifiers placed in the production area can significantly reduce static electricity. However, the increased humidity must be managed carefully, as it can cause discomfort to personnel, create corrosion in machines, and promote bacterial growth.

In principle, a plan for static elimination must be based on the product type, raw material (dielectric properties), process steps, and humidity levels in the production area. The main tools of this plan—resting, humidification, grounding, and ion generators (bars, guns, etc.)—must be positioned and utilized according to this system. Collaboration between packaging manufacturers and food producers is essential, as this prevents static build-up at different stages and ensures that hygienic and visually appealing products reach consumers.

SEM Plastik conducts extensive work in this field, both internally and through universities and independent consultants. In addition to working jointly with leading food producers in the industry, our company also shares its knowledge and experience with colleagues in the sector.

Yavuz EROĞLU
General Manager
SEM Plastik San. ve Tic. A.Ş.