posted on January 07, 2013 10:47
Kevin Coldren discusses how to overcome static control challenges on flexible packaging processes.
Q: Explain in novice terms what static control for flexible films entails and why is it so important, especially coming into the winter months.
A: In the world of static electricity, flexible film is classified as an insulator. As such, film does not have the ability to dissipate the static charges that build on the surface due to friction created during the production process.
Managing static electricity is important for several reasons. The most notable reason being contamination control, operator safety, and minimizing process equipment issues that can occur due to high static charges. Contamination control is a significant issue in film manufacturing environments, especially in critical applications such as food, medical or pharmaceutical packaging. Operator safety is also a critical concern because high static charges can cause significant electrostatic shocks to unsuspecting personnel, or worse, an electrostatic discharge in a solvent coating application could cause a fire hazard. The biggest issue for most manufacturers is that all of these problems resulting from static electricity impact their bottom-line.
Due to the low relative humidity levels, the winter months present major static electricity problems for film producers or converters in colder regions of the country. Relative humidity (RH) is really a measure of the moisture content of the air. Moisture, or water, is a conductor of electricity; so the more moisture there is in the air, the less static will be generated, and the lower the moisture level, the greater the static problem will be. Unfortunately, this condition is not isolated to simply the winter months in colder regions of the country, but actually any region/environment with low RH levels such as California or Arizona. As a result of low humidity, triboelectric charging that occurs during the handling of flexible films intensifies.
Q: Where does static control fit in the flexible packaging process?
A: Quality problems created by static, like surface contamination, can occur throughout the process, and static control systems offer powerful and flexible solutions to address these problems where they occur. Additionally, high static charge levels on flexible films can result in roller wraps and mechanical feed problems. Discharges from charged film surfaces can cause lockup or unpredictable failures in control electronics or PLCs. The common areas within the flexible packaging process where static electricity is typically a problem are winders, nip rolls, coating rolls, lay-on rolls, and accumulators.
Q: Do all flexible packaging films need static control measures included in the manufacturing line? In what applications would it be required?
A: Flexible films generate static electricity which can become problematic at many points in the application. However, the need for static control is really determined by the critical nature of the application and the stage in the process. For packaging applications, especially where there is a high-end print or coating requirement, static control equipment is generally used from the base film manufacturing process all the way through the final converting stages to avoid quality/defect issues due to contamination. This could include additional applications such as laminating, slitting and winding. Debris on the surface of the film will cause print defects, and can impact coating applications ranging from thickness to clarity if there is an optical requirement.
Q: Are you seeing any new developments or new techniques in static control?
A: Companies are becoming more aggressive in protecting operators and ensuring product quality by lowering the threshold at which they consider static a problem. There has been a noticeable increase in demand for static eliminators to provide effective, monitored, and balanced static neutralization without air assist, pin replacement, or operator involvement. The high-end converters today are looking for equipment that is capable of interfacing with their process controls, or PLC. Manufacturing operations are running leaner, and customers are looking for equipment that helps minimize maintenance requirements by providing alarm features that announce maintenance needs or fault conditions.
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