Because an ESD can be painful and cause burns, cardiac problems, and even death, controlling ESD is very much an important workplace safety issue. In addition to the direct health effects of exposure to electrical current, there is also the secondary hazard of operators suddenly recoiling from the shock and injuring themselves by falling against dangerous machinery.
Another concern is a possible explosion and the resulting equipment damage. Because static discharge manifests itself in the form of a spark, it is imperative to keep areas with flammable liquids or gases, such as solvents, absolutely spark-free at all times.
In relation to adhesive systems, static build-up and ESD events can significantly damage the PSA release liner of the product being unwound.
When the silicone coating is disrupted by static, it will no longer be able to function as a release system in the area affected by the discharge—causing the adhesive to “split” between two sides of the release liner. Alternatively, the liner can fail to release where it is damaged, making it difficult to remove the liner as designed.
Because electrostatic fields also attract dust particles, fibers, bugs and hair, the resulting surface contamination often leads to irreparable product damage and unacceptable levels of product defects in printing, coating and laminating applications.
Moreover, static charges can cause uneven coatings and “wicking” of inks, and pressure-sensitive tape carrying a static charge can case considerable damage to sensitive electronic components.
There are two general types of ionizers available to help users control static on coating and converting machines: passive ionizers and active ionizers.
Passive ionizers—also called induction ionizers and non-permanent static control devices—include static tinsel and static string, which are simply grounded emitters placed parallel and close to the charged material. A properly-positioned ionizer can offer great help in successfully reducing the electrostatic charge.
Also called permanent static control devices, active ionizers such as high-output static neutralizer bars and static blowers are typically powered by an external source of electrical voltage or, alternatively, radioactive material can be used as an ion source. To date, the relatively high purchase cost of active ionizers has limited their use in the converting industry.
While tinsel, also know as garland, is relatively inexpensive and remains one of the most widely-used methods for controlling static, product contamination caused by the pieces of this soft copper breaking off can often pose its own set of problems.
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