Types of antistatic yarn
Antistatic yarns are available in three common types. The first is a standard antistatic yarn made from spun antistatic fibres, such as antistatic polyester yarns. A common use of such yarns is to The second is a standard yarn which is spun together with a purely antistatic yarn, meaning that you can take advantage of the antistatic properties of the purely antistatic yarn in a larger yarn. Essentially, you can bulk-up the yarn without adding significant extra cost. The final type of antistatic yarn is a conductive copper yarn, which is a standard yarn twisted with a very thin copper filament.
What is static electricity and what causes it to build up?
Static electricity occurs when there is an imbalance between protons and electrons on or in an object. A neutral object, with no static charge, has a balance of protons and electrons.
One common cause of static electricity build-up is when two surfaces, at least one being an electrical insulator, contact, rub together and abrade, and then separate. As this happens, an imbalance in electric charge develops, which remains in place until it can be discharged. One surface will gain electrons, giving it a net negative charge, and one surface will lose electrons, giving it a net positive charge. This build-up of static electricity can also occur when mechanical stress is applied to certain materials, when heat is applied to certain materials, and when a neutral object is exposed to a charged object.
Despite the risky downsides of static electricity, which you can read about below, it can be used intentionally in processes, like industrial paint-spraying, filtering air and printing.
Risks of static electricity
Static electricity can cause three types of damage to electronic equipment which are upset failures, direct catastrophic failures, and latent catastrophic failures.
Upset failures are caused by a minimal amount of electrostatic discharge, where the damage is not enough to cause the component to fail entirely, but there can be intermittent errors. Direct catastrophic failures are where the electrostatic discharge is large enough to cause a device to fail completely and immediately. Latent catastrophic failures are where the electrostatic discharge is sufficient to damage a component, but not quite enough to cause a complete failure. In this situation, some intermittent errors can occur, and a full failure requires a minimal electrostatic discharge or surge in current.
Fires & explosions
The risks of static electricity are not only to electronic devices; static electricity discharge can cause a fire or explosion when in an atmosphere with flammable gases, solvent vapours, and powders in the air. Very little electrostatic discharge is required to ignite flammable gases and vapours in the air. These can be fuels like petrol or kerosene, which can explode when they are at a specific concentration in the air.
Similarly, solvent vapours can explode when in a specific range of concentrations in the air. These include commonly used solvents like acetone, ammonia and alcohols. When in a concentration out of the necessary explosive range, the fuels and solvents can still ignite posing a large risk of fire.
Dust and powder explosions can be a particularly vicious and hidden danger. Coal and sawdust powders are understandably explosive in the correct concentrations, but common foodstuffs such as grain, flour, sugar, and powdered milk can also be explosive. Additionally, certain metal powders can be explosive in in the air. These risks can be of particular concern in the food industry.
Making sure that all personnel and equipment are grounded when using these chemicals and powders is a vital tool for avoiding any sparking and ignition. Equipment can be grounded with standard earth wires, but people need a more flexible solution; antistatic yarns are a vital tool to ground any personnel while ensuring full mobility and flexibility. You can read more about how these are applied further down.
What antistatic yarn does
An antistatic yarn contains, or is solely made from, conductive fibres and filaments. These conductive properties allow whatever products that are made from antistatic yarns to pass a current, meaning that when the fibre is exposed to an electrostatic charge, rather than itself gaining a net positive or negative charge, the conductive fibres or filaments allow the fibres and to whatever they are connected to maintain a net neutral charge.
With antistatic yarn, excess electrons deposited on a surface that would give a net negative charge are able to flow away to whichever grounded surface the yarn is attached to. Similarly, if a net positive charge occurs, the conductive fibres or filaments allow electrons to flow towards the positively charged area to balance out the charge in the positively charged material.
Where antistatic yarn can be used
Antistatic yarns are used to produce antistatic fabrics that can in turn be used in antistatic garments. Antistatic articles of clothing include shirts, t-shirts, jumpers, hair nets, facemasks, gloves, shoes, high visibility jackets, and lab coats. The anti-static yarns are often in a blend with other yarns to produce a garment that is like any other, just with antistatic properties. Polyester antistatic yarns are a common and convenient yarn for this purpose.
The most simple way to ensure that you are grounded is to use an antistatic wristband, which ensures that at least your body is connected to the ground, although this won’t prevent non-antistatic articles of clothing from remaining charged. Any of these items will require some connection to the ground. Normally these are connected via a cable to a grounded and conductive surface, or to an earth bonding plug. Below you can see somebody wearing an antistatic wristband with a grounding lead, and an antistatic article of clothing. When properly grounded, antistatic clothing is ESD safe, so an errant electrostatic discharge will not risk your people and production.