Whether permanent or non-permanent, internal or external, various anti-static and / or conductive agents are available to meet the needs of the industry and application in question. Here, we explore the characteristics, opportunities and limitations of different anti-static / conductive additives and ask whether graphene nanotubes are the superior choice.
Electrical insulators have numerous applications and multiple benefits in both daily life and industry. They cover and protect electrical conductors, ensuring safety and helping reduce the cost of energy. However, due to their inability to dissipate electricity, static charges can build up on their surface. This can lead to electrostatic discharge (ESD) that can cause sparks, damage to electronic components, or – in mining or certain industrial environments for example – even explosions. On a lesser, but equally relevant scale, this charge build-up attracts dust, generates discomfort and can affect the performance of appliances. This represents an extensive issue for industry, causing damage to electronic components and leading to faulty devices that need to be replaced (often at significant cost) along with the safety aspect, with the risk of electric shocks to employees and, in some cases, fire and explosions that can cause further damage and even loss of life. This is where anti-static or conductive agents and anti-static coatings come in.
These chemicals can mitigate these issues and eliminate risks by lowering the surface resistivity of the material in question by either being conductive themselves or absorbing moisture from the air, and therefore reducing the build-up of electrostatic charges. They exist in liquid, semi-solid or solid form and can be added to the surface of products or included in the material itself during the manufacturing process. Their ability to migrate determines whether they are a permanent or non-permanent anti-static additive. Key ways in which anti-static or conductive agents and anti-static coatings differ are the method of their application, their mechanism of action and the duration of the anti-static effect and different options are available according to these requirements.
Internal anti-static additives are incorporated into the polymer by blending into the plastic during processing. This would seemingly make them permanent but a range of traditional anti-static agents are migratory and so, with time, they migrate to the surface of the material and can eventually be removed with surface wiping. Broadly speaking, higher temperatures and lower degree of crystallinity of the polymer facilitate the migration process. Permanent anti-static agents tend to be based on polymers or conductive fillers and form a network within the base polymer, producing longlasting anti-static effects. External anti-static coatings, on the other hand, are applied to the surface of the material after processing via a spray or by dipping. Typically, external anti-static coatings can be removed using solvents or simply by wiping. They tend to be applied to textile fibres or plastic packaging and, naturally, have a limited lifespan compared to internal anti-static agents due to their easy elimination. Anti-static agents are either ionic or non-ionic additives. The majority are based on organic molecules bearing polar groups, but they also exist as inorganic salts. Certain anti-static agents for polymers depend on humidity to be effective, which limits their applications and is a factor to consider. Further important considerations are the level of anti-static protection required and how long it needs to last, as non-permanent anti-static additives or coatings lose their effectiveness over time. As can be expected, in many applications, permanent anti-static properties are required.
Anti-static agents can be incorporated through the use of concentrates or masterbatches that can be used as a tool against static electricity. They tend to be based on fatty acid esters and work by neutralising the charges on the surface of a polymer, with potential and proven applications in the automotive, aerospace, construction, electronics, extraction, personal protective equipment, packaging and consumer goods industries and also represent an attractive anti-static agent for textiles. Other common types of anti-static agents include ionic liquids and electrically conductive polymers such as PEDOT:PSS, while further examples of carbon-based anti-static agents are carbon black, graphite powder, graphene and carbon fibres.
Common anti-static agents with permanent effect include carbon black, conductive fibres and nanomaterials and this is an area in which carbon nanotube agents excel. Graphene nanotubes, also known as single wall carbon nanotubes, add anti-static properties to materials and are widely used in epoxy, acrylic, polyester and polyurethanes (PUs) in the production of composites, primers, car parts, tires, floorings, lining and powder coatings, gelcoats and moldcoats, rubber industrial parts, personal protective equipment (PPE), lithium-ion batteries and many other applications. These diverse applications are due to their unique, desired properties such as providing uniform conductivity, effective anti-static performance, good safety performance, extreme durability and economic viability. For example, OCSiAl’s graphene nanotubes lend uniform anti-static properties to PU shafts, with resultant benefits that include reduced production costs for manufacturers and, importantly, ensured safety. Polypropylene is a type of thermoplastic polymer resin with widespread applications both in households and industry due to its durability and rigidity. Anti-static agents for polypropylene enable potential buildup of static electricity to be controlled and anti-static masterbatches can control electrical discharges that can occur, for example in packaging applications.
In numerous applications, polymers offer advantages over metals. For example, engineering plastics boast high levels of strength for lower weight, robustness and good resistance to heat, wear and chemicals / corrosion, while synthetic rubber is resistant to ageing and demonstrates high thermal stability and resistance to oils and oxidising agents. However, sometimes polymers require a higher level of electrical conductivity that typically metals provide, such as in, for example, organic solar cells or biosensors. In such instances, conductive agents in polymers prove invaluable. Conductive agents such as conductive carbon black, metallised fillers and carbon fibres can be added, providing the required level of electrical conductivity.
Applying innovations in anti-static coatings for plastics, OCSiAl developed a graphene nanotube concentrate that provides targeted conductivity in thermoplastics for electrostatic painting, enabling car manufacturers to enhance cost efficiency by optimising the painting process. Another example of an effective anti-static coating for plastics are the powder coatings developed by Erie Powder Coatings in Canada using OCSiAl’s TUBALL graphene nanotubes. These coatings demonstrate conductive and static dissipative properties, along with high resistance, ultimately enhancing aesthetic performance.
Turning our attention to anti-static coatings and anti-static additives for resins, a common example is the anti-static resin flooring used in factories and workplaces. An anti-static resin coating is applied to the flooring and inhibits or redirects electrical charges or doesn't generate any electrical charge at all so no ESD occurs. This is important in industry, particularly in an environment where flammable substances are used and ultimately saves lives. Examples of industrial anti-static agents for rubber include anti-static rubber matting and sheeting in the electronics industry, as well as in floor manufacturing. Graphene nanotubes promise great potential for anti-static agents here due to their ability to perform at low working dosage while retaining or improving the properties of rubber. When single walled carbon nanotubes are used in static control flooring, the benefits include cost effectiveness and improved quality, as well as the fact that they take up minimal space in the coating which means there is room for other materials with further desirable properties to be added.
Anti-static coatings are commonplace in a wide range of industries. These electrically conductive coatings reduce or prevent the effects of static charges and thereby can help functionalise the surface of myriad components. Anti-static spray coatings tend to consist of a conducting polymer and a solvent that evaporates, leaving a thin conducting layer behind that serves to prevent the build-up of static. An example of an application for anti-static composites is in the aerospace industry and carbon nanotubes can be added here to provide strength and protect against lightning strikes.
Ultimately, the vast potential of polymers can be further expanded and enhanced with the use of anti-static agents and anti-static coatings. There is a great variety of anti-static or conductive agents available depending on the requirements of the application and, often, carbon nanotubes and graphene prove to be the superior choice owing to their attractive electric physical and chemical properties, including efficiency at very low dosages, low weight in use and flexibility. In the context of conductive agents, they have the powerful ability to control or enhance electrical conductivity in polymers, facilitating the development of high performance dissipative or conductive polymers, with applications spanning industries including engineering and medicine.
The myriad benefits afforded by graphene nanotubes are obtained thanks to their ultra-low working dosage, which can be several dozen times lower than that of standard additives, and their unique properties, including diverse compatibility, good thermal and chemical stability, high conductivity and impressive strength. As such, they have potential applications across up to 50 per cent of global materials markets, spanning diverse commercial applications and industries and, in most cases, will prove to be the superior choice.
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