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Electrostatic charging of plastics can cause the failure of electronic components and computer chips and is even capable of igniting combustible gases, vapours and dusts. On the surface of a polymer, which is at first electrically neutral, charge may be generated by contact with another surface and subsequent rapid separation. Additives with antistatic properties help preventing these hazards.
The antistatic TPU masterbatch opens up large fields of application, particularly for industrial packaging such as big bags and plastic drums or cans. (photo: BASF)
Most polymers have insulating properties and are therefore susceptible to electrostatic charging. BASF has now for the first time developed an antistatic thermoplastic polyurethane (TPU) granulate – under the Elastostat brand name in the TPU portfolio. Elastostat is available as a masterbatch, a ready-to-use granular mix. Through the addition of Elastostat, materials can be rendered antistatic. The masterbatch is said to have the edge over existing solutions in that its antistatic effect is permanent and does not require any specific ambient conditions such as a certain atmospheric humidity. What is more, the product is said to be easy to process. The material is compatible with standard plastics like polyethylene (PE), polypropylene (PP), polystyrene (PS) and acrylonitrile butadiene styrene (ABS). Simply mixing it with the polymers yields homogeneity and thus eliminates the need for elaborate compounding. 7.5 to 15% volume of the antistatic TPU masterbatch is added. The properties of the matrix materials are scarcely affected and the material can be dyed in any colour.
Safely dissipating electrostatic charge
Plastics with defined electrical properties are capable of dissipating electrostatic charge in a controlled and permanent way. The decisive characteristic for assessing the electrostatic charging or discharging of a material is its surface resistivity. TRBS 2153 (German technical rules for operational safety “Preventing ignition risks resulting from electrostatic charging”) defines a material’s electrostatic properties in terms of its conductive, dissipative and insulating capacities. A material with a surface resistivity of less than 106 ohm is said to be conductive. Such materials are capable of rapidly dissipating generated charges, and this can cause damage to sensitive electronic components. Materials with a surface resistivity greater than 1,012 ohm are defined as insulating. Most plastics are insulators that are easily electrostatically charged by friction. Owing to their very low conductivity, the applied charges can remain on their surfaces for a long time and electric charging of several thousand volts (on synthetic sweaters, for example) is therefore possible. Materials with a surface resistivity of 106 to 1,012 ohm are termed dissipative and are known as intrinsic dissipative polymers (IDPs). The new antistatic additives cover the range of IDPs.
Antistatic treatment for industrial packaging and transport
The new TPU masterbatch opens up fields of application particularly for industrial packaging made of polyolefins. Antistatic treatment is an absolute must for containers in which combustible liquids or dusty goods are transported. These packages include big bags and plastic drums or cans. Such materials are also transported in intermediate bulk containers (IBCs). In their most common form, IBCs consist of a polyethylene inner container, a tubular metal outer frame and a pallet. The TPU additive could also be used in pipelines, hoses and conveyor belts to prevent the electrostatic charging of the transported material.
Anti-dust applications
Another application sector is the automotive industry, which is increasingly demanding dirt-insensitive materials. Plastic surfaces in vehicles are also susceptible to electrostatic charging. An elevated surface tension can cause the materials to attract dust and dirt particles. The antistatic masterbatch can be used in both film extrusion and injection moulding to reduce the surfaces’ dust effect. The possible applications here are mainly in the vehicle interior, for instance, in linings, covers, instrument panels, headliners, sun visors and seat covers.
Electronics packaging – protection from electromagnetic interference
A third field of use comprises packaging and transport systems for electronics. Electronic components have to be protected particularly well, as peak voltages can cause damage when rapidly discharged. Electronic components can also be damaged by electrostatic charging. Such packages include transport trays and tablets for small electronic parts like microchips as well as air bubble film bags and resealable bags for mobile phones, circuit boards, drives and other electronic devices.
www.polyurethanes.basf.de
