Electrically conductive plastics
Use of plastics nowadays
Plastics are contributing to an ever-increasing range of applications in our modern-day life. They are used in the chemical industry and the manufacture of tanks, apparatus and pipelines. There they are used not only because of their good cost/benefit ratio but also because of their high chemical resistance and good processing capability. The plastics predominantly used in the above-mentioned sectors are polyethylene (PE) and polypropylene (PP).
Plastics have many advantages over other materials. With regard to potentially explosive atmospheres, however, the non-conductive properties of plastics have to be taken into account. Owing to this property, there is a risk of static developing. If such charged materials discharge owing to sparking, they can cause explosive atmospheres, such as mixtures of solvents and air or mixtures of dust and air, to explode. These types of plastics cannot be used in such applications. In order to exploit the advantages of plastics such as polyethylene or polypropylene for those fields of applications, special types of carbon are added, so-called conductivity carbons. As a result, their conductivity is much higher, i.e. their electrical resistance is much lower. On account of this precaution, the electrical volume resistivity of PE, for example, can be reduced from 1016 ohms to < 106 ohms.
The plastics become capable of conducting an electrical discharge. If they are earthed, a static charge can be reliably prevented. In addition to the decrease in volume resistivity, the black staining also provides excellent UV protection, e.g. in the case of electrically conductive polyethylene (PE-EL).
Electrically conductive plastics manufactured by SIMONA AG, which have a volume resistivity of < 106 ohms, can be used in appliances and protective systems which are subject to ATEX Directive 2014/34/EC, provided they are sufficiently earthed. The material can be certified by means of an acceptance test certificate, 3.1, and a technical data sheet can be provided.
According to EN 13463-1, it may be assumed that static will be prevented if the surface resistivity is <= 109 ohms.