Electrically conductive materials

With appropriate formulations, the resistivity of plastics can be reduced by over ten orders of magnitude, reaching typical values in the range of 10¹-10⁴ ohm*cm. Excluding strictly antistatic materials (10^8-10^10 ohm), the constitutive nature of these products does not allow for guaranteeing precise electrical resistivity values but rather within a reasonable range or below certain maximum values.

In all situations where the accumulation of electrostatic charges and potential differences pose a danger or hinder the proper functioning of the part. For example, in explosive atmospheres referred to by the ATEX regulation or to protect electronic equipment; but also in all situations where you want to avoid the accumulation of static electricity that can, for example, attract dust or create dangerous sparks.

Although low, the electrical resistivity of LATIOHM is still much higher than that of copper and aluminum. Therefore, LATIOHM compounds are not suitable for transporting high currents but will work correctly, for example, in the field of sensors.

To ensure excellent shielding, it is better to adopt the grades of the LATISHIELD family, made by dispersing a variable amount of steel fibers in the plastic matrix with which widely sufficient shielding can be obtained for most sensitive applications.

Conductivity is ensured by the number of contacts between the conductive particles: the material begins to show electrical properties only above a certain number of contacts (percolation threshold). It is therefore essential to preserve the integrity of the particles, for example, steel or carbon fibers. Excessive mechanical stress in molding should be avoided: high speeds, walls, and feeding systems that are too thin.

The natural color of LATISTAT and LATIOHM compounds is black due to the fillers used, consisting of carbon in the form of graphite, carbon black, fibers, or nanotubes. However, LATIOHM PD02 features conductive polymeric additives, macromolecules that allow both antistaticity and colorability in any shade. There is also an entire family of LATIOHM with carbon fibers (PD01, PD03, PD08) that are, with some limitations, still colorable.

Very low resistivity can create problems, for example, in the case of overmolded metal inserts to which an electrical voltage is applied. In such a case, there could indeed be a dispersion to the ground or a short circuit. If intended for enclosures containing transmission systems or antennas, too high conductivity can also create electrical problems in this case.

With an intrinsically conductive plastic material, it is possible to secure parts subject to the accumulation of electrostatic charges without resorting to complex and costly grounding operations. Enclosures for ATEX environments can be made by replacing metal. Products with steel fibers make demanding metallization treatments on plastic parts unnecessary. All to the advantage of the final cost of the object and naturally the environment.

Resistivity depends on the geometry of the artifact, the injection parameters, and the method by which it is measured. These three variables could lead to detecting, on the molded piece, different values than those reported on the technical sheet. However, it is always recommended to perform the measurement with instruments and methods imposed by the ATEX regulation, with suitable contact surfaces (the use of conductive paint is recommended) and appropriate test voltages (100-500 V).

Although most of the fillers and additives used in these products are not suitable for food contact, some particular formulations of PD02 (antistatic on PP base) and PD10 have been developed that are suitable for food contact according to European regulations.