Plastic polymers are not only excellent electrical insulators but can also be conductors

It is universally known that, normally, objects made with plastic polymers are excellent electrical insulators, so much so that in the presence of appliances or accessories in which there is of a passage of electricity, we can easily find a plastic element.

By electrical insulation of a plastic body we mean its ability to drastically reduce or completely block the passage of an electric current within its mass, avoiding danger to people or things.

For this reason we find many objects such as switches, electric cables, lighting systems and printed circuits in which there is the presence of plastic elements.

To determine the degree of electrical insulation or its ability to inhibit the passage of current, we use a parameter called CTI (Comparative Tracking Index) , obtainable through a specific test, which provides an evaluation of the electrical insulation resistance of a material to surface discharges.

On the other hand, it may also be necessary that this flow of electric current, which is normally prevented by plastic materials, must pass in a controlled way through the polymeric body, with the aim, for example, to reduce electrostatic charges, to shield plastic parts from electromagnetic waves, to produce electrodes, light emitting diodes and many other products.

To do this, it is necessary to rely on polymers, which by their nature or formulation, can allow the passage of electricity, while maintaining the other chemical-physical characteristics typical of plastics unchanged.

To create or enhance conductive thermoplastic compounds, we rely on specific fillers or reinforcing agents that conduct electricity, precisely creating , a conducting polymer.

The study of conducting polymers had to balance, over time, the characteristics of electrical conductivity with those of workability and productivity of the elements, factors which were sometimes in open conflict with each other.

In fact, the first conducting polymers were insoluble and melted with difficulty, thus leading research to find the right balance between solubility, thermal characteristics of fusion and electrical conductivity.

The principle of electrical conductivity is based on the inclusion, in mixtures, of donors or acceptors of electrons, atoms or molecules, which give or accept electrons, significantly increasing their mobility.

By virtue of this high mobility, single free electrons are found, i.e. not linked to the body of the atom, which slip on the molecules carrying the electric charge.

Another characteristic of conductive polymers is electroluminescence , understood as the ability to emit light when an electrical voltage is applied, allowing the development of organic diodes that emit light, defined as OLED (Organic Light Emitting Dios).

The main conducting polymers are:

- Polyacetylene (PAC)

- Polyphenylene

- Polyparaphenylvinylene (PPV)

- Polyheteroaromatic

- Polyaniline (PANI)

- Polyphenyleneamine

- Polyethylenedioxythiophene (PEDT)

- Polyethylenedioxythiophene - Polystyrene sulfanate (PEDT - PSS)

- Polyphenylene sulfide (PPS)

- Polyphenylenebutadines (PPB)

- Polyparapyrridine (PPYR)

- Polyparapyrridinevinylene (PPYV)

- Polypyrrole (PPY)

- Polythiophene (PT)

- Polyfuran (PFU)

- Polyethylenedioxythiophene (PEDT)

- Polyacene

The most common applications are as follows:

- Antistatic features

- Tapes for resistances

- Fuses

- Sensors

- Batteries

- Electrolytic capacitors

- Conductive layers on glass and plastic

- Transparent antistatic layers on photographic film, glass, light emitting diodes

Category: news - technique - conducting polymers - luminescence

Machine translation. We apologize for any inaccuracies. Original article in Italian.