One of the most important technological advances in the field of plastics over the last half of the twentieth century has been the extensive replacement of metals with plastics. While plastics have been engineered to outperform steel and other structural metals by providing the strength or stiffness necessary, at lower weight and cost, to allow plastic replacement of metals in structural applications, a key property advantage that metals have over plastics, is in electrical conductivity. While their extraordinarily good electrical insulative properties has given rise to many widespread and important uses of plastics, the applications for plastics can be broadened substantially with good methods to make these materials conductive. Various routes have been pursued to render polymers conductive.

Types of Conductive Polymers

Conductive polymers include conductive filled plastics, inherently conductive polymers (ICPs) and a third group of very highly specialized polymers, ICPs that have both electrical and optical characteristics (electro-optic polymers). Dominating the field of conductive polymers, conductive filled plastics are traditional plastics, almost exclusively thermoplastics containing fillers such as powdered metals (stainless steel, silver, copper, gold) or carbon (usually carbon black or fiber but increasingly, carbon nanotubes and other nanosized materials) that render them conductive. ICPs upon doping, conduct electricity on their own via a conjugated backbone (alternating single and double bonds) that enable electrons to be delocalized. The conductivity of ICPs can be altered or tuned over many orders of magnitude by doping, by degree and nature of dopant, chemical alterations/substitu-tions on the polymer backbone, and may be used in conjunction with conventional polymers as composites, blends, and laminates. Electro-optic polymers are ICPs that develop optical characteristics under influence of an applied electric field. The most common polymers used for modern ICPs and electro-optic polymers are polyanilines (PANI), polythiophenes (P3AT) including polyethylenedioxythiophene (PEDOT), polypyrroles (PPy), Polyphenylene vinylenes (PPV), and Polyfluorenes (PFO).

Conductive Polymers Market

Compounded (or filled) conductive polymers play a critical role in the successful proliferation and miniaturization of electronic devices. Driven by the need to provide an inexpensive means of protecting sensitive electronic devices against the threat of electrostatic discharge and electromagnetic or radio frequency interference, the market for electrically conductive polymers compounded from thermoplastics and conductive fillers is large and robust. At the same time, a complementary market for polymers that conduct electricity without the assistance of fillers is creating considerable enthusiasm and drawing headlines as the basis for devices of the future such as inexpensive radio-frequency identification tags, electronic paper, lightweight solar cells, sensors, smart materials, actuators and artificial muscles.

Experts in the field estimated the total North American market for conductive polymers to be 141 million pounds in 2006 with a value of $US 845 million. This market, growing at an AAGR (average annual growth rate) of 9.9% and 15.2% in volume and value respectively is expected to reach 226 million pounds valued at nearly $1.70 billion in 2011. The market is dominated by conductive plastic compounds however, over the next five years, ICPs with the higher growth rate will increase their market share in volume, and, more dramatically, in dollar value.

The explosive growth of sensitive electronic devices, the increased need to protect them electrostatically/electromagnetically, and the emergence of exciting new technologies has stimulated considerable research and development activity with attendant funding, together with numerous technical and corporate acquisitions/alliances. While ICPs remain an emerging market, they are penetrating the traditional filled conductive plastics market mainly electrostatic packaging, which is the major outlet for conductive plastics. Currently the largest ICP application is in organic light emitting diodes (OLEDs). Other conductive plastic applications are corrosion resistant coatings, electrostatic paintable plastics, batteries, capacitors, transistors, sensors, solar cells and other potential uses.