Electrical properties conductive plastics

Many ingredients, especially those that are conductive, may affect electrical properties. Most plastics, which are poor conductors of current, build up a charge of static electricity. Antistatic agents can be added to attract-moisture, reducing the likelihood of a spark or discharge. 

The electrical properties of plastics vary from being excellent insulators to being quite conductive in different environments. Depending on the application, plastics may be formulated and processed to exhibit a single property or a designed combination of electrical, mechanical, chemical. 

Organizations involved in conducting and/or preparing specifications/ standards on the electrical properties on plastics include the Underwriters Laboratories (UL), American Society for Testing and Materials (ASTM), Canadian Standards Association (CSA), International Electrotechnical Commission (lEC), International Organization for Standardization (ISO), and American National Standards Institute (ANSI). 

Electrical Resistance—Conductivity. Most fillers are composed of nonconducting substances that should, therefore, provide electrical resistance properties comparable to the plastics in which they are used. However, some fillers contain adsorbed water or other conductive species that can gready reduce their electrical resistance. Standard tests for electrical resistance of filled plastics include dielectric strength, dielectric constant, arc resistance, and d-c resistance. 

Most polymers are very good electrical insulating materials because of their chemical composition, i.e., their electrical conductivity is exceptionally low. Because of this important property, many plastics are used to produce electrically nonconductive parts. However, the high surface resistance leads to an unwanted property the material is prone to electrostatic charge accumulation. To facilitate dissipation of the charge, antistatic agents are incorporated, which combine with atmospheric moisture on the plastic surface to form a conductive film. 

One of the most desirable aspects of plastics and composites is the ability to make net-shaped parts. The same process that creates the material also creates the structure. The penalty for this advantage is that the process of curing a thermosetting plastic or composite part is irreversible. Any part that is not properly processed represents a loss of part, material and the money and time required to make that part, although larger parts are usually repaired if possible. Proper shape becomes a controlled property in addition to the bulk material properties, such as mechanical (stiffness or strength), physical (density, void content, etc.), chemical (degree of cure or carbonization, chemical resistance), electrical (resistivity, conductivity), or any combination of these. 

But conducting plastics were not the only oddball substances that had started to pique the curiosity of researchers hunting for better ways to transport electrical current, not to mention trying to surpass the 23° K Tc that seemed as impassable as the sound barrier had been to fast flight. There was another group of materials still to be looked at, the mixed metallic oxides substances with the mechanical and physical properties of ceramics. They weren t exactly the sort of thing one might expect to find at the center of attention in a modern physics laboratory. 

Among conductive plastics, polyaniline has attracted much interest because of its environmental stability and its tunable electrical properties. Composite materials consisting of polyaniline nanofibers... 

Fillers may decrease thermal conductivity. The best insulation properties of composites are obtained with hollow spherical particles as a filler. Conversely, metal powders and other thermally conductive materials substantially increase the dissipation of thermal energy. Volume resistivity, static dissipation and other electrical properties can be influenced by the choice of filler. Conductive fillers in powder or fiber form, metal coated plastics and metal coated ceramics will increase the conductivity. Many fillers increase the electric resistivity. These are used in electric cable insulations. Ionic conductivity can be modified by silica fillers. 

Besfight MC and HTA-CF - carbon fiber nickel-coated with excellent mechanical properties of carbon fiber and good electric conductivity of nickel. The material for conductive plastics. 

Carbon black is produced industrially in the form of different products (e.g., furnace black, thermal black, channel black, lampblack, acetylene black) with specific properties. In addition to the relevance of carbon black for basic research on adsorption, or as a reference sohd, appUcations of this material in fields such as elastomer reinforcement, as modifier of certain properties of plastics (UV protection, electrical conductance, color), or as xerographic toners make its surface and interfacial properties extremely important. Soot is a randomly formed particulate material similar in nature to carbon black. The main (pragmatic, rather than conceptual) difference between these two carbon forms is that soot is generally formed as an unwanted by-product of incomplete combustion of pyrolysis, whereas carbon black is produced under strictly controlled conditions. Bansal and Donnet [78] have reviewed various possible mechanisms for the formation of soot and carbon black. Soot can retain a number of tars and resins on its surface. There is therefore some interest in studying the adsorption of polyaromatic hydrocarbons in soots, especially those of environmental significance such as diesel soot. 

Electrical properties of polymers that are subject to low electric field strengths can be described by their electrical conductivity, dielectric constant, dissipation factor, and triboelectric behavior. Materials can be classified as a function of their conductivity (k) in (Q/cm)- as follows conductors, O-IO" dissipatives, and insulators, lO or lower. Plastics are considered nonconductive materials (if the newly developed conducting plastics are not included). The relative dielectric constant of insulating materials (s) is the ratio of the capacities of a parallel plate condenser with and without the material between the plates. A correlation between the dielectric constant and the solubility parameter (6) is given by 6 7.0s. There is also a relation between resistivity R (the inverse of conductivity) and the dielectric constant at 298 K log R = 23 - 2s. 

BeryUiuin oxide-filled resins gain high conductivity without loss of electrical properties. Metal particles have heen used as fillers for plastics to improve or impart certain properties. Thus, aluminum has heen used for applications ranging from making a decorative finish to improving thermal conductivity. Copper particles are used in plastics to provide electrical conductivity. Lead is used because it dampens vibrations, acts as barrier to gamma-radiation, and has high density. 

---