Conductive polymers and plastics are increasingly desired for a growing number of sophisticated end-uses. Most plastics are naturally non-conductive, hence their wide use as electrical insulators.  Because of their ease of fabrication, however, polymers are highly desirable materials of construction. Where some transfer of electrical charge is desired modifications to the polymer must be made to increase conductivity.  This has resulted in plastics being formulated for use in four distinct application categories of increasing conductivity:

1. Insulating (e.g. wire coating)
    
2. Dissipative ("anti-static" polymers)
    
3. Conductive (materials capable of conducting modest amounts of electrical current)
    
4. Highly Conductive or Shielding (materials capable of conducting significant amounts of electrical current)

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Discussion of Electrically Conductive Polymers

The tendency of materials to conduct electricity is generally expressed in terms of surface resistivity - i.e. how resistant they are to the transfer of electrical charges.  In the natural state thermoplastic polymers have surface resistivities of 10¹² to 10¹⁶ ohms per square which characterizes very poor conductors of electrical charge.  As noted above, because of their very poor conductivity polymers are widely used as insulating wire coatings for numerous end-use applications. 

For some applications, however, poor conductivity leads to undesirable consequences - specifically the tendency to build-up and retain static electrical charges.  Static charge build-up can reach several thousand volts and is capable of delivering a startling shock and/or electrical spark albeit, fortunately, at very low amperage.

As a result, plastics with anti-static properties are highly desirable for many end uses.  For other applications even higher conductivities are desired.

While many highly conducting materials are widely available (e.g. metals), most of these are not easy to economically fabricate into complex shapes.  Thermoplastics on the other hand are easily and inexpensively moldable or extrudable into an almost unlimited variety of shapes and sizes.  Because of their ease of fabrication, plastics that conduct electrical charges are frequently desired for various applications where the conductivity of metal is not required.  Plastics can, in fact, be formulated to have specific conductivity characteristics from very low to very high conductivity as necessary and desirable.

Increasing  the Capability of Polymers to Conduct Electrical Charges 

The easiest "conducting" attribute to achieve in a polymer is to make it "anti-static".  Anti-static polymers do not conduct electrical charges in a conventional sense. They do, however, permit electrons to move across the surface from areas of high charge to areas of lower charge thereby eliminating the tendency to deliver a shock or create a spark.  "Anti-static" compositions are generally characterized by surface restivities of 10⁹ to 10¹¹ ohms/square.

Additives used to achieve anti-static performance are often referred to as "migrating" additives.  These are materials which have very limited solubility and/or compatibility with the polymer in which they are used.  In addition, they generally have the capability to absorb small amounts of atmospheric moisture thereby enhancing their capability to transfer electrons.  Because of their limited solubility in the polymer, anti-static additives tend to migrate to the surface of the part where they are most effective.  These additives work very well at relative humidities above 10% and provide static decay times of 1 second or less under these conditions. 

A very important ancillary benefit of anti-static additives is that they generally do not have a significant effect on polymer properties.  HiTech Polymers offers a wide variety of anti-static polymer products ranging from anti-static olefins to PVC"s, acrylics, urethanes, polystyrenes and ABS"s.  Custom formulations can be easily optimized for specific applications and can be readily provided. For more specific information on anti-static polymers click this link to go to our anti-stat polymer page.  To review representative anti-static polymer formulations

click here.  For additional information call or email us below to find out what we might be able to do for you.

Electrically Conductive Polymers

Conductive polymers are generally classified as those materials with surface resistivities from 10¹ to 10⁷ ohms/square.  To achieve true electrical conductivity in plastics one must add electrically conductive additives to the polymer. For modest conductivity (surface resistivity 10³ to 10⁷ ohms/square) "conductive carbon" additives are generally used very cost effectively.  For highly conducting thermoplastics  (surface resistivities of 10² ohms/square and higher) carbon or stainless steel fibers are often necessary.  

In most commercial compositions, additives used for conductive plastics tend to have increasingly significant effects on polymer properties.  Not all of these effects are undesirable. Stiffness (flexural modulus) and tensile properties often increase.  Impact behavior and elongation, however, generally drop significantly as the type and loading of additive is increased.

HiTech Polymers is very experienced in choosing the right type and combination of additives to deliver the optimum balance of properties and performance for your application.  Through our proprietary technology we can often achieve high levels of conductivity without significant loss of polymer properties.  Please let us know what your needs for a conductive plastic may be.  For a representative sample of what we can do with conductive polymers click here to view properties of several HiTech conductive polymers.

To find out more about our conductive polymers email us or call (859) 334-4500 to speak with a HiTech representative.

Representative Properties Available With HiTech Conducting Polymers

	Conductive Nylon 8715	Polyester Urethane 4931	Polyether Urethane 4901
Ultimate Tensile (psi)	6,000	2,010	2,294
Elongation (%)	17	177	469
100% Modulus (Kpsi)	---	2,000	2,039
Hardness, Shore	75D	45D/95A	95A/46D
Specific Gravity (g/cc)	1.13	1.16	1.16
Surface Resistivity (ohms/sq.)	6,000	1,500	1,000