Many familiar resins, such as polyethylene, polyvinyl chloride (PVC), and polystyrene, first saw commercial development in the 1930s and 1940s. Further developments, particularly stemming from the area of synthetic-rubber research, occurred as a result of the raw materials shortages during the Second World War. Since that time, the plastics industry has enjoyed significant growth as more and more resins have been developed to fit increasing numbers of commercial and industrial applications.

The tremendous success of polymeric materials in modern industry is due in no small part to the wide range of properties and characteristics they exhibit. From low-cost flexible packaging to strength and temperature properties that approach metals, polymers have managed to fit an extraordinary range of applications. It is the job of the polymer engineer to understand which resins, fillers, and processes are needed to supply required properties. This article explains some of the principles of polymer science and how they relate to the materials commonly used in static control applications. It also includes a brief explanation of the important relationship between chemical structure and physical properties for a range of polymer resins, as well as of the common methods by which these resins are made electrically conductive.

Polymers, as a class of material, are unique because of their molecular size and chemistry. A polymer is a giant molecule made up of many smaller units called monomers. These monomers are chemically bonded to each other. The easiest way to envision this is to imagine a polymer molecule as a long string of beads: each bead represents a monomer chemically bonded to its neighbors. An example of the relationship between the monomer and polymer for the case of polystyrene is shown in Figure 1.

Figure 1. Styrene monomer and polystyrene.

Many of the special properties of polymers can be explained in terms of their size (how these long chains interact with each other) and their chemistry (the chemical features of the monomer). Looking again at the bead analogy, imagine that instead of just a single beaded chain, thousands of long beaded chains are mixed together in a bowl. Try to remove one chain and what happens? The beads are pulled up together in one mass. This is because the chains are randomly (amorphously) distributed and so entangled that they behave as a single unit. Polymer molecules behave in the same way: They can become wrapped and twisted around each other.

However, the bead analogy fails in two important ways. First, polymer chains are not static; they are constantly in motion, bumping, rubbing, and sliding against each other. They behave more like a bowl of snakes than a bowl of chains. Second, they are not always randomly distributed or amorphous. Polymer molecules can align themselves into organized crystalline units.

Some polymers are completely amorphous. Others are a mix of amorphous and crystalline regions. Still others, like polyethylene, are largely crystalline and only 5% amorphous. This property is demonstrated in Figure 2.

Figure 2. Polymer chains in amorphous and crystalline regions.

Both the amorphous and crystalline regions undergo a thermodynamic transition at a particular temperature. The amorphous regions undergo what is called the glass transition. Below the glass transition temperature (Tg), the polymer chains do not have the thermal energy to move and slide against each other. Molecular motion slows down, and the polymer resin becomes brittle and glassy. Above Tg, the polymer chains are mobile and the polymer is ductile, soft, and plastic.

The second transition is the melting temperature (Tm) of the crystalline regions. These crystalline regions are important to the resin because they impart strength and heat stability. Above Tm, the resin is fluid and putty-like.

A good example of the importance of these two temperatures is polyethylene, in which Tg is –80°C and Tm is 110°C. Below the glass transition temperature, polyethylene is glassy and brittle (not well suited for commercial use). Above the melting point, the polymer is fluid, like Silly Putty. This is the temperature at which processing (injection molding, extrusion, etc.) occurs. The interim temperatures (between –80° and 110°C) are the region where polyethylene is tough and plastic, yet strong and rigid. A diagram of this region, where most of the resin's applications occur, is shown in Figure 3.

Figure 3. Processing temperatures of polyethylene.

Another important property often used to compare resins is strength. Although there are many ways to determine strength, the most common method is to measure the tensile strength and modulus. Tensile strength is the force (per cross-sectional area) required to pull apart a sample when it is gripped at either end. The modulus is a measure of resistance to deformation or stiffness, the same force as tensile strength but normalized (divided) by the length the sample is stretched. Both are reported in terms of force per unit area.

This section discusses the physical and chemical properties of some resins commonly found in static control applications.

Polyolefins. Polyolefins (also known as hydrocarbon polymers) are the most common polymer resins in use today. This group includes polyethylene and polypropylene. Domestic production of polyethylene alone reached nearly 28 billion pounds in 1998.² The general structure for polyolefins is given in Figure 4.

Figure 4. Polyolefin structures.

Polyethylene is so common that the resin is further subdivided into several classes of material based on density. The best known of these are low-density polyethylene (LDPE), with densities ranging from 0.91 to 0.94 g/cm³, and high-density polyethylene (HDPE), with densities between 0.95 and 0.97 g/cm³.

LDPE is among the cheapest resins available. Physically, it is considered a low-strength, low-melting-point resin (see Table I for physical properties). LDPE, however, also shows good chemical resistance and good electrical properties. It finds its widest applications in food packaging and wire insulation. In static control applications, it is most often used as a carbon-filled conductive material for injection-molded containers and totes.

HDPE molecules are linear and flexible. They are easily folded into crystalline structures and, as a consequence, exhibit crystallinities of 90% or more. This high level of crystallinity provides the resin with higher strength than LDPE and chemical resistance second only to polytetrafluoroethylene (PTFE). However, a melting point of only 130°C limits its use to low-temperature applications. HDPE is commonly found in juice and food containers, and in larger structures like kayaks and buoys. Static control applications include carbon-loaded resins for bags and injection-molded articles such as containers and totes.

Polypropylene is of the same family as polyethylene, but a careful look at Figure 4 shows that this resin has an additional methyl (CH₃) group on one side of each monomer. Going back to the analogy of the polymer chain as a string of beads, where polyethylene is a string of plain beads, polypropylene is a string of beads with an extra piece hanging off each bead.

Two important changes occur as a result of this extra methyl group. First, the chains do not slide past each other as readily. This means that more thermal energy is needed to move these big polymer chains. The result of this increased thermal energy requirement is seen in higher Tg and Tm values. As noted in Table I, polypropylene's glass transition occurs at around –30°C and its melting point is about 165°C. The second effect is that polypropylene has a lower degree of crystallinity.

The higher processing temperatures mean somewhat broader applications for polypropylene, which is stronger, stiffer, and more brittle than polyethylene. For example, this resin has a high-enough thermal tolerance to withstand sterilization and is therefore used in molded parts for the health industry. Because of its easy processability and glossy surface, polypropylene is also used in nonstructural molding applications for appliances and automobiles, and in filament rope. It should be noted that commercial polypropylene resins are often modified with rubber to improve their impact resistance.

Polystyrene. Polystyrene is itself a commercially important resin, as well as a modifier for other resins. Unmodified polystyrene is clear, glossy, and easily processed, but it is limited by its low resistance to heat and susceptibility to attack by common solvents such as gasoline and acetone.

A study of polystyrene's chemical structure (shown in Figure 1) and a brief return to the beaded-chain analogy can help explain these features. Polystyrene's structure is similar to polypropylene in that each individual monomer unit or bead has an extra chemical feature attached at the side. This pendant unit greatly influences the resin's properties. In the case of polypropylene, the pendant unit is a methyl (CH₃) group. In the case of polystyrene, the pendant unit is the much larger phenyl () ring. Bulky side groups make molecular motion and organization more difficult, thereby raising the transition temperatures and decreasing the degree of crystallinity. This effect is greatly magnified in polystyrene, which has a Tg of 105°C and no crystalline regions. The high Tg value explains the brittle nature of the resin, and the lack of protective crystalline regions explains the susceptibility to chemical attack. Polystyrene applications tend to be limited to low-end injection-molded parts.

Many of polystyrene's limitations can be overcome by forming two- and three-component mixtures. Perhaps the best-known such alloy is the mixture of acrylonitrile, butadiene, and styrene to form ABS. Here, the acrylonitrile content enhances chemical resistance and the butadiene rubber improves impact strength. Similarly, high-impact polystyrene (HIPS) has a rubber component.

ABS resins, although still limited by low heat resistance, have found many applications in appliance housings, automotive parts, and children's toys. Static control applications include trays and carriers.

Fluorinated Resins. PTFE, also known commercially as Teflon, is famous for its extreme properties. This material is almost completely immune to chemical attack (except from concentrated alkali metals) and is thermally stable to more than 250°C. On the other hand, it is soft and easily deformed, making it difficult to process. A simple look at the beaded-chain model won't explain these unusual properties because they are inherent in the chemical makeup of the polymer. This chemical structure is shown in Figure 5.

Figure 5. PTFE structure and bond energies.

The actual structure of PTFE is the same as polyethylene, except that the hydrogen atoms are replaced with fluorine atoms. This swapping of atoms greatly improves the chemical stability of the chains because it takes much more energy to break the carbon-fluorine bond found in PTFE than the carbon-hydrogen bond in polyethylene (see Figure 5).³ This is what chemical and thermal stability is all about: resistance to breaking bonds. Stronger bonds in the polymer chain mean better chemical resistance and greater thermal stability. These strengths are further helped by PTFE's high level of crystallinity, which, like HDPE, ranges from 93 to 98% (but can decrease during processing).

In addition to its chemical and thermal inertness, PTFE has excellent electrical properties and high lubricity. This resin finds application in a wide array of products, including insulation for wires, cables, and high-frequency electronics, as well as in chemical- and food-processing products. For electronics applications, PTFE is often used in areas requiring cleanliness, such as wafer processing and cleanrooms. PTFE is highly triboelectric and often creates static control problems by generating static charges during handling. Although PTFE is not itself found in conductive forms, other fluorinated polymers are available with conductive fillers.

Polyesters. Polyester is a generic name for a wide class of polymers that share a common trait: they contain an ester group on the chain. The most common and widely used polyester resin is polyethylene terephthalate (PET). The structure of PET is shown in Figure 6, where the ester link is highlighted. Physical properties are given in Table I.

Figure 6. Polyethylene terephthalate.

Polyesters, particularly PET, are like polystyrene in that they contain bulky groups and exhibit high thermal-transition temperatures. The Tg and Tm of PET are well above room temperature, at 70° and 265°C, respectively. But unlike polystyrene, which is brittle under these conditions, PET shows great flexibility, toughness, and impact strength. These properties are made possible by molecular motion. Whereas polystyrene has little or no molecular motion below its Tg and is brittle, PET still has significant polymer-chain motion. As previously mentioned, it is the motion of the chains, moving and sliding against each other, that imparts toughness and flexibility to the polymer.

A second look at Figure 6 shows two different parts to the PET chain: a long, slender portion that contains the oxygen and CH₂, and the larger, slow-moving phenyl ring. The molecular motion responsible for toughness is found in the flexible ethylene oxide (CH₂CH₂O) segment. In a sense, this short section of the chain behaves in the same way as the butadiene segments of ABS—it provides a rubbery element to the polymer.

PET and its derivatives, such as PETG, are easily drawn into fibers for fabrics and are easily molded. PET resins show excellent chemical and moisture barrier properties and are nontoxic, making them preferred plastics for food and pharmaceutical applications. Similarly, in the electronics industry, PET resins are most often found in packaging applications in which the resin is modified to be static dissipative or electrically conductive.

Perhaps PET's weakest link as a commercial resin is its chemical and thermal resistance. PET is highly susceptible to degradation when heated above 150°C in the presence of moisture. PET cannot be exposed to elevated temperatures and, like most polymers used in engineering, must be thoroughly dried prior to processing.⁴

Engineering Resins. The commercial resins investigated so far have shown a wide variety of properties, including chemical inertness and great toughness. However, most of these resins are limited to temperatures below 125°C—a severe limitation for the automotive and electronics industries. A new generation of polymer materials addresses the need for high temperature resistance and high strength. These resins are grouped together as engineering resins and include polyetheretherketone (PEEK), polycarbonate (PC), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), and polyether sulfone (PES), among others. The structures of PEEK and PC are given in Figure 7.

Figure 7. Polyetheretherketone and polycarbonate.

The success of these resins is due in part to the absence of weaker, thermally intolerant segments. For example, methyl groups (CH₂), when not crystallized, are extremely susceptible to chemical and oxidative attack. While this chemical unit is found in virtually all the common low-temperature resins, it is not found in any of the engineering resins.⁵ To reinforce this quality, the polymer chain is bulked up with stable, thermally tolerant chemical segments. The phenyl ring () is a highly stable chemical entity and plays a prominent role in the structure of engineering resins. It appears several times in the monomer units of both PEEK and PC, and not as a side group (as it appears in polystyrene) but as part of the main chain. These and other methods have been used to increase the useful working temperature of PEEK to 240°C and higher.⁶

To maximize the usefulness of these resins, they are often available as reinforced composites. Using PEEK as an example, carbon-fiber reinforcement increases the heat-distortion temperature from 150° to 300°C and the tensile modulus from 0.5 Mpsi to 1.9 Mpsi.

Use of these resins is limited by cost and processing concerns. The resins can cost considerably more than standard commercial resins. Furthermore, their high processing temperature may not be suitable for all plastics-processing equipment. Still, their high purity, good wear, low flammability, and outstanding physical properties have made engineering resins important components for automatic-transmission and engine parts, as well as for cleanroom products. In static control applications, these resins are often made conductive by the addition of carbon fibers for use in equipment and carriers for wafer processing.

In their natural state, without any additives or modifiers, almost all commercial plastics are electrical insulators. Like any insulating material, electrical charges deposited on a polymer surface are long-lived. The longer the lifetime of the charge, the more likely it is to cause damage to electronics that come near or into contact with it. A considerable amount of time and energy has been spent to develop ways to make these polymers either static dissipative or electrically conductive. Some of the most common of these methods can be divided into three categories: chemical additives, conductive fillers, and inherently dissipative and conductive polymers.

Chemical Additives. Resins can often be brought into the dissipative range (10⁴ to 10¹¹ W) by incorporating a chemical additive such as an antistatic agent (antistat) into the mix. Antistats can be either topical or internal.⁷ A topical antistat is simply sprayed or coated onto the surface of the finished article. Because they are easily wiped or rubbed off, these agents are at best transient. Internal antistats, on the other hand, are dissolved into the molten plastic during processing and therefore represent a more permanent fix. Internal antistats are partially soluble in the polymer resin. After the plastic has solidified, the antistat slowly "blooms," or migrates to the surface, where it becomes electrically active. Over time, rubbing and washing may remove some of the antistat. However, unlike topical additives, internal antistats constantly replenish themselves by migrating from the interior to the surface.⁸

A closer look at the chemical structure of a typical antistat will help explain its behavior. Most antistats have two halves of opposite chemical nature: a hydrophilic (water-loving) head and a hydrophobic (water-hating) tail (see Figure 8). Both segments play a critical role in the operation of the antistatic agent. The hydrophobic tail is often a short-chain hydrocarbon, almost like a short section of polyethylene. It avoids water but interacts well with polymers. This interaction explains why antistats are at least partially soluble in bulk plastic.

Figure 8. Antistatic agent structure and properties.

A hydrophilic head, however, is usually a very polar chemical, sometimes even ionic. This means that the head interacts poorly with most plastics, but well with water, salts, and other ionic chemicals. This represents the electrically conducting part of the antistat.

The antistat action is characterized by the hydrophobic tail burying itself in the body of the plastic and the hydrophilic head staying just above the surface. Like a buoy in the water, the antistat remains half submerged and half exposed. The highly polar head attracts water, ions, and salts from the environment onto the plastic surface to form a thin layer of conductive soup. This is the conductive layer that allows electric charge to flow over the surface and renders the plastic electrically dissipative.⁹ This action is shown in Figure 8.

Antistats are widely used because they are cheap and efficient. However, they are limited in several important ways. First, by operating only in the dissipative region, they provide limited conductivity. Second, antistats need to absorb atmospheric moisture and salts, meaning that conductivity can vary significantly with humidity. Finally, they tend to impart a greasy feel to the surface and are therefore not suitable for cleanroom applications because of the potential for ionic and chemical contamination. They are most often employed in commodity static control applications such as vinyl and rubber work surfaces, polyethylene bags, and polypropylene containers and trays.

Conductive Fillers. Perhaps the oldest and best-known method of making a plastic electrically conductive is to load the resin with a conductive filler to make a composite. Many conductive fillers are available, including metal particles and metal-coated-glass and carbon fibers. Most common to static control applications is carbon powder, also known as carbon black, which has been in use since the 1950s.⁹

Numerous factors can affect the properties of a conductive filler or polymer composite. The polymer engineer must decide among filler type, loading level, process conditions, surface treatments, etc., in order to achieve the desired conductivity. Three of the most basic factors are particle conductivity, loading level, and particle shape.

As might be expected, the resistivity of the composite is closely related to the resistivity of the filler. For example, carbon black, which in pure powder form has a volume resistance of approximately 0.1 W-cm, can produce polymer composites with resistivities down to 1 W-cm. However, silver powder with a resistance of only 1.5 x 10^–6 W-cm can be used to make polymer composites with volume resistances as low as 10^–2 W-cm.⁹ This difference becomes important when considering EMI shielding. Metal coatings and fillers may be used for EMI shielding applications, whereas carbon-black composites cannot.

The effect of filler loading on the composite resistivity follows a nearly universal pattern regardless of which fillers are chosen. At low filler loadings, the composite properties remain almost undisturbed. As the filler loading reaches a critical point, the resistivity suddenly and precipitously drops. This point is called the percolation threshold and represents the moment when there is enough conductive filler present to make a continuous network within the composite. This phenomenon is illustrated in Figure 9, which shows the resistance of a polymer-silver composite as a function of the volume of silver spheres. As seen in this graph, network formation occurs with a slight increase in filler volume and yet results in a tremendous change in the electrical resistance.

Figure 9. Resistivity as a function of filler volume.

Figure 10 gives a simplified view of this percolation transition. At low filler loadings, the filler particles act like conductive islands in a sea of electrically insulating resin. Little or no change in resistance occurs because electrons moving through the composite still encounter the insulating polymer. As more particles are introduced (filler volume increases), the conductive particles become more crowded and are more likely to come into contact with each other. Finally, at the percolation threshold, a majority of filler particles are in contact with at least two of their nearest neighbors, thereby forming a continuous chain or network. An electrical charge can now pass through the composite via this network without encountering the high-resistance polymer resin. Additional filler loading beyond the percolation threshold does not greatly reduce the resistance of the composite.¹⁰

Figure 10. Approaching the percolation threshold.

The shape of the particle plays a critical role in where (at what filler volume) percolation occurs. The more structured or elaborately shaped the particle, the more likely it is to contact a nearest neighbor and form a continuous network. Perfectly spherical fillers, which arguably have the least elaborate and least structured shape, can require as much as 40% loading in order to reach the percolation threshold. Carbon-black particles are more irregularly shaped and often have long branches reaching out from the main body of the particle. These moderately structured fillers can require anywhere from 5 to 35% loading to reach the percolation threshold (see Figure 11).¹¹ Finally, highly shaped fillers such as carbon or stainless-steel fibers may be present in as little as a few percent by volume in order to achieve low resistance.

Figure 11. Resistivity of high- and low-structure carbon-black composites.

The great majority of commercial resins are available as conductive composites. Most often these resins are compounded with 15–30% carbon black to make containers, trays, bags, work surfaces, wrist straps, etc. Polymer and carbon-black composites are versatile, relatively inexpensive, and permanently conductive. But there are several disadvantages. Carbon-black composites are not usable in cleanroom environments because of the possibility of contamination by shedding of carbon particles, a process known as sloughing. Also, because of the steepness of the percolation curve (Figure 9), it is difficult to precisely control the level of conductivity for a particular resin or to achieve resistivity levels in the 10⁶- to 10⁹-W range. Some of these problems have been overcome using innovative processing techniques and materials.^12–14

High-temperature composites made with engineering resins such as PEEK and polyamide often incorporate carbon fibers instead of particles. The fibers provide excellent levels of resistivity while reinforcing the polymer resin, for stronger, more temperature-resistant products. Since carbon fibers are much less likely to slough, these resins are often used in cleanrooms and for electronics processing.

Inherently Dissipative and Conductive Polymers. Inherently dissipative polymers (IDPs) and inherently conductive polymers (ICPs) represent two new classes of materials in static control applications. While their names may sound similar, these two materials have very different chemistries and properties. Inherently dissipative polymers show resistivities more along the lines of an antistatic agent, whereas inherently conductive polymers have conductivities approaching those of metals and are even referred to as synthetic metals.

Inherently Dissipative Polymers. Inherently dissipative resins are usually employed as additives for more-common commercial resins. Typically, an IDP is mixed in with a host resin, say polypropylene, at a level of 10 to 30%. At this level, there is enough IDP present to lower the resistance of the polymer mixture to the 10⁹- to 10¹²-W range, about the same level of resistance that would be expected when using an antistat. This is because IDPs act on similar principles, by using the conduction associated with the movement of ions and charged species.¹⁵ A look at the IDP structure can explain this principle.

Inherently dissipative polymers are really copolymers; that is, they contain two or more polymer species on the same chain. One of those polymer species is polyethylene oxide (PEO), shown in Figure 12. The only difference in structure between PEO and polyethylene (Figure 4) is the oxygen atom jammed between the methyl groups. But this oxygen atom makes a big difference in the chemistry of the polymer, by adding a polar character to the chain. The oxygen atoms attract and interact with both water and ions. Conduction occurs when ions hop or jump from oxygen to oxygen, thus traveling along the chain length.

Figure 12. Inherently dissipative polymer.

Another important aspect of IDP operation is the process by which they blend in with their host polymers. IDPs are blended into the host polymer, meaning that they form a separate interpenetrating network within the host polymer (see Figure 12). While antistatic agents must migrate to the surface of the host polymer in order to be effective, IDPs conduct charges while buried within the host resin.

Taking all these factors into account, IDPs provide several important advantages over antistatic agents. Because they are large polymer molecules, IDPs are much less likely to migrate or leach out of the system the way antistats do. This also makes IDPs cleaner than antistats. Furthermore, because IDPs form a network buried within the host resin, they are largely independent of atmospheric humidity. However, care must also be taken during processing to ensure that the IDP network is not broken up during extrusion or injection molding.

IDPs can be blended with a range of commercial polymers, including ABS, polycarbonate, polystyrene, and polyolefins, without greatly changing the mechanical properties of the host polymer. Inherently dissipative polymers are finding uses in a number of static control applications and in cleanroom environments.

Inherently Conductive Polymers. Up to this point, the polymers we have looked at have been rendered conductive by adding electrically conductive elements such as metal particles, ions, and salts. The polymers themselves merely provide a supporting role as the matrix or host material for the conductor. This situation changes completely in the case of inherently conductive polymers, in which it is the polymer chain that provides the conductive path for the electrons. This is caused by a dramatic change in polymer architecture. An explanation of these changes requires the introduction of several terms: double bond, conjugation, and doping.

A regular chemical bond occurs when two atoms share a pair of electrons. A single line drawn between atoms (such as C–C) denotes this. It is this sharing of electrons that binds atoms together and keeps molecules from flying apart. A double bond occurs when the atoms share an extra pair of electrons, bringing the total number to four. This is denoted by a double line drawn between the participating atoms (C=C). Keep in mind that extra electrons can be useful for conducting electricity.

Conjugation occurs when a molecule contains both single and double bonds. In particular, the single and double bonds must alternate within the structure. A good example of this is polyacetylene (Figure 13), which is constructed entirely of alternating single and double bonds.

Figure 13. Polyacetylene structures.

Conjugated systems are special because the extra electrons of the double bonds are free to roam or move throughout the system. In fact, they are so free and move so rapidly that it is impossible to know exactly where they are. This movement and freedom is indicated by drawing a dashed line throughout the conjugated system. This is the equivalent of saying, "We know the extra electrons are in there somewhere; we just don't know exactly where."

Two important elements for conduction exist: extra electrons and mobility. One could rightfully expect that a polymer chain like polyacetylene would conduct electricity throughout its length. Unfortunately, this is not the case. Very long conjugated systems like polyacetylene tend to revert into conjugated systems of limited length and therefore cannot conduct charges like a metal. In order for a conjugated polymer to conduct electricity, it must first be doped.

Doping a polymer is not the same as doping silicon, in which there is a substitution of atoms. Conductive polymers are doped with oxidizing or reducing agents, chemicals that remove electrons from or add electrons to the polymer. Without going into great detail, the oxidation or reduction changes the electronic structure of the polymer so that it can conduct electricity. The degree of conductivity is related to many factors, including the polymeric structure, degree of doping, and type of dopant.

From a practical standpoint, the first generation of intrinsically conductive polymers did not achieve great commercial success. These polymers tended to be insoluble, unprocessable, and extremely sensitive to environmental conditions. For example, iodine-doped polyacetylene had to be stored in an oxygen-free environment in order to prevent degradation of its conductivity. However, several more-recent polymers have been developed that exhibit much greater stability and show the promise of commercial success. These include polyaniline, polypyrrole, and polythiophene (see Figure 14).

Figure 14. Inherently conductive polymers.

ICP conductivity can reach as high as 10⁴ S/cm (10^–4 W-cm ).¹⁶ However, typical conductivity is in the range of 1–100 S/cm. ICPs are still most often used as additives or coatings for static control applications. ICPs are used for coating materials for films and electronic packaging and can be melt-processed with conventional resins such as polyethylene to form static control articles such as films and trays. These ICP alloys exhibit much greater thermal and chemical stability than their predecessors. ICPs still impart some color (green or blue) to their host polymers, but they can be used to make clear films and sheeting.

The popularity of polymers in static control applications is due in no small part to the wide variety of physical and chemical properties available in commercial polymer resins. This flexibility is further enhanced by a large and steadily increasing number of ways in which polymers can be rendered electrically conductive or dissipative by additives and treatments.