2. Plastic has many attributes, including light weight, corrosion resistance and design flexibility. An unlimited number of shapes and sizes of parts can easily be created with thousands of different grades of polymer. The material also appeals to engineers because it allows them to create single-piece components that simplify assembly.
3. Traditionally, one of the only drawbacks of plastic has been its lack of electrical conductivity. But, that’s starting to change. Nanotechnology is enabling engineers to create hybrid materials that can be processed with traditional production methods, such as injection molding and laser welding.
4. Polymers that are electrically conductive typically fall into three categories:
- Inherently conductive thermoset resins, such as polyaniline, polythiophene and polypyrolle.
- Inherently static-dissipative thermoplastic resins based on thermoplastic polyurethanes or similar-structure materials.
- Modified or compounded resins with conductive and static-dissipative or anti-static additives.
5. Unmodified plastics have a resistivity of 1016 ohm-meters; conductive additives can lower conductivity levels in steps down to the 104 ohm-meters resistivity range.
6. Conductive compounds are available with multiple levels of resistivity, such as antistatic, static-dissipative, static control, grounding and electromagnetic interference shielding, depending on end use requirements. Additive choice and additive loading levels affect the level of conductivity that can be obtained in a thermoplastic compound.
7. To achieve true electrical conductivity in plastics, formulators often must inject additives, such as carbon or stainless steel fibers. However, that can have adverse affects on the polymer. For instance, stiffness and tensile properties often increase. Choosing the right type and combination of additives is critical to performance.
GROWTH POTENTIAL
1. Although natural thermoplastic resins typically act as electric insulators, plastics can be formulated to have specific conductivity characteristics. However, the word ‘conductive’ may be misleading, Because, without absolute numbers, it is a relative term. Typical examples are metals such as copper, silver and aluminum. The electrical conductivity of conductive polymers is typically several orders of magnitude lower than that of metals.
2. Conductive polymers are ideal for use in products where space and weight considerations are critical, such as automobiles, aircraft and portable consumer electronics.
3. Common applications for conductive polymers utilize their conductivity or electroactivity, the former includes electrostatic materials, conducting adhesives, electromagnetic shielding, artificial nerves, antistatic clothing, piezoceramics, active electronics and aircraft structures. The latter includes electrical displays, chemical, thermal and biochemical sensors, rechargeable batteries, solid electrolytes, optical computers, ion exchange membranes, actuators and switches.
4. According to the Freedonia Group Inc., conductive polymer demand in the United States is expected to grow 3 percent annually over the next four years. Gains will be fueled by the greater susceptibility of electrical and electronic products to damage by static discharge.
APPLICATION
1. Poor conductivity can lead to undesirable consequences, such as static charge buildup that is capable of creating an electrical spark. As a result, any type of automotive or aerospace components through which fuel flows, such as pumps, filters, tanks or hoses, are ideal candidates for electrically conductive plastic.
2. Engineers at Robert Bosch recently faced that dilemma when developing a fuel filter housing for use in Audi A4 and A5 sedans. Traditionally, automotive fuel pumps and supply units are made from polyoxymethylene (POM).
3. But, to comply with the SAE J1645 standard, which addresses electrostatic discharge in fuel systems and components, the Bosch engineers were forced to use a conductive material. So, they turned to Ultraform N2320 C from BASF. The electrically conductive plastic eliminates the risk of electrostatic discharge and sparking as fuel flows through the filter.
4. Other German automotive suppliers have also been experimenting with conductive polymers. For instance, engineers at Mann+Hummel have developed a fuel filter housing made from Durethan DP BCF 30, a polyamide 6 from Lanxess that is reinforced with carbon fibers. It is a cost-effective alternative to traditional die-cast aluminum.
5. Aerospace engineers also see long-range potential for conductive polymers. Goodrich Corp. is currently working with the University of Dayton Research Institute (UDRI) to develop a nanomaterial with metal-like conductive properties in sizes suitable for large-scale commercial aerospace applications. They are collaborating with Owens-Corning and Renegade Materials to build and equip a facility capable of producing the hybrid composite material, dubbed “fuzzy fiber,” in sheets up to 60 inches wide.
6. Goodrich has already committed $1 million to the R&D effort. It intends to use the hybrid composite material in new-generation nacelles, wheels, brakes and landing gear. Other potential applications include aircraft structural health monitoring and electrical de-icing systems.
7. In Australia, a biomedical engineer at the University of New South Wales is developing conductive polymers that can carry electrical signals for use in implantable medical devices, such as eyes and ears.
8. The process involves incorporating natural body proteins into conductive polymers, then using them as coatings on the tiny electrodes that connect implants to nerve tissue. “These biopolymers overcome problems such as scarring encountered with metal electrodes, where the body recognizes them as foreign objects and forms scar tissue, eventually shortening the useful life of the implant,” Green points out.
(Source:
https://www.assemblymag.com/articles/88381-plastics-assembly-electrically-conductive-polymers
