Conductive Steel Fiber Capsules

Embed a web of metal fibers in the plastic case of electronics to provide RF shielding.

What is this?

The small bunch of capsules pictured-on the photo of the sample-(picture has been re-sized for closer viewing) contains steel fibers bundled inside. The capsules can be added to plastic to create a web of metal fibers throughout. The capsules deliver the metal fibers by breaking apart during the molding process.

This manufacturing process is unique for two reasons: 1) it is an effective method for dispersing something within plastic; and 2) it makes plastic electrically conductive. If you were to clip to wires to it you could run electricity through it and light a bulb.

Compared with other ways of making plastic electrically conductive, this one does not significantly change the properties of the plastic. This is because the steel fibers are more conductive per unit area than many other additives, so it takes fewer of them added to the plastic. Some other conductive additives can cause the plastic to become brittle, a problem not seen with conductive steel fiber capsules. Another benefit of a web of metal fibers is that the plastic can be used for RF shielding.

Think about other things you could disperse throughout plastic using this method. Metal fibers could be used to embed an antenna directly in the plastic casing of a phone. Or glow-in-the-dark fibers could be dispersed through clear plastic. Resistive heating fibers could also be dispersed throughout to make a plastic that can heat up.

Is there anything unique about the steel fibers in the capsules?

Bekaert, the company behind this process is a company specialized in steel fibers. They use a unique process called bundle drawing that allows for the creation of all-metal continuous filaments with diameters as low as 1 micron. Most of the fibers are made of pure stainless steel and have extremely high durability.

Can fabrics other than steel be used with this process? (Ex. copper fibers, glass fibers, carbon fibers etc.)

Nickel along with some specialty alloys of steel can also be manufactured.

There are several ways to make plastic conductive, what are the advantages of this process?

Because of the physical properties of stainless steel, the conductivity is more durable than other approaches. Also, the shrinkage properties are much more like the unfilled polymer material than other conductive fillers.

What is the maximum and minimum conductivities possible?

Surface conductivities range from 10 to the second to 10 to the twelfth ohms / square.

Does it produce heat as current is passed through because of resistance?

Yes, the plastic would heat up if current passed through it.

Can this heat be used for functional purposes?

Yes, the same fibers are being used in automotive seat heaters because of their superior flex life.

How thick are these fibers?

8 or 11 microns

How does the thickness of the fibers effect the performance?

Lower diameter fiber gives more fibers per pound. Higher diameter fiber gives more resistance to shear. Process parameters in the molding and compounding process determine which fiber will give the greatest results.

What are some current applications?

• Automotive fuel filter canisters
• Automotive gas caps
• LCD screens
• Enclosures for PLC’s

What are some possible future applications?

• Heatable plastics
• Moldable plastic antennas
• RFID tags
• Magnetic plastics

What are these stainless steel fibers in the capsules also used for?

These same stainless steel fibers are used in commercial applications in filtration, electronic textiles, lead wires, heatable textiles, heat resistant textiles and anti-static textiles. Also check stainless steel yarn item published in this issue.