In some industrial Ethernet cable constructions, you may find filler material. Fillers are used to give a cable a more rounded and smooth construction and to give the inside of the cable a cleaner appearance. Additionally, it strengthens a cable, so that when a cable is moved or flexed, you can control the conductors moving inside of the cable. Most importantly filler material supports the cable’s outer layers.
Several types of fillers are available, each with their own advantages and disadvantages.
Plastic is one of the most common filter materials and is available in numerous sizes. A common plastic filler design is the star filler, used in Cat5 and Cat6 cables. This design also reduces electrical interference such as crosstalk. Often made of PVC or Polyethylene, plastic fillers are costly and reduce a cable’s flexibility.
Fibrillated Fluoropolymers or foams are created through extrusion, which gives the plastic tape material a mesh-like pattern. They can be used as a flat design or twisted into a round shape. Either flat or round, the soft filler easily fills the vacant areas in a cable in a uniform manner.
Softer materials, such as cotton and rayon, are some of the most low-cost options available. They also fill the empty spaces in a cable more easily than harder designs like plastic.
At the strongest end is Kevlar, which is the most costly. It is best for longitudinal strength and increases performance in fiber optic cables.
Paper fillers are twisted into round designs and must be treated to be flame and moisture resistant. Their design tends to break down quicker during flexing and motion, however, so their use is limited mostly to high-voltage power cables.