In the Wire and cable industry, various types of pigments are used to color polyolefins. Mainly they are employed for Wire Identification Methods. As in cables, it can be seen the coloring done on the outer layer is govened by a different set of requirements as from the inner layers. Pigments that are used in the wire and cable industries can be of two types inorganic and organic. Newer alternatives that are coming in to the market are known as the "mixed-phase metal oxide" pigments. Examples can be given of, yellow nickel titanates and blue and green cobalt aluminates. A relatively new entrant is the brilliant yellow bismuth vanadate. Organic pigments are also used but not as popular because they are more difficult to disperse than inorganic ones leading to possible loss in mechanical strength.

Some common examples are given in this table.

There are various factors that govern the choice of colorants when it comes to the Wire and Cable industries. They are:

Resistance to fading- This is a very critical factor. The pigment selection can become more complex, if a formulation that is free of heavy metals or free of diarylides is asked for.

Exposure (Outdoor or Indoors)- It is to be noted here that outdoor environments are much more challenging on pigments than indoor applications and it has been seen that many pigments that perform exceptionally well indoors are prone to fading once exposed to outside.

Humidity

Thermal cycling

Sunlight

Air pollution

Light stabilty

In moden Wire and cable industry, there is a constant need for effective wire identification. For our subject of discussion we will limit our discussion to just two methods of wire identification.

Inkjet Marking- Inkjet technology has vastly improved over the years. With features of less maintenance and faster start-ups, Inkjet marking systems are now more reliable and user friendly. For the wire and cable industry, a dye or pigmented ink, with an Methyl Ethyl Ketone base is applied.


Hot Stamp Marking- Hot stamp marking is still among the most inexpensive techniques for wire identification and is perhaps with exception of laser the only viable option for marking of the Teflon insulated wire. Four important factors here are correct air pressure, dwell time, wheel temperature, and lastly foil. Use of pigments come in the foil part. The foil comprises of a backing and pigment. The pigment gets transferred to wire insulation through the heat emanating from the character wheels. It is vital to note here that certain types of pigments can stick to only particular substrates and would need different temperatures to transfer them.