The Wire and cable industry use various types of pigments 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 governed 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: 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:
Pigment |
Color |
Application |
Titanium dioxide |
White |
Used in Variety of resins |
Zinc sulphide |
White |
Wide use |
Iron oxides |
Red, yellow, brown, and black |
Wide use |
Lead chromates and lead chromate molybdates |
Colors can include bright yellow and orange |
Good use |
Cadmium |
Comes in reds, yellows, oranges and maroons |
Excellent for engineering resins |
Chromium oxides |
Green |
Shows good heat and light fastness, variety of uses |
Ultramarines |
Comes in blue, pink and violet shades |
Works in a wide gamut of resins |
There are various factors that govern the choice
of colorants when it comes to the Wire and Cable industries:
- Humidity
- Thermal cycling
- Sunlight
- Air pollution
- Light stability
- Resistance to fading
- Exposure (Outdoor & Indoor)
Wire Identification Methods
In modern Wire and cable industry, there is a constant need for effective
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.