polyethylene

PE is for Polyethylene

Posted on Wednesday, November 11, 2015 by Paige DiAntonio

Polyethylene is an insulation material within the thermoplastic family. For a quick refresher- a thermoplastic is a material that can be continuously heated, softened, and formed into any shape when hot. Polyethylene, more specifically, is part of the polyolefin group, and with common use of both terms, the words are now synonymous.  Polyethylene (PE) has a relatively low dielectric constant, which makes is useful for a wide array of applications. PE offers good resistance to many acids, alkalis and organic solvents and it can withstand a temperature range from -65°C to 90°C.   The most popular reason for using PE insulation is because of its superior low level signal transmission properties.

Here are a few types of PE compounds used:

  • Foamed (cellular) PE: Creating bubbles of air in the PE compound results in better electrical properties and a cost savings, since less compound is needed to be used to maintain electrical characteristics. Properties like these are important where high quality signals are to be transmitted, such as in coaxial and telephone circuits. However, conductors with cellular PE insulations are subject to a high degree of moisture ingress, since the open structure (bubbles) is weak and has very little tensile strength. This leaves them vulnerable to crushing and mechanical abuse. Dual wall extrusions help by providing a solid layer of PE over the foamed one.
  • Solid PE: This type of Polyethylene is available in a few forms such as:
    • Linear low-density polyethylene (LLDPE)
    • Low density polyethylene (LDPE)
    • Medium density polyethylene (MDPE)
    • High-density polyethylene (HDPE) 
  • Cross-Linked or Irradiated Polyethylene (XLPE): This compound is used as both insulation and jacketing material with a maximum operation temperature of 125°C. Cross-linking is a process that transforms the thermoplastic material into a thermoset material. This transaction is done either chemically or by irradiation. Whichever method is used, the compound achieves the same basic characteristics and provides better chemical and thermal properties than non-cross-linked compounds.

 

Interested in other thermoplastics, check out last week’s blog here.

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