Handbook  of  Cable & Wire  Producer

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Cross Linked Polyethylene (XLPE)

Plastic Type Thermoplastic
Melting Temp 150-170 0C
Density 0,93 g/cm3
Tensile Strength

18 MPa

Dielectric constant 2,2@1MHz
Resistance (ohm.cm)


Polyethylene(PE) is one of the most common thermoplastic that used in cable production. Cross-linked Polyethylene is abbreviated either XLPE or PEX.  In cable production XLPE is more common. PE has good electrical properties and a high electric resistivity, that gives it potential for use at much higher voltages than PVC. Plus, cross-linking results in better mechanical properties which makes XLPE the most compatible for cable types rated over 0,60/1 kV and higher.  After cross linking XLPE would not melt down anymore. Thermoset Plastic PE changed into Thermoset XLPE. Meanwhile,  Abrasion resistance, impact strength, thermal stability, tensile strength and scratch resistance would be enhanced significantly.
There are a few different ways to cross link polyethylene.  Cross-links can be formed by chemical reactions that are initiated by heat, pressure, change in pH, or irradiation. For example, mixing of an unpolymerized or partially polymerized resin with specific chemicals called crosslinking reagents results in a chemical reaction that forms cross-links. Cross-linking can also be induced in materials that are normally thermoplastic through exposure to a radiation source, such as electron beam exposure,[5] gamma radiation, or UV light. For example, electron beam processing is used to cross-link the C type of cross-linked polyethylene. Other types of cross-linked polyethylene are made by addition of peroxide during extruding (type A) or by addition of a cross-linking agent (e.g. vinylsilane) and a catalyst during extruding and then performing a post-extrusion curing.1

Polyethylene was cross linked for the first time in 1930 with electron beam technology. Engel cross-linking was developed in 1960's. Using vinylsilane was developed in 1986.