Cross-Linked PE (PE-X)

Cross-linked PE

Strengths

Compared to regular PE, improved resistance to creep, stress cracking, and temperature.  Low temperature impact resistance.

Limitations

Hardness and stiffness slightly reduced. Irradiation cross-linking requires an expensive plant, peroxide cross-linking can adversely affect the electrical properties.

Typical uses

Cable covering, shrink-wrap film, heat-shrinkable tubing, pipe for domestic heating systems, rotationally molded tanks.

Compositional summary

(CH2-CH2)n with a high degree of cross-linking by one of four methods. (A) peroxide, C-C cross-links; (B) silane, C-Si-O-Si-C cross-links; (C) electron beam processing; (D) azo (nitrogen) cross-links.

Material familyPlastic (thermoplastic, semi-crystalline)
Base materialPE-X (Polyethylene, crosslinked)

Effect of composition

With increasing cross-linking density, the shear modulus increases, even at elevated temperatures. Peroxide cross-linked PE is softer and tougher than irradiation cross-linked PE.

Processing properties

Forming

Not as easy to process as L/HDPE. Very suitable for extrusion, rotational molding, and structural foam-molding. Less suited to injection molding than L/HDPE.

Machining

Very difficult to machine.

Joining

Very difficult to bond. Suitable for friction, hot plate, and ultrasonic welding. Hot gas welding difficult, radio freq. not possible.

Surface treatment

Difficult to paint.

PE-X / XLPE (cross-linked, molding)

PE-X / XLPE (cross-linked, wire and cable grade)