Technological characterisation of thermoshrinking cross-linked polyethylene by destructive and non-destructive techniques

The attention of the present work is focused on the characterisation of thermoshrinking cross-linked polyethylene, which is produced at the Megarad s.r.l. firm and which is mostly used as insulation for electrical cables of low and medium voltage, protection for communication cables, anti-corrosion protection for gas pipes. Two cross-linking processes: chemical (silane grafting) and electron beam irradiation are employed. The performance of the end product is verified by means of both destructive and non-destructive tests. Some parameters such as: gel fraction, modulus of elasticity at 150 °C and elongation percent are measured. Non-destructive tests are carried out by means of lock-in thermography; the variation of the phase angle with increasing the cross-linking degree is related to the variation of the modulus of elasticity. It is found that the thermographic technique is capable of giving information about material modifications arising under cross-linking and is also able to detect defects which may form during manufacturing.