Ionization and electrophoretic migration of the crosslinking byproducts in low-density polyethylene

Crosslinked polyethylene (XLPE) -the main material used in high voltage cable- is made by the crosslinking of low-density polyethylene (LDPE). It has been reported that space charge aggregates in XLPE can give rise to the local electric fields leading to early failure of the dielectric. The main source of space charge aggregates is crosslinking byproducts such as acetophenone. Acetophenone ionization in an electric field produces charged species. The electrophoretic migration of the charges alters the local electric field. The scope of this study is to determine the electrophoretic transport in polyethylene.
LDPE films were placed in a fixture with acetophenone on top. Positive and negative polling was applied to the fixture. Then, the samples characterized by IR spectroscopy mapping to determine migration extent of any charged species.
Early results showed more penetration of acetophenone into the LDPE when the positive electrode was on the acetophenone side. This suggests that acetophenone ionization and electrophoretic transport of the ions enhance acetophenone penetration.
Ionization of the crosslinking byproducts and subsequent electrophoretic migration of the charges may be one reason for high local electric fields and ultimate dielectric failure.