Physico-chemical characterization of the blooming of Irganox 1076® antioxidant onto the surface of a silane-crosslinked polyethylene

Abstract

This study aims at investigating the blooming of Irganox 1076® onto the surface of a silane-crosslinked polyethylene. Preliminary studies on the commercial Irganox 1076® powder enabled to identify its crystalline structure and determine its main physico-chemical properties (characteristic IR absorption bands, melting properties, etc.). Then, the behaviour of Irganox 1076® in silane-grafted polyethylene was studied. Several films containing a concentration of Irganox 1076® ranged between 0.1 wt% and 2.1 wt% were characterized with FTIR spectroscopy and DSC. A peculiar attention was paid to the phase separation within the polymer bulk and the blooming of the antioxidant onto the polymer film surface. Then, this methodology was transposed to an industrial silane-crosslinked polyethylene containing at least 1 wt% of Irganox 1076® as in-service protective antioxidant. For this latter, optical microscopy was of great help for monitoring the blooming of Irganox 1076® onto the polymer film surface. In addition, the polymorphism phenomenon of Irganox 1076® was revealed by FTIR spectroscopy and DSC after thermal treatment at 70 C under vacuum.

Ageing Assessment of XLPE LV Cables for Nuclear Applications Through Physico-Chemical and Electrical Measurements

“…These new bands could be assigned to different crystalline structures of antioxidants formed on the insulation surface. This phenomenon called polymorphism have already been observed in literature for several phenol antioxidants [7], [38].…”

“…Such an exudation process was already evidenced during the thermal treatment at moderate temperature (typically 70 • C) of model XLPE samples stabilized with a phenol antioxidant [7]. As shown by these authors, the reorganization of antioxidant molecules in different forms (dissociated or crystalline structures) results in the appearance of new IR absorption bands of antioxidants.…”

“…However, in service, these additives can be consumed by specific chemical reactions [3], [4] and leave the insulation by migration, i.e. by diffusing through the insulating layer, then crossing its outer surface to reach the outside environment [5]- [7].…”

Thermal ageing of a silane-crosslinked polyethylene stabilised with a thiodipropionate antioxidant

“…In addition, films of about 100 mm thick of Si-g-LLDPE with concentrations of DSTDP ranging from 0 wt% to 1.5 wt% were produced by compression moulding at 150 C for 4 min, i.e. according to the same experimental protocol described in a previous article [18]. The DSTDP powder used to prepare these films was supplied by Sigma Aldrich.…”

“…0 wt% of DSTDP) was also aged under the same exposure conditions as control sample. It should be mentioned that this sample contains a very small amount (about 0.1 wt%) of storage antioxidants, mainly BHT and Irganox 1076 [18].…”