Recyclable power cable comprising a blend of slow-crystallized polyethylenes

Abstract

Crosslinked polyethylene (XLPE) has a successful history as a cable insulation material. Nevertheless, in recent years, as environmental awareness has grown, concerns about the ease with which it can be recycled have emerged. Although technologies have been developed for XLPE recycling, this report concentrates instead on the development of a thermoplastic alternative. Specifically, a 20 : 80 blend of high density and low density polyethylene (HDPE : LDPE) was selected and subjected to a non-isothermal crystallization procedure. It was found that, provided the cooling rate falls between 0.5 and 10 K min -1 , the blend exhibits superior breakdown strengths and high temperature mechanical stiffness compared to XLPE. A trial cable was then extruded from this blend using such a cooling rate. The breakdown behavior of the morphologically-designed cable was finally compared with that of LDPE and XLPE reference systems.

Thermoplastic cable insulation comprising a blend of isotactic polypropylene and a propylene-ethylene copolymer

“…Thin film samples were prepared between aluminium foils in accordance with the procedure described elsewhere [4]. Following initial pressing, the samples were either crystallized by quenching or by being subjected to the required controlled cooling program in the hot-stage.…”

“…For dynamic mechanical thermal analysis (DMTA), plaque samples measuring 40 mm by 4 mm by 1.7 mm thick were prepared and analyzed using a Rheometrics RSA II DMTA, as described previously [4]. Melting traces were obtained from selected samples using a Perkin Elmer DSC7 differential scanning calorimeter using standard procedures [4].…”

“…In a previous paper [4], we discussed the practical manufacture of a cable employing insulation based upon a 20 wt:80wt blend of high density (HDPE) and low density polyethylene (LDPE). In comparison with XLPE, this system exhibited both an enhanced AC ramp breakdown strength over a wide temperature range and a reduction in the rate at which the mechanical modulus decreased with increasing temperature.…”

Thermoplastic high performance cable insulation systems for flexible system operation

“…Complete details of these procedures are provided elsewhere [5,6]. Mini-cable, with a nominal insulation thickness of 4 mm, was manufactured on a Troester triple extrusion line using a 7-stranded aluminium conductor of cross-sectional area 25 mm 2 .…”

“…For HDPE/LDPE blends of the composition specified above, an isothermal crystallization temperature (T c ) window (113 -119 ˚C) exists in which material with enhanced properties are formed [5]. These properties stem from a twostage crystallization process that generates a space-filling array of lamellar crystals composed primarily of HDPE; such a morphology is shown in Fig.…”