Evaluation of Recycling Technology of Insulation of Cross-linked Polyethylene Insulated Cable using Supercritical Alcohol

Abstract

The waste of cross-linked polyethylene is burned as fuel or buried in the ground. But material recycling is more and more important for the environment in these days. But the material recycling of the cross-linked polyethylene is difficult because the processability is too low because of the cross-linking element.In this study, we successfully obtained thermoplastic recycled polyethylene from silane cross-linked polyethylene by using chemical reaction which can decompose the cross-linking element selectively in supercritical alcohol. The chemical reaction is shown in Fig. 1. Siloxane bond was decomposed by supercritical alcohol and turn to be the alcoxy silane. The new continuous process using twin screw extruder was constructed for the development of the mass production technology for the recycling of silane cross-linked PE. The new continuous process for supercritical alcohol is shown in Fig. 2.The recycled PE was successfully made by the continuous process as shown in Fig. 3. The results of the tensile tests and the measurement of the dielectric loss and volume resistivity of the recycled PE satisfied the requirement of the cable insulation. Then we made the recycled wire made frome recycled PE. The properties of recycled PE wire show that the recycled PE can be recycled as the insulation of 600 V polyethylene wire.These results indicate that the cable to cable and wire to wire recycling of silane cross-linked polyethylene will possibly be accomplished by supercritical technology using extruder.Moreover the environmental effect of this technology was evaluated by the amount of the carbon dioxide generated from the continuous process. These results indicate that recycling method using supercritical alcohol must be useful for the reduction of the environmental influence.

Selective decomposition of the siloxane bond constituting the crosslinking element of silane‐crosslinked polyethylene by supercritical alcohol

“…5,6 For this reason, supercritical fluid was applied to the recycling of silane-XLPE, which is a hydrophobic polymer. [7][8][9] The general problem of treating polymer waste by a supercritical fluid is the chemical process for com-mercialization. To solve this problem, we propose a continuous process for the treatment of XLPE by supercritical methanol.…”

“…The general problem of treating polymer waste by a supercritical fluid is the chemical process for commercialization. To solve this problem, we propose a continuous process for the treatment of XLPE by supercritical methanol 10–12. This means that the process for the industrialization of this technique will appear.…”

Use of Single-Screw Extruder for Continuous Silane Cross-Linked Polyethylene Recycling Process Using Supercritical Alcohol

“…These results were the same as those for the product obtained using the twin-screw extruder. 1,12 Despite the fluctuation of pressure, as shown in Figure 4, the samples exhibit uniform properties; this indicates that this level of fluctuation does not affect the properties of the product. It also indicates that the process represented here is sufficiently stable to use for recycling silane-XLPE.…”

“…These results reveal the potential of recycling silane-XLPE for either cable-to-cable or wire-to-wire applications. 11,12 Moreover, this reveals the potential of extruders as a solution for the development of a continuous supercritical fluid process to treat solid materials. As an additional advantage, the energy consumption of this method is less than that of other current recycling technologies.…”

“…A potential solution is the use of extruders, which can be applied as the feeder and reactor of the continuous process for the reaction of silane-XLPE in supercritical alcohol. , Accordingly, a continuous process to feed solid materials such as silane-XLPE into supercritical alcohol was developed in order to commercialize this technique. This process automatically generates a pellet of recycled PE from waste silane-XLPE .…”