408 / 2022-03-15 20:46:23

Effect and mechanism of hindered phenol antioxidants on crosslinking characteristics of XLPE insulating materials

cable,antioxidant,crosslinked polyethylene,crosslinking characteristics,molecular simulation

Purpose

Hindered phenol antioxidants are added to cable insulating materials to prevent the low-temperature crosslinking that seriously threatens the extrusion processing and molding precision of insulation, but antioxidants will decrease the crosslinking efficiency and degree, which is not conducive to maintaining the excellent mechanical and thermal properties.

Experiment and simulation methods

Four kinds of cable insulating materials with different antioxidants are prepared. The crosslinking characteristics of insulating materials are measured by electromagnetic rheometer (MCR302, Anton Paar) under 140 ℃. Besides, bond dissociation energy (BDE) and molecular orbitals of antioxidants are calculated by using DMol3 module in Material Studio (Accelrys, Inc.).

Results

As shown in Fig. 1, S300 has the best properties of hindering low-temperature crosslinking and S1010 has the best properties of crosslinking efficiency and degree comparing with other insulating materials. But comprehensively considering the requirements of crosslinking characteristics of insulating materials used in cables, antioxidant 245 is the better choice.

Conclusions

The crosslinking characteristics of insulating materials are closely related to molecular structure of antioxidants, including functional group, substituent and molecular weight. Antioxidant 300 has phenolic hydroxyl of quite low BED and thioether group, which effectively inhibits low-temperature crosslinking but consumes too much DCP, leading to low crosslinking efficiency and degree. Antioxidant 245 has one phenolic hydroxyl of lower BED, which can both restrain low-temperature crosslinking and maintain higher crosslinking efficiency and degree.

Appendix