4 / 2022-02-16 14:45:10

Effect of POE Content on Properties of Polypropylene based Semiconductive Shielding Material for Cable

carbon black; polypropylene; polyolefin elastomer; volume resistivity; space charges

Purpose/Aim

At present, cross-linked polyethylene (XLPE) cables face the problem of being difficult to handle after their life is exhausted. Thermoplastic non-cross-linked cable materials meet the requirements of green development. and the research and development of non crosslinked shielding materials also need to follow up. In this paper, PP/POE is used as the matrix resin and carbon black is added as conductive filler to prepare different Semi-conductive shielding material with POE ratio. The volume resistivity at different temperatures, the thermal conductivity and thermal diffusivity of the material, the crystallization and thermal properties of semiconducting materials, the space charge properties of semiconducting materials and the tensile properties of the samples were measured.

Experimental/Modeling methods

The polypropylene used is produced by Yanshan Petrochemical, the brand is K8303. The ethylene-octene copolymer elastomer is produced by Exxon Mobil Corporation, the brand is POE8201, and the conductive carbon black is Cabot Carbon Black Vxc72 (particle size 30nm). All materials were dried in a vacuum oven for 8 hours to remove the influence of moisture absorption. The materials were blended in different proportions into the torque rheometer. The processing temperature was 190 ºC and the speed was 40 rpm. After blending for 15 minutes, take out the hot-press setting for subsequent testing.

Results/discussion

The higher the POE content, the stronger the tensile performance but the greater the decrease in the elastic modulus. The effect of POE content on space charge suppression appears to be that high POE content will reduce the average spacing of carbon black particles, and low POE content will cause carbon black to agglomerate and increase the particle size, which is not conducive to space charge suppression.

Conclusions

Some conclusions can be drawn that high content of POE will hinder the crystallization of PP and reduce the crystallization temperature and crystallinity of PP. With the increase of the POE content, the thermal diffusivity of the sample decreases and the thermal conductivity increases, which is not conducive to the operation and production of the cable, so it is necessary to control the POE content to an appropriate ratio.