Research on the properties of water-tree in PP/POE composites for cable insulation

In order to investigate the water tree characteristics of polypropylene/elastomer composites with different elastomer contents, water tree accelerated aging experiments were carried out in this paper using the water needle electrode method. The water tree morphology as well as the phase structure of the specimens were observed using polarized light microscope and scanning electron microscope, respectively. The stress-strain characteristics of the materials were investigated by a universal testing machine. The differences between the groups in the samples before and after the water tree accelerated aging experiment were examined using microscopic infrared spectroscopy. The results showed that the modulus of elasticity of the specimens decreased as the POE content increased, leading to an increase in the water tree initiation rate. The sample's after water tree aging experiment can be divided into water tree zone and non water tree zone, in which carboxyl groups will appear in the water tree zone, indicating that oxidation reaction will occur in the water tree channel to generate carboxylic acid, which will lead to the formation of carboxylate salt or carboxylate salt dimer with stronger hydrophilicity, thus improving the hydrophilicity of the water tree channel, and the diffusion of the salt solution will be more rapid, which will promote the growth of the water tree.