Two commercial crosslinkable polyethylene insulation cable granules

used for 35 kV and 110 kV voltage insulation respectively

with the similar melting point and crosslinking temperature

were chosen as experimental samples for examining their linear dynamic responses during cross-linking.In order to detect the structure evolution of the two samples during crosslinking

dynamic time sweep test was carried out at 140℃

145℃ and 150℃ using parallel plates model with an Advanced Rheometric Expansion System.It can be found that the pre-crosslinking time decreased with the increase of crosslinking temperature for both samples during the dynamic time sweep test

but the rising rates of the dynamic viscosity (η′) and dynamic rigidity (η″) for both samples were independent of temperature.Compared with 110 kV insulation cable granules，35 kV insulation cable granules showed higher rising rate of η″

similar rising rate of η′and longer pre-crosslinking time at the same temperature during crosslinking.As a criteria of crosslinking density

the number-average molecular weight between the junction of the networks for crosslinked samples

Mc

was calculated on the basis of the rubber elasticity theory

using the data of dynamic modulus G′ obtained from plotting dynamic storage modulus (G′) versus frequency (ω) at terminal zone where ω approaches 0.The value of Mc of 35 kV insulation cable granules calculated through rheological method was lower than that of 110 kV insulation cable granules.Moreover

the Mc dependence on crosslinking time was probed through the equilibrium swelling method.The values of Mc of totally crosslinked insulation cable getting from rheological method were similar to those from equilibrium swelling method although they crosslinked at different conditions.