The silane crosslinking method includes two processes of grafting and crosslinking. The grafting reaction is that the initiator is thermally decomposed to capture the hydrogen atoms in the polyethylene molecule, and the silane crosslinking agent is grafted to the main chain of the polyethylene molecule; the crosslinking reaction is that under the action of warm water and a catalyst, the polymer undergoes a condensation reaction to form cross-linked.
Silane Crosslinking LSZH insulation material has high volume resistivity, low dielectric loss, good heat aging resistance, good environmental stress crack resistance, simple process control, easy processing, and low price, and is in a leading position in medium and low voltage cable materials.
The one-step silane-grafted polyethylene has a simple production process and low cost, but the pre-crosslinking reaction in the production process will affect the processing rheology and mechanical properties of the material.
A university has disclosed a preparation method of anti-precrosslinking one-step silane crosslinked polyethylene insulating material for medium and low voltage cables of 35kV and below.
The tensile strength of the insulating material is 14.2MPa, the elongation at break is 452%, the change rate of the thermal aging tensile strength is 17.6%, the change rate of the thermal aging elongation at break is 19.1%, and the thermal elongation rate is 89.7%. The permanent deformation rate after cooling was 4.7%, and the thermal shrinkage rate was 2.5%. The insulating material has good anti-aging effect, controllable induction time, and no pre-crosslinking during production and cross linked polyethylene uses.
Medium and low voltage overhead wires and cables need to have strong weather resistance. Aerial insulation materials have significant weather resistance at higher carbon black content. Adding high content of carbon black masterbatch and ensuring the uniform dispersion of carbon black has become the key problem to be solved.
A method for preparing a weather-resistant silane cross-linked polyethylene insulating material for overhead wires and cables is disclosed. The tensile strength of the insulating material is 27.61MPa, the elongation at break is 752.06%, the thermal shrinkage is 1%, the permanent deformation rate after thermal stretching and cooling is 5%, and the volume resistivity at 20°C is 3×10- 14Ω·m, the dielectric strength is 35MV/m, the gel content is 63%, and the maximum change rate of tensile strength is 0.9%.
The silane cross linked polyethylene xlpe insulating material has remarkable weather resistance, and at the same time has the advantages of high volume resistivity, low dielectric loss, good heat aging resistance, and good environmental stress crack resistance.