Power Cable Insulation Resin With Silane-Treated MgO Filler
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Solution Overview
Problem
DC power cables experience deterioration in DC characteristics due to temperature changes, primarily attributed to the low adhesiveness of inorganic fillers in the insulating layer, leading to thermal stress and subsequent space charge accumulation.
Innovation Solution
A resin composition comprising a polyolefin base resin, a modified polyolefin with grafted polar groups, and magnesium oxide inorganic filler surface-treated with a silane coupling agent, ensuring a remaining rate of 50% or more in a fractured frozen surface, and a content of 0.1 to 5 parts by mass of the filler per 100 parts of resin, which improves adhesiveness and space charge trapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic filler is added to suppress space charge accumulation, then DC characteristics are improved, but adhesiveness between filler and resin deteriorates under thermal stress
Solution Approach 1:
A silane coupling agent is introduced as an intermediary substance between the inorganic filler particles and the polyolefin resin. The silane coupling agent chemically bonds to both the inorganic filler surface and the polyolefin matrix, creating a strong interfacial connection that prevents filler detachment under thermal stress while maintaining space charge suppression capability
Solution Approach 2:
The invention creates a composite material system consisting of polyolefin base resin, modified polyolefin with polar groups, surface-treated inorganic filler, and silane coupling agent. This multi-component composite structure combines the space charge suppression ability of inorganic filler with the adhesive properties of silane-treated interfaces, resolving the contradiction between filler effectiveness and interfacial strength
2Reliability
If inorganic filler content is increased to improve space charge suppression, then DC breakdown field strength is enhanced, but thermal stress resistance deteriorates
Solution Approach 1:
The silane coupling agent serves as a stress-transfer intermediary that distributes thermal stresses uniformly across the filler-resin interface. This prevents stress concentration and filler particle detachment even at high filler loadings, enabling the system to maintain both high DC breakdown field strength and thermal stress resistance
Solution Approach 2:
The invention modifies the chemical and physical parameters of the filler-resin interface through silane treatment, changing the surface energy, chemical bonding characteristics, and thermal expansion compatibility. These parameter changes enable the composite to withstand thermal cycling without filler-matrix debonding, maintaining compositional stability at elevated filler contents
3Ease of manufacture
If conventional inorganic filler is used, then manufacturing is simple, but adhesiveness under thermal cycling deteriorates
Solution Approach 1:
The silane coupling agent is incorporated into the existing extrusion manufacturing process as an additional compound in the resin composition. The filler is pre-treated with silane during mixing, and the entire composite is extruded in one step, maintaining manufacturing simplicity while dramatically improving thermal cycling adhesion through the intermediary coupling mechanism
Solution Approach 2:
The silane surface treatment of the inorganic filler is performed in advance during the compound preparation stage, before extrusion. This preliminary action ensures that the filler particles are pre-equipped with adhesive properties, eliminating the need for post-processing or complex multi-step manufacturing while guaranteeing reliable adhesion under thermal cycling conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses the deterioration of DC characteristics by maintaining high adhesiveness of the inorganic filler to the base resin, even under thermal stress, thereby enhancing the insulating properties and extending the dielectric breakdown time in the DC power cable.
Implementation Method 1
an inorganic filler including magnesium oxide and surface-treated with a silane coupling agent
Implementation Method 2
a modified polyolefin obtained by grafting a polar group onto a polyolefin
Implementation Method 3
an inorganic filler having polarity such as carbon black or magnesium oxide (MgO) is sometimes added to a resin composition constituting the insulating layer
Data Source
AI summary
A resin composition contains: a base resin including a polyolefin; a modified polyolefin obtained by grafting a polar group onto a polyolefin; and an inorganic filler including magnesium oxide and surface-treated with a silane coupling agent. A remaining rate R of the inorganic filler in a fractured frozen surface is 50% or more. The remaining rate R is calculated using the following expression (1). R=(Df/Dc)×100 . . . (1). Df represents a density of the inorganic filler remaining in a fractured surface of a sheet formed of the resin composition containing the base resin, the modified polyolefin, and the inorganic filler, when the sheet is immersed in liquid nitrogen for 1 hour and then fractured. Dc represents a reference density of the inorganic filler detected in a cut surface of the sheet formed of the resin composition, when the sheet is cut at 24° C. using a focused ion beam without being frozen.