Unsaturated Polyester Resin Impregnation for Electrical Windings
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Solution Overview
Problem
Existing impregnating, potting, and coating compounds for electrical components, particularly those using unsaturated polyester resins, face challenges with reaction shrinkage during curing, leading to cracks in thick layers, and require reactive diluents that pose ecological and toxicological concerns.
Innovation Solution
A resin formulation comprising 80-99% unsaturated polyester resin with dihydrodicyclopentadiene structural units and 1-20% polybutadiene, along with emulsion-stabilizing additives and curing accelerators, forming a two-phase system that cures without cracks and exhibits excellent electrical, thermal, and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If unsaturated polyester resin is used for impregnating electrical windings, then good electrical insulation and thermal stability are achieved, but reaction shrinkage during curing causes cracks in thick layers
Solution Approach 1:
The patent combines unsaturated polyester resin with polybutadiene rubber to create a composite impregnating compound. The polybutadiene acts as a flexible modifier that compensates for the shrinkage stresses during curing, preventing crack formation while maintaining the electrical insulation properties of the polyester resin base system.
Solution Approach 2:
The patent modifies the chemical composition parameters of the impregnating compound by incorporating polybutadiene at specific concentrations (5-20 parts by weight per 100 parts polyester resin). This parameter change alters the curing behavior and shrinkage characteristics of the resin system, enabling thick layer application without cracks.
2Ease of operation
If reactive diluents such as styrene are added to unsaturated polyester resin, then viscosity is reduced and ease of application is improved, but ecological and toxicological problems arise requiring special emission control measures
Solution Approach 1:
The patent replaces traditional reactive diluents like styrene with polybutadiene, changing the chemical composition parameters. This substitution maintains the necessary fluidity and application characteristics while eliminating the harmful emissions and toxicological issues associated with styrene and similar monomers.
Solution Approach 2:
The patent uses polybutadiene as a non-volatile, environmentally friendly alternative to volatile reactive diluents. This substitution eliminates the need for complex emission control infrastructure while maintaining proper impregnation properties.
3Area of stationary object
If thick layers are applied to accommodate large generator and motor windings, then complete coverage is achieved, but cracks form during curing due to reaction shrinkage
Solution Approach 1:
The patent creates a composite system where polybutadiene rubber particles are dispersed in the polyester resin matrix. This composite structure provides the flexibility needed to accommodate shrinkage stresses in thick layers, enabling complete coverage of large generator and motor windings without crack formation.
Solution Approach 2:
The polybutadiene additive acts as a pre-built cushioning element within the resin system, providing built-in stress relief capacity before curing begins. This allows the thick impregnating layer to withstand shrinkage forces during curing without developing cracks.
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 formulation provides crack-resistant, thermally stable coatings suitable for large electrical machines, with stable properties in both storage and cured states, and can be used for insulating equipment like motors and transformers without the need for reactive diluents.
Implementation Method 1
a two-phase system of an unsaturated polyester resin and a polybutadiene resin that is incompatible with it—that is, not homogeneously miscible with the polyester resin in any proportion—cures without cracks
Implementation Method 2
0 to 5.0% by weight of one or more curing accelerators as component D
Data Source
AI summary
The invention relates to a resin formulation containing a) 80 to 99 wt % of at least one unsaturated polyester resin or a mixture of an unsaturated polyester resin and a further resin as component A; b) 1 to 20 wt % of at least one polybutadiene as component B; c) 0 to 5.0 wt % of one or more emulsion stabilizing additives as component C; d) 0 to 5.0 wt % of one or more curing accelerators as component D, wherein the sum of the components A to D is 100 wt %.