Acrylate Resin Impregnation for Mica-Aramid Insulating Laminates
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Solution Overview
Problem
Aramid/mica insulating sheets face issues with mica detachment due to poor mechanical strength and cohesive properties, making them difficult to laminate and impregnate effectively with resins, and existing solutions either do not penetrate deeply or are complex and costly.
Innovation Solution
A multilayer laminate structure with nonwoven backing sheets containing crystalline silicate mineral powder, an inner layer without the powder, and a coating of low-viscosity acrylate resin that penetrates deeply into the sheets, stabilizing the mica particles and improving compactness and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mica is introduced into the aramid paper structure, then resistance to partial discharge is improved, but mechanical strength and surface cohesion deteriorate
Solution Approach 1:
A polymeric binder is introduced as an intermediary substance between the mica particles and the aramid fibers. This binder acts as a bonding agent that adheres to both the mica surface and the aramid fiber surface, creating a stable composite structure where mica particles are firmly attached to the fiber network, preventing detachment while maintaining the electrical insulation properties
Solution Approach 2:
The invention creates a composite material system consisting of three components: aramid fibers providing the base structure, mica particles providing electrical insulation and partial discharge resistance, and a polymeric binder providing mechanical cohesion. This composite approach allows each component to contribute its advantageous properties while the binder ensures the structural integrity of the combined system
2Strength
If adhesive resin layer is applied to the already-formed aramid/mica paper, then surface bonding between aramid fibers and mica is improved, but penetration depth into the sheet is limited
Solution Approach 1:
The polymeric binder is incorporated into the aramid/mica paper during the paper formation process itself, before the paper is completed. This preliminary incorporation allows the binder to be distributed throughout the paper matrix and to bond mica particles to fibers as the paper structure is being built, rather than attempting to bond already-formed structures
Solution Approach 2:
The binder is not uniformly distributed throughout the entire paper thickness, but is concentrated at the interfaces between mica particles and aramid fibers where bonding is needed. This localized presence of the binder ensures effective adhesion at the critical interfaces while minimizing unnecessary material throughout the bulk of the paper
3Area of stationary object
If aramid nanofibers are used instead of microfibers, then surface area of interaction between aramid and mica is increased, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of changing the fiber dimension to the nanoscale (which would require complex nanofiber production processes), the invention changes other parameters: it uses conventional microfiber aramid with optimized dimensions and introduces a polymeric binder with specific molecular weight and functional groups. This parameter change achieves the bonding objective through chemical and physical adhesion mechanisms rather than through increased surface area alone
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 enhances the surface cohesion and compactness of aramid/mica sheets, preventing mica detachment and improving mechanical and electrical properties, facilitating their use in high-stress applications like electric motors without affecting their electrical properties.
Implementation Method 1
a coating of an impregnating resin based on acrylate derivatives which penetrates into the nonwoven backing sheet
Data Source
AI summary
The present invention relates to a multilayer laminate comprising at least three layers, wherein the two outer layers are each nonwoven backing sheet (7) containing a crystalline silicate mineral powder impregnated with a coating of an impregnating resin based on acrylate derivatives, which is suitable for increasing the compactness of the insulating sheet and for preventing the silicate mineral powder from detaching from the aramid fiber during use; the multilayer laminate having an inner layer being free of crystalline silicate mineral powder that comprises either i) heat resistant floc and binder, or ii) heat resistant polymeric film. The impregnating resin also comprises an organic solvent, which is capable of reducing the viscosity thereof and of promoting its deep penetration into the sheet. In addition, the impregnating resin comprises a UV polymerization photoinitiator which is suitable for curing the resin, only after said resin has been applied to the sheet and has penetrated deeply therein. The invention also describes the method for impregnating the insulating sheets.