Cellulose Pressboard Insulation with Polyelectrolyte Additives
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Solution Overview
Problem
Cellulose-based pressboard used in electrical transformers lacks improved mechanical properties, specifically in-plane and out-of-plane stiffness and strength, which affects manufacturing and longevity, without compromising dielectric properties.
Innovation Solution
Incorporating polyvinylamine (PVAm) and polyacrylamide (PAM) additives in a combined amount of 0.01% to 20% by weight into the cellulose-based pressboard, enhancing fibre bonding and mechanical performance through layer-by-layer polyelectrolyte formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional cellulose pressboard is used, then dielectric properties are maintained, but in-plane and out-of-plane mechanical properties remain insufficient
Solution Approach 1:
The patent applies composite materials by combining cellulose fibers with polyelectrolyte additives (PVAm and PAM) to create a pressboard with enhanced mechanical properties. The polyelectrolytes form bridges between cellulose fibers, creating a composite structure that maintains dielectric properties while significantly improving in-plane tensile strength and out-of-plane compressibility resistance.
Solution Approach 2:
The patent changes the chemical parameters of the pressboard by introducing polyelectrolyte compounds that modify the fiber bonding characteristics. The addition of PVAm and PAM alters the electrochemical properties of the cellulose matrix, enabling stronger inter-fiber bonds through electrostatic interactions, thereby improving mechanical strength without compromising electrical insulation.
2Strength
If conventional cellulose pressboard is used, then ease of manufacture is maintained, but out-of-plane compressibility is insufficient
Solution Approach 1:
The patent uses polyelectrolytes as intermediary substances that mediate between cellulose fibers to create stronger bonds. These polyelectrolyte intermediaries form bridges between adjacent fibers, providing enhanced out-of-plane compressive strength while maintaining a manufacturing process that is relatively simple and compatible with existing pressboard production methods.
3Strength
If pressboard mechanical properties are improved, then bending stiffness increases, but dielectric properties may be degraded
Solution Approach 1:
The patent applies local quality by concentrating the polyelectrolyte additives at the fiber bonding interfaces rather than uniformly distributing them throughout the bulk material. This localized enhancement of fiber bonding provides improved bending stiffness and mechanical strength while maintaining the bulk dielectric properties of the cellulose matrix, as the polyelectrolytes primarily affect the inter-fiber regions.
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 addition of PVAm and PAM significantly increases in-plane tensile strength and reduces out-of-plane compressibility, resulting in improved mechanical performance and stability of pressboard components in transformers.
Implementation Method 1
mixing an amount of cationic PVAm into the pulp, mixing an amount of anionic PAM into the pulp
Data Source
Figure 1~2
AI summary
The present invention relates to a cellulose based pressboard for insulation in an electrical power transformer. The pressboard comprises polyvinylamine (PVAm), and polyacrylamide (PAM), in a combined amount of between 0.01% and 20% by weight of the pressboard. The invention also relates to the use of such a pressboard as insulation in a power transformer, to a power transformer comprising such pressboard, as well as to a method of producing the pressboard.