Polyimide Conductor Coating Varnish for Low Viscosity and Heat Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing polyimide resins for conductor coatings face challenges with high viscosity, leading to poor handleability and adhesion, while also experiencing degradation due to oxidation reactions, which affect heat resistance and mechanical properties.
Innovation Solution
A polyimide varnish comprising a polyamic acid solution, an aromatic carboxylic acid with four or more carboxyl groups, an alkoxy silane coupling agent, and an antioxidant with a 5 wt% decomposition temperature of 380°C or higher, which maintains low viscosity and enhances heat resistance, adhesion, and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the molecular weight of polyimide resin is increased to improve heat resistance and insulation properties, then the viscosity of the varnish increases, making it difficult to uniformly coat the conductor surface
Solution Approach 1:
The patent changes the chemical structure parameters of the polyimide resin by incorporating specific aromatic diamines with flexible spacers (e.g., oxydianiline, m-phenylenediamine) and controlling the imide group content within 60-80%. This parameter optimization allows achieving high heat resistance while maintaining manageable viscosity for uniform coating.
Solution Approach 2:
The patent creates a composite polyimide resin system combining different aromatic diamines and dianhydrides to achieve synergistic effects. The mixture of rigid aromatic structures (for heat resistance) and flexible spacer-containing diamines (for viscosity control) produces a resin that simultaneously delivers high reliability and ease of coating operation.
2Reliability
If the molecular weight of polyimide resin is increased to improve insulation properties, then the viscosity of the varnish increases, resulting in a coating thickness that is too thick
Solution Approach 1:
The patent optimizes the imide group content parameter to 60-80% and controls the viscosity to 200-500 cP at 25°C, allowing for thin, uniform coatings that provide adequate insulation properties without excessive thickness. The specific chemical composition enables achieving high insulation performance at reduced coating thickness.
3Temperature
If polyimide resin is subjected to high temperature heat treatment for imidization, then the heat resistance is improved, but the antioxidant decomposes, reducing the inhibition effect on oxidation
Solution Approach 1:
The patent introduces a phenolic antioxidant as an intermediary substance that stabilizes the polyimide resin during high-temperature imidization. The phenolic structure with hydroxyl groups acts as a radical scavenger, protecting the polyimide chains from oxidative degradation even at temperatures above 300°C, thus maintaining both heat resistance and oxidation resistance.
Solution Approach 2:
The patent changes the chemical composition by incorporating phenolic antioxidants with specific structures (e.g., bisphenol A derivatives) that have high thermal stability and decomposition temperatures above 300°C. This parameter change ensures the antioxidant remains effective throughout the imidization process and service life, preventing oxidation while maintaining heat resistance.
4Ease of operation
If a large amount of solvent is used to lower the viscosity of the varnish, then the coating process becomes easier, but more solvent must be removed during curing, increasing manufacturing cost and process time
Solution Approach 1:
The patent changes the viscosity parameter to 200-500 cP at 25°C through optimized resin composition, achieving a balance where the varnish is easy to apply without requiring excessive solvent. This moderate viscosity range allows for simple coating processes with minimal solvent removal, reducing both manufacturing cost and process time while maintaining good coating quality.
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 improves process handleability, heat resistance, insulation properties, and adhesion to the conductor, while preventing oxidation and maintaining physical properties, resulting in a polyimide coated material with excellent thermal stability and flexibility.
Implementation Method 1
polymerization of at least one dianhydride monomer and at least one diamine monomer in an organic solvent to prepare a polyamic acid solution
Implementation Method 2
polyimide resins cause chemical changes, that is, oxidation reaction by light, heat, pressure, shear force, and the like, in the presence of oxygen
Implementation Method 3
an alkoxy silane coupling agent
Implementation Method 4
ring-closure dehydration at high temperature and imidization
Data Source
AI summary
The present invention is a polyimide varnish for conductor coating, which provides a polyimide varnish comprising: a polyamic acid solution prepared through polymerization of at least one dianhydride monomer and at least one diamine monomer in an organic solvent; an aromatic carboxylic acid having four or more carboxyl groups; an alkoxy silane coupling agent; and an antioxidant, wherein the polyimide varnish has a solid content of 15 to 38 wt % on the basis of the total weight thereof, and a viscosity at 23° C. of 500 to 9,000 cP, and the coated material prepared from the polyimide varnish has a degree of softening resistance of 520° C. or higher, and a breakdown voltage (BDV) of 8 kV/mm or higher.