Polyimide Nanoweb Surface Amidization for Hydrolytic Stability
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Solution Overview
Problem
Polyimides are hydrolytically unstable above 100 °C and require specialized adhesives for substrate adhesion, limiting their applications, and there is a need to modify their surface chemistry for improved compatibility and chemical resistance while maintaining porosity.
Innovation Solution
Aromatic polyimide nanowebs with amide-modified surfaces are created by contacting the nanowebs with a primary amine solution, altering the surface chemistry to enhance compatibility, reduce chemical attack, and retain porosity, suitable for filtration and battery separator applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyimide nanowebs are used as filtration media or battery separators, then they provide strength, chemical inertness, and thermal stability, but they exhibit hydrolytic instability above 100 °C and require specialized adhesives for substrate adhesion
Solution Approach 1:
The patent applies surface modification only to the outer surface of the polyimide nanoweb, leaving the bulk material properties unchanged. The amide-modified surface layer provides enhanced chemical resistance and hydrophobicity, while the interior polyimide structure maintains its inherent thermal stability and mechanical strength. This localized modification resolves the contradiction by protecting the material from hydrolysis without compromising its reliable bulk properties.
Solution Approach 2:
The patent creates a composite structure where an amide-modified surface layer is formed on the polyimide nanoweb. This composite combines the hydrolytic resistance and hydrophobicity of amide groups with the thermal stability and mechanical strength of polyimide, resolving the contradiction between chemical inertness and hydrolytic instability.
2Reliability
If the surface chemistry of aromatic polyimide nanowebs is modified to improve compatibility and chemical resistance, then chemical inertness and hydrophobicity are enhanced, but the porosity of the nanoweb structure may be compromised
Solution Approach 1:
The surface modification is applied locally to the outer surface of the nanoweb fibers, creating a thin amide-modified layer that does not penetrate deeply into the fiber structure. This localized approach enhances chemical resistance at the surface while preserving the internal porosity and pore structure necessary for filtration and battery separator functions.
Solution Approach 2:
The patent maintains the porous nanoweb structure by ensuring that the surface modification process does not block or significantly reduce the pore openings. The amide modification occurs on the fiber surface while leaving the inter-fiber porosity intact, thus achieving chemical resistance without compromising the essential porosity for fluid and ion transport.
3Strength
If polyimide films are adhered to substrates such as epoxies, then structural integrity is achieved, but specialized adhesives are required between the layers
Solution Approach 1:
The patent changes the surface chemistry parameters of the polyimide nanoweb by introducing amide functional groups. This chemical modification alters the surface energy and functional group composition, enabling direct adhesion to substrates like epoxies without requiring specialized adhesive formulations. The amide groups provide reactive sites that can form bonds with substrate materials, simplifying the overall structure by eliminating the need for separate adhesive layers.
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 surface-modified aromatic polyimide nanowebs exhibit enhanced chemical resistance, improved compatibility, and maintained porosity, effectively functioning as filtration media and battery separators, particularly in lithium-ion batteries, with improved hydrophobicity and reduced swelling in humid environments.
Implementation Method 1
contacting an aromatic polyimide nanoweb with a solution of a primary amine... wherein said primary amine comprises a functional group comprising a hydrocarbyl radical... said nanoweb having a free surface area at least a portion of which comprises a secondary amide
Implementation Method 2
causing a mixture of a solid and a fluid to wettably impinge upon the surface of a surface modified polyimide nanoweb in such manner that a fluid-rich portion of said mixture is transported through said surface-modified polyimide nanoweb
Implementation Method 3
said functional group comprising a hydrocarbyl radical... improved hydrophobicity and reduced swelling in humid environments
Data Source
AI summary
The present invention is directed to the preparation and use of aromatic polyimide nanowebs with amide-modified surfaces. Uses include as a filtration medium, and as a separator in batteries, particularly lithium-ion batteries. The invention is also directed to a filtration apparatus comprising the aromatic polyimide nanoweb with amide-modified surface. The invention is further directed to a multi-layer article comprising the aromatic polyimide nanoweb with amide-modified surface, and to an electrochemical cell comprising the multi-layer article.