Curable Ion-Exchange Membrane for Thin-Film Strength and Hydrolysis Resistance
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Solution Overview
Problem
The production of ion exchange membranes faces challenges in achieving thin membranes with minimal defects, good permselectivity, low electrical resistance, strength, flexibility, and resistance to chemicals, while also requiring cost-effective and scalable production processes.
Innovation Solution
A curable composition comprising 2.5 to 50 wt% crosslinker with two acrylamide groups, 12 to 65 wt% curable ionic compound, 10 to 70 wt% solvent, and 0 to 10 wt% free radical initiator, with a non-curable salt, is used to create membranes with improved storage stability, permselectivity, and resistance to hydrolysis, allowing for continuous and inexpensive mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thin membranes are produced to improve ion transport efficiency, then permselectivity and electrical resistance improve, but mechanical strength and flexibility deteriorate
Solution Approach 1:
The patent uses a composite structure consisting of a thin active ion-exchange layer supported on a porous substrate. This composite design allows the active layer to be extremely thin (micrometer or sub-micrometer scale) for optimal ion transport, while the porous substrate provides the necessary mechanical strength and flexibility. The support structure carries the thin layer without significantly impeding ion permeation, thus resolving the contradiction between thinness and strength.
Solution Approach 2:
The patent employs thin film technology to create the active ion-exchange layer with controlled thickness in the micrometer or sub-micrometer range. This thin film approach maximizes ion transport efficiency and permselectivity while the film is deposited on a flexible porous support that maintains mechanical integrity and flexibility, allowing the membrane to be wound into tight circumferential structures.
2Manufacturing precision
If membrane thickness is reduced to improve ion transport, then electrical resistance decreases, but manufacturing defects increase
Solution Approach 1:
The patent prepares a porous support structure before depositing the thin active layer. This preliminary preparation provides a stable foundation that guides uniform deposition of the thin ion-exchange layer, preventing defects such as pinholes or uneven thickness. The support structure is pre-treated or pre-formed to ensure optimal adhesion and uniformity of the subsequent thin layer, thereby reducing manufacturing defects.
Solution Approach 2:
The patent creates a structure where different regions have different functions: the porous substrate provides mechanical support and structural stability, while the thin active layer provides ion-exchange functionality. This local differentiation of quality allows the thin layer to be optimized for ion transport without compromising overall reliability, as the substrate compensates for potential weaknesses in the thin layer.
3Strength
If crosslinking density is increased to improve membrane strength, then mechanical strength improves, but flexibility and resistance to hydrolysis may deteriorate
Solution Approach 1:
The patent optimizes the crosslinking density within a specific range (2.5 to 50 wt% crosslinker) to achieve the desired balance between strength and hydrolysis resistance. By carefully controlling the crosslinking parameters and using appropriate crosslinking agents with two acrylamide groups, the membrane achieves sufficient mechanical strength while maintaining flexibility and resistance to hydrolysis through proper composition formulation.
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 resulting membranes exhibit good permselectivity, resistance to hydrolysis, and low electrical resistance, with enhanced burst strength and flexibility, enabling their use in various applications such as water purification and electricity generation while being cost-effective to manufacture.
Implementation Method 1
A curable composition comprising 2.5 to 50 wt% crosslinker with two acrylamide groups, 12 to 65 wt% curable ionic compound, 10 to 70 wt% solvent, and 0 to 10 wt% free radical initiator
Implementation Method 2
2.5 to 50 wt% crosslinker with two acrylamide groups
Data Source
AI summary
A device selected from the group consisting of an electrodialysis or reverse electrodialysis unit, an electrodeionization module and a flow through capacitor, the device comprising a membrane obtained from a process comprising the following steps: applying a curable composition to a support; and curing the composition to form a membrane; wherein the curable composition comprises:(i) 2.5 to 50 wt % crosslinker comprising at least two acrylamide groups;(ii) 12 to 65 wt % curable ionic compound comprising an ethylenically unsaturated group and a cationic group;(iii) 10 to 70 wt % solvent;(iv) 0 to 10 wt % of free radical initiator; and(v) non-curable salt comprising a cation and an anion, wherein the anion is not sulfate; wherein the molar ratio of (i):ii) is greater than 0.10 and less than 5.