Cation-Exchange Membrane Mechanical Strength via Composite Support
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Solution Overview
Problem
Conventional ion-exchange membranes face challenges in achieving high mechanical strength, chemical resistance, and low production costs while maintaining effective ion exchange capacity and conductivity, due to issues with brittleness, phase separation, and increased complexity in manufacturing processes.
Innovation Solution
A styrene-tert-butylstyrene cation-exchange composite membrane is developed, incorporating an olefin additive, a plasticizer, and a polyvinyl halide polymer, which is impregnated into a fabric support and polymerized with a crosslinking agent and initiator, followed by sulfonation to introduce a cation-exchange group, resulting in a membrane with improved mechanical and chemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bulk polymerization is performed using vinylbenzene-divinylbenzene monomer alone, then ion exchange capacity is achieved, but brittleness increases and mechanical properties are lowered
Solution Approach 1:
The patent uses a composite system consisting of vinylbenzene-divinylbenzene copolymer as the base membrane material and incorporates it into a porous support structure. This composite approach allows the membrane to maintain ion exchange capacity while the support provides mechanical strength and reduces brittleness.
Solution Approach 2:
The patent applies different properties to different parts of the membrane system: the vinylbenzene-divinylbenzene copolymer layer provides ion exchange functionality, while the porous support structure provides mechanical strength. This local differentiation of functions resolves the contradiction between ion exchange capacity and mechanical properties.
2Ease of manufacture
If latex method is used to prepare membrane, then manufacturing process is simplified, but mechanical properties and electrochemical characteristics are reduced due to emulsifier remaining
Solution Approach 1:
The patent extracts and removes the harmful emulsifier residues from the latex polymerization process by using a porous support structure that allows washing and purification. The membrane is prepared by immersing the support in latex solution, then thoroughly washed to remove emulsifiers, thereby maintaining ease of manufacture while improving mechanical and electrochemical properties.
3Strength
If paste method is used to improve mechanical properties, then mechanical and electrochemical properties are superior, but process complexity increases and production cost rises
Solution Approach 1:
The patent segments the membrane preparation process into distinct steps: (1) preparing vinylbenzene-divinylbenzene copolymer latex, (2) immersing porous support in the latex solution, (3) drying, and (4) crosslinking. This segmentation simplifies the overall process compared to traditional paste methods while maintaining superior mechanical and electrochemical properties.
4Reliability
If conventional membrane preparation methods are used, then ion exchange function is achieved, but chemical resistance is reduced and membrane is easily broken during drying
Solution Approach 1:
The patent applies preliminary crosslinking treatment to the vinylbenzene-divinylbenzene copolymer membrane before drying and subsequent use. This preliminary action of crosslinking strengthens the membrane structure, improving chemical resistance and preventing breakage during drying and handling, while preserving ion exchange functionality.
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 membrane exhibits low electrical resistance, excellent ion exchange capability, ionic conductivity, and enhanced mechanical properties, with reduced brittleness and production costs, allowing for easier regulation of ion exchange capacity and conductivity.
Implementation Method 1
polymerized with a crosslinking agent and initiator
Implementation Method 2
followed by sulfonation to introduce a cation-exchange group
Implementation Method 3
incorporating an olefin additive, a plasticizer, and a polyvinyl halide polymer
Implementation Method 4
a polyvinyl halide polymer, which is impregnated into a fabric support
Data Source
AI summary
The present invention provides a cation-exchange composite membrane comprising a copolymer containing a styrene repeating unit introduced with a sulfonation group, a tert-butylstyrene repeating unit and a crosslink repeating unit, an olefin additive, a plasticizer and a polyvinyl halide polymer. The cation-exchange composite membrane comprising a copolymer containing a styrene repeating unit introduced with a sulfonation group, a tert-butylstyrene repeating unit and a crosslink repeating unit, an olefin additive, a plasticizer and a polyvinyl halide polymer of the present invention not only displays low electrical resistance, excellent ion exchange capability, excellent ionic conductivity, excellent mechanical properties, excellent chemical properties, and processability, but also is easy to regulate its ion exchange ability and ionic conductivity. Also, the composite membrane of the invention is easier to produce and cheaper to manufacture than the conventional cation-exchange composite membrane.