Polyimide Membrane Crosslinking for Solvent Resistance and Processability
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Solution Overview
Problem
Conventional membrane separation technologies, such as those using polytetrafluoroethylene (PTFE), ceramic, or glass fiber membranes, face challenges in processability and limited application to ultrafiltration (UF) and nanofiltration (NF) due to poor solvent resistance and limited functionality beyond microfiltration (MF).
Innovation Solution
A polyimide composition comprising a dissolvable polyimide, a crosslinking agent, and a solvent is used to create a separation membrane with good solvent resistance and processability, achieved through a crosslinking process followed by a wet phase inversion method, allowing for the formation of membranes suitable for UF and NF applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional materials like PTFE, ceramic, or glass fiber are used for membrane separation, then good solvent resistance is achieved, but poor processability and limited application to only microfiltration occur
Solution Approach 1:
The invention uses a composite material system consisting of polyimide polymer matrix combined with inorganic fillers (such as ceramic particles or glass fibers). This composite structure allows the membrane to inherit the solvent resistance of inorganic materials while gaining the processability and flexibility of polymers, enabling applications beyond microfiltration into ultrafiltration and nanofiltration ranges.
Solution Approach 2:
The invention changes the physical and chemical parameters of the membrane material by controlling the molecular weight, composition, and crosslinking degree of the polyimide matrix. By adjusting these parameters, the membrane achieves both good solvent resistance and improved processability, allowing it to be processed into various configurations for different filtration applications (MF, UF, NF).
2Reliability
If conventional materials like PTFE, ceramic, or glass fiber are used for membrane separation, then good solvent resistance is achieved, but application is limited to microfiltration only
Solution Approach 1:
The polyimide-inorganic composite membrane structure enables versatile applications across multiple filtration stages. The polyimide matrix provides tunable pore sizes for UF and NF applications, while embedded inorganic particles maintain solvent resistance, expanding the material's adaptability from single-use MF to multi-stage separation processes.
Solution Approach 2:
The invention creates a universal membrane material that can serve multiple functions: it acts as a support layer for thin-film composite membranes, functions as a standalone filtration membrane for UF/NF, and maintains chemical stability for solvent-resistant applications. This multi-functionality is achieved through the synergistic combination of polyimide's flexibility and inorganic materials' stability.
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 polyimide membranes exhibit excellent solvent resistance and processability, enabling their use in UF and NF processes with improved porosity and flux, as demonstrated by the stability in solvent tests and pure water permeation flux measurements.
Implementation Method 1
A crosslinking process is performed on the polyimide composition
Implementation Method 2
A wet phase inversion process is performed on the polyimide membrane
Data Source
AI summary
A preparation method of separation membrane is provided. First, a polyimide composition including a dissolvable polyimide, a crosslinking agent and a solvent is provided. The dissolvable polyimide is represented by formula 1:wherein B is a tetravalent organic group derived from a tetracarboxylic dianhydride containing aromatic group, A is a divalent organic group derived from a diamine containing aromatic group, A′ is a divalent organic group derived from a diamine containing aromatic group and carboxylic acid group, and 0.1≤X≤0.9. The crosslinking agent is an aziridine crosslinking agent, an isocyanate crosslinking agent, an epoxy crosslinking agent, a diamine crosslinking agent, or a triamine crosslinking agent. A crosslinking process is performed on the polyimide composition. The polyimide composition which has been subjected to the crosslinking process is coated on a substrate to form a polyimide membrane. A wet phase inversion process is performed on the polyimide membrane.