Three-Layer Porous Polyimide Membrane for High Permeability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional porous polyimide membranes lack high porosity, material permeability, and strength while being susceptible to compression stress, and existing production processes are inefficient.
Innovation Solution
A three-layer structured porous polyimide membrane with macrovoids and a specific production process involving a polyamic acid solution composition cast into a film shape, followed by coagulation and thermal treatment to achieve imidation, resulting in a membrane with high porosity, excellent air permeability, and enhanced strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional porous polyimide membranes are used, then they have basic membrane structure, but they lack high porosity and material permeability
Solution Approach 1:
The membrane is divided into three distinct layers: two surface layers and a central macrovoid layer. This segmentation allows each layer to have optimized properties - the surface layers provide structural integrity while the central macrovoid layer provides high porosity (70-95%) and material permeability, resolving the contradiction between achieving high porosity and maintaining controllable membrane structure
Solution Approach 2:
Different regions of the membrane have different properties tailored to specific functions. The surface layers have lower porosity for strength and stability, while the central macrovoid layer has high porosity for material permeability. This local differentiation allows the membrane to achieve high overall porosity while maintaining structural control during manufacture
2Quantity of substance
If high porosity is achieved in porous polyimide membranes, then material permeability improves, but strength and resistance to compression stress deteriorate
Solution Approach 1:
The membrane is divided into two functional zones: surface layers with lower porosity that provide structural strength and support, and a central macrovoid layer with high porosity (70-95%) that provides material permeability. This segmentation allows the high-porosity region to perform permeation while the stronger surface layers maintain overall membrane strength and compression resistance
Solution Approach 2:
The membrane combines different polyimide compositions in different layers. The surface layers use polyimide compositions optimized for mechanical strength, while the central macrovoid layer uses polyimide compositions optimized for porosity and permeability. This composite structure resolves the contradiction between high porosity and strength by distributing these properties across different material regions
3Quantity of substance
If porous structure is created for filtration, then permeability improves, but smoothness of surfaces deteriorates
Solution Approach 1:
The membrane structure is segmented into surface layers and a central macrovoid layer. The surface layers are designed with controlled porosity and smooth surfaces, while the central layer contains the macrovoids for high material permeability. This segmentation allows the surface layers to maintain smoothness for filtration applications while the internal macrovoid layer provides enhanced permeability
Solution Approach 2:
The smooth surface property is localized to the surface layers where it is needed for filtration and handling, while the high porosity and material permeability are localized to the central macrovoid layer. This spatial distribution of properties resolves the contradiction between surface smoothness and bulk permeability
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 high porosity, excellent air permeability, and improved strength, with a symmetric structure and ladder-like surface layers that provide offset yield strength against compression stress, making it suitable for various applications.
Implementation Method 1
dipping the film in or bringing it into contact with a coagulating solvent containing water as an essential component to fabricate a porous membrane of a polyamic acid
Implementation Method 2
a step of thermally treating the porous membrane of a polyamic acid obtained in the foregoing step to achieve imidation
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3~4
AI summary
Disclosed is a porous polyimide membrane of a three-layer structure having two surface layers (a) and (b) and a macrovoid layer interposed between the surface, layers (a) and (b), herein the macrovoid layer has a partition wall joined to the surface layers (a) and (b) and plural macrovoids surrounded by the partition wall and the surface layers (a) and (b), with an average void diameter in a membrane plane direction of from 10 to 500 µm; each of the partition wall of the macrovoid layer and the surface layers (a) and (b) has a thickness of from 0.1 to 50 µm and has plural pores having an average pore diameter of from 0.01 to 5 µm, the pores being communicated with each other and also communicated with the macrovoids; and the membrane has a total membrane thickness of from 5 to 500 µm and a porosity of from 70 to 95%.