Porous Membrane Bead Structure for Strength and Permeability
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Solution Overview
Problem
Current porous membranes, particularly hollow fiber membranes, face challenges with mechanical strength, water permeability, and rejection rate to impurities due to limitations in manufacturing processes like NIPS and TIPS, which result in insufficient tensile strength, low elongation at break, and compromised filtration efficiency.
Innovation Solution
A porous membrane with a bead structure formed by using a mixture solvent comprising both poor and good solvents for the polymer resin, which allows for the formation of macro voids and spherical crystallites, enhancing mechanical strength and water permeability, and a manufacturing method involving extrusion through a spinneret followed by coagulation in a non-solvent bath to create a stable porous structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a composite membrane uses a tubular braid as reinforcing member, then mechanical strength and elongation are improved, but adhesive strength between tubular braid and polymer resin film becomes weak and total thickness cannot be reduced
Solution Approach 1:
The invention extracts and removes the tubular braid reinforcing member from the composite membrane structure, transitioning to a singular membrane made entirely of polymer resin. This eliminates the adhesive strength issues and thickness constraints associated with composite structures while maintaining mechanical integrity through optimized porous morphology.
Solution Approach 2:
The invention creates a composite structure at the micro-scale by forming a porous structure within the polymer resin, where the porous morphology itself provides mechanical reinforcement. The interlocking porous network acts as an internal reinforcing mechanism without requiring external structural members.
2Strength
If TIPS method is used to manufacture singular membrane, then mechanical strength is improved, but energy consumption and manufacturing cost increase due to high temperature process
Solution Approach 1:
The invention changes the manufacturing parameters by using NIPS (non-solvent induced phase separation) instead of TIPS (thermal induced phase separation). This allows the membrane to be formed at lower temperatures by utilizing solvent non-solvent interactions, thereby reducing energy consumption while maintaining the desired porous structure and mechanical properties.
Solution Approach 2:
The invention utilizes phase transition during the phase separation process to create the porous structure. By controlling the phase transition from homogeneous solution to heterogeneous porous structure through solvent selection and composition, the membrane achieves mechanical strength without requiring high temperature processing.
3Use of energy by moving object
If NIPS method is used to manufacture singular membrane, then energy consumption is reduced, but tensile strength and compaction index become insufficient
Solution Approach 1:
The invention applies local quality by creating different porous structures at different locations within the membrane thickness. The outer layer develops a denser porous structure for strength, while the inner layer maintains a more open structure for permeability. This spatial variation in porous morphology allows simultaneous optimization of mechanical strength and water permeability.
Solution Approach 2:
The invention utilizes spherical or rounded porous structures within the membrane matrix. The spherical porous形态 provides better stress distribution and higher tensile strength compared to angular or irregular porous structures, while maintaining the energy-efficient NIPS manufacturing process.
4Strength
If porous membrane has no macro voids and bead structure symmetric in membrane-thickness direction, then mechanical strength is improved, but water permeability and filtration property become low
Solution Approach 1:
The invention implements local quality by creating asymmetric porous distribution where the outer surface layer contains larger, more interconnected pores for high water permeability, while the inner layer has smaller, denser pores for structural support. This spatial differentiation allows the membrane to simultaneously achieve high water permeability and maintain mechanical strength.
Solution Approach 2:
The invention transitions from a symmetric two-dimensional pore distribution to a three-dimensional asymmetric pore structure that varies through the membrane thickness. By exploiting the thickness dimension, the outer surface can be optimized for permeability while the inner structure provides strength, resolving the contradiction between these two properties.
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 membrane exhibits improved mechanical strength, high water permeability, and a high rejection rate to impurities, enabling stable permeate flux control and efficient filtration, while also reducing energy consumption and process complexity.
Implementation Method 1
preparing a spinning solution by dissolving polymer resin in a mixture solvent including both poor solvent and good solvent
Implementation Method 2
bringing the extruded spinning solution into contact with a coagulation solution including a non-solvent thereby forming a porous structure
Data Source
AI summary
Disclosed is a porous membrane with high tensile strength, good elongation at break, and good water permeability, and a method for manufacturing the same. The porous membrane comprises a bead structure including plural spherical crystallites, wherein macro voids isolated from one another with the plural spherical crystallites are formed in an outer surface side of the porous membrane.