Microporous Semicrystalline Polymer Films via Phase Separation
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Solution Overview
Problem
Existing methods for manufacturing microporous films of semicrystalline polymers face challenges in achieving uniform pore size and distribution, high permeability, and maintaining pore integrity during the stretching process, particularly when using foaming agents or fillers, which can complicate the manufacturing process and result in films with weak physical properties.
Innovation Solution
A method involving phase separation between a semicrystalline polymer and a diluent to create sheets with a cross-section comprising a crystalline region, a pore region, and a swollen non-crystalline region, where the sheets are stretched at a temperature below the melting point of the crystalline portion, and the diluent is extracted, generating micropores without destroying the pore boundary, resulting in films with superior permeability and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a foaming agent is used to generate pores internally during molding, then pore formation is achieved, but cell size control becomes difficult and permeability cannot be maintained uniformly
Solution Approach 1:
The invention extracts and removes the foaming agent from the system by using a diluent that can be easily separated and removed after phase separation, avoiding the problems associated with foaming agents while achieving the desired pore structure
Solution Approach 2:
The invention changes the parameter of pore formation from chemical (foaming agent decomposition) to physical (phase separation and stretching), allowing precise control of pore size and distribution through processing parameters rather than chemical reactions
2Object-affected harmful factors
If open cells are formed to increase permeability, then gas permeability improves, but pore walls become too thin and physical strength decreases
Solution Approach 1:
The invention creates local quality differentiation by forming a swollen non-crystalline region with specific properties that provides both permeability pathways and structural support, allowing different regions to fulfill different functions (permeability vs. strength)
Solution Approach 2:
The invention creates a composite structure with crystalline regions providing strength and a swollen non-crystalline region providing permeability, combining the benefits of both phases into a single functional material
3Manufacturing precision
If a filler is added and interface tearing is used to form pores, then microporous structure is achieved, but uniform distribution of filler is difficult and the process becomes complicated
Solution Approach 1:
The invention extracts and removes the diluent after phase separation to create pores, eliminating the need for filler addition and extraction steps while achieving uniform pore distribution through the inherent phase separation process
Solution Approach 2:
The invention allows the polymer-diluent system to self-organize into a phase-separated structure with uniform pore distribution through controlled cooling, eliminating the need for external filler materials and complex processing steps
4Object-affected harmful factors
If stretching is applied to destroy pore boundaries for permeability, then gas permeability improves, but pore integrity is lost and physical properties weaken
Solution Approach 1:
The invention changes the parameter of pore boundary properties by maintaining the integrity of the swollen non-crystalline region during stretching, allowing permeability to improve while pore integrity is preserved through controlled thermal and mechanical parameters
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 method produces microporous films with high gas permeability and puncture strength, maintaining pore integrity and achieving uniformity without significant changes in permeability before and after stretching, thereby overcoming the limitations of previous techniques.
Implementation Method 1
phase separation between a semicrystalline polymer resin and a diluent
Implementation Method 2
stretching the sheets at a temperature below the melting point of the crystalline portion
Implementation Method 3
extracting the diluent
Data Source
AI summary
Microporous films of the semicrystalline polymer according to the present invention are obtained by stretching semicrystalline polymer sheets extruded through a die with the phase separation between a semicrystalline polymer resin and a diluent, of which sheet is comprised of a crystalline region, a pore region, and a non-crystalline region which is a swollen region swollen by the diluent, and extracting the diluent.