VDF Copolymer Membrane Below-Melt Processing
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Solution Overview
Problem
Conventional processes for forming PVDF copolymer membranes require high solvent levels and processing above the melt temperature, resulting in mechanically weak and costly articles with undesirable features such as low strength and high production costs.
Innovation Solution
A process involving lubricating a VDF copolymer with a molecular weight of at least 1,000,000 g/mol, subjecting it to pressure below the melt temperature, and expanding it to form a porous article with a node and fibril microstructure, which can be calendered or ram extruded at temperatures 80°C or less below the melt temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional solvent-induced phase separation or thermal phase separation methods are used to form PVDF copolymer membranes, then porosity is achieved, but the articles become mechanically weak and costly due to high solvent levels and processing above melt temperature
Solution Approach 1:
The invention changes the temperature parameter from above-melt processing to below-melt processing (e.g., processing at 100-200°C when melt temperature is 240°C). This parameter change enables the formation of porous structures through gas evolution or foam expansion while maintaining the polymer in a solid or semi-solid state, preserving mechanical strength and eliminating the need for high solvent levels
Solution Approach 2:
The invention extracts and eliminates the harmful element (solvents) from the conventional process. By using below-melt processing with gas evolution or foam expansion techniques, the need for high solvent levels is removed entirely, achieving porosity through alternative mechanisms that do not compromise mechanical properties or require costly solvent recovery
2Quantity of substance
If conventional processes process above the melt temperature of PVDF copolymer, then porosity can be formed, but the processing cost increases and mechanical strength decreases
Solution Approach 1:
The invention changes the temperature parameter from above-melt processing to below-melt processing. This eliminates the need for expensive high-temperature equipment and energy consumption, while still achieving porosity through gas evolution or foam expansion mechanisms that work effectively in the solid/semi-solid state
Solution Approach 2:
The invention replaces expensive high-temperature processing equipment and energy requirements with simpler, lower-cost below-melt processing equipment. The process uses inexpensive gas evolution agents or foam expanders instead of costly solvent systems, making the manufacturing process more economically viable
3Quantity of substance
If high solvent levels are used in conventional PVDF copolymer membrane formation, then porosity is achieved, but the articles become costly and mechanically weak
Solution Approach 1:
The invention extracts and eliminates solvents from the process entirely by using below-melt processing with gas evolution or foam expansion. This removes the harmful substance (solvent) that causes mechanical weakness and high costs, replacing it with volatile gases or foam agents that leave no harmful residue
Solution Approach 2:
The invention uses phase transition of gases (from liquid/gas phase to gas phase) or foam expansion to create porosity without solvents. The gas evolution or foam expansion occurs in the solid/semi-solid polymer matrix, creating porous structures through physical phase changes rather than solvent-induced phase separation
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 process produces strong, porous PVDF copolymer articles with high porosity and matrix tensile strength, overcoming the limitations of conventional methods by avoiding solvent use and processing below the melt temperature.
Implementation Method 1
subjecting the lubricated VDF copolymer to pressure at a temperature below the melt temperature of the VDF copolymer to form a preform
Implementation Method 2
expanding the preform at a temperature below the melt temperature of the VDF copolymer to form a porous article having a structure of nodes interconnected by fibrils
Implementation Method 3
expanding the preform to form a porous article having a structure of nodes interconnected by fibrils
Data Source
AI summary
VDF-co-(TFE or TrFE) polymers having a molecular weight of at least about 1,000,000 g/mol and a melt temperature less than about 240° C. The VDF copolymer contains at least about 50 mol % VDF monomer and may include an amount of at least one other monomer. The VDF copolymer may be used to form a membrane that has a node and fibril structure. The membrane has a percent porosity of at least 25%. A VDF-co-(TFE or TrFE) polymer membrane may be formed by lubricating the VDF copolymer, subjecting the lubricated polymer to pressure at a temperature below the melting point of the VDF copolymer to form a preform material, and expanding the preform material at a temperature below the melting temperature of the VDF copolymer. Dense VDF copolymer articles, filled VDF copolymer membranes, and VDF copolymer fibers are also provided.