ePTFE Membrane Matting and Sintering for Strength
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Solution Overview
Problem
Existing methods for producing expanded polytetrafluoroethylene (ePTFE) membranes and tubes are limited by the need for a wetting liquid applied before expansion, which restricts the ability to achieve unique properties post-expansion and high-temperature sintering.
Innovation Solution
A method involving the provision of unsintered or partially sintered ePTFE membranes or tubes, followed by matting and immediate sintering, without subsequent stretching, to enhance properties such as strength, friction, and lamination bond, while allowing for unique surface textures and increased light transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a wetting liquid is applied before expansion in conventional ePTFE production, then the material can be extruded and formed, but the ability to achieve unique properties post-expansion is restricted
Solution Approach 1:
The invention applies the wetting liquid after expansion rather than before, reversing the conventional sequence. This preliminary action of expanding first creates the porous structure, then the wetting liquid is applied to achieve unique surface properties and enhanced functionality in the expanded state, allowing for greater adaptability while maintaining process simplicity
2Length of moving object
If ePTFE membranes are stretched to reduce thickness, then thinner walls are achieved, but tensile strength decreases
Solution Approach 1:
The invention changes the physical state parameters by applying a wetting liquid to the expanded membrane. This causes the fibers to mat together and densify, reducing thickness while simultaneously increasing tensile strength through enhanced fiber bonding, thus resolving the trade-off between thinness and strength
Solution Approach 2:
The wetting liquid acts as a bonding agent between PTFE fibers, creating a composite structure where the liquid facilitates strong inter-fiber connections. This composite approach allows the membrane to achieve both reduced thickness and enhanced tensile strength through the synergistic effect of fiber matting and liquid bonding
3Ease of operation
If ePTFE membranes are made thinner for small diameter arteries, then device flexibility improves, but friction increases
Solution Approach 1:
The wetting liquid treatment changes the surface parameters of the thin ePTFE membrane by causing fibers to mat and reorient. This creates a smoother surface topology that reduces friction while preserving the thin profile needed for flexibility in small diameter artery applications
4Stability of the object's composition
If conventional sintering is performed after wetting liquid application, then material structure is locked in, but unique surface textures cannot be achieved
Solution Approach 1:
The invention performs expansion before applying the wetting liquid and subsequent sintering. This sequence allows the porous expanded structure to form first, then the wetting liquid is applied to create unique surface textures through fiber matting, and finally sintering locks in both the structural stability and the desired surface texture characteristics
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
This approach results in ePTFE membranes and tubes with improved tensile strength, reduced thickness, lower friction, enhanced lamination bond, and increased light transmittance, making them suitable for various medical and industrial applications.
Implementation Method 1
stretched in one or more directions at an elevated temperature below the crystalline melting point of the resin
Implementation Method 2
the stretched material is typically sintered, or heated to a temperature ranging from just below to significantly above its melting point, depending on the time at the elevated temperature, in order to lock in the physical state of the material
Implementation Method 3
The extruded material may be calendered or compressed after extruding to reduce the cross section. Next, the wettable liquid is removed from the extruded material by evaporating the wettable liquid through drying
Data Source
AI summary
A method of making an expanded polytetrafluoroethylene (ePTFE) membrane including the steps of: providing an unsintered or partially sintered ePTFE membrane; matting the unsintered or partially sintered ePTFE membrane; and immediately thereafter, sintering the matted ePTFE membrane. A method for making ePTFE tubes includes the steps of: providing an unsintered or partially sintered ePTFE membrane; wrapping the ePTFE membrane around a mandrel or form tool to form an ePTFE tube; matting the ePTFE tube; immediately thereafter, sintering the matted ePTFE tube; and removing the sintered ePTFE tube from the mandrel or form tool.