PTFE Porous Film Processing for Small Pores and High Strength
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Solution Overview
Problem
Existing PTFE porous films struggle to achieve a small pore diameter, small film thickness, high porosity, and high strength, which are essential for applications requiring high water resistance, sound transmission, and fine particle filtration without signal damping or degeneration.
Innovation Solution
A production method involving the addition of a hydrocarbon solvent to PTFE, followed by extrusion molding, drying, and biaxial stretching at controlled temperatures and shear rates, resulting in a PTFE porous film with a bubble point of at least 400 kPa, tensile strength of 65 MPa, and porosity of 70% or higher, achieved through specific calorimetric and stretching conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pore diameter is reduced to achieve high water resistance, then the water pressure resistance is improved, but the film strength decreases
Solution Approach 1:
The invention changes the physical and chemical parameters of PTFE by controlling the crystal fusion heat (H1-H2 ≥ 10 J/g) and specific gravity (≤ 2.15), which allows achieving small pore diameter (high water resistance) while maintaining film strength through optimized molecular structure and crystallinity
Solution Approach 2:
The invention utilizes phase transition of PTFE during extrusion molding and stretching processes, where the material transitions between crystalline and amorphous states to form a porous structure with small pore diameter while maintaining mechanical strength through controlled cooling and stretching rates
2Loss of information
If the film thickness is reduced to achieve high sound transmission, then the sound transmission is improved, but the film strength and filtration capability decrease
Solution Approach 1:
The invention optimizes film thickness (10-30 μm) combined with specific PTFE parameters (crystal fusion heat and specific gravity) to achieve a balance where thin films maintain sufficient strength and filtration capability while allowing high sound transmission through the porous structure
3Productivity
If the porosity is increased to achieve high air permeability, then the air permeability is improved, but the film strength decreases
Solution Approach 1:
The invention changes the porosity parameter to an optimal range (60-80%) combined with controlled PTFE crystal fusion heat and specific gravity, creating a porous network structure that provides high air permeability while the optimized PTFE matrix maintains film strength
Solution Approach 2:
The invention creates a composite porous structure where PTFE forms a continuous matrix with controlled porosity, combining the benefits of high air permeability through pores with the mechanical strength provided by the PTFE matrix network
4Manufacturing precision
If the pore diameter is reduced to achieve fine particle filtration, then the filtration precision is improved, but the film strength and manufacturing complexity increase
Solution Approach 1:
The invention achieves fine particle filtration (pore diameter 0.03-0.1 μm) by precisely controlling PTFE parameters (crystal fusion heat and specific gravity) and processing conditions (extrusion rate, stretching rate, temperature), creating a uniform porous structure through phase transition without requiring complex multi-step manufacturing processes
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 PTFE porous film exhibits a small pore diameter, thin thickness, high porosity, and robust strength, enabling effective filtration of fine particles and maintaining sound transmission properties, suitable for waterproof and sound-transmitting applications, vent filters, and filtration of corrosive liquids.
Implementation Method 1
shear (shearing force) is applied to the PTFE by extrusion molding to obtain a sheet-like or bead-like extruded product while fibrillizing the substance
Implementation Method 2
drying the bead-like extruded product for 1.5 hours at 25±1°C and drying for 2 more hours at 150°C
Implementation Method 3
calcined at a temperature not lower than the melting point of PTFE (347°C or higher) to obtain a PTFE porous film
Data Source
Figure 1a~2
Figure 3~4
Figure 5
AI summary
The problem of the present invention is to provide a novel polytetrafluoroethylene porous film having a small pore diameter, small film thickness, high porosity, and high strength, and a production method thereof. The present invention provides a polytetrafluoroethylene porous film, wherein a bubble point in isopropyl alcohol (IPA) according to JIS K3832 is not less than 400 kPa, and a tensile strength based on JIS K6251 is not less than 50 MPa.