Dense TFE Core Shell Copolymer Films for Barrier Applications
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Solution Overview
Problem
Current TFE-based barrier films lack a combination of thermal stability, strength, and effective barrier properties, with PTFE films exhibiting poor mechanical integrity and low porosity films showing limited utility due to low strength and poor resistance to low surface tension fluids.
Innovation Solution
The development of dense TFE core shell copolymers with specific endotherm profiles and a process involving copolymerization of TFE with comonomers, followed by densification and stretching to create films with improved mechanical and barrier properties, including methane permeability less than 20 μg*micron/cm2/min and matrix tensile strength greater than 5,000 psi.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTFE is used as barrier film material, then chemical resistance and temperature range are improved, but mechanical properties deteriorate
Solution Approach 1:
The patent uses composite materials by combining PTFE with other polymers (such as polyvinylidene fluoride or chlorotrifluoroethylene) to create multilayered barrier films. This allows the PTFE to provide chemical resistance and temperature stability while the other polymer components contribute improved mechanical strength and integrity, resolving the contradiction between chemical resistance and mechanical properties.
2Reliability
If PTFE is densified to reduce porosity, then barrier performance is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent employs composite materials in multilayered structures where densified PTFE layers provide barrier performance while adjacent layers of other polymers provide mechanical strength. This composite approach allows the film to achieve low porosity for barrier performance without sacrificing overall mechanical strength, as the different layers compensate for each other's weaknesses.
Solution Approach 2:
The patent applies local quality by creating regions of different porosity and material composition within the barrier film. The PTFE regions are densified to provide local barrier performance, while other regions or layers maintain higher porosity or different material properties to preserve mechanical strength. This localized differentiation allows simultaneous optimization of barrier performance and mechanical properties.
3Strength
If ePTFE is expanded to improve strength, then tensile strength is improved, but barrier performance deteriorates
Solution Approach 1:
The patent uses composite materials to combine expanded PTFE (ePTFE) layers that provide tensile strength with densified layers of PTFE or other polymers that provide barrier performance. The ePTFE layers contribute mechanical strength through their expanded microstructure, while the densified layers provide the low porosity needed for barrier performance, thus resolving the contradiction between strength and barrier performance.
4Reliability
If low porosity PTFE articles are produced by skiving process, then barrier performance is improved, but mechanical integrity deteriorates
Solution Approach 1:
The patent employs composite materials by combining skived low porosity PTFE layers that provide barrier performance with layers of other polymers or different PTFE structures that provide mechanical integrity. The multilayered composite structure allows the skived layers to deliver low porosity for barrier performance while the other layers compensate for the poor mechanical integrity, achieving both goals simultaneously.
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 dense TFE copolymer films demonstrate enhanced physical and mechanical properties, such as high tensile strength and reduced permeability, making them suitable for applications requiring improved barrier and mechanical performance.
Implementation Method 1
densifying a TFE copolymer film to form a dense TFE copolymer film
Implementation Method 2
heat treating the TFE copolymer film prior to and/or after densifying the TFE copolymer film
Implementation Method 3
stretching the dense TFE copolymer film to form a dense article
Implementation Method 4
copolymerization of TFE with comonomers
Data Source
AI summary
A tetrafluoroethylene (TFE) copolymer film having a first endotherm between about 50° C. and about 300° C., a second endotherm between about 320° C. and about 350° C., and a third endotherm between about 350° C. and about 400° C. is provided. In exemplary embodiments, the third endotherm is approximately 380° C. In some embodiments, the second endotherm is between about 320° C. and about 330° C. or between about 330° C. and about 350° C. TFE copolymer films have a methane permeability less than about 20 μg*micron/cm2/min. In addition, the dense articles have a void volume of less than about 20%. Methods for dense articles from core shell tetrafluoroethylene copolymers are also provided. The dense articles exhibit improved physical and mechanical properties such as adhesion and barrier properties.