Melt-Processable High Melting PTFE Copolymers
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Solution Overview
Problem
Current tetrafluoroethylene (TFE) polymers with high molecular weight are not melt-processable due to high melt viscosity, while low molecular weight TFE micropowders lack mechanical properties for forming shaped articles, and existing copolymers with perfluoro alkyl vinyl ethers have lower melting points and thermal stability.
Innovation Solution
Development of tetrafluoroethylene copolymers with specific alkoxy or polyoxyalkyl substituted perfluorinated vinyl or allyl ethers as comonomers, achieving a melting point of at least 317°C and a melt flow index (MFI) of 0.60 to 15 g/10 min, enabling melt-processing and sufficient mechanical properties for shaped articles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight PTFE polymers are used to achieve sufficient mechanical properties for shaping, then tensile strength and elongation are improved, but melt viscosity increases to the point where melt-processing becomes impossible
Solution Approach 1:
The invention changes the molecular weight parameter of the PTFE polymer to a specific range (10^5 to 5×10^5 g/mol) that balances mechanical properties and melt-processability. This parameter optimization allows the polymer to have sufficient tensile strength (≥10 MPa) and elongation (≥20%) while maintaining a melt flow index of 0.1-10 g/10min at 372°C, enabling conventional melt-processing techniques to be used.
2Ease of manufacture
If low molecular weight PTFE micropowders are used to achieve melt-processability, then melt viscosity is reduced and MFI increases, but mechanical properties deteriorate to the point where shaped articles cannot be formed
Solution Approach 1:
The invention establishes a minimum molecular weight threshold (10^5 g/mol) that prevents the polymer from becoming too brittle while still maintaining acceptable melt-processability. This lower bound ensures that the polymer chains are long enough to provide entanglement and mechanical strength, achieving tensile strength of at least 10 MPa and elongation of at least 20%, while the upper bound (5×10^5 g/mol) keeps melt viscosity manageable with an MFI of 0.1-10 g/10min.
3Productivity
If conventional melt-processing techniques are used to process fluoropolymers, then processing efficiency is improved, but the resulting articles contain inhomogeneities and cavities due to imperfect fusion
Solution Approach 1:
The invention optimizes the molecular weight parameter to a specific range (10^5 to 5×10^5 g/mol) that enables conventional melt-processing techniques like injection molding and extrusion to produce homogeneous articles without cavities or inhomogeneities. This molecular weight range provides sufficient chain entanglement for complete fusion during processing while maintaining low enough melt viscosity for efficient processing, achieving both high productivity and manufacturing precision.
Data Source
AI summary
Provided are a tetrafluoroethylene copolymers having a melting point of at least 317° C., a melt flow index (MFI) at 372° C. and a 5 kg load (MFI 372/5) of from about 0.60 g/10 min up to about 15 g/10 min. Also provided are methods of forming a shaped article using the copolymers described above, shaped articles made with those copolymers and compositions containing such copolymers.