Abstract
Functionalization of Polytetrafluoroethylene (PTFE) powders of ~6 μm particle size is carried out using low-pressure 2.45 GHz H2, NH3 microwave plasmas for various durations (2.5, 10 h) to chemically modify their surface and alter their surface energy. The X-ray Photoelectron Spectroscopy (XPS) analyses reveal that plasma treatment leads to significant defluorination (F/C atomic ratio of 1.13 and 1.30 for 10 h NH3 and H2 plasma treatments, respectively vs. 1.86 for pristine PTFE), along with the incorporation of functional polar moieties on the surface, resulting in enhanced wettability. Analysis of temperature dependent XPS revealed a loss of surface moieties above 200 °C, however, the functional groups are not completely removable even at higher temperatures (>300 °C), thus enabling the use of plasma treated PTFE powders as potential tribological fillers in high temperature engineering polymers. Ageing studies carried over a period of 12 months revealed that while the surface changes degenerate over time, again, they are not completely reversible. These functionalised PTFE powders can be further used for applications into smart, high performance materials such as tribological fillers for engineering polymers and bio-medical, bio-material applications.
Highlights
Polytetrafluoroethylene (PTFE) offers outstanding properties such as high chemical inertness, heat resistance and excellent dielectric properties
The lowest fluorine to carbon atomic ratio was observed on the sample treated for ten hours with NH3 as a process gas (PTFE NH3/10 h; F/C ratio: 1.13), followed by the sample treated for ten hours with H2 (PTFE H2/10 h/2012; ratio: 1.30) as compared to pristine PTFE (F/C ratio 1.86)
The PTFE powders were treated with 2.45 GHz H2 and NH3 microwave plasmas to functionalize and chemically modify their surface; which were further characterized by wettability measurements, X-ray Photoelectron Spectroscopy (XPS), Fourier Transformed Infrared (FTIR) and Differential Scanning Calorimetry (DSC) analysis
Summary
Polytetrafluoroethylene (PTFE) offers outstanding properties such as high chemical inertness, heat resistance and excellent dielectric properties. The use of plasma techniques for the treatment of polymers is a versatile method to create novel surface functionalities by incorporating surface functional groups without altering the bulk properties. The high surface to volume ratio and macroscopic behavior of the powder mainly depends on the surface chemistry and structure of the individual powder particles, and it is of prime importance to develop processes that can impart functionality and modification at the particle scale while keeping the bulk properties unaffected. As mentioned earlier, the huge differences in surface energy, inherent low chemical reactivity and poor interfacial adhesion of PTFE with other polymers hampers its applications. It is important to develop processes which can impart surface functionality to PTFE powders to enhance their dispersion in the thermoplastic materials while maintaining the excellent frictional properties. The enhanced interaction between the plasma functionalised PTFE and the host polymer matrix due to the polar functional groups, allows enhanced force absorption capabilities, lower coefficient of friction and wear rates as compared to the pristine PTFE compounds [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
