Surprisingly long lifetime of high adhesion property of plasma-treated PTFE

April 12, 2017

Polytetrafluoroethylene (PTFE), or Telfon® as it is better known, is used in a variety of daily products, from cookware to carpets, because of its non-sticky property. However, this very same non-stickiness has limited its application to other fields including medicine. Scientists at the Osaka University Graduate School of Engineering in collaboration with Hyogo Prefectural Institute of Technology have reported how heat-assisted plasma treatment can modify PTFE to solve this problem. The report can be seen in RSC Advances

Kazuya Yamamura, associate professor and Yuji Ohkubo, assistant professor at Osaka University, who first authored the study, note a need for better lubricants in medical procedures. Many people do not give it much thought, but "the rubber in syringes has to be stable and non-sticky to give accurate amounts of a medical agent," Ohkubo said.

In current procedures, the rubber is normally lubricated with a coating such as silicon oil, but this coating can contaminate the agent. PTFE would be an ideal lubricant because it would not mix with the agent, but to be effective it must also adhere to the rubber.

To increase the adhesiveness, scientists will treat PTFE with either corrosive sodium-based compounds or plasma. Plasma treatment is safe, but the adhesion is inferior.

"Conventional plasma treatment leaves a weak boundary layer (WBL) on the plasma-treated PTFE. This WBL weakens the adhesion between PTFE and the rubbe," Yamamura explains.

Determined to make a safe PTFE-based adhesive, Ohkubo considered the pressure and temperature under which the plasma treatment was done.

Suitable conditions for increasing adhesion were the result of new chemical bonds and etching of a WBL on the PTFE surface. "Carbon-fluoride bonds were exchanged with carbon-carbon crosslinks" as the plasma power was increased, said Katsuyoshi Endo, professor, who managed the study. These crosslinks and etching recovered the WBL, strengthening the adhesion between PTFE and rubber.

Further investigation showed that the increase in crosslinks was a result of the higher PTFE surface temperature that came with plasma treatment at higher power. To maximize these crosslinks, the scientists decided to heat the PTFE to several hundred degrees Celsius before plasma treatment.

"The surface of PTFE sheet generally has a WBL containing many scratches and pits ", which could affect the adhesion, explained Ohkubo. The heat-assisted plasma treatment improved the adhesion property by recovering the WBL.

The impact of the heat and power on the adhesion was very clear. At lower plasma power, peel tests showed that the PTFE could be easily split from the rubber. However, at higher power, the adhesion was so strong that the rubber tore apart instead of separating from PTFE. Moreover, this effect was seen one year after the treatment, demonstrating the stability of the adhesion.

That this strong adhesion could be achieved without any toxic chemicals suggests the already large use of PTFE could be further expanded. "Our method is straightforward and could increase the number of medical applications," said Ohkubo. The heat-assisted plasma treatment should also be useful for enhancing the adhesion of other materials.
-end-


Osaka University

Related Plasma Articles from Brightsurf:

Plasma treatments quickly kill coronavirus on surfaces
Researchers from UCLA believe using plasma could promise a significant breakthrough in the fight against the spread of COVID-19.

Fighting pandemics with plasma
Scientists have long known that ionized gases can kill pathogenic bacteria, viruses, and some fungi.

Topological waves may help in understanding plasma systems
A research team has predicted the presence of 'topologically protected' electromagnetic waves that propagate on the surface of plasmas, which may help in designing new plasma systems like fusion reactors.

Plasma electrons can be used to produce metallic films
Computers, mobile phones and all other electronic devices contain thousands of transistors, linked together by thin films of metal.

Plasma-driven biocatalysis
Compared with traditional chemical methods, enzyme catalysis has numerous advantages.

How bacteria protect themselves from plasma treatment
Considering the ever-growing percentage of bacteria that are resistant to antibiotics, interest in medical use of plasma is increasing.

A breakthrough in the study of laser/plasma interactions
Researchers from Lawrence Berkeley National Laboratory and CEA Saclay have developed a particle-in-cell simulation tool that is enabling cutting-edge simulations of laser/plasma coupling mechanisms.

Researchers turn liquid metal into a plasma
For the first time, researchers at the University of Rochester's Laboratory for Laser Energetics (LLE) have found a way to turn a liquid metal into a plasma and to observe the temperature where a liquid under high-density conditions crosses over to a plasma state.

How black holes power plasma jets
Cosmic robbery powers the jets streaming from a black hole, new simulations reveal.

Give it the plasma treatment: strong adhesion without adhesives
A Japanese research team at Osaka University used plasma treatment to make fluoropolymers and silicone resin adhere without any adhesives.

Read More: Plasma News and Plasma Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.