Surface Chemistry Stabilization by Esterification of Polypropylene Treated by Direct Fluorination

Area of Science:

• Polymer Science
• Surface Chemistry
• Materials Science

Background:

• Direct fluorination modifies polymer surface properties like energy and friction.
• Oxygen in fluorine gas or air exposure causes side reactions during fluorination.
• Acyl fluoride (COF) groups form and can hydrolyze into carboxylic acid (COOH) groups.

Purpose of the Study:

• Investigate the impact of direct fluorination on polypropylene surface chemistry.
• Analyze the formation and evolution of COF and COOH groups.
• Develop a post-treatment to stabilize fluorinated polypropylene surfaces.

Main Methods:

• Direct gas/solid fluorination of polypropylene at varying temperatures.
• Analysis of surface chemistry changes.
• Gas-phase esterification post-treatment of fluorinated surfaces.

Main Results:

• Fluorination of polypropylene forms COF groups, which convert to COOH groups over time.
• Despite fluorination, the polar component of surface energy increased.
• Esterification post-treatment stabilized the surface chemistry, preventing hydrolysis.
• Post-treated surfaces exhibited reduced hydrophilicity compared to direct fluorination alone.

Conclusions:

• Direct fluorination of polypropylene leads to surface instability due to COF group hydrolysis.
• Esterification offers an effective method to stabilize fluorinated polymer surfaces.
• This stabilization reduces surface hydrophilicity, enhancing material performance.