From Inert to "Active" - Monitoring of Surface Treatment
The streaming potential method detects small changes in the surface properties of polymers and is thus a sensitive technique to tune surface modification processes.
Polymers are widely used in many industrial applications. Despite of their well-suited bulk properties, the use of polymers is often limited by their inert surface. A modification or activation of the polymer surface is often required to enhance polymer wettability, printability or adhesion.
Industrial-scale processes for surface treatment like flame treatment, corona discharge and plasma treatment are usually performed in air with little control of the chemistry of the activated polymer surface.
In order to introduce specific functional surface groups, modification processes in a well controlled atmosphere like UV exposure in the presence of a reactive gas are required.
Low density polyethylene (LDPE) foils were irradiated by UV light while exposed to sulfur dioxide (SO2). The zeta potential monitors the introduction of sulfonic acid groups (-SO3H) onto the LDPE surface during this photosulfonation process.
With longer irradiation time the number of -SO3H groups increases making the LDPE surface more hydrophilic while the surface chemistry is maintained.The IEP at pH 2 (extrapolated) of photosulfonated LDPE is independent of the UV exposure time indicating the introduction of solely -SO3H groups.
S. Temmel, W. Kern, T. Luxbacher, Progr. Colloid Polym. Sci. 132 (2005) 83-90