AVS 46th International Symposium
    Applied Surface Science Division Thursday Sessions
       Session AS-ThA

Paper AS-ThA8
Monitoring the Kinetics of Migration/ Absorption/ Desorption/ and Cross-linking in a Curing Silicone Coating, using the QCM-D Technique

Thursday, October 28, 1999, 4:20 pm, Room 6A

Session: Polymer Surfaces, Films, and Interfaces
Presenter: M. Rodahl, Chalmers, Sweden
Authors: P. Dahlqvist, Q-Sense AB, Sweden
M. Rodahl, Chalmers, Sweden
P. Bjoorn, Q-Sense AB, Sweden
M. Berglin, Chalmers, Sweden
P. Gatenholm, Chalmers, Sweden
Correspondent: Click to Email
The Quartz Crystal Microbalance - Dissipation (QCM-D) technique allows real time measurements of properties and processes in nm-um thin polymer and bio-films (M.Rodahl et al., Faraday Discuss. 107, 229 (1997)). Via changes in the resonant frequency, f, small mass changes (ng/cm2) are measured. Via changes in the energy dissipation factor, D, energy losses due to internal and interfacial friction in the polymer film are measured. This makes the technique a versatile tool to, e.g., phase transitions and polymerisation kinetics. In this work we studied the cross-linking kinetics of approximately 0.5 um thick films of silicone (PDMS) in the presence of various concentrations of catalyst and cross-linker (Tridecafluoro - 1,1,2,2, - tetrahydro - octyl triethoxysilane) (FTEOS), at varying humidity. The fluorine-rich FTEOS migrates to the surface due to phase separation and due to minimisation of the systems surface energy. The kinetics of the migration has been monitored and found rapid, most of the migration take place in the first 15 minutes. Water adsorption and ethanol desorption were monitored over time. The water absorption is dominant in the start of the reaction, but after a few minutes to hours, depending on relative humidity, catalyst and FTEOS concentration, the ethanol desorption becomes dominant. The cross-linking rate monitored with the dissipation factor, is highest in the beginning and slowed after 0.5 - 5 hours, depending on relative humidity and catalyst concentration.