Monitoring the crosslinking behavior of PDMS via Rheometry and Raman Spectroscopy
Sprache des Vortragstitels:
Austrian Chemistry Days 2013
Sprache des Tagungstitel:
Depending on the desired features the wide variety of polydimethylsiloxanes (PDMS) types with different properties (viscosity, hardness, elongation modulus) and applications makes it necessary to select the used type properly. Additionally, knowledge about the crosslinking behavior of PDMS is very important for scientists dealing with it or its composites.
During this work different types of PDMS (WACKER Elastosil, DOW Sylgard and SMOOTH-ON Ecoflex) were investigated to find a fully crosslinked PDMS with the desired properties. Therefore the crosslinking behavior was examined with Rheometry and Raman spectroscopy.
The rheological measurements were carried out with an ANTON PAAR UDS 200 Rheometer. There are different ways of following the curing via Rheometry, namely stress-controlled time tests and strain-controlled time resolved frequency sweeps (=time-resolved mechanical spectroscopy = TRMS). The first type of measurements was done with constant stress = 75 Pa and constant frequency = 1 Hz, TRMS at a frequency range between 0.1 and 100 rads-1 (both at 25°C). We found a reasonable accordance between the two ways. Through the rheological data we gain the parameters after which we can select the appropriate PDMS for our application.
Raman measurements were done with a WITEC Alpha 300. First the spectra of the uncured PDMS and the crosslinking agent were compared and afterwards a time series with changing curing time was measured as well. The Raman spectra show some chemical information (in addition to the rheological data) about our systems.
By combining the rheological and the Raman measurements a proper investigation of the crosslinking kinetics was realized.