Journal of Colloid and Interface Science, Vol.525, 243-250, 2018
Wetting dynamics of polydimethylsiloxane mixtures on a poly(ethylene terephthalate) fiber
Hypothesis: The wetting dynamics of liquids with identical surface tensions are mostly controlled by their viscosities. We therefore hypothesized that the wetting dynamics of one- (pure liquid) and two-component (mixture) polydimethylsiloxane (PDMS) on a poly(ethylene terephthalate) (PET) fiber with similar surface tensions and viscosities should be controlled by the same underlying physical mechanisms. Experiments: We studied the capillary rise of PDMS liquids on a PET fiber. We compared the different contact angle relaxations and characterized the transitions between the molecular-kinetic theory (MKT) and hydrodynamic approach (HD) for the PDMS mixtures and the pure liquids as a function of their viscosities. Findings: Compared to the pure PDMS liquid with a viscosity of 20 mm(2)/s that presents a contact angle relaxation following a t(-1/2) scale law in agreement with HD, the PDMS mixture with a higher viscosity (27.4 mm(2)/s) shows a t(-1/2) behavior predicted by the MKT. Moreover, the transition between MKT and HD appears in a regime with higher viscosities for PDMS mixtures than for pure liquids. Surface segregation of shorter PDMS chains or precursor film may be responsible for this shift. (C) 2018 Elsevier Inc. All rights reserved.