Lubrication Forces in Polydimethylsiloxane (PDMS) Melts

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dc.contributor.authorChatchaidech, Ratthapornen
dc.contributor.committeechairDucker, William A.en
dc.contributor.committeememberDavis, Richey M.en
dc.contributor.committeememberWalz, John Y.en
dc.contributor.departmentChemical Engineeringen
dc.date.accessioned2014-03-14T20:41:43Zen
dc.date.adate2011-08-04en
dc.date.available2014-03-14T20:41:43Zen
dc.date.issued2011-07-07en
dc.date.rdate2011-08-04en
dc.date.sdate2011-07-20en
dc.description.abstractThe flow properties of polydimethylsiloxane (PDMS) melts at room temperature were studied by measurement of lubrication forces using an Atomic Force Microscopy (AFM) colloidal force probe. A glass probe was driven toward a glass plate at piezo drive rates in the range of 12 – 120 μm/s, which produced shear rates up to ~10⁴ s⁻¹. The forces on the probe and the separation from the plate were measured. Two hypotheses were examined: (1) when a hydrophilic glass is immersed in a flow of polymer melt, does a thin layer of water form at the glass surface to lubricate the flow of polymer and (2) when a polymer melt is subject under a shear stress, do molecules within the melt spatially redistribute to form a lubrication layer of smaller molecules at the solid surface to enhance the flow? To examine the effect of a water lubrication layer, forces were compared in the presence and the absence of a thin water layer. The presence of the water layer was controlled by hydrophobization of the solid. In the second part, the possibility of forming a lubrication layer during shear was examined. Three polymer melts were compared: octamethyltrisiloxane (OMTS, n = 3), PDMS (n <sub>avg</sub> = 322), and a mixture of 70 weight% PDMS and 30 weight% OMTS. We examined whether the spatial variation in the composition of the polymer melt would occur to relieve the shear stress. The prediction was that the trimer (OMTS) would become concentrated in the high shear stress region in the thin film, thereby decreasing the viscosity in that region, and mitigating the shear stress.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-07202011-003445en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-07202011-003445/en
dc.identifier.urihttp://hdl.handle.net/10919/34085en
dc.publisherVirginia Techen
dc.relation.haspartChatchaidech_R_T_2011.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectSolid-Liquid Interfaceen
dc.subjectAFMen
dc.subjectPolymer Melten
dc.subjectChain Migrationen
dc.subjectNo-slip Boundary Conditionen
dc.subjectLubrication forcesen
dc.subjectHydrodynamic forcesen
dc.titleLubrication Forces in Polydimethylsiloxane (PDMS) Meltsen
dc.typeThesisen
thesis.degree.disciplineChemical Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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